Suche Bilder Maps Play YouTube News Gmail Drive Mehr »
Anmelden
Nutzer von Screenreadern: Klicke auf diesen Link, um die Bedienungshilfen zu aktivieren. Dieser Modus bietet die gleichen Grundfunktionen, funktioniert aber besser mit deinem Reader.

Patentsuche

  1. Erweiterte Patentsuche
VeröffentlichungsnummerWO2017032903 A1
PublikationstypAnmeldung
AnmeldenummerPCT/EP2016/070267
Veröffentlichungsdatum2. März 2017
Eingetragen26. Aug. 2016
Prioritätsdatum27. Aug. 2015
VeröffentlichungsnummerPCT/2016/70267, PCT/EP/16/070267, PCT/EP/16/70267, PCT/EP/2016/070267, PCT/EP/2016/70267, PCT/EP16/070267, PCT/EP16/70267, PCT/EP16070267, PCT/EP1670267, PCT/EP2016/070267, PCT/EP2016/70267, PCT/EP2016070267, PCT/EP201670267, WO 2017/032903 A1, WO 2017032903 A1, WO 2017032903A1, WO-A1-2017032903, WO2017/032903A1, WO2017032903 A1, WO2017032903A1
ErfinderBernhard Gleich
AntragstellerKoninklijke Philips N.V.
Zitat exportierenBiBTeX, EndNote, RefMan
Externe Links:  Patentscope, Espacenet
Magnet arrangement and magnetic particle imaging device
WO 2017032903 A1
Zusammenfassung
The present invention relates to magnet arrangement, in particular for use in a magnetic particle imaging (MPI) device. To make the MPI device suitable for monitoring scenarios, preferably with fast scanning, less bulky and consume less electrical power than known MPI apparatus, the magnet arrangement comprises a magnet unit (501, 100a, 100b, 100c, 100d) for generating a magnetic field free area and a manipulator unit (200) to move the magnet unit in order to move the magnetic field free zone along a desired trajectory.
Ansprüche  (OCR-Text kann Fehler enthalten)
CLAIMS:
1. Magnet arrangement, in particular for use in a magnetic particle imaging device, said magnet arrangement comprising:
a magnet unit (501, 100, 100a, 100b, 100c, lOOd) for generating in a field of view a magnetic field (50) having a pattern in space of its magnetic field strength such that a first sub-zone (52) having a lower magnetic field strength and a second sub-zone (54) having a higher magnetic field are formed in the field of view (60), and
a manipulator unit (230) comprising a first manipulator (200) connected to the magnet unit (501, 100, 100a, 100b, 100c, lOOd) for rotating the magnet unit about a first rotation axis (201) that does not intersect the first sub-zone (52).
2. Magnet arrangement as claimed in claim 1,
wherein said magnet unit (501, 100, 100a, 100b, 100c, lOOd) is non-uniformly magnetized at said surface (506) facing the field of view (60).
3. Magnet arrangement as claimed in claim 1 ,
wherein said magnet unit (501, 100, 100a, 100b, 100c, lOOd) comprises magnetic elements (502, 503) forming first and second magnetic pole areas (504, 505) of opposite magnetic polarity at said surface (506) facing the field of view (60) for generating said magnetic field (50).
4. Magnet arrangement as claimed in claim 1,
wherein said manipulator unit (230) comprises a second manipulator (240) connected to the first manipulator (200) for rotating the first manipulator (200) about a second rotation axis (301) that is offset from the first rotation axis (201) and does not intersect the first sub-zone (52).
5. Magnet arrangement as claimed in claim 4, further comprising a driving unit
(140) provided with an opening to receive the magnet unit (501, 100, 100a, 100b, 100c,
1 OOd) therein in such a way that the magnet unit can be rotated within this opening about said first rotation axis (201), the driving unit (140) being further arranged to be connected with the second manipulator (240) such that the driving unit (140) can be rotated together with the first rotation axis (201) about the second rotation axis (301).
6. Magnet arrangement as claimed in claim 5, wherein the driving unit (140) comprises a permanent magnetic material having a magnetic polarity identical and/or similar to at least some of the magnetic elements of the second magnetic pole areas (103, 134) and opposite to the polarity of the magnetic elements of the first magnetic pole area (102, 133).
7. Magnet arrangement as claimed in claim 4,
wherein the magnet unit is rotatable about the second rotation axis (145, 301) and comprises, on a first surface area (101) of said surface (135), a first magnetic pole area (102) showing a first magnetic polarity and a second magnetic pole area (103) showing a second magnetic polarity different from the first magnetic polarity, wherein the second magnetic pole area (103) at least partly surrounds the first magnetic pole area (102) and wherein the center of gravity (104) of the first magnetic pole area (102) is offset from the second rotation axis (145, 301).
8. Magnet arrangement as claimed in claims 6 and 7,
wherein the driving unit (140) has, on a second surface area (141) of said surface (135), a third magnetic pole area (142, 142a) showing a third magnetic polarity identical to the second magnetic polarity, wherein the third magnet pole area (142, 142a) at least partly surrounds the second magnetic pole area (103).
9. Magnet arrangement as claimed in claim 4,
wherein said manipulator unit (230) comprises a third manipulator (203, 204) connected to the second manipulator (240) for laterally translating the second manipulator (240) in at least one direction.
10. Magnet arrangement as claimed in claim 1 or 5,
wherein the first rotation axis (201, 1 14) is arranged through the center of gravity (104) of the magnet unit (130, 130a) and/or the second rotation axis (301, 145) is arranged through the center of gravity (143) of the driving unit (140).
1 1. Magnet arrangement as claimed in claim 7,
wherein the outline (108, 108a)) of the surface of the first magnetic pole area (102, 102a) is substantially circular or bar-shaped.
12. Magnet arrangement as claimed in claim 5,
wherein the second magnetic pole area (103) completely circumferentially surrounds the first magnetic pole area (102) and/or the driving unit (140) completely circumferentially surrounds the magnet unit (100, 100a, 100b, 100c , lOOd).
13. Magnet arrangement as claimed in claim 7,
wherein the magnet unit (100b) further comprises, on said first surface area (101), a first nonmagnetic area (1 10), at least partly surrounding said second magnetic pole area (103b).
14. Magnet arrangement as claimed in claim 8,
wherein the driving unit (140a) further comprises, on a second surface area (141) of said surface (135), a second non-magnetic area (146), at least partly surrounding said second and/or third magnetic pole area (142a).
15. Magnetic particle imaging device for influencing and/or detecting magnetic particles in a field of view (28), which device comprises:
a magnet arrangement (300, 500) as claimed in claim 1 for generating a magnetic selection field (50) having a pattern in space of its magnetic field strength such that (i) a first sub-zone (52) having a low magnetic field strength where the magnetization of the magnetic particles is not saturated and (ii) a second sub-zone (54) having a higher magnetic field strength where the magnetization of the magnetic particles is saturated are formed in the field of view (60),
a drive field unit (410) comprising a drive field signal generator unit (41 1) and one or more drive coils (412) for generating a magnetic drive field which changes the position in space of the two sub-zones (50, 52) in the field of view, and
- a control unit (420) for controlling the manipulator (230) of said magnet arrangement and said drive field unit (410) to move the position in space of the first sub-zone along a predetermined trajectory.
Beschreibung  (OCR-Text kann Fehler enthalten)

MAGNET ARRANGEMENT AND MAGNETIC PARTICLE IMAGING DEVICE

FIELD OF THE INVENTION

The present invention relates to a magnet arrangement, in particular for use in a magnetic particle imaging (MPI) device. Further, the present invention relates to a magnetic particle imaging for influencing and/or detecting magnetic particles in a field of view.

