WO2014072866A1 - System for rf hyperthermia - Google Patents

System for rf hyperthermia Download PDF

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Publication number
WO2014072866A1
WO2014072866A1 PCT/IB2013/059650 IB2013059650W WO2014072866A1 WO 2014072866 A1 WO2014072866 A1 WO 2014072866A1 IB 2013059650 W IB2013059650 W IB 2013059650W WO 2014072866 A1 WO2014072866 A1 WO 2014072866A1
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WO
WIPO (PCT)
Prior art keywords
energy application
temperature
electromagnetic radiation
application devices
devices
Prior art date
Application number
PCT/IB2013/059650
Other languages
French (fr)
Inventor
Sascha Krueger
Peter Boernert
Ulrich Katscher
Peter Vernickel
Peter Forthmann
Tim Nielsen
Juergen Rahmer
Original Assignee
Koninklijke Philips N.V.
Philips Deutschland Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by Koninklijke Philips N.V., Philips Deutschland Gmbh filed Critical Koninklijke Philips N.V.
Publication of WO2014072866A1 publication Critical patent/WO2014072866A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/40—Applying electric fields by inductive or capacitive coupling ; Applying radio-frequency signals
    • A61N1/403—Applying electric fields by inductive or capacitive coupling ; Applying radio-frequency signals for thermotherapy, e.g. hyperthermia
    • A61N1/406—Applying electric fields by inductive or capacitive coupling ; Applying radio-frequency signals for thermotherapy, e.g. hyperthermia using implantable thermoseeds or injected particles for localized hyperthermia
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/08—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by means of electrically-heated probes
    • A61B18/082—Probes or electrodes therefor
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00053—Mechanical features of the instrument of device
    • A61B2018/00107—Coatings on the energy applicator
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00636—Sensing and controlling the application of energy
    • A61B2018/00773—Sensed parameters
    • A61B2018/00791—Temperature
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A61B18/14—Probes or electrodes therefor
    • A61B2018/147—Electrodes transferring energy by capacitive coupling, i.e. with a dielectricum between electrode and target tissue

Definitions

  • the invention relates to an energy application system and an energy application method for applying energy to an object.
  • the invention relates further to a set of energy application devices used by the energy application system.
  • RF needle applicators are often used for ablating a tumor of a living being by applying RF energy to the tumor.
  • the RF needle applicator can comprise a single RF electrode or a multi RF electrodes arrangement for ablating the tumor.
  • the single RF electrode applicator has significant limitations for complexly shaped tumors. Thus, for these kinds of tumors the multi RF electrodes arrangements are preferentially used. However, using these multi RF electrodes
  • an energy application system for applying energy to an object comprising:
  • the energy application devices are adapted to receive electromagnetic radiation and to generate heat depending on a frequency distribution of the received electromagnetic radiation, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices, an electromagnetic radiation providing device for providing electromagnetic radiation having a certain frequency distribution for stimulating the energy application devices to generate a predefined heat pattern.
  • a first energy application device may be adapted to generate heat, when electromagnetic radiation having a first frequency distribution is received, and a second energy application device may be adapted to generate heat, when electromagnetic radiation having a second frequency distribution is received, wherein the electromagnetic radiation providing device can be adapted to provide electromagnetic radiation having the first frequency distribution, if the predefined heat pattern defines that the first energy application device should generate heat, and to provide electromagnetic radiation having the second frequency distribution, if the predefined heat pattern defines that the second energy application device should generate heat.
  • the energy application devices may be selectively activated or deactivated, in order to generate heat in the predefined heat pattern.
  • the object is a clinical target region like a tumor region within a living being, wherein the energy application devices are selectively activated and deactivated, in order to generate a heat pattern that corresponds to the shape of the clinical target region.
  • the frequency distribution is preferentially defined by the frequency bands of the electromagnetic radiation.
  • the energy application devices are preferentially adapted such that to each energy application device a certain frequency band is assigned, wherein the respective energy application device generates heat, if the electromagnetic radiation comprises the respective frequency band assigned to the respective energy application device.
  • the frequency band assigned to the respective energy application device defines therefore the dependency of the heat generation on the frequency distribution of the electromagnetic radiation for the respective energy application device.
  • the electromagnetic radiation is preferentially RF radiation.
  • the frequency bands are preferentially positioned around typical RF ablation frequencies, i.e. they are preferentially arranged around about 500 kHz.
  • the energy application devices are preferentially implantable seeds, which can be implanted into a body of a living being for applying energy to the body. They are preferentially adapted such that the heat generated by a respective energy application device depends on the power of the electromagnetic radiation in the frequency band assigned to the respective energy application device.
  • the energy application devices are preferentially adapted to comprise a resonant absorption of the electromagnetic radiation within the respective frequency band assigned to the respective energy application device. The heat generated by a certain energy application device can therefore relatively easily be adjusted by controlling the power in the respective frequency bands as required for obtaining the predefined heat pattern.
  • the electromagnetic radiation providing device preferentially comprises an electromagnetic generator and an antenna for providing the electromagnetic radiation.
  • the antenna preferentially comprises RF transmit coils for providing the electromagnetic radiation.
  • the electromagnetic generator can be an N-channel tunable generator connected to an N-channel antenna array, wherein each channel corresponds to a certain frequency band. This allows providing the respective electromagnetic radiation, which is required for addressing desired energy application devices, technically relatively easily.
  • the energy application devices can be adapted to generate heat by heating the respective energy application device, wherein the heat is transferred into the surrounding, and/or by generating the heat directly in the surrounding.
  • the energy application devices may be adapted to generate electrical currents in surrounding tissue, in order to heat the tissue by resistive heating.
  • the energy application devices comprise electrically conductive elements for generating the heat depending on the received electromagnetic radiation.
  • the electrically conductive elements focus the received electromagnetic radiation and produce local heating.
  • the energy application system can comprise electrical circuits for generating the heat based on the received electromagnetic radiation.
  • the electrically conductive elements are preferentially coils. For instance, they can be micro coils. The micro coils have preferentially a diameter in the order of one millimeter.
  • the electrically conductive elements can also include a printed-circuit board foil.
  • the printed-circuit board foil may have a thickness of about 50 ⁇ and a width of about 600 ⁇ .
  • the electrically conductive elements of different energy application devices are preferentially tuned to different frequencies of the electromagnetic radiation, in order to allow the electromagnetic radiation providing device to selectively address the energy application devices by selecting the frequency of the electromagnetic radiation accordingly.
  • the energy application devices are preferentially biocompatible and/or biodegradable. It may therefore not be necessary to remove the energy application devices from the object, in particular, from a tumor region of a living being, because they do not cause rejection reactions or because they just disappear over time.
  • the energy application system preferentially further comprises a temperature determination system for determining the temperature of an energy application device and a control unit for controlling the generation of the heat depending on the determined temperature.
  • the control unit can be adapted to control the generation of the heat performed by an energy application device depending on the temperature of the energy application device.
  • a local temperature control is provided, wherein each energy application device is individually controlled based on the temperature of the respective energy application device. The temperature dependent control of the energy application devices can improve the accuracy of applying the energy to the object.
  • the temperature determining system is formed in parts by elements of the energy application devices and the electromagnetic radiation providing device, which allow the respective energy application device to provide an electromagnetic spectral response to the electromagnetic radiation providing device, which is indicative of the temperature of the respective energy application device, and wherein the temperature determining system further comprises a temperature determining unit for determining the temperature of the respective energy application device based on the electromagnetic spectral response.
  • At least some elements of the energy application devices are preferentially temperature sensitive components which can be used for providing the electromagnetic spectral response to the electromagnetic radiation providing device.
  • the energy application devices can comprise capacitors and/or inductors, which are based on materials having a significant thermal expansion in the expected temperature ranges, i.e. having appropriate thermal expansion coefficients. These elements of the energy application devices can cause changes of the capacitance and/or the inductivity of the respective energy application device, if the temperature changes. This leads to spectral response changes in the electromagnetic radiation, which are indicative of the local temperature of the respective energy application device and which can be detected by the electromagnetic radiation providing device by using, for instance, an antenna, wherein these spectral response changes can be used by the temperature determining unit for determining the local temperature.
  • the energy application devices may comprise a resonating circuit comprising a positive temperature coefficient (PTC) material.
  • the PTC material can influence the resonance of the circuit depending on the temperature of the respective energy application device and thus the electromagnetic spectral response.
  • the PTC material can influence the quality factor of the resonance and the respective spectral width of the response, which can be measured by the electromagnetic radiation providing device, in particular, by a corresponding antenna arrangement of the electromagnetic radiation providing device, for each energy application device, in particular, for each frequency band assigned to an energy application device.
