WO2008139374A1

WO2008139374A1 - Method for planning 2d x-ray examinations

Info

Publication number: WO2008139374A1
Application number: PCT/IB2008/051785
Authority: WO
Inventors: Vladimir Pekar; Rafael Wiemker; Daniel Bystrov; Roland Opfer; Jens Von Berg; Michael H. Kuhn
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N. V.
Priority date: 2007-05-11
Filing date: 2008-05-07
Publication date: 2008-11-20

Abstract

It is described a method for automatically determine the optimal patient pose and system positioning for X-ray radiographic examinations. The method is based on a first acquiring of one or more ultra- low-dose scout images, which are automatically analyzed by an image processing system. The aim is to compute the parameters for optimal positioning of the patient and the X-ray system such that the diagnostic image corresponds optimally either to an earlier examination in a follow-up study, or to predefined examination-specific standard pose.

Description

METHOD FOR PLANNING 2D X-RAY EXAMINATIONS

Field of invention

The present invention relates to a method for the planning of imaging parameters that are used by an 2D-X-ray system. Art Background

Daily clinical practice often requires the comparison of an earlier received and a current X-ray image of a patient. Particularly, direct visual appraisal is done of the former received image and the current received image. Further, digital subtraction techniques are applied to detect subtle interval changes such as newly developed pulmonary nodules, tumors, infiltration, pleural effusions, or changes in heart size.

Due to the now wide-spread availability of digital X-ray systems and digital picture archiving and communication systems (PACS), automated electronic comparison (Computer Assisted Reading) is gaining importance. Usually, in medical imaging, picture archiving and communication systems (PACS) are computers or networks dedicated to the storage, retrieval, distribution and presentation of images. Typically a PACS network consists of a central server which stores a database containing the images. This server is usually connected to one or more clients via a LAN or a WAN which provide or utilize the images.

For optimal comparison of the earlier and the follow-up image, it is crucial that a, usually predefined, pose of the patient and/or the scan parameter, particularly, the projection geometry is as similar as possible. , Projection images cannot be coregistered like three-dimensional (3D) datasets, because the depth information is irretrievably lost in the pysical projection. To achieve optimal geometric set-up of a patient and an X-ray system (image planning), it is known to use scout images using very low X-ray dose settings. The dose setting to acquire a scout image is typically less than 5% of a standard-dose for the diagnostic image. Thus, scout imaging made with ionizing radiation is maintainable if the overall rate af of unusable diagnostic-dose images is reduced. Especially the growing avaibility of dynamic flat-panel detectors makes the use of scout images feasible, since one detector may be used for scout images as well as for diagnostic images. Thus, mixed systems with dynamic digital image intensifiers to acquire the scout images and analogue film cassettes for acquiring diagnostic images are no longer a necessary prerequisite.

WO 2006/038165 Al describes a method and an assistance system for the planning of geometrical imaging parameters like the active dose-measuring-fϊeld and/or the opening of a collimator of an X-ray device. An optical image of a patient is generated by a camera and transferred to a computer. The computer then overlays said optical image of the patient with a graphical representation of the geometrical image parameters. The user may thus control and interactively select values of the imaging parameters on the overlay image.

Summary of the Invention

Based on this situation, it is an object of the present invention to provide a method and means that facilitate the planning for 2D X-ray examinations, particularly, to provide a method and means that facilitate to determine an optimal patient pose and system positioning for 2D X-ray determination.

The object may be achieved by a method according to claim 1, by an X- ray system according to claim 8, and by a software according to claim 17.

As said, for the detection of interval changes of images of a patient's organs, the previous and the follow-up image must be optimally aligned. This is because 2D projection images cannot be three-dimensionally co-registered in retrospect without a loss of information. The method is based on acquiring one or more ultra-low-dose scout images, which are automatically analyzed by an imaging processing system. One aim of the method is to compute parameters for an optimal positioning of the patient and the X-ray system such that a diagnostic image corresponds optimally either to an earlier examination in a follow-up study, or to a pre-defined examination- specific standard pose.

At this point, it should be understood that "examination" or "image of a patient" may correspond to a partial examination such as the image of a part of a chest, e.g. an organ such as the pleura, the heart or the lungs of a patient.

For the step of automatic analysis of divergence several known models as analysis of variance may be used in an iterative process.