BACKGROUND OF THE INVENTION

Magnetic Particle Imaging (MPI) is an emerging medical imaging modality. The first versions of MPI were two-dimensional in that they produced two-dimensional images. Newer versions are three-dimensional (3D). A four-dimensional image of a non- static object can be created by combining a temporal sequence of 3D images to a movie, provided the object does not significantly change during the data acquisition for a single 3D image.

MPI is a reconstructive imaging method, like Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). Accordingly, an MP image of an object's volume of interest is generated in two steps. The first step, referred to as data acquisition, is performed using an MPI scanner. Conventionally, the MPI scanner has means to generate a static magnetic gradient field, called the "selection field", which has a (single or more) field-free point(s) (FFP(s)) or a field-free line (FFL) at the isocenter of the scanner (in the following reference is mostly made to the field-free point, which shall however include the option of using a field-free line instead). Moreover, this FFP (or the FFL; mentioning "FFP" in the following shall generally be understood as meaning FFP or FFL) is surrounded by a first sub- zone with a low magnetic field strength, which is in turn surrounded by a second sub-zone with a higher magnetic field strength. In addition, the scanner has means to generate a time- dependent, spatially nearly homogeneous magnetic field. Actually, this field is obtained by superposing a rapidly changing field with a small amplitude, called the "drive field", and a slowly varying field with a large amplitude, called the "focus field". By adding the time- dependent drive and focus fields to the static selection field, the FFP may be moved along a predetermined FFP trajectory throughout a "volume of scanning" surrounding the isocenter. The scanner also has an arrangement of one or more, e.g. three, receive coils and can record any voltages induced in these coils. For the data acquisition, the object to be imaged is placed in the scanner such that the object's volume of interest is enclosed by the scanner's field of view, which is a subset of the volume of scanning.

The object must contain magnetic nanoparticles or other magnetic non-linear materials; if the object is an animal or a patient, a tracer containing such particles is administered to the animal or patient prior to the scan. During the data acquisition, the MPI scanner moves the FFP along a deliberately chosen trajectory that traces out / covers the volume of scanning, or at least the field of view. The magnetic nanoparticles within the object experience a changing magnetic field and respond by changing their magnetization. The changing magnetization of the nanoparticles induces a time-dependent voltage in each of the receive coils. This voltage is sampled in a receiver associated with the receive coil. The samples output by the receivers are recorded and constitute the acquired data. The parameters that control the details of the data acquisition make up the "scan protocol".

In the second step of the image generation, referred to as image reconstruction, the image is computed, or reconstructed, from the data acquired in the first step. The image is a discrete 3D array of data that represents a sampled approximation to the position-dependent concentration of the magnetic nanoparticles in the field of view. The reconstruction is generally performed by a computer, which executes a suitable computer program. Computer and computer program realize a reconstruction algorithm. The reconstruction algorithm is based on a mathematical model of the data acquisition. As with all reconstructive imaging methods, this model can be formulated as an integral operator that acts on the acquired data; the reconstruction algorithm tries to undo, to the extent possible, the action of the model.

Such an MPI apparatus and method have the advantage that they can be used to examine arbitrary examination objects - e. g. human bodies - in a non- destructive manner and with a high spatial resolution, both close to the surface and remote from the surface of the examination object. Such an apparatus and method are generally known and have been first described in DE 101 51 778 Al and in Gleich, B. and Weizenecker, J. (2005),

"Tomographic imaging using the nonlinear response of magnetic particles" in Nature, vol. 435, pp. 1214-1217, in which also the reconstruction principle is generally described. The apparatus and method for magnetic particle imaging (MPI) described in that publication take advantage of the non-linear magnetization curve of small magnetic particles.

An MPI apparatus and method are based on a new physical principle (i.e. the principle referred to as MPI) that is different from other known conventional medical imaging techniques, as for example nuclear magnetic resonance (NMR). In particular, this MPI-principle, does, in contrast to NMR, not exploit the influence of the material on the magnetic resonance characteristics of protons, but rather directly detects the magnetization of the magnetic material by exploiting the non-linearity of the magnetization characteristic curve. In particular, the MPI-technique exploits the higher harmonics of the generated magnetic signals, which result from the non-linearity of the magnetization characteristic curve in the area where the magnetization changes from the non-saturated to the saturated state.

US 2012/0310076 Al discloses a single-sided MPI apparatus, in which all essential coil elements of the MPI apparatus are arranged on one side of the object, e.g. in a support or patient table underneath the patient. Such a single sided design has the advantage that the size of the object does not matter as much as for other MPI apparatus where the object is surrounded by coils or where coils are placed at least on two different sides of the object.

The known MPI apparatus, in particular MPI apparatus that are designed for fast scanning, have in common that they are quite bulky and consume a significant amount of electrical power. This means that they are less suitable for a monitoring scenario where an object shall be monitored for some time, either continuously or at intervals.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a magnet arrangement, in particular for use in an MPI apparatus, and an MPI apparatus, which are suitable for monitoring scenarios, preferably with fast scanning, are less bulky and consume less electrical power than known MPI devices.

In a first aspect of the present invention a magnet arrangement is presented comprising

a magnet unit for generating in a field of view a magnetic field having a pattern in space of its magnetic field strength such that a first sub-zone having a lower magnetic field strength and a second sub-zone having a higher magnetic field are formed in the field of view, and

- a manipulator unit comprising a first manipulator connected to the magnet unit for rotating the magnet unit about a first rotation axis that does not intersect the first sub- zone.

In a further aspect of the present invention an MPI apparatus is presented comprising a magnet arrangement as disclosed herein for generating a magnetic selection field having a pattern in space of its magnetic field strength such that (i) a first sub-zone having a low magnetic field strength where the magnetization of the magnetic particles is not saturated and (ii) a second sub-zone having a higher magnetic field strength where the magnetization of the magnetic particles is saturated are formed in the field of view,

a drive field unit comprising a drive field signal generator unit and one or more drive coils for generating a magnetic drive field which changes the position in space of the two sub-zones in the field of view, and

a control unit for controlling the manipulator of said magnet arrangement and said drive field unit to move the position in space of the first sub-zone along a predetermined trajectory.