  • the temperature determining unit can then be adapted to determine the temperature based on the quality factor of the resonance and the spectral width.
  • the temperature determining system comprises temperature signal providing units and sending units, wherein each energy application device includes a temperature signal providing unit and a sending unit, wherein the temperature signal providing unit is adapted to provide a temperature signal being indicative of the temperature of the respective energy application device and wherein the sending unit is adapted to send the temperature signal to a temperature determining unit of the temperature determining system for allowing the temperature determining unit to determine the temperature of the respective energy application device depending on the temperature signal.
  • the temperature signal providing unit is preferentially a temperature sensor, which may be based on changes of temperature-dependent properties of components of the energy application device.
  • the sending unit and the temperature determining unit are preferentially adapted to use RFID technology for sending the temperature signal to the temperature determining unit.
  • the temperature determining system and the control unit may be integrated in the energy application devices.
  • a local control can be provided, which allows an energy application device to control itself depending on the temperature determined by the respective energy application device. It may therefore not be necessary to provide an external control unit for controlling the provision of the electromagnetic radiation depending on the locally measured temperature.
  • the electromagnetic radiation providing device may only be adapted to provide electromagnetic radiation providing energy above a minimum energy level, wherein the control of the energy actually applied to the object can be performed by the respective energy application device itself.
  • the energy application devices may comprise a switching element with a magnetic material having a Curie temperature, wherein the switching element is adapted to activate the respective energy application device, if the magnetic material has a temperature below the Curie temperature, and to deactivate the respective energy application device, if the magnetic material has a temperature above the Curie temperature.
  • the switching element can comprise, for instance, an inductor with a magnetic core material or a semiconductor having a Curie temperature.
  • the frequency distribution is preferentially defined by frequency bands, which are non-overlapping or which overlap by not more than the half-width-at-half-maximum. Especially if the energy application devices are used for generating heat, the frequency bands may overlap by not more than the half-width-at-half-maximum. If the temperature determination procedure is performed and depends on the electromagnetic spectral response, the frequency bands are preferentially non-overlapping.
  • a set of several energy application devices for being used in the energy application system as defined in claim 1 is presented, wherein the energy application devices are adapted to be introduced into an object, to receive electromagnetic radiation and to generate heat depending on a frequency distribution of the received electromagnetic radiation, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices.
  • an energy application method for applying energy to an object comprising:
  • an electromagnetic radiation providing device for stimulating several energy application devices, which have been introduced into the object, to generate a predefined heat pattern, receiving the electromagnetic radiation and generating heat depending on the frequency distribution of the received electromagnetic radiation by the several energy application devices, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices.
  • Fig. 1 shows schematically and exemplarily an embodiment of an energy application system for applying energy to an object
  • Fig. 2 shows schematically and exemplarily an embodiment of an energy application device and an electromagnetic radiation providing device of the energy application system shown in Fig. 1,
  • Fig. 3 shows a flowchart exemplarily illustrating an embodiment of an energy application method for applying energy to an object
  • Figs. 4 and 5 show schematically and exemplarily further embodiments of an energy application device of the energy application system shown in Fig. 1.
  • Fig. 1 shows schematically and exemplarily an energy application system for applying energy to an object.
  • the object is a tumor 7 within a person 4 lying on a support unit like a patient table 5.
  • Several energy application devices 3 have been introduced into the tumor 7 for applying energy to the tumor 7.
  • the energy application devices 3 are adapted to receive electromagnetic radiation 2 and to generate heat depending on a frequency distribution of the received electromagnetic radiation 2, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation 2 is different for different energy application devices 3.
  • the energy application system further comprises an electromagnetic radiation providing device 1 for providing electromagnetic radiation 2 having a certain frequency distribution for stimulating the energy application devices 3 to generate a predefined heat pattern.
  • a first energy application device may be adapted to generate heat, when electromagnetic radiation having a first frequency distribution is received, and a second energy application device may be adapted to generate heat, when electromagnetic radiation having a second frequency distribution is received, wherein the electromagnetic radiation providing device 1 can be adapted to provide electromagnetic radiation having the first frequency distribution, if the predefined heat pattern defines that the first energy application device should generate heat, and to provide electromagnetic radiation having the second frequency distribution, if the predefined heat pattern defines the second energy application device should generate heat.
  • the electromagnetic radiation 2 provided by the electromagnetic radiation providing device 1 is preferentially RF radiation.
  • the electromagnetic radiation providing device 1 preferentially comprises an electromagnetic generator 9 and an antenna 10 with RF transmit coils for providing the RF radiation 2 as schematically and exemplarily shown in Fig. 2.
  • the electromagnetic generator 9 is an N-channel tunable generator connected to an N-channel antenna array 10, wherein each channel corresponds to a certain frequency band.
  • the frequency distribution is defined by the frequency bands of the electromagnetic radiation, wherein the energy application devices 3 are adapted such that to each energy application device a certain frequency band is assigned and wherein the respective energy application device generates heat, if the electromagnetic radiation 2 comprises the respective frequency band assigned to the respective energy application device.
  • the frequency band assigned to the respective energy application device defines therefore the dependency of the heat generation on the frequency distribution of the electromagnetic radiation 2 for the respective energy application device.
  • the different frequency bands are non-overlapping and are preferentially positioned around about 500 kHz. The amount of heat generated by the respective energy application device, which has been addressed by using the respective frequency band, then depends on the power of the provided electromagnetic radiation 2 in the respective frequency band.
  • the frequency bands can have a bandwidth between, for instance, 10 to 20 kHz.
  • the frequency bands may be centered around, for example, ..., 480 kHz, 490 kHz, 500 kHz, 510 kHz, 520 kHz, ... .
  • the electrically conductive elements include a coil 13 and a capacitor 12 as schematically and exemplarily shown in Fig. 2.
  • the coil 13 is a micro coil having a diameter of about 1 mm, which is tuned to the respective frequencies of the RF radiation, in order to allow the electromagnetic radiation providing device 1 to selectively address the energy application devices 3 by selecting the frequency of the electromagnetic radiation accordingly. Electrical current is induced in the coil 13, thereby generating heat by resistive heating.
  • the capacitor 12 comprises a dielectric core 15 and is adapted to allow high electric fields 16 to leak into the tissue, in order to cause currents and resistive heating of the tissue directly.
  • the capacitor 12 and the coil 13 are connected by electrical connectors 14 for forming an electrical circuit 17.
  • the electrical circuit 17 is arranged within a casing 11 made of biocompatible material.
  • the energy application devices can also comprise other electrically conductive elements for transforming the received electromagnetic radiation 2 into heat.
  • the energy application devices may comprise a printed circuit board based 50 ⁇ foil layout having a width of about 600 ⁇ .
  • the energy application devices and the electromagnetic radiation providing device can be adapted to, for instance, locally increase the temperature by 30 K after, for instance, a few seconds or a few minutes of RF transmission at a global whole-body specific absorption rate (SAR) level of 2 W/kg.
  • SAR whole-body specific absorption rate
  • the energy application devices 3 are preferentially made of or coated with a biocompatible material known from the state-of-the art of implantable active or passive devices like implantable cardioverter defibrillators (ICD), neurostimulators, joints et cetera.
  • the biocompatible material is, for instance, nitinol, silver, polytetrafluoroethylen (PTFE) and/or a hydrophilic polymer.
  • the energy application devices can be made of biodegradable materials like magnesium, biodegradable plastics, for instance, aliphatic polyesters, et cetera.
  • the energy application system further comprises a temperature determination system for determining the temperature of the energy application devices 3 and a control unit 8 for controlling the generation of the heat depending on the determined temperature.
  • the control unit 8 is adapted to control the generation of the heat performed by a respective energy application device depending on the temperature of the respective energy application device, wherein each energy application device is individually controlled based on the temperature of the respective energy application device, i.e. a local temperature control is provided.
  • the temperature determining system is formed in parts by elements of the energy application devices 3 and the electromagnetic radiation providing device 2, which allow the respective energy application device to provide an electromagnetic spectral response to the electromagnetic radiation providing device 1, which is indicative of the temperature of the respective energy application device, and wherein the temperature determining system further comprises a temperature determining unit 6 for determining the temperature of the respective energy application device based on the electromagnetic spectral response.
  • the electromagnetic spectral responses can be provided in the frequency bands, which are assigned to the respective energy application devices, in order to allow the temperature determining unit 6 to determine which temperature belongs to which energy application device.
  • the elements of the energy application devices, which are used for providing the electromagnetic spectral response are preferentially temperature sensitive components, wherein the electromagnetic spectral response can be detected by the electromagnetic radiation providing device 1.
  • the sub miniature capacitors 12 and/or inductors 13 can be based on materials with appropriate thermal expansion coefficients, resulting in a change of the capacitance and/or inductance and therefore of the spectral response due to local temperature changes at the respective energy application device.