The step of automatic simulation is based preferably on a mathematical representation of a three-dimensional model of the body part or organ. According to the present invention, a method for the planning of 2D X- ray examinations with a 2D X-ray system, comprises the steps of obtaining of a previous obtained 2D X-ray image of a patient or, alternatively, supplying an image of a pre-defined examination specific standard pose of a patient, acquiring of at least one low-dose 2D X-ray scout image of the patient in a first position, analysis of divergence between the image data of the previous obtained 2D X-ray image or the image of the pre-defined examination specific standard pose and the image data of the at least one low-dose 2D X-ray scout image by an image processing algorithm and automatic simulation of changes in said divergence due to changes of values of position data of the patient and/or position data or values of setup-parameters of the said 2D X-ray system. Further, the method comprises the steps of computation of correction position parameters and/or correction setup parameters, at which correction position parameters and/or correction setup parameters achive a minimum of said divergence between the previous obtained 2D X-ray image of the patient or the image of a pre-defined examination specific standard pose and a follow-up final standard dose diagnostic image.

Advantageous embodiments of the present invention are described by the dependent claims.

According to an embodiment of the present invention, the method comprises the step, moving at least one device of the X-ray system such, that position parameters of the X-ray system and or the patient of the previous obtained 2D X-ray image or position parameters due to the pre-defined examination standard pose are reached. Thus, the X-ray system or rather a device as the X-ray tube of the X-ray system is guided to an estimated position corresponding to the pre-defined position or standard pose.

To optimize the position of the X-ray tube and/or patient the said position with respect to the detector has to be known. Therefore, previous position data are stored in a storage and evaluated with the actual position settings.

According to a further embodiment of the present invention, the method comprises the step of generating a final standard dose diagnostic image using the computed correction position parameters and/or correction setup parameters. According to an embodiment of the present invention, the automatic simulation is a 3D simulation using a geometrical anatomic model.

According to an embodiment of the present invention, the method comprises, an optional input of correction data of an operator that is stored on storage means and used for further simulation/computation. According to a further embodiment of the present invention, the method comprises the step of displaying at least one of the said images and/or the said anatomic model.

According to an other embodiment of the present invention, the method comprises, displaying the correction position parameters and/or correction setup parameters, particularly as reference symbols.

According to an embodiment of the present invention, a clinical 2D X- ray based system arranged for applying one of the claimed methods, comprises an X-ray tube to emit X-rays and an X-ray detector to detect X-rays.

According to an other embodiment of the present invention, the clinical 2D X-ray based system further comprises a movable tube carrier carrying the X-ray tube. The tube carrier is preferably mounted on a ceiling with the ability to move in longitudinal, transversal, and vertical direction. Alternatively, the tube carrier is embodied as a mobile floor stand mount.

According to an other embodiment of the present invention, the clinical 2D X-ray based system further comprises a rotatable patient table bearing the patient. Assuming, the patient has no other vertical position as during pre-examination a correction of an angle of rotation is one of the main corrections.

According to an other embodiment of the present invention, a path of ray trough a patient is modifiable by moving the X-ray tube. According to an other embodiment of the present invention, a path of X- ray trough a patient is modifiable by rotating the patient table.

According to an other embodiment of the present invention, the X-ray tube and/or the patient table is movable manually by an operator and/or automatically by motor control. In a preferred calibration step, the X-ray tube is moved by the operator and the relative position of the tube with respect to the X-ray detector is measured by a positioning measurement system described below.

According to an other embodiment of the present invention, the clinical 2D X-ray based system further comprises a position measurement device to measure the position of the patient and/or the X-ray tube. In a preferred embodiment of the present invention, the position measuring device is giving the relative position of the X-ray tube with respect to the detector to the operator or, alternatively, to a motor control. In a further embodiment, the said device is implemented in the mechanics of the said carrier in known manner. An alternative device uses optical measuring methods.

According to an other embodiment of the present invention, the position measurement device comprises at least one light source, preferably an infrared light source or laser, to emit light and at least on reflective marker to reflect incident light of the light source.

In an embodiment, two light sources, precisely laser, are used. The light sources are mounted on the X-ray detector. A motor control is guiding the lasers and thus, rays of the light sources to meet each other at a desired tube position, which is preferably the same position as during a pre-examination procedure or a pre-defined position. To optimize the tube position, the operator or a motor control has to move the tube until the two rays of the light sources meet each other on the tube, preferably on a screen mounted on the tube, such until the said desired tube position is reached. In one embodiment, the position data are stored by a storing device of the system. The stored data can easily be used at later examination purposes. According to an other embodiment of the present invention, the position measurement device comprises an image acquisition device, preferably a charge- coupled device camera, to acquire the reflected light from a marker.