Preferred embodiments of the invention are defined in the dependent claims. It shall be understood that the claimed MPI apparatus has similar and/or identical preferred embodiments as the claimed magnet arrangement and as defined in the dependent claims.

The present invention is based on the idea to use a single-sided MPI apparatus comprising a suitable (single-sided) magnet arrangement that generates a field-free point (FFP) or field-free line (FFL) (representing the "first sub-zone") by use of permanent magnets. To achieve encoding, a mechanical assembly, i.e. a manipulator unit, is used that allows moving the FFP or at least a point of the FFL on a predetermined trajectory, in particular on an epitrocoidal curve. This is achieved by an eccentric rotational movement of the magnet unit around a rotational axis that does not intersect the first sub-zone. In this way, the first sub-zone can be moved quickly and easily through the field of view.

The devices according to the proposed invention can be used with a field-free line or a field-free point, depending on the design of the magnet unit. In case of using a FFP a disk of permanent magnets (with suitable local orientation) may be used to provide a FFP off the center of the disk. This disk is rotated. Therefore, the FFP rotates in space. In addition, as provided in an embodiment, this disk is rotated about a second rotational axis parallel, but not identical to the first rotational axis. Therefore, the FFP can easily cover a whole plane if appropriate relative rotation speeds are chosen.

The proposed magnet arrangement and the corresponding MPI apparatus comprising such a magnet arrangement can be made smaller in size compared to known MPI apparatus and magnet arrangement and consume less electrical power, which makes them suitable for use in a monitoring scenario, e.g. for monitoring a patient to early detect a brain bleeding. Brain bleedings after stroke or traumatic brain injuries are a significant risk for patient. While plenty of diagnostic tools exist to detect a bleeding (especially CT), none is suitable for constant monitoring of patients. It has been found, however, that magnetic particle imaging offers the option of monitoring, for instance - as one example of detection - labeled red blood cells or multiple tracer boluses using a small single-sided MPI scanner with low resolution. Multiple boluses may offer the additional advantage of perfusion monitoring if the scanning speed is high enough.

In an embodiment said magnet unit is non-uniformly magnetized at said surface facing the field of view (60). In this way a field free zone can be generated in front of the surface, which is preferably flat and forms an even plane, whereby different designs of the magnet unit are possible. For instance a homogenously magnetized ring of magnetic material, e.g. of a single piece of constructed of many separate magnetic elements, can generate such a field free zone.

Generally, the design of the magnet unit is not essential. In a preferred embodiment said magnet unit comprises magnetic elements forming first and second magnetic pole areas of opposite magnetic polarity at said surface facing the field of view for generating said magnetic field. This provides the ability to precisely control the position of the field free zone.

In another embodiment said manipulator unit comprises a second manipulator connected to the first manipulator for rotating the first manipulator about a second rotation axis that is offset from the first rotation axis and does not intersect the first sub-zone. In this way rotational movements of different parts of the magnet unit are superposed, wherein the rotational axes are displaced with respect to each other. In an implementation the magnet unit may be mounted in its center on the axis of a (geared) motor representing the first

manipulator. This assembly may be further mounted eccentrically on a second motor representing the second manipulator. A suitable counterweight may be provided, if needed to reduce dynamic forces in the magnet arrangement.

In an embodiment the magnet arrangement further comprises a driving unit provided with an opening to receive the magnet unit therein in such a way that the magnet unit can be rotated within this opening about said first rotation axis, the driving unit being further arranged to be connected with the second manipulator such that the driving unit can be rotated together with the first rotation axis about the second rotation axis. This provides a useful and mechanically simple construction for implementing the rotations about the different rotation axes. Generally, the rotated portions should mainly (at least 50% or even at least 80% or even completely) be made of (hard) magnetic material or magnetizable material. Preferably, no out of balances should be generated during rotation. If needed, balancing material (for balancing out of balances) may be used, which may also be made from

(permanent) magnetic material used for increasing the magnetic field gradient. The driving unit may be a disk-like structure comparable to the disk-like structure of the magnet unit. Preferably, the driving unit may further comprise a permanent magnetic material having a magnetic polarity identical and/or similar to at least some magnetic elements of the second magnetic pole areas and opposite to the polarity of the magnetic elements of the first magnetic pole area. For instance, in a practical implementation of the driving unit it has, on a second surface area of said surface, a third magnetic pole area showing a third magnetic polarity identical to the second magnetic polarity, wherein the third magnet pole area at least partly surrounds the second magnetic pole area. The size and/or form of the drive unit is particularly designed to achieve a desired size and/or form of the complete magnetic assembly (comprising the magnet unit and the drive unit) which preferably does not show any imbalances.

In other embodiments, the magnet unit further comprises, on said first surface area, a first non-magnetic area, at least partly surrounding said second magnetic pole area and/or the driving unit further comprises, on a second surface area of said surface, a second non-magnetic area, at least partly surrounding said second and/or third magnetic pole area. If non-magnetic material is used for avoiding imbalances during rotation, less magnetic material is required. If magnetic material is used, the generated magnetic field may be shaped more freely and a field-free zone may be generated more precisely.

In a more practical implementation, the magnet unit is rotatable about the second rotation axis and comprises, on a first surface area of said surface, a first magnetic pole area showing a first magnetic polarity and a second magnetic pole area showing a second magnetic polarity different from the first magnetic polarity, wherein the second magnetic pole area at least partly surrounds the first magnetic pole area and wherein the center of gravity of the first magnetic pole area is offset from the second rotation axis.

Preferably, said first surface area and said second surface area are parallel, in particular coplanar. Preferably, they lie in the same plane and thus form a flat surface towards a patient.

In an embodiment said manipulator unit comprises a third manipulator connected to the second manipulator for laterally translating the second manipulator in at least one direction. This further improves the variability of the trajectory, along which the FFP can be moved. For instance, the whole magnet unit may be mounted on a linear motor for out-of-plane encoding. This linear movement may be assisted by a spring (ideally operated in full resonance) to provide a fast and low power third encoding direction movement.

According to an embodiment the first rotation axis is arranged through the center of gravity of the first magnet sub-unit and/or the second rotation axis is arranged through the center of gravity of the of the magnet unit. This avoids the appearance of imbalances during rotation.

The outline of the magnet unit and/or the outline of the driving unit is substantially circular, although other outlines are generally possible. A circular outline, however, enables a better prediction of the generated magnetic fields. Further, during rotation of the magnet unit and the driving unit (including the magnet unit) a circular area is covered. Since the circular area cannot be used for other purposes, it should preferably be covered with magnetic material completely.