  • the dielectric material 15 of the capacitor 12 can be temperature dependent and also a nearby material, which may influence the capacitance of the capacitor 12 in a temperature depending way, like water may be present.
  • the dielectric material 15 is, for instance, a ceramic material like a piezo ceramic material, or a glass material.
  • the spectral response changes are provided to the temperature determining unit 6 for determining the local temperature of the respective energy application device.
  • the temperature determining unit 6 can be adapted to determine reflection and/or transmission coefficients as known in the field of RF engineering, wherein based on these determined reflection and/or transmission coefficients as a function of the frequency, the temperature of the respective energy application device can be determined.
  • the temperature determining unit 6 comprises assignments between these coefficients and temperatures, which may be provided in the form of a table, wherein based on these assignments and the actually measured reflection and/or transmission coefficients the temperature of the respective energy application device can be determined.
  • the assignments can be determined in advance by calibration measurements, wherein the reflection and/or transmission coefficients are determined, while the temperature of the respective energy application device is known.
  • the temperature determining unit 6 is adapted to determine the temperature of the respective energy application device depending on the ratio of the S 11 reflection coefficients to the S21 transmission coefficients, wherein this determination can be based on known assignments between this kind of ratio and possible temperatures. Also in this case the assignments are preferentially known from previously performed calibration measurements.
  • the energy application devices 3 can be implanted into the tumor 7 by using, for instance, a needle or a catheter, before the energy application treatment is performed.
  • known monitoring techniques can be used for ensuring that the energy application devices are arranged at desired positions within the person 4. These known monitoring techniques can include, for instance, x-ray
  • a treatment plan can be defined based on the dimensions of a clinical target region like a tumor region and the locations of the implanted energy application devices, wherein the treatment plan preferentially defines in which time intervals which energy application devices should apply which heat for which temporal duration.
  • the energy application devices can then be activated in accordance with this treatment plan by using the electromagnetic radiation providing device 1 , without necessarily requiring additional imaging and/or location determination devices.
  • electromagnetic radiation having a certain frequency distribution is provided by an electromagnetic radiation providing device for stimulating several energy application devices, which have been introduced into an object, to generate a predefined heat pattern.
  • the heat pattern is a spatial and temporal heat pattern and a sequence of activating and deactivating the different energy application devices is predefined such that the predefined heat pattern is generated.
  • the object is preferentially a tumor and the heat pattern and, thus, the sequence of activation and deactivation times of the energy application devices are preferentially predefined such that the tumor region and preferentially also a surrounding safety margin are completely destroyed, i.e. ablated, by the generated heat.
  • step 102 the electromagnetic radiation is received by the energy application devices and the energy application devices generate heat depending on the frequency distribution of the received electromagnetic radiation, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices.
  • the frequency distribution is defined by frequency bands of the received electromagnetic radiation, wherein each energy application device can be addressed by using a certain frequency band assigned to the respective energy application device.
  • Percutaneous focal therapy is a subset of therapies which involve placement of delivery devices into the patient.
  • RF ablation is the most frequently used modality among ablative procedures.
  • Other modalities are, for example, laser ablation, cryo ablation or brachytherapy.
  • Percutaneous non-ablative procedures like hyperthermia are based, for instance, on RF or microwave radiation.
  • An RF based therapy is typically applied via an RF needle applicator.
  • Needles can be unipolar with, for example, a patch electrode or multi-polar with umbrella-like structures that can be expanded inside the tissue to be treated.
  • the single-applicator approach has limitations in larger or more complexly shaped tumors. For this reason multi-electrode RF or multi-antenna microwave based systems may be used. However, this increases device complexity and therapy costs, especially when sequential treatment sessions have to be performed. Still the probe has to be moved to different positions inside the tumor for sequential energy delivery to achieve full coverage. In even larger tumors, i.e. tumors being larger than a few centimeters, or over-treatment therapy regimes, current RF ablation techniques become inefficient.
  • the energy application system described above with reference to Fig. 1 can therefore be adapted to form a multi-channel percutaneous tissue therapy system that consists of a generator that provides electromagnetic energy and an applicator, i.e., for instance, an antenna, to apply that energy to the patient, which is enhanced to therapeutic level by local interstitial, implanted seeds, i.e. the energy application devices, which may be biodegradable, at their respective location.
  • the generator can control the local temperature of each seed individually.
  • the technology described above with reference to Fig. 1 may appear similar to low dose brachytherapy, where seeds are placed interstitially and irradiate tissue locally until radiation dose depletes finally after a few weeks to months.
  • the energy application system described above with reference to Fig. 1 has the advantage that individual seeds, i.e. individual energy application devices, can be activated or deactivated for therapy delivery after interstitial placement. This allows for a dramatic reduction of side effects by the possibility to leave out ill-placed seeds and moreover allows inexpensive sequential treatment in an out-patient or general practitioner setting, once the seeds have been placed.
  • this energy application system can be of special interest for people living in rural areas or in less developed countries who are facing a high associated effort to access hospital services.
  • the energy application system described above with reference to Fig. 1 has the advantage that larger or more complexly shaped target regions can be treated, which increases the clinical applicability of RF therapy while avoiding the cost associated with disposable RF ablation needle devices, especially multi-polar devices.
  • the energy application system described above with reference to Fig. 1 several very inexpensive disposable seeds may be placed and used for treatment in combination with a slightly more complex front-end generator compared to standard RF therapy.
  • the disposable costs and therefore therapy costs may be significantly reduced.
  • the energy application system described above with reference to Fig. 1 is preferentially a multi-channel RF therapy system with implantable RF therapy seeds, i.e. the energy application devices, which can be selectively driven via individual spectral response functions of the seeds, and with an RF generator front-end for selective heating a full set of RF seeds, wherein possible implementations preferentially include an N-channel tunable generator connected to an N-channel antenna array forming the electromagnetic radiation providing device, with N equal to or larger than one.
  • the energy application system preferentially further comprises a local SAR control for safe therapy delivery, which does not necessarily require imaging.
  • the local SAR control is preferentially provided by the above described temperature determination system and the control unit.
  • the generator of the electromagnetic radiation providing device preferentially provides RF energy transmission at various non overlapping frequency bands. Each individual band preferentially corresponds to one seed of a set.
  • the bands could be positioned around an RF therapy band of about 500 kHz for equivalence to standard RF therapy.
  • the generator transmits the electromagnetic energy into the patient using preferentially RF transmit coil technology.
  • the electromagnetic energy is preferentially such that without focusing, the field strengths are such that no therapeutic effect exists.
  • the therapeutic transmit coils can be individually designed and optimized per application and body target region or can be multi-purpose.
  • the seeds, i.e. the energy application devices preferentially have a sharp resonant absorption of electromagnetic energy within their respective frequency band.
  • the energy application system is preferentially capable of adjusting the local energy as prescribed in a treatment plan, wherein the temperature may be locally controlled.
  • the treatment plan can define, for instance, that a first seed should be heated to 50 degrees Celsius for 10 min every 3 days, that a second seed should be heated to 65 degrees Celsius for 15 min daily, that a third seed should be heated to 50 degrees Celsius for 20 min every 2 days, et cetera.
  • the temperature determining system can be adapted to use the spectral temperature response of the seeds.
  • a capacitor can be used, which does not comprise a dielectric material, but air between the capacitor plates.
  • the capacitor plates can comprise comb-like engaging structures such that a deformation of these structures leads to a capacitance change.
  • These structures are made of a material, which provides a temperature-dependent change of its dimensions, such that the comb-like structures deform and the capacitance is modified, if the temperature changes.
  • the comb-like structures can be made of, for instance, metal, in particular, bi-metal. The change in capacitance leads to a change of the spectral response such that by detecting the change of the spectral response, the temperature of the respective energy application device can be determined.
  • capacitors and inductors which are based on materials having a significant thermal expansion in the expected temperature ranges, are used by the energy application devices to provide the electromagnetic spectral response, which depends on the temperature of the respective energy application device and which can therefore be used to determine the temperature of the respective energy application device
  • the energy application devices can also be configured in another way for providing an electromagnetic spectral response that depends on the local temperature of the respective energy application device.
  • the energy application devices can comprise a resonating circuit with a PTC material that can influence the resonance of the circuit depending on the temperature of the respective energy application device and, thus, the electromagnetic spectral response.
  • the PTC material can influence the quality factor of the resonance and the respective spectral width of the response, which can be measured by the electromagnetic radiation providing device, in particular, by a corresponding antenna arrangement, which may also be regarded as being a generator front end, of the electromagnetic radiation providing device, for each frequency band and therefore for each energy application device.