Further, the outline of the surface of first magnetic pole area is substantially circular or bar-shaped. With a circular outline a first sub-zone having a low magnetic field strength in the form of a small spot or point (FFP) is substantially generated. With a bar- shaped outline a first sub-zone having a low magnetic field strength in the form of a field-free line (FFL) is substantially generated.

According to an embodiment the second magnetic pole area completely circumferentially surrounds the first magnetic pole area and/or the driving unit completely circumferentially surrounds the magnet unit. The resulting magnet arrangement enables movements of the FFP along a desired trajectory.

The proposed MPI apparatus may further comprise a receiving coil for receiving signals detected by said receiving coil and processing means for processing the received signals, in particular for reconstructing an image of the area from which the detection signals are detected. However, the proposed MPI apparatus may also be used for moving magnetic particles or a magnet element, e.g. a medial instrument, a probe or a medicament provided with magnetic material through a subject's body.

Further, at least one of said drive field coils is used as receiving coil, i.e. a single set of claims may be commonly used as drive coils and receiving coils.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter. In the following drawings Fig. 1 shows an embodiment of a known MPI apparatus,

Fig. 2 shows an example of the selection field pattern produced by an apparatus as shown in Fig. 1,

Fig. 3 shows a first embodiment of a first magnet unit according to the present invention for generating an FFP,

Fig. 4 shows a first manipulator according to the present invention, to which the first magnet sub-unit is mounted, and an exemplary trajectory of the FFP,

Fig. 5 shows a first embodiment of a magnet assembly according to the present invention comprising the magnet unit as shown in Fig. 3 and a driving unit,

Fig. 6 shows a first embodiment of a magnet arrangement according to the present invention,

Fig. 7 shows an embodiment of an MPI apparatus according to the present invention,

Fig. 8 shows a second embodiment of a magnet unit according to the present invention for generating an FFL,

Fig. 9 shows a third embodiment of a magnet unit according to the present invention using a non-magnetic counterweight,

Fig. 10 shows a second embodiment of a magnet assembly according to the present invention using a non-magnetic counterweight,

Fig. 1 1 shows a fourth embodiment of a magnet unit according to the present invention using a plurality of magnetic elements,

Fig. 12 shows a second embodiment of a magnet arrangement according to the present invention, and

Fig. 13 shows a third embodiment of a magnet arrangement according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Before the details of the present invention shall be explained, basics of magnetic particle imaging shall be briefly explained in detail with reference to Figs. 1 and 2. In particular, an embodiment of a known MPI scanner for medical diagnostics will be described. An informal description of the data acquisition will also be given.

The embodiment 10 of an MPI scanner shown in Fig. 1 has three pairs 12, 14, 16 of coaxial parallel circular coils, these coil pairs being arranged as illustrated in Fig. 1. These coil pairs 12, 14, 16 serve to generate the selection field as well as the drive and focus fields. The axes 18, 20, 22 of the three coil pairs 12, 14, 16 are mutually orthogonal and meet in a single point, designated the isocenter 24 of the MPI scanner 10. In addition, these axes 18, 20, 22 serve as the axes of a 3D Cartesian x-y-z coordinate system attached to the isocenter 24. The vertical axis 20 is nominated the y-axis, so that the x- and z-axes are horizontal. The coil pairs 12, 14, 16 are named after their axes. For example, the y-coil pair 14 is formed by the coils at the top and the bottom of the scanner. Moreover, the coil with the positive (negative) y-coordinate is called the y+-coil (y"-coil), and similarly for the remaining coils.

The scanner 10 can be set to direct a predetermined, time-dependent electric current through each of these coils 12, 14, 16, and in either direction. If the current flows clockwise around a coil when seen along this coil's axis, it will be taken as positive, otherwise as negative. To generate the static selection field, a constant positive current Is is made to flow through the z+-coil, and the current -Is is made to flow through the z"-coil. The z-coil pair 16 then acts as an anti-parallel circular coil pair.

The magnetic selection field, which is generally a magnetic gradient field, is represented in Fig. 2 by the field lines 50. It has a substantially constant gradient in the direction of the (e.g. horizontal) z-axis 22 of the z-coil pair 16 generating the selection field and reaches the value zero in the isocenter 24 on this axis 22. Starting from this field-free point (not individually shown in Fig. 2), the field strength of the magnetic selection field 50 increases in all three spatial directions as the distance increases from the field-free point. In a first sub-zone or region 52 which is denoted by a dashed line around the isocenter 24 the field strength is so small that the magnetization of particles present in that first sub-zone 52 is not saturated, whereas the magnetization of particles present in a second sub-zone 54 (outside the region 52) is in a state of saturation. In the second sub-zone 54 (i.e. in the residual part of the scanner's field of view 28 outside of the first sub-zone 52) the magnetic field strength of the selection field is sufficiently strong to keep the magnetic particles in a state of saturation.

By changing the position of the two sub-zones 52, 54 (including the field-free point) within the field of view 28 the (overall) magnetization in the field of view 28 changes. By determining the magnetization in the field of view 28 or physical parameters influenced by the magnetization, information about the spatial distribution of the magnetic particles in the field of view 28 can be obtained. In order to change the relative spatial position of the two sub-zones 52, 54 (including the field-free point) in the field of view 28, further magnetic fields, i.e. the magnetic drive field, and, if applicable, the magnetic focus field, are superposed to the selection field 50. To generate the drive field, a time dependent current IDi is made to flow through both x-coils 12, a time dependent current ID 2 through both y-coils 14, and a time dependent current ID 3 through both z-coils 16. Thus, each of the three coil pairs acts as a parallel circular coil pair. Similarly, to generate the focus field, a time dependent current IFi is made to flow through both x-coils 12, a current IF 2 through both y-coils 14, and a current IF 3 through both z-coils 16.

It should be noted that the z-coil pair 16 is special: It generates not only its share of the drive and focus fields, but also the selection field (of course, in other

embodiments, separate coils may be provided). The current flowing through the z±-coil is ID 3 + IF 3 ± Is. The current flowing through the remaining two coil pairs 12, 14 is IDk + IFk, k = 1, 2. Because of their geometry and symmetry, the three coil pairs 12, 14, 16 are well decoupled. This is wanted.

Being generated by an anti-parallel circular coil pair, the selection field is rotationally symmetric about the z-axis, and its z-component is nearly linear in z and independent of x and y in a sizeable volume around the isocenter 24. In particular, the selection field has a single field-free point (FFP) at the isocenter. In contrast, the

contributions to the drive and focus fields, which are generated by parallel circular coil pairs, are spatially nearly homogeneous in a sizeable volume around the isocenter 24 and parallel to the axis of the respective coil pair. The drive and focus fields jointly generated by all three parallel circular coil pairs are spatially nearly homogeneous and can be given any direction and strength, up to some maximum strength. The drive and focus fields are also time- dependent. The difference between the focus field and the drive field is that the focus field varies slowly in time and may have a large amplitude, while the drive field varies rapidly and has a small amplitude. There are physical and biomedical reasons to treat these fields differently. A rapidly varying field with a large amplitude would be difficult to generate and potentially hazardous to a patient.

In a practical embodiment the FFP can be considered as a mathematical point, at which the magnetic field is assumed to be zero. The magnetic field strength increases with increasing distance from the FFP, wherein the increase rate might be different for different directions (depending e.g. on the particular layout of the device). As long as the magnetic field strength is below the field strength required for bringing magnetic particles into the state of saturation, the particle actively contributes to the signal generation of the signal measured by the device; otherwise, the particles are saturated and do not generate any signal. The embodiment 10 of the MPI scanner has at least one further pair, preferably three further pairs, of parallel circular coils, again oriented along the x-, y-, and z- axes. These coil pairs, which are not shown in Fig. 1 , serve as receive coils. As with the coil pairs 12, 14, 16 for the drive and focus fields, the magnetic field generated by a constant current flowing through one of these receive coil pairs is spatially nearly homogeneous within the field of view and parallel to the axis of the respective coil pair. The receive coils are supposed to be well decoupled. The time-dependent voltage induced in a receive coil is amplified and sampled by a receiver attached to this coil. More precisely, to cope with the enormous dynamic range of this signal, the receiver samples the difference between the received signal and a reference signal. The transfer function of the receiver is non-zero from zero Hertz ("DC") up to the frequency where the expected signal level drops below the noise level. Alternatively, the MPI scanner has no dedicated receive coils. Instead the drive field transmit coils may be used as receive coils as is the case according one embodiment according to the present invention using combined drive-receiving coils.

The embodiment 10 of the MPI scanner shown in Fig. 1 has a cylindrical bore

26 along the z-axis 22, i.e. along the axis of the selection field. All coils are placed outside this bore 26. For the data acquisition, the patient (or object) to be imaged is placed in the bore 26 such that the patient's volume of interest - that volume of the patient (or object) that shall be imaged - is enclosed by the scanner's field of view 28 - that volume of the scanner whose contents the scanner can image. The patient (or object) is, for instance, placed on a patient table. The field of view 28 is a geometrically simple, isocentric volume in the interior of the bore 26, such as a cube, a ball, a cylinder or an arbitrary shape. A cubical field of view 28 is illustrated in Fig. 1.

The patient's volume of interest is supposed to contain magnetic nanoparticles. Prior to the diagnostic imaging of, for example, a tumor, the magnetic particles are brought to the volume of interest, e.g. by means of a liquid comprising the magnetic particles which is injected into the body of the patient (object) or otherwise administered, e.g. orally, to the patient.

Generally, various ways for bringing the magnetic particles into the field of view exist. In particular, in case of a patient into whose body the magnetic particles are to be introduced, the magnetic particles can be administered by use of surgical and non-surgical methods, and there are both methods which require an expert (like a medical practitioner) and methods which do not require an expert, e.g. can be carried out by laypersons or persons of ordinary skill or the patient himself / herself. Among the surgical methods there are potentially non-risky and/or safe routine interventions, e.g. involving an invasive step like an injection of a tracer into a blood vessel (if such an injection is at all to be considered as a surgical method), i.e. interventions which do not require considerable professional medical expertise to be carried out and which do not involve serious health risks. Further, non- surgical methods like swallowing or inhalation can be applied.

Generally, the magnetic particles are pre-delivered or pre-administered before the actual steps of data acquisition are carried out. In embodiments, it is, however, also possible that further magnetic particles are delivered / administered into the field of view.

An embodiment of magnetic particles comprises, for example, a spherical substrate, for example, of glass which is provided with a soft- magnetic layer which has a thickness of, for example, 5 nm and consists, for example, of an iron-nickel alloy (for example, Permalloy). This layer may be covered, for example, by means of a coating layer which protects the particle against chemically and/or physically aggressive environments, e.g. acids. The magnetic field strength of the magnetic selection field 50 required for the saturation of the magnetization of such particles is dependent on various parameters, e.g. the diameter of the particles, the used magnetic material for the magnetic layer and other parameters.

In practice, magnetic particles commercially available under the trade name Resovist (or similar magnetic particles) are often used, which have a core of magnetic material or are formed as a massive sphere and which have a diameter in the range of nanometers, e.g. 40 or 60 nm.

During the data acquisition, the x-, y-, and z-coil pairs 12, 14, 16 generate a position- and time-dependent magnetic field, the applied field. This is achieved by directing suitable currents through the field generating coils. In effect, the drive and focus fields push the selection field around such that the FFP moves along a preselected FFP trajectory that traces out the volume of scanning - a superset of the field of view. The applied field orientates the magnetic nanoparticles in the patient. As the applied field changes, the resulting magnetization changes too, though it responds nonlinearly to the applied field. The sum of the changing applied field and the changing magnetization induces a time-dependent voltage Vk across the terminals of the receive coil pair along the Xk-axis. The associated receiver converts this voltage to a signal Sk, which it processes further.

For further details of the generally usable magnetic particles and particle compositions, as well as details of MPI in general and various embodiments of MPI scanners and their function reference is made to a plurality of patent applications and other publications of the applicant, including but not limited to EP 1224542, WO 2004/091386, WO 2004/091390, WO 2004/091394, WO 2004/091395, WO 2004/091396, WO

2004/091397, WO 2004/091398, WO 2004/091408, US 2012/0310076 Al are herewith referred to, which are herein incorporated by reference.

To use MPI for monitoring e.g. the brain of a patient, e.g. to detect brain bleeding in an early stage, the size and power consumption of an MPI apparatus should be reduced to allow easy integration into the ICU environment. This is achieved according to the present invention. Details of a proposed MPI apparatus and of a first embodiment of a magnet arrangement used in such an MPI apparatus will be explained in the following in a stepwise fashion by stepwise explaining the various elements with reference to Figs. 3 to 7.

Fig. 3 shows a first magnet unit 100 according to the present invention, in particular a top view (Fig. 3A) and a cross-sectional view (Fig. 3B). The first magnet unit 100 has, on a first surface 101, a first magnetic pole area 102 showing a first magnetic polarization (e.g. in this example a magnetic south pole S) and a second magnetic pole area

103 showing a second magnetic polarization (e.g. in this example a magnetic north pole N). The second magnetic pole area 103 at least partly (in this example completely) surrounds the first magnetic pole area 102. The center 104 of the first magnet unit 100 is displaced with respect to the center 105 of the first magnetic pole area 102.

In this exemplary embodiment both the surface 106 of first magnetic pole area 102 and the surface 107 of the second magnetic pole area 103 are lying in the plane of the first surface 101 of the magnet unit 100. Further, the outline 108 of the surface 106 of first magnetic pole area 102 and the outline 109 of the surface 107 of magnet unit 100 are substantially circular.