  • the temperature determining unit can then be adapted to determine the temperature based on the quality factor of the resonance and/or the spectral width within the respective frequency band.
  • the temperature determining system and the control unit can also be integrated in the energy application devices.
  • a local control can be provided, which allows an energy application device to control itself depending on the temperature determined by the respective energy application device.
  • the energy application devices can comprise a switching element with a magnetic material having a Curie temperature, wherein the switching element is adapted to activate the respective energy application device, if the magnetic material has a temperature below the Curie temperature, and to deactivate the respective energy application device, if the magnetic material has a temperature above the Curie temperature.
  • the respective energy application device can comprise an inductor with a core material having an appropriate Curie
  • the energy application device i.e. the switching element
  • the switching element is preferentially adapted such that it auto deactivates itself, when the Curie temperature has been surpassed, and reactivates again, when the temperature falls below the Curie temperature.
  • the switching element may also be based on semiconductor materials with a Curie temperature above the room temperature.
  • Fig. 4 schematically and exemplarily shows such an energy application device 203 having a local control for auto deactivating and auto reactivating itself.
  • the energy application device 203 comprises a capacitor 12 with a dielectric material 15, electrical conductors 14, a biocompatible casing 11 and an inductor 13, which are similar to the corresponding components described above with reference to Fig. 2.
  • the energy application device 203 further comprises a core material 21 having a magnetic susceptibility being larger than zero for temperatures, which are smaller than the Curie temperature, and having a magnetic susceptibility being substantially zero for temperatures, which are larger than the Curie temperature.
  • the magnetic susceptibility of the core material 21 has either a first value, if the temperature is smaller than the Curie temperature, or a second value, if the temperature is larger than the Curie temperature. If the magnetic susceptibility of the core material 21 changes, also the frequency band of the energy application device 203, in which the energy application device 203 can generate heat, changes. This change of the frequency band can be such that, if the temperature of the energy application device 203 is smaller than the Curie temperature, the frequency band is within the bandwidth of the electromagnetic radiation provided by the electromagnetic radiation providing device 1 and, if the temperature of the energy application device 203 is larger than the Curie temperature, the frequency band is outside of the bandwidth of the electromagnetic radiation provided by the electromagnetic radiation providing device 1.
  • the energy application device 203 deactivates itself, if the temperature of the energy application device 103 is larger than the Curie temperature, and activates itself, if the temperature of the energy application device 203 is smaller than the Curie temperature.
  • the inductor 13 with the core material 21 can therefore be regarded as being a switching element.
  • the temperature determining system can comprise temperature signal providing units and sending units, wherein each energy application device includes a temperature signal providing unit and a sending unit.
  • the temperature signal providing unit is adapted to provide a temperature signal being indicative of the temperature of the respective energy application device and the sending unit is adapted to send the temperature signal to a temperature determining unit of the temperature determining system for allowing the temperature determining unit to determine the temperature of the respective energy application device depending on the temperature signal.
  • the sending unit and the temperature determining unit are adapted to use a passive or semi-passive RFID-like transponder technology for providing the temperature signal to the temperature determining unit.
  • the temperature signal providing unit can be adapted to measure a temperature dependent signal and to store the measured temperature dependent signal in a register before sending the same to the temperature determining unit.
  • the measured temperature signal is preferentially an electrical signal like an electrical current, which may be modified by temperature dependent electrical components of the energy application device.
  • the temperature signal providing unit can be regarded as being a temperature sensor providing the temperature signal, which is sent to the temperature determining unit via the sending unit by using, for instance, RFID technology.
  • a corresponding energy application device 303 is schematically and exemplarily shown in Fig. 5.
  • the energy application device 303 is similar to the energy application device 3 exemplarily and schematically shown in Fig. 2.
  • the energy application device 303 comprises a current measuring unit 19 being the temperature signal providing unit for providing the temperature signal being indicative of the temperature of the energy application device 303 and a sending unit 20 for sending the measured temperature signal to the temperature determining unit by using RFID technology.
  • the resulting electrical circuit comprising the capacitor 12, the coil 13, the temperature signal providing unit 19 and the sending unit 20 is indicated by reference number 18.
  • the energy application system is preferentially configured such that a generator and a transmit coil of the electromagnetic radiation providing device generate electromagnetic fields at the different frequency bands and adjust the power level for each seed, i.e. in each frequency band, according to the treatment plan, wherein a spectral temperature response may be used, which can be determined by using, for instance, spectral measurements of reflection or transmission coefficients with one of the seed implementations described above.
  • the electromagnetic radiation providing device in particular, the generator with the antenna, is preferentially capable of calibrating the frequency band and spectral response of each individual seed after interstitial placement at normal body temperature.
  • the seeds self-control their individual maximum temperature using, for instance, a switching mechanism based on magnetic Curie transition as described above, the electromagnetic radiation providing device may be controlled such that each seed hits the temperature limit for a prescribed time duration according to the treatment plan.
  • the energy application system is preferentially adapted to perform minimally- invasive tissue ablation in percutaneous intervention and therapy procedures in oncology.
  • the energy application system may also be adapted to locally apply energy in a controlled way in other application areas like hyperthermia in combination with radiation therapy.
  • a single unit or device may fulfill the functions of several items recited in the claims.
  • the mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
  • Procedures like the generation of the electromagnetic radiation, the generation of the heat, the determination of the temperature, etc. performed by one or several units or devices can be performed by any other number of units or devices.

Abstract

The invention relates to an energy application system for applying energy to an object like a tumor. The system comprises several energy application devices (3) to be introduced into the object, which are adapted to receive electromagnetic radiation (2) and to generate heat depending on a frequency distribution of the received electromagnetic radiation, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices. The system further comprises an electromagnetic radiation providing device (1) for providing electromagnetic radiation having a certain frequency distribution for stimulating the energy application devices to generate a predefined heat pattern. Since the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices, even a relatively complexly shaped predefined heat pattern can relatively easily be generated by selectively addressing the energy application devices accordingly.

Description

Energy application system
FIELD OF THE INVENTION
The invention relates to an energy application system and an energy application method for applying energy to an object. The invention relates further to a set of energy application devices used by the energy application system.
BACKGROUND OF THE INVENTION
In the field of radio frequency (RF) ablation RF needle applicators are often used for ablating a tumor of a living being by applying RF energy to the tumor. The RF needle applicator can comprise a single RF electrode or a multi RF electrodes arrangement for ablating the tumor. The single RF electrode applicator has significant limitations for complexly shaped tumors. Thus, for these kinds of tumors the multi RF electrodes arrangements are preferentially used. However, using these multi RF electrodes
arrangements, which may be umbrella-like multi-electrode probes, leads to an increased technical complexity of the ablation system.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an energy application system and an energy application method for applying energy to an object, wherein the energy can be applied to relatively complexly shaped objects, without necessarily requiring a technically very complex system. It is a further object of the present invention to provide a set of energy application devices that can be used by the energy application system.
In a first aspect of the present invention an energy application system for applying energy to an object is presented, wherein the energy application system comprises:
several energy application devices to be introduced into the object, wherein the energy application devices are adapted to receive electromagnetic radiation and to generate heat depending on a frequency distribution of the received electromagnetic radiation, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices, an electromagnetic radiation providing device for providing electromagnetic radiation having a certain frequency distribution for stimulating the energy application devices to generate a predefined heat pattern.
Since the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices, even a relatively complexly shaped predefined heat pattern can relatively easily be generated by selectively addressing the energy application devices accordingly, wherein a correspondingly adapted frequency distribution of the electromagnetic radiation is provided. In particular, different energy application devices can have different spectral response functions defining the respective dependency of the heat generation on the frequency distribution of the electromagnetic radiation.
For example, a first energy application device may be adapted to generate heat, when electromagnetic radiation having a first frequency distribution is received, and a second energy application device may be adapted to generate heat, when electromagnetic radiation having a second frequency distribution is received, wherein the electromagnetic radiation providing device can be adapted to provide electromagnetic radiation having the first frequency distribution, if the predefined heat pattern defines that the first energy application device should generate heat, and to provide electromagnetic radiation having the second frequency distribution, if the predefined heat pattern defines that the second energy application device should generate heat. Thus, the energy application devices may be selectively activated or deactivated, in order to generate heat in the predefined heat pattern. Preferentially, the object is a clinical target region like a tumor region within a living being, wherein the energy application devices are selectively activated and deactivated, in order to generate a heat pattern that corresponds to the shape of the clinical target region.