The first magnetic pole area 102 and the second magnetic pole area 103 are thus two areas with opposite magnetization. Each may e.g. be formed in a disk-like form, wherein the disk of the first magnetic pole area 102 is integrated into the disk of the second magnetic pole area 103. Other forms are, however, generally possible, such as honey-comb forms, bar-like forms, polygonal forms, etc.

In the embodiment shown in Fig. 3 the centers 104, 105 represent the crossing points of respective symmetry axes 1 14, 1 15, as shown in Fig. 3B. The axis 1 15 going through the center 105 is laterally displaced with respect to the axis 1 14 going through center

104 of the complete first magnet sub-unit 100, wherein the central axis 1 14 preferably goes through the center of gravity of the first magnet sub-unit 100. Fig. 3B shows the magnetic field lines 120 of the stationary magnetic field generated by the magnet unit 100. A field free point 121 is formed above the first surface 101, which is not lying on the axis 1 14, but displaced there from, e.g. which is lying on the axis 1 15. Usually, all field lines are generated and terminated at the surface of the magnetic material. But this is only true, if the magnetic field strength is not exactly zero. One can think of magnetic material at the field free point (and at infinite distance) that generates the magnetic field line, but the amount is set to an infinitely small amount.

Fig. 4A shows a cross-sectional view of a first manipulator 200 according to the present invention, to which the magnet unit 100 is mounted. Fig. 4B shows an exemplary trajectory 250 of the FFP 121 achievable with the first manipulator 200. The first manipulator 200 is connected to the magnet unit 100 for rotating the magnet unit 100 about a first rotation axis 201, which is perpendicular to the first surface 101 and which is preferably identical (but at least parallel) to the central axis 1 14 of the magnet unit 100.

The first manipulator 200 may comprise a motor 202 for rotating the first magnet sub-unit 100 about the rotation axis 201. Further, actuators 203, 204 may be provided for laterally translating the motor 202 including the magnet unit 100 horizontally and/or vertically.

An example of an achievable trajectory 250 is shown in Fig. 4B, wherein the trajectory may generally be three-dimensional.

Fig. 5 shows a top view of a magnet assembly 130 according to the present invention, in particular a top view (Fig. 5A) and a cross-sectional view (Fig. 5B). The magnet assembly 130 comprises the magnet unit 100 and a driving unit 140. The driving unit 140 comprises, on a second surface 141 parallel to the first surface 101, a third magnetic pole area 142 showing a third magnetic polarization identical to the second magnetic polarization of the second magnetic pole area 103. In this exemplary embodiment the third magnetic pole area 142 forms another magnetic north pole. The third magnet pole area 142 at least partly surrounds the magnet unit 100. The center 143 of the magnet assembly 130 is displaced with respect to the center 104 of the magnet unit 100.

In this exemplary embodiment both the first surface 101 of magnet unit 100 and the second surface 141 of the driving unit 140 are lying in the same plane. Further, the outline 144 of the second surface 141 of the driving unit 140 and, hence, of the magnet assembly 130 is substantially circular.

The third magnetic pole area 142 may e.g. be formed in a disk-like form (or part of a disk), wherein the disk of the magnet unit 100 is integrated into the disk of the driving unit 140. Other forms are, however, generally possible, such as honey-comb forms, bar-like forms, polygonal forms, etc. The third magnetic pole area 142 has in this

embodiment the form of a sickle. Preferably, the magnet assembly 130 is formed from magnetic material.

The driving unit 140 is preferably provided with an opening to receive the magnet unit 100 therein in such a way that the magnet unit 100 can be rotated within this opening about a first rotation axis 1 14. Further, the driving unit further arranged to be rotated together with the first rotation axis 1 14 about a second rotation axis 145.

In the embodiment shown in Fig.5 the driving unit 140 comprises a permanent magnetic material having a magnetic polarity identical and/or similar to at least some of the magnetic elements of the second magnetic pole areas 103 and opposite to the polarity of the magnetic elements of the first magnetic pole area 102, i.e. the driving unit 140 represents a kind of second magnet unit.

In the embodiment shown in Fig. 5 the center of gravity 143 of the magnet assembly 130 represents the crossing point of a respective (geometric) symmetry axis 145 of the magnet assembly 130. This symmetry axis 145 going through the center of gravity 143 is laterally displaced with respect to the symmetry axis 1 14 of the magnet unit 100.

Fig. 5B shows the magnetic field lines 150 of the stationary magnetic field generated by the magnet unit 130. A field free point 151 is formed above the magnet unit 130, which is not lying on the axis 145, but displaced there from, e.g. which is lying on the axis 1 15.

Fig. 6 A shows an embodiment of a magnet arrangement 300 according to the present invention. Fig. 6B shows an exemplary trajectory 251 of the FFP 151 achievable with the magnet arrangement 300. It comprises the magnet assembly 130 and a manipulator unit 230. The manipulator unit 230 comprises the first manipulator 202 shown in Fig. 4A and a second manipulator 240. The second manipulator 240 is connected to the magnet assembly 130 and the first manipulator 200 for rotating the magnet assembly 130 and the first manipulator 200 about a second rotation axis 301, which is perpendicular to the second surface 141 and parallel to the first rotation axis 201.

The second manipulator 240 mainly comprises a motor. Further, a third manipulator 250 may be provided, as shown in Fig. 6A, which is connected to the second manipulator 240 for laterally translating the second manipulator 240 in at least one direction. Preferably, the third manipulator 250 comprises actuators 203 and/or 204 as shown in Fig. 4A, which are, however, in this embodiment connected to the motor 240 to manipulate the magnet assembly 130.

Through the independent rotational movements of the magnet assembly 130 about the rotation axis 301 (preferably leading through the center of gravity 143 of the magnet assembly 130) and of the magnet unit 100 about the parallel rotation axis 201 (preferably leading through the center of gravity 104 of the magnet unit 100), and, optionally, the additional translational movements of the magnet assembly 130, a movement of the FFP along e.g. a trajectory 251 as shown in Fig. 6B can be achieved, which is generally three- dimensional and by which a field of view can be quickly and arbitrarily scanned with arbitrary density.

Fig. 7 shows an embodiment of an MPI apparatus 400 according to the present invention for influencing and/or detecting magnetic particles in a field of view, in particular for imaging a patient 1. The MPI apparatus 400 comprises a magnet arrangement 300 according to the present invention, as e.g. shown in Fig. 6A for generating a magnetic selection field having a pattern in space of its magnetic field strength such that (i) a first sub- zone (e.g. an FFP 151 in Fig. 5B) having a low magnetic field strength where the

magnetization of the magnetic particles is not saturated and a second sub-zone (i.e. the areas around the FFP 151) having a higher magnetic field strength where the magnetization of the magnetic particles is saturated are formed in the field of view. This is e.g. achieved by the magnetic field (e.g. 150 in Fig. 5B) generated by the magnet assembly 130.

The MPI apparatus 400 further comprises a drive field unit 410 comprising a drive field signal generator unit 41 1 and drive coils 412 for generating a drive magnetic field which changes the position in space of the two sub-zones in the field of view. Such a drive field unit 410 is generally known in the art and can be configured as explained above with reference to Fig. 1 or as explained in the prior art related to MPI.

The MPI apparatus 400 further comprises a control unit 420 for controlling the manipulator 230 of said magnet arrangement 300 and said drive field unit 410 to move the position in space of the first sub-zone along a predetermined trajectory. Hence, in addition to the fast movement effected by the drive field unit 410, a slow movement effected by the manipulator 230 of the magnet arrangement 300 is overlaid. Such a slow movement can be compared to the movement conventionally effected by focus field means, e.g. separate coils generating a magnetic focus field for moving slowly moving the field of view.

For receiving signals detected by said receiving coil the MPI apparatus 400 further comprises a receiving coil, which is preferably identical to one or more of said one or more drive coils 412 and is not separately shown in Fig. 7. Further, a processing means 430, such as a computer or processer, is provided for processing the received signals.

The total magnet arrangement 300 is preferably enclosed in an RF cage 302 to not disturb the drive field when moving the magnets. In addition, the control electronics 420 should be contained in this RF cage 302 to limit the feed-throughs to power supply and data link.

For very fast operation, the front face may be split and a capacitive coupling of the patches may be done to have an RF shield and not to dissipate too much power. The drive field coil(s) 412 is (are) not enclosed in the RF cage 302, but are, in this example, placed around the head of the patient 1. Some of the x-direction (non-rotational) movement may be done by an electric focus field, which may e.g. be generated by e.g. coupling a DC current on the drive field coil or, as an alternative, by use of an extra coil near the patient's head. A field strength in the order of 5 to 20 mT may be used and power can be supplied in a resonant mode.

In general, mass balanced rotational and oscillatory movements are used to achieve efficient mechanical movement in an MPI apparatus. Hence, according to the present invention, to achieve encoding, a mechanical assembly is used that allows moving a substantially field free zone (e.g. a field free point or line) of a permanent magnet assembly (i.e. the magnet arrangement) on a desired curve, in particular an epitrochoidal curve. This may be achieved by mounting the permanent magnet assembly in its center on the axis of a (geared) motor. This assembly may be further mounted eccentrically on a second motor (while a suitable counterweight may be provided). The whole assembly may be mounted on a linear motor for the out of plane encoding. This linear movement may be assisted by a spring (ideally operated in full resonance) to provide a fast and low power third encoding direction movement. Such a spring may e.g. be placed between the actuator 203 and the RF cage 302 (left wall) in the arrangement shown in Fig. 7. The spring acts on the linear movement stage and pulls the support of the rotator, if near to the patient and pushes, if far away of the patient. It would further be beneficial to provide a counterweight to reduce dynamic forces in the scanner assembly.

The proposed idea works for field free point as well as for field free line scanners. In case of a field free point scanner a disk of permanent magnets, as e.g. shown in Fig. 3, with suitable local magnetic orientation provides a field free point off the center of the disk. This disk is rotated. Therefore, the FFP rotates in space. In addition, this disk is rotated around an axis parallel, but not identical to the first one. Therefore, the FFP covers a whole plane if appropriate relative rotation speeds are chosen.

In case of a field free line scanner a slightly modified magnet unit 100a may be used as shown in Fig. 8 in an exemplary embodiment, instead of the magnet unit 100a shown in Fig. 3. Fig 8A shows a top view of such a modified magnet unit 100a and Fig. 8B shows a cross-sectional view. In particular, the outline 108a of the surface 106a of the first magnetic pole area 102a may be substantially bar-shaped rather than circular. The magnetic pole area 102a may be provided by a bar-shaped permanent magnet that can be rotated around the rotation axis 1 15 leading through the center 105a of the magnetic pole area 102a. A FFL 121a may thus be formed above the magnet unit 100a, said line being perpendicular to the plane of projection.

In the embodiments explained so far, a possible counter- weight assembly is to use a disk (e.g. of constant thickness) that rotates about its center. In this disk (the driving unit 140), a second, off-center disk (the magnet unit 100) is arranged that rotates at a higher speed, and at least this disk is magnetic. It may be advantageous to make the rest of the disk also magnetic to boost the performance. This may have the effect that the field free zone will not stay symmetric and/or keep always in the same relative position to the smaller rotating disk.

Fig. 9 shows a third embodiment of a magnet unit 100b according to the present invention using a non-magnetic counterweight (Fig. 9A shows a top view, Fig. 9B shows a cross-sectional view). In this embodiment the magnet unit 100b further comprises, on said first surface 101, a first non-magnetic area 1 10. This first non-magnetic area 1 10 serves as counterweight and at least partly surrounds the second magnetic pole area 103b, which in turn surrounds the first magnetic pole area 102b. Compared to the second pole area 103 shown in Fig. 4A, the second pole area 103b, is smaller, i.e. less magnetic material is required. The first non-magnetic area 1 10 is particularly provided to avoid imbalances during rotation of the magnet unit 100b about the rotation axis 1 14 going through the center of gravity 104.

Fig. 10 shows a second embodiment of a magnet assembly 130a according to the present invention using a non-magnetic counterweight (Fig. 10A shows a top view, Fig. 10B shows a cross-sectional view). In this embodiment the driving unit 140a further comprises, on said second surface 141, a second non- magnetic area 146. This second nonmagnetic area 146 serves as counterweight and at least partly surrounds the third magnetic pole area 142a, which in turn surround the magnet unit 100c. The magnet unit 100c (comprising a first magnetic pole area 102c and a second magnetic pole area 103c) may hereby be configured as shown in Figs. 5 A, 8A or 9A. Compared to the third pole area 142 shown in Fig. 5 A, the third pole area 142a, is smaller, i.e. less magnetic material is required. The second non- magnetic area 146 is particularly provided to avoid imbalances during rotation of the magnet assembly 130a about the rotation axis 145 going through the center of gravity 143.

Fig. 1 1 shows a fourth embodiment of a magnet unit lOOd according to the present invention using a plurality of magnetic elements 1 1 1, 1 12 (Fig. 1 1 A shows a top view, Fig. 1 IB shows a cross-sectional view). Magnetic elements 1 1 1, e.g. bars of permanent magnets having a cross-section in the form of a honey-comb, hexagon, bar, or, more generally, polygon, are used to construct the first magnetic pole area 102d. Similar magnetic elements 1 12 are used to construct the second magnetic pole area 103d. The magnetic elements 1 12 may not all have the same direction of magnetization, but the direction

(indicated by arrows 1 16) may be adapted to "design" the magnetic flux in a favorable direction.