The frequency distribution is preferentially defined by the frequency bands of the electromagnetic radiation. In particular, the energy application devices are preferentially adapted such that to each energy application device a certain frequency band is assigned, wherein the respective energy application device generates heat, if the electromagnetic radiation comprises the respective frequency band assigned to the respective energy application device. The frequency band assigned to the respective energy application device defines therefore the dependency of the heat generation on the frequency distribution of the electromagnetic radiation for the respective energy application device. The electromagnetic radiation is preferentially RF radiation. The frequency bands are preferentially positioned around typical RF ablation frequencies, i.e. they are preferentially arranged around about 500 kHz.
The energy application devices are preferentially implantable seeds, which can be implanted into a body of a living being for applying energy to the body. They are preferentially adapted such that the heat generated by a respective energy application device depends on the power of the electromagnetic radiation in the frequency band assigned to the respective energy application device. The energy application devices are preferentially adapted to comprise a resonant absorption of the electromagnetic radiation within the respective frequency band assigned to the respective energy application device. The heat generated by a certain energy application device can therefore relatively easily be adjusted by controlling the power in the respective frequency bands as required for obtaining the predefined heat pattern.
The electromagnetic radiation providing device preferentially comprises an electromagnetic generator and an antenna for providing the electromagnetic radiation. The antenna preferentially comprises RF transmit coils for providing the electromagnetic radiation. For instance, the electromagnetic generator can be an N-channel tunable generator connected to an N-channel antenna array, wherein each channel corresponds to a certain frequency band. This allows providing the respective electromagnetic radiation, which is required for addressing desired energy application devices, technically relatively easily.
The energy application devices can be adapted to generate heat by heating the respective energy application device, wherein the heat is transferred into the surrounding, and/or by generating the heat directly in the surrounding. For instance, the energy application devices may be adapted to generate electrical currents in surrounding tissue, in order to heat the tissue by resistive heating.
In a preferred embodiment the energy application devices comprise electrically conductive elements for generating the heat depending on the received electromagnetic radiation. In particular, the electrically conductive elements focus the received electromagnetic radiation and produce local heating. The energy application system can comprise electrical circuits for generating the heat based on the received electromagnetic radiation. The electrically conductive elements are preferentially coils. For instance, they can be micro coils. The micro coils have preferentially a diameter in the order of one millimeter. The electrically conductive elements can also include a printed-circuit board foil. The printed-circuit board foil may have a thickness of about 50 μιη and a width of about 600 μιη. The electrically conductive elements of different energy application devices are preferentially tuned to different frequencies of the electromagnetic radiation, in order to allow the electromagnetic radiation providing device to selectively address the energy application devices by selecting the frequency of the electromagnetic radiation accordingly.
The energy application devices are preferentially biocompatible and/or biodegradable. It may therefore not be necessary to remove the energy application devices from the object, in particular, from a tumor region of a living being, because they do not cause rejection reactions or because they just disappear over time.
The energy application system preferentially further comprises a temperature determination system for determining the temperature of an energy application device and a control unit for controlling the generation of the heat depending on the determined temperature. In particular, the control unit can be adapted to control the generation of the heat performed by an energy application device depending on the temperature of the energy application device. Thus, preferentially a local temperature control is provided, wherein each energy application device is individually controlled based on the temperature of the respective energy application device. The temperature dependent control of the energy application devices can improve the accuracy of applying the energy to the object.
It is preferred that the temperature determining system is formed in parts by elements of the energy application devices and the electromagnetic radiation providing device, which allow the respective energy application device to provide an electromagnetic spectral response to the electromagnetic radiation providing device, which is indicative of the temperature of the respective energy application device, and wherein the temperature determining system further comprises a temperature determining unit for determining the temperature of the respective energy application device based on the electromagnetic spectral response.
At least some elements of the energy application devices are preferentially temperature sensitive components which can be used for providing the electromagnetic spectral response to the electromagnetic radiation providing device. For instance, the energy application devices can comprise capacitors and/or inductors, which are based on materials having a significant thermal expansion in the expected temperature ranges, i.e. having appropriate thermal expansion coefficients. These elements of the energy application devices can cause changes of the capacitance and/or the inductivity of the respective energy application device, if the temperature changes. This leads to spectral response changes in the electromagnetic radiation, which are indicative of the local temperature of the respective energy application device and which can be detected by the electromagnetic radiation providing device by using, for instance, an antenna, wherein these spectral response changes can be used by the temperature determining unit for determining the local temperature.
Moreover, the energy application devices may comprise a resonating circuit comprising a positive temperature coefficient (PTC) material. The PTC material can influence the resonance of the circuit depending on the temperature of the respective energy application device and thus the electromagnetic spectral response. For instance, the PTC material can influence the quality factor of the resonance and the respective spectral width of the response, which can be measured by the electromagnetic radiation providing device, in particular, by a corresponding antenna arrangement of the electromagnetic radiation providing device, for each energy application device, in particular, for each frequency band assigned to an energy application device. The temperature determining unit can then be adapted to determine the temperature based on the quality factor of the resonance and the spectral width.
In an embodiment, the temperature determining system comprises temperature signal providing units and sending units, wherein each energy application device includes a temperature signal providing unit and a sending unit, wherein the temperature signal providing unit is adapted to provide a temperature signal being indicative of the temperature of the respective energy application device and wherein the sending unit is adapted to send the temperature signal to a temperature determining unit of the temperature determining system for allowing the temperature determining unit to determine the temperature of the respective energy application device depending on the temperature signal. The temperature signal providing unit is preferentially a temperature sensor, which may be based on changes of temperature-dependent properties of components of the energy application device. The sending unit and the temperature determining unit are preferentially adapted to use RFID technology for sending the temperature signal to the temperature determining unit.
The temperature determining system and the control unit may be integrated in the energy application devices. Thus, a local control can be provided, which allows an energy application device to control itself depending on the temperature determined by the respective energy application device. It may therefore not be necessary to provide an external control unit for controlling the provision of the electromagnetic radiation depending on the locally measured temperature. The electromagnetic radiation providing device may only be adapted to provide electromagnetic radiation providing energy above a minimum energy level, wherein the control of the energy actually applied to the object can be performed by the respective energy application device itself. The energy application devices may comprise a switching element with a magnetic material having a Curie temperature, wherein the switching element is adapted to activate the respective energy application device, if the magnetic material has a temperature below the Curie temperature, and to deactivate the respective energy application device, if the magnetic material has a temperature above the Curie temperature. The switching element can comprise, for instance, an inductor with a magnetic core material or a semiconductor having a Curie temperature.
The frequency distribution is preferentially defined by frequency bands, which are non-overlapping or which overlap by not more than the half-width-at-half-maximum. Especially if the energy application devices are used for generating heat, the frequency bands may overlap by not more than the half-width-at-half-maximum. If the temperature determination procedure is performed and depends on the electromagnetic spectral response, the frequency bands are preferentially non-overlapping.
In a further aspect of the present invention a set of several energy application devices for being used in the energy application system as defined in claim 1 is presented, wherein the energy application devices are adapted to be introduced into an object, to receive electromagnetic radiation and to generate heat depending on a frequency distribution of the received electromagnetic radiation, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices.
In a further aspect of the present invention an energy application method for applying energy to an object is presented, wherein the energy application method comprises:
providing electromagnetic radiation having a certain frequency distribution by an electromagnetic radiation providing device for stimulating several energy application devices, which have been introduced into the object, to generate a predefined heat pattern, receiving the electromagnetic radiation and generating heat depending on the frequency distribution of the received electromagnetic radiation by the several energy application devices, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices.
It shall be understood that the energy application system of claim 1, the set of several energy application devices of claim 14, and the energy application method of claim 15 have similar and/or identical preferred embodiments, in particular, as defined in the dependent claims. It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claim.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. 1 shows schematically and exemplarily an embodiment of an energy application system for applying energy to an object,
Fig. 2 shows schematically and exemplarily an embodiment of an energy application device and an electromagnetic radiation providing device of the energy application system shown in Fig. 1,
Fig. 3 shows a flowchart exemplarily illustrating an embodiment of an energy application method for applying energy to an object, and
Figs. 4 and 5 show schematically and exemplarily further embodiments of an energy application device of the energy application system shown in Fig. 1.
DETAILED DESCRIPTION OF EMBODIMENTS
Fig. 1 shows schematically and exemplarily an energy application system for applying energy to an object. In this embodiment the object is a tumor 7 within a person 4 lying on a support unit like a patient table 5. Several energy application devices 3 have been introduced into the tumor 7 for applying energy to the tumor 7. The energy application devices 3 are adapted to receive electromagnetic radiation 2 and to generate heat depending on a frequency distribution of the received electromagnetic radiation 2, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation 2 is different for different energy application devices 3. The energy application system further comprises an electromagnetic radiation providing device 1 for providing electromagnetic radiation 2 having a certain frequency distribution for stimulating the energy application devices 3 to generate a predefined heat pattern. In particular, a first energy application device may be adapted to generate heat, when electromagnetic radiation having a first frequency distribution is received, and a second energy application device may be adapted to generate heat, when electromagnetic radiation having a second frequency distribution is received, wherein the electromagnetic radiation providing device 1 can be adapted to provide electromagnetic radiation having the first frequency distribution, if the predefined heat pattern defines that the first energy application device should generate heat, and to provide electromagnetic radiation having the second frequency distribution, if the predefined heat pattern defines the second energy application device should generate heat.
The electromagnetic radiation 2 provided by the electromagnetic radiation providing device 1 is preferentially RF radiation. For generating the RF radiation the electromagnetic radiation providing device 1 preferentially comprises an electromagnetic generator 9 and an antenna 10 with RF transmit coils for providing the RF radiation 2 as schematically and exemplarily shown in Fig. 2. In this embodiment the electromagnetic generator 9 is an N-channel tunable generator connected to an N-channel antenna array 10, wherein each channel corresponds to a certain frequency band.
The frequency distribution is defined by the frequency bands of the electromagnetic radiation, wherein the energy application devices 3 are adapted such that to each energy application device a certain frequency band is assigned and wherein the respective energy application device generates heat, if the electromagnetic radiation 2 comprises the respective frequency band assigned to the respective energy application device. The frequency band assigned to the respective energy application device defines therefore the dependency of the heat generation on the frequency distribution of the electromagnetic radiation 2 for the respective energy application device. The different frequency bands are non-overlapping and are preferentially positioned around about 500 kHz. The amount of heat generated by the respective energy application device, which has been addressed by using the respective frequency band, then depends on the power of the provided electromagnetic radiation 2 in the respective frequency band.
The frequency bands can have a bandwidth between, for instance, 10 to 20 kHz. The frequency bands may be centered around, for example, ..., 480 kHz, 490 kHz, 500 kHz, 510 kHz, 520 kHz, ... .
The energy application devices 3, which are preferentially heat emanating seeds, comprise electrically conductive elements for focusing the received electromagnetic radiation and for producing local heat. In this embodiment the electrically conductive elements include a coil 13 and a capacitor 12 as schematically and exemplarily shown in Fig. 2. The coil 13 is a micro coil having a diameter of about 1 mm, which is tuned to the respective frequencies of the RF radiation, in order to allow the electromagnetic radiation providing device 1 to selectively address the energy application devices 3 by selecting the frequency of the electromagnetic radiation accordingly. Electrical current is induced in the coil 13, thereby generating heat by resistive heating. The capacitor 12 comprises a dielectric core 15 and is adapted to allow high electric fields 16 to leak into the tissue, in order to cause currents and resistive heating of the tissue directly. The capacitor 12 and the coil 13 are connected by electrical connectors 14 for forming an electrical circuit 17. The electrical circuit 17 is arranged within a casing 11 made of biocompatible material.
The energy application devices can also comprise other electrically conductive elements for transforming the received electromagnetic radiation 2 into heat. For instance, the energy application devices may comprise a printed circuit board based 50 μιη foil layout having a width of about 600 μιη. The energy application devices and the electromagnetic radiation providing device can be adapted to, for instance, locally increase the temperature by 30 K after, for instance, a few seconds or a few minutes of RF transmission at a global whole-body specific absorption rate (SAR) level of 2 W/kg.
The energy application devices 3 are preferentially made of or coated with a biocompatible material known from the state-of-the art of implantable active or passive devices like implantable cardioverter defibrillators (ICD), neurostimulators, joints et cetera. The biocompatible material is, for instance, nitinol, silver, polytetrafluoroethylen (PTFE) and/or a hydrophilic polymer. Alternatively or in addition, the energy application devices can be made of biodegradable materials like magnesium, biodegradable plastics, for instance, aliphatic polyesters, et cetera.
The energy application system further comprises a temperature determination system for determining the temperature of the energy application devices 3 and a control unit 8 for controlling the generation of the heat depending on the determined temperature. In particular, the control unit 8 is adapted to control the generation of the heat performed by a respective energy application device depending on the temperature of the respective energy application device, wherein each energy application device is individually controlled based on the temperature of the respective energy application device, i.e. a local temperature control is provided.
In this embodiment the temperature determining system is formed in parts by elements of the energy application devices 3 and the electromagnetic radiation providing device 2, which allow the respective energy application device to provide an electromagnetic spectral response to the electromagnetic radiation providing device 1, which is indicative of the temperature of the respective energy application device, and wherein the temperature determining system further comprises a temperature determining unit 6 for determining the temperature of the respective energy application device based on the electromagnetic spectral response. The electromagnetic spectral responses can be provided in the frequency bands, which are assigned to the respective energy application devices, in order to allow the temperature determining unit 6 to determine which temperature belongs to which energy application device. The elements of the energy application devices, which are used for providing the electromagnetic spectral response, are preferentially temperature sensitive components, wherein the electromagnetic spectral response can be detected by the electromagnetic radiation providing device 1.
For instance, the sub miniature capacitors 12 and/or inductors 13 can be based on materials with appropriate thermal expansion coefficients, resulting in a change of the capacitance and/or inductance and therefore of the spectral response due to local temperature changes at the respective energy application device. In particular, the dielectric material 15 of the capacitor 12 can be temperature dependent and also a nearby material, which may influence the capacitance of the capacitor 12 in a temperature depending way, like water may be present. The dielectric material 15 is, for instance, a ceramic material like a piezo ceramic material, or a glass material. These changes of the spectral response can be detected by the electromagnetic radiation providing device 1 by using the above mentioned antenna. The spectral response changes are provided to the temperature determining unit 6 for determining the local temperature of the respective energy application device. For instance, the temperature determining unit 6 can be adapted to determine reflection and/or transmission coefficients as known in the field of RF engineering, wherein based on these determined reflection and/or transmission coefficients as a function of the frequency, the temperature of the respective energy application device can be determined. Preferentially, the temperature determining unit 6 comprises assignments between these coefficients and temperatures, which may be provided in the form of a table, wherein based on these assignments and the actually measured reflection and/or transmission coefficients the temperature of the respective energy application device can be determined. The assignments can be determined in advance by calibration measurements, wherein the reflection and/or transmission coefficients are determined, while the temperature of the respective energy application device is known. In an embodiment, the temperature determining unit 6 is adapted to determine the temperature of the respective energy application device depending on the ratio of the S 11 reflection coefficients to the S21 transmission coefficients, wherein this determination can be based on known assignments between this kind of ratio and possible temperatures. Also in this case the assignments are preferentially known from previously performed calibration measurements. The energy application devices 3 can be implanted into the tumor 7 by using, for instance, a needle or a catheter, before the energy application treatment is performed. For this initial placing of the energy application devices 3 known monitoring techniques can be used for ensuring that the energy application devices are arranged at desired positions within the person 4. These known monitoring techniques can include, for instance, x-ray
fluoroscopy, magnetic resonance imaging, computed tomography imaging, nuclear imaging like positron emission tomography imaging or single photon emission tomography imaging, ultrasound imaging, et cetera. Once the energy application devices have been arranged at the desired locations within the person 4, the actual treatment can be performed without necessarily requiring these monitoring technologies anymore, wherein it is assumed that the energy application devices remain at their respective locations within the person 4. A treatment plan can be defined based on the dimensions of a clinical target region like a tumor region and the locations of the implanted energy application devices, wherein the treatment plan preferentially defines in which time intervals which energy application devices should apply which heat for which temporal duration. The energy application devices can then be activated in accordance with this treatment plan by using the electromagnetic radiation providing device 1 , without necessarily requiring additional imaging and/or location determination devices.
In the following an embodiment of an energy application method for applying energy to an object will exemplarily be described with reference to a flowchart shown in Fig. 3.
In step 101 electromagnetic radiation having a certain frequency distribution is provided by an electromagnetic radiation providing device for stimulating several energy application devices, which have been introduced into an object, to generate a predefined heat pattern. Preferentially, the heat pattern is a spatial and temporal heat pattern and a sequence of activating and deactivating the different energy application devices is predefined such that the predefined heat pattern is generated. The object is preferentially a tumor and the heat pattern and, thus, the sequence of activation and deactivation times of the energy application devices are preferentially predefined such that the tumor region and preferentially also a surrounding safety margin are completely destroyed, i.e. ablated, by the generated heat. In step 102 the electromagnetic radiation is received by the energy application devices and the energy application devices generate heat depending on the frequency distribution of the received electromagnetic radiation, wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation is different for different energy application devices. The frequency distribution is defined by frequency bands of the received electromagnetic radiation, wherein each energy application device can be addressed by using a certain frequency band assigned to the respective energy application device.