In particular, at the borders of the first magnetic pole area 102d and the second magnetic pole area 103 d magnetic elements 1 13 are preferably provided, in which the magnetic polarization is not directed in vertical direction (as seen in Fig. 1 IB), but in which the magnetic polarization is directed in horizontal direction (as seen in Fig. 1 IB), whereby direction of polarization is different for the different magnetic elements 1 13 (i.e., as seen in Fig. 1 IB) the direction quasi "rotates" around the center of the first magnetic pole area 102d (i.e. all arrows 1 16 representing the direction point to said center). Further, also at the outer border of the second magnetic pole area 103 d such magnetic field shaping magnetic elements 1 13 may be used (not shown). Still further, even more magnetic elements 1 13 of this kind may be used in areas near the described borders to even further improve the shaping of the magnetic flux. In practice, the number of magnetic elements and the number of different magnetic polarization directions thereof might be much larger than shown in the example of Fig. 1 1.

The magnetic elements 1 1 1, 1 12, 1 13 may have different cross-sections, different sizes and different directions of magnetization than shown in Fig. 1 1. Similar elements can also be used to form the third magnetic pole area 142.

Fig. 12 shows a second embodiment of a magnet arrangement 500 according to the present invention. The magnet unit 501 comprises magnetic elements 502, 503 forming first and second magnetic pole areas 504, 505 of opposite magnetic polarity at a surface 506 facing a field of view 60. The magnet unit 502 thus generates a magnetic field 50 having a pattern in space of its magnetic field strength such that a first sub-zone 52 (e.g. a field free zone like a FFP or FFL) having a lower magnetic field strength and a second sub-zone 54 having a higher magnetic field are formed in the field of view 60.

The manipulator unit 200 is substantially identical as the manipulator unit used in the first embodiment of the magnet arrangement 300 shown in Fig. 6. It comprises a first manipulator 202 connected to the magnet unit 501 for rotating the magnet unit about a first rotation axis 201 that does not intersect the first sub-zone 52 (including the center 53 of the first sub-zone 52) and a second manipulator 240 connected to the first manipulator 202 for rotating the first manipulator 202 about a second rotation axis 301 that is offset from the first rotation axis 201 and does not intersect the first sub-zone 52. In this, similar as explained above, the first sub-zone 52 can be moved through the field of view 60 along a desired trajectory.

The magnetic elements 502, 503 may be configured as disks, where the smaller disk 502 (having a central axis 303) is part of the larger disk 503 (having a central axis 201, and where the smaller disk 502 mainly forms a south pole at its surface facing the field of view 60 and the larger disk 503 mainly forms a north pole at its surface facing the field of view 60.

Fig. 13 shows a third embodiment of a magnet arrangement 600 according to the present invention. Compared to the magnet arrangement 500 of the second embodiment it comprises only a single manipulator 202 connected to the magnet unit 501 for rotating the magnet unit about a single rotation axis 201 that does not intersect the first sub-zone 52 (i.e. the field free zone). The rotation axis 201 leads, in this example, through the center of gravity, but may also be arranged differently to achieve a rotational movement of the field free zone 52 around the rotation axis. The magnet unit 501 is only schematically shown in Fig. 13.

Generally, any magnet unit that is able to generate the desired magnetic field. The magnet unit 501 is preferably non-uniformly magnetized at the surface 506 facing the field of view. For instance, a ring of permanent magnetic material may be used, but other designs are possible.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. 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 element or other unit 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.

Any reference signs in the claims should not be construed as limiting the scope.

Patentzitate
Zitiertes PatentEingetragen Veröffentlichungsdatum Antragsteller Titel
WO2004091386A215. Apr. 200428. Okt. 2004Philips Intellectual Property & Standards GmbhArrangement and method for the spatially resolved determination of state variables in an examination area
WO2004091390A215. Apr. 200428. Okt. 2004Philips Intellectual Property & Standards GmbhDevice and method for examination and use of an electrical field in an object under examination containing magnetic particles
WO2004091394A215. Apr. 200428. Okt. 2004Philips Intellectual Property & Standards GmbhMethod to determine the spatial distribution of magnetic particles and magnetic particle administering compositions
WO2004091395A215. Apr. 200428. Okt. 2004Philips Intellectual Property & Standards GmbhMethod for spatially resolved determination of magnetic particle distribution in an area of examination
WO2004091396A215. Apr. 200428. Okt. 2004Philips Intellectual Property & Standards GmbhMethod for the spatially resolved determination of physical, chemical and/or biological properties or state variables
WO2004091397A215. Apr. 200428. Okt. 2004Philips Intellectual Property & Standards GmbhMethod of determining state variables and changes in state variables
WO2004091398A215. Apr. 200428. Okt. 2004Philips Intellectual Property & Standards GmbhMethod and apparatus for improved determination of spatial non-agglomerated magnetic particle distribution in an area of examination
WO2004091408A215. Apr. 200428. Okt. 2004Philips Intellectual Property & Standards GmbhElastography device and method for determining and imaging of mechanical and elastic parameters of an examination object
DE10151778A119. Okt. 20018. Mai 2003Philips Corp Intellectual PtyVerfahren zur Ermittlung der räumlichen Verteilung magnetischer Partikel
EP1224542A213. Okt. 200024. Juli 2002Thomson Licensing S.A.A user interface for a bi-directional communication system
US5186181 *27. Juli 199016. Febr. 1993Cafiero FranconiRadio frequency thermotherapy
US20110210261 *23. Febr. 20111. Sept. 2011Accuray IncorporatedGantry Image Guided Radiotherapy System And Related Treatment Delivery Methods
US2012031007628. Jan. 20116. Dez. 2012Koninklijke Philips Electronics N.V.Apparatus and method for influencing and/or detecting magnetic particles in a field of view having an array of single-sided transmit coil sets
US20150073264 *12. Sept. 201312. März 2015General Electric CompanySystems and methods for magnetic material imaging
Nichtpatentzitate
Referenz
1 *BAGHERI H ET AL: "A novel scanner architecture for MPI", 2015 5TH INTERNATIONAL WORKSHOP ON MAGNETIC PARTICLE IMAGING (IWMPI), IEEE, 26 March 2015 (2015-03-26), pages 1, XP032775958, ISBN: 978-1-4799-7269-2, [retrieved on 20150513], DOI: 10.1109/IWMPI.2015.7107089
2GLEICH, B.; WEIZENECKER, J.: "Tomographic imaging using the nonlinear response of magnetic particles", NATURE, vol. 435, 2005, pages 1214 - 1217, XP002368326, DOI: doi:10.1038/nature03808
Klassifizierungen
Internationale KlassifikationA61B5/05
UnternehmensklassifikationA61B2562/0223, A61B5/0515
Juristische Ereignisse
DatumCodeEreignisBeschreibung
19. Apr. 2017121Ep: the epo has been informed by wipo that ep was designated in this application
Ref document number: 16757887
Country of ref document: EP
Kind code of ref document: A1