An important clinical need in focal therapy is improved accuracy of delivery of therapeutic energy to the target tissue like tumor tissue for improved outcomes and reduced side effects. Percutaneous focal therapy is a subset of therapies which involve placement of delivery devices into the patient. Among percutaneous focal therapies, RF ablation is the most frequently used modality among ablative procedures. Other modalities are, for example, laser ablation, cryo ablation or brachytherapy. Percutaneous non-ablative procedures like hyperthermia are based, for instance, on RF or microwave radiation.
An RF based therapy is typically applied via an RF needle applicator. Needles can be unipolar with, for example, a patch electrode or multi-polar with umbrella-like structures that can be expanded inside the tissue to be treated. The single-applicator approach has limitations in larger or more complexly shaped tumors. For this reason multi-electrode RF or multi-antenna microwave based systems may be used. However, this increases device complexity and therapy costs, especially when sequential treatment sessions have to be performed. Still the probe has to be moved to different positions inside the tumor for sequential energy delivery to achieve full coverage. In even larger tumors, i.e. tumors being larger than a few centimeters, or over-treatment therapy regimes, current RF ablation techniques become inefficient.
The energy application system described above with reference to Fig. 1 can therefore be adapted to form a multi-channel percutaneous tissue therapy system that consists of a generator that provides electromagnetic energy and an applicator, i.e., for instance, an antenna, to apply that energy to the patient, which is enhanced to therapeutic level by local interstitial, implanted seeds, i.e. the energy application devices, which may be biodegradable, at their respective location. The generator can control the local temperature of each seed individually.
In some aspects, the technology described above with reference to Fig. 1 may appear similar to low dose brachytherapy, where seeds are placed interstitially and irradiate tissue locally until radiation dose depletes finally after a few weeks to months. However, in comparison to the low dose brachytherapy the energy application system described above with reference to Fig. 1 has the advantage that individual seeds, i.e. individual energy application devices, can be activated or deactivated for therapy delivery after interstitial placement. This allows for a dramatic reduction of side effects by the possibility to leave out ill-placed seeds and moreover allows inexpensive sequential treatment in an out-patient or general practitioner setting, once the seeds have been placed. Besides the enormous cost saving potential for hospitals, this energy application system can be of special interest for people living in rural areas or in less developed countries who are facing a high associated effort to access hospital services.
In comparison to current RF based therapy systems the energy application system described above with reference to Fig. 1 has the advantage that larger or more complexly shaped target regions can be treated, which increases the clinical applicability of RF therapy while avoiding the cost associated with disposable RF ablation needle devices, especially multi-polar devices. Instead, with the energy application system described above with reference to Fig. 1, several very inexpensive disposable seeds may be placed and used for treatment in combination with a slightly more complex front-end generator compared to standard RF therapy. Thus, the disposable costs and therefore therapy costs may be significantly reduced.
In order to provide these advantages the energy application system described above with reference to Fig. 1 is preferentially a multi-channel RF therapy system with implantable RF therapy seeds, i.e. the energy application devices, which can be selectively driven via individual spectral response functions of the seeds, and with an RF generator front-end for selective heating a full set of RF seeds, wherein possible implementations preferentially include an N-channel tunable generator connected to an N-channel antenna array forming the electromagnetic radiation providing device, with N equal to or larger than one. The energy application system preferentially further comprises a local SAR control for safe therapy delivery, which does not necessarily require imaging. The local SAR control is preferentially provided by the above described temperature determination system and the control unit.
The generator of the electromagnetic radiation providing device preferentially provides RF energy transmission at various non overlapping frequency bands. Each individual band preferentially corresponds to one seed of a set. The bands could be positioned around an RF therapy band of about 500 kHz for equivalence to standard RF therapy. The generator transmits the electromagnetic energy into the patient using preferentially RF transmit coil technology. The electromagnetic energy is preferentially such that without focusing, the field strengths are such that no therapeutic effect exists. The therapeutic transmit coils can be individually designed and optimized per application and body target region or can be multi-purpose. The seeds, i.e. the energy application devices, preferentially have a sharp resonant absorption of electromagnetic energy within their respective frequency band. The energy application system is preferentially capable of adjusting the local energy as prescribed in a treatment plan, wherein the temperature may be locally controlled. The treatment plan can define, for instance, that a first seed should be heated to 50 degrees Celsius for 10 min every 3 days, that a second seed should be heated to 65 degrees Celsius for 15 min daily, that a third seed should be heated to 50 degrees Celsius for 20 min every 2 days, et cetera. For temperature read out of the seeds the temperature determining system can be adapted to use the spectral temperature response of the seeds.
Although in an above described embodiment a temperature dependent dielectric material of a capacitor is used for changing the spectral response detected by the electric magnetic radiation providing device, wherein the temperature is determined based on the change of the spectral response, in other embodiments a capacitor can be used, which does not comprise a dielectric material, but air between the capacitor plates. For instance, the capacitor plates can comprise comb-like engaging structures such that a deformation of these structures leads to a capacitance change. These structures are made of a material, which provides a temperature-dependent change of its dimensions, such that the comb-like structures deform and the capacitance is modified, if the temperature changes. The comb-like structures can be made of, for instance, metal, in particular, bi-metal. The change in capacitance leads to a change of the spectral response such that by detecting the change of the spectral response, the temperature of the respective energy application device can be determined.
Although in an above described embodiment capacitors and inductors, which are based on materials having a significant thermal expansion in the expected temperature ranges, are used by the energy application devices to provide the electromagnetic spectral response, which depends on the temperature of the respective energy application device and which can therefore be used to determine the temperature of the respective energy application device, the energy application devices can also be configured in another way for providing an electromagnetic spectral response that depends on the local temperature of the respective energy application device. For instance, the energy application devices can comprise a resonating circuit with a PTC material that can influence the resonance of the circuit depending on the temperature of the respective energy application device and, thus, the electromagnetic spectral response. For instance, the PTC material can influence the quality factor of the resonance and the respective spectral width of the response, which can be measured by the electromagnetic radiation providing device, in particular, by a corresponding antenna arrangement, which may also be regarded as being a generator front end, of the electromagnetic radiation providing device, for each frequency band and therefore for each energy application device. The temperature determining unit can then be adapted to determine the temperature based on the quality factor of the resonance and/or the spectral width within the respective frequency band.
Moreover, the temperature determining system and the control unit can also be integrated in the energy application devices. Thus, a local control can be provided, which allows an energy application device to control itself depending on the temperature determined by the respective energy application device. For example, the energy application devices can comprise a switching element with a magnetic material having a Curie temperature, wherein the switching element is adapted to activate the respective energy application device, if the magnetic material has a temperature below the Curie temperature, and to deactivate the respective energy application device, if the magnetic material has a temperature above the Curie temperature. For instance, the respective energy application device can comprise an inductor with a core material having an appropriate Curie
temperature which corresponds, for instance, to the maximal heat that should be applied to the object, wherein the core material may be Monel. The energy application device, i.e. the switching element, is preferentially adapted such that it auto deactivates itself, when the Curie temperature has been surpassed, and reactivates again, when the temperature falls below the Curie temperature. The switching element may also be based on semiconductor materials with a Curie temperature above the room temperature.
Fig. 4 schematically and exemplarily shows such an energy application device 203 having a local control for auto deactivating and auto reactivating itself. The energy application device 203 comprises a capacitor 12 with a dielectric material 15, electrical conductors 14, a biocompatible casing 11 and an inductor 13, which are similar to the corresponding components described above with reference to Fig. 2. However, in this embodiment the energy application device 203 further comprises a core material 21 having a magnetic susceptibility being larger than zero for temperatures, which are smaller than the Curie temperature, and having a magnetic susceptibility being substantially zero for temperatures, which are larger than the Curie temperature. Thus, the magnetic susceptibility of the core material 21 has either a first value, if the temperature is smaller than the Curie temperature, or a second value, if the temperature is larger than the Curie temperature. If the magnetic susceptibility of the core material 21 changes, also the frequency band of the energy application device 203, in which the energy application device 203 can generate heat, changes. This change of the frequency band can be such that, if the temperature of the energy application device 203 is smaller than the Curie temperature, the frequency band is within the bandwidth of the electromagnetic radiation provided by the electromagnetic radiation providing device 1 and, if the temperature of the energy application device 203 is larger than the Curie temperature, the frequency band is outside of the bandwidth of the electromagnetic radiation provided by the electromagnetic radiation providing device 1. Thus, the energy application device 203 deactivates itself, if the temperature of the energy application device 103 is larger than the Curie temperature, and activates itself, if the temperature of the energy application device 203 is smaller than the Curie temperature. The inductor 13 with the core material 21 can therefore be regarded as being a switching element.
In an alternative embodiment the temperature determining system can comprise temperature signal providing units and sending units, wherein each energy application device includes a temperature signal providing unit and a sending unit. The temperature signal providing unit is adapted to provide a temperature signal being indicative of the temperature of the respective energy application device and the sending unit is adapted to send the temperature signal to a temperature determining unit of the temperature determining system for allowing the temperature determining unit to determine the temperature of the respective energy application device depending on the temperature signal. Preferentially, the sending unit and the temperature determining unit are adapted to use a passive or semi-passive RFID-like transponder technology for providing the temperature signal to the temperature determining unit. The temperature signal providing unit can be adapted to measure a temperature dependent signal and to store the measured temperature dependent signal in a register before sending the same to the temperature determining unit. The measured temperature signal is preferentially an electrical signal like an electrical current, which may be modified by temperature dependent electrical components of the energy application device. The temperature signal providing unit can be regarded as being a temperature sensor providing the temperature signal, which is sent to the temperature determining unit via the sending unit by using, for instance, RFID technology.
A corresponding energy application device 303 is schematically and exemplarily shown in Fig. 5. The energy application device 303 is similar to the energy application device 3 exemplarily and schematically shown in Fig. 2. However, in addition the energy application device 303 comprises a current measuring unit 19 being the temperature signal providing unit for providing the temperature signal being indicative of the temperature of the energy application device 303 and a sending unit 20 for sending the measured temperature signal to the temperature determining unit by using RFID technology. In Fig. 5 the resulting electrical circuit comprising the capacitor 12, the coil 13, the temperature signal providing unit 19 and the sending unit 20 is indicated by reference number 18.
The energy application system is preferentially configured such that a generator and a transmit coil of the electromagnetic radiation providing device generate electromagnetic fields at the different frequency bands and adjust the power level for each seed, i.e. in each frequency band, according to the treatment plan, wherein a spectral temperature response may be used, which can be determined by using, for instance, spectral measurements of reflection or transmission coefficients with one of the seed implementations described above. The electromagnetic radiation providing device, in particular, the generator with the antenna, is preferentially capable of calibrating the frequency band and spectral response of each individual seed after interstitial placement at normal body temperature. Alternatively, if the seeds self-control their individual maximum temperature using, for instance, a switching mechanism based on magnetic Curie transition as described above, the electromagnetic radiation providing device may be controlled such that each seed hits the temperature limit for a prescribed time duration according to the treatment plan.
The energy application system is preferentially adapted to perform minimally- invasive tissue ablation in percutaneous intervention and therapy procedures in oncology. The energy application system may also be adapted to locally apply energy in a controlled way in other application areas like hyperthermia in combination with radiation therapy.
Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.
In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.
A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
Procedures like the generation of the electromagnetic radiation, the generation of the heat, the determination of the temperature, etc. performed by one or several units or devices can be performed by any other number of units or devices.
Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:
1. An energy application system for applying energy to an object, the energy application system comprising:
several energy application devices (3) to be introduced into the object (7), wherein the energy application devices (3) are adapted to receive electromagnetic radiation (2) and to generate heat depending on a frequency distribution of the received
electromagnetic radiation (2), wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation (2) is different for different energy application devices (3),
an electromagnetic radiation providing device (1) for providing electromagnetic radiation (2) having a certain frequency distribution for stimulating the energy application devices (3) to generate a predefined heat pattern.
2. The energy application system as defined in claim 1, wherein the frequency distribution is defined by the frequency bands of the electromagnetic radiation (2).
3. The energy application system as defined in claim 2, wherein the energy application devices (3) are adapted such that to each energy application device a certain frequency band is assigned, wherein the respective energy application device generates heat, if the electromagnetic radiation (2) comprises the respective frequency band assigned to the respective energy application device.
4. The energy application system as defined in claim 3, wherein the frequency bands assigned to different energy application devices (3) are non-overlapping or overlap by not more than the half-width-at-half-maximum.
5. The energy application system as defined in claim 3, wherein the energy application devices (3) are adapted such that the heat generated by a respective energy application device depends on the power of the electromagnetic radiation (2) in the frequency band assigned to the respective energy application device.
6. The energy application system as defined in claim 1, wherein the
electromagnetic radiation (2) is radio frequency radiation.
7. The energy application system as defined in claim 1, wherein the energy application devices (3) comprise electrically conductive elements for generating the heat depending on the received electromagnetic radiation (2).
8. The energy application system as defined in claim 1, wherein the energy application devices are biocompatible and/or biodegradable.
9. The energy application system as defined in claim 1, wherein the energy application system further comprises a temperature determination system for determining the temperature of an energy application device and a control unit (8) for controlling the generation of the heat depending on the determined temperature.
10. The energy application system as defined in claim 9, wherein the temperature determining system is formed in parts by elements of the energy application devices (3) and the electromagnetic radiation providing device (1), which allow the respective energy application device to provide an electromagnetic spectral response to the electromagnetic radiation providing device (1), which is indicative of the temperature of the respective energy application device, and wherein the temperature determining system further comprises a temperature determining unit (6) for determining the temperature of the respective energy application device based on the electromagnetic spectral response.
11. The energy application system as defined in claim 9, wherein the temperature determining system comprises temperature signal providing units and sending units, wherein each energy application device includes a temperature signal providing unit and a sending unit, wherein the temperature signal providing unit is adapted to provide a temperature signal being indicative of the temperature of the respective energy application device and wherein the sending unit is adapted to send the temperature signal to a temperature determining unit of the temperature determining system for allowing the temperature determining unit to determine the temperature of the respective energy application device depending on the temperature signal.
12. The energy application system as defined in claim 9, wherein the temperature determining system and the control unit are integrated in the energy application devices (3).
13. The energy application system as defined in claim 12, wherein the energy application devices (3) comprise a switching element with a magnetic material having a Curie temperature, wherein the switching element is adapted to activate the respective energy application device, if the magnetic material has a temperature below the Curie temperature, and to deactivate the respective energy application device, if the magnetic material has a temperature above the Curie temperature.
14. A set of several energy application devices (3) for being used in the energy application system as defined in claim 1, wherein the energy application devices (3) are adapted to be introduced into an object (7), to receive electromagnetic radiation (2) and to generate heat depending on a frequency distribution of the received electromagnetic radiation (2), wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation (2) is different for different energy application devices (3).
15. An energy application method for applying energy to an object (7), the energy application method comprising:
providing electromagnetic radiation (2) having a certain frequency distribution by an electromagnetic radiation (2) providing unit for stimulating several energy application devices (3), which have been introduced into the object (7), to generate a predefined heat pattern,
- receiving the electromagnetic radiation (2) and generating heat depending on the frequency distribution of the received electromagnetic radiation (2) by the several energy application devices (3), wherein the dependency of the heat generation on the frequency distribution of the electromagnetic radiation (2) is different for different energy application devices (3).
PCT/IB2013/059650 2012-11-08 2013-10-25 System for rf hyperthermia WO2014072866A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060020313A1 (en) * 2002-01-18 2006-01-26 Calfacior Corporation Now Apsara Medical Corporation System, method and apparatus for evaluating tissue temperature
US20060095103A1 (en) * 2003-12-11 2006-05-04 Apsara Medical Corporation Aesthetic thermal sculpting of skin
US20070250139A1 (en) * 2004-05-07 2007-10-25 John Kanzius Enhanced systems and methods for RF-induced hyperthermia II
US20080045879A1 (en) * 2004-05-28 2008-02-21 Georgia Tech Research Corporation Methods and Devices for Thermal Treatment
US20110224479A1 (en) * 2010-03-11 2011-09-15 Empire Technology Development, Llc Eddy current induced hyperthermia using conductive particles
US20120190910A1 (en) * 2011-01-24 2012-07-26 Actium BioSystems, LLC System for defining energy field characteristics to illuminate nano-particles used to treat invasive agents

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060020313A1 (en) * 2002-01-18 2006-01-26 Calfacior Corporation Now Apsara Medical Corporation System, method and apparatus for evaluating tissue temperature
US20060095103A1 (en) * 2003-12-11 2006-05-04 Apsara Medical Corporation Aesthetic thermal sculpting of skin
US20070250139A1 (en) * 2004-05-07 2007-10-25 John Kanzius Enhanced systems and methods for RF-induced hyperthermia II
US20080045879A1 (en) * 2004-05-28 2008-02-21 Georgia Tech Research Corporation Methods and Devices for Thermal Treatment
US20110224479A1 (en) * 2010-03-11 2011-09-15 Empire Technology Development, Llc Eddy current induced hyperthermia using conductive particles
US20120190910A1 (en) * 2011-01-24 2012-07-26 Actium BioSystems, LLC System for defining energy field characteristics to illuminate nano-particles used to treat invasive agents

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