Preferably, the image acquisition unit as the light sources are attached at the X-ray tube or its carrier. The said reflective marker is preferably attached on the X- ray detection device or alternatively sticking on the patient to detect patient motion due to breath or heart beat.

According to an other embodiment of the present invention, a software is arranged to execute the steps of one of the aforesaid methods. In the following there will be described several exemplary embodiments of the present invention with reference to a method for planning of chest 2D X-ray examinations. It has to be pointed out that of course any combination of features relating to different subject matters is also possible.

At this point it has to be pointed out that the described method for planning of chest 2D X-ray examinations is a pre-requisite for providing a diagnosis or about treating patients. The described method and all other aspects and embodiments of the present invention provide additional and more detailed information, which may assist a physician in reaching more accurate diagnosis and/or in deciding about appropriate therapy procedures. One way to make use of the planning is the calculation of subtraction images between follow-up images that have been planned with the method described in the invention. The diagnostic quality of subtraction images depends on the registration accuracy and the registration is complicated by differences in patient pose or acquisition geometry. It has to be noted that a person skilled in the art will gather from the above and the following description that, unless other notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters, in particular between features of the system type claim and features of the method type claims is considered to be disclosed with this application. The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the example of the embodiment. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

On the basis of the above given and the following explanation of the method for planning of chest 2D X-ray examinations a skilled person will we able to translate the steps of the method into a computer program for carrying out the method.

Brief Description of the Drawings

Figure 1 shows a picture flow chart for a method for planning of chest 2D X-ray examinations.

Figure 2 shows a side view of a 2D X-ray system and a patient according to the invention.

Figure 3 shows a top view of a 2D X-ray system and a patient according to the invention.

Figure 4 shows a side view of an alternative 2D X-ray system and a patient according to the invention.

Detailed Description

The illustration in the drawing is schematic.

Figure 1 shows in a flowchart several steps for method for the planning of chest 2D X-ray examinations with a 2D X-ray system. First a previous obtained 2D X-ray image 1 of a patient's chest 2 is retrieved. Alternatively, an image of a predefined examination specific standard pose 3 of a patient's chest is supplied.

In a second step one low-dose 2D X-ray scout image 4 of the chest of the patient in a first position is acquired. In a third step 5 of the method, the divergence between the image data of the previous obtained 2D X-ray image 1 and the image data of the low-dose 2D X-ray scout image 4 is automatically analyzed by an image processing algorithm.

For the said alternative the image data of the pre-defined examination specific standard pose and the image data of the said low-dose 2D X-ray scout image 4 may be automatically analyzed by the same image processing algorithm automatic. Preferably, the result of each analysis is displayed at an image 6 and, for the alternative at an image 7.

In a further step 8, the changes of values of position data of the patient and/or values of setup-parameters of the said 2D X-ray system are simulated. As a result of said changes divergence also changes to other values. Preferably, the result of the simulation/the iterative modeling process is displayed at an image 9. The result for the alternative is not shown here.

In a further step 10, the correction position parameters and/or correction setup parameters at which a minimum of said divergence between the previous obtained 2D X-ray image 1 or the image of the standard pose 3 was reached are computed. A reference symbol 11 in the accordingly displayed image 12 shows the operator how the position of the patient has to be changed for finally obtaining a follow-up final standard dose diagnostic image 13 which optimally corresponds to the earlier obtained image 1 or the standard pose 3, not shown here. Preferably, the operator can provide a correctional input, which is saved and integrated into further planning, such as a learning effect for the method can be archived.

Figure 2 shows a side view of a 2D X-ray system 14 and a patient 15 according to the invention. The clinical 2D X-ray based system 14 is arranged to apply the method described above. The 2D X-ray system 14 comprises an X-ray tube 16 to emit X-rays, an X-ray detector 17 to detect X-rays and a movable tube carrier 18 carrying the X-ray tube 16. Due to the movable carrier 18 a path of X-ray trough a patient not shown here is modifiable by moving the X-ray tube 16. In the embodiment of Fig. 2, the X-ray tube 16 and/or a patient table not shown here is movable manually by an operator and/or automatically by motor control. Further, the clinical 2D X-ray based system 14 comprises a position measurement device 19 to measure the position of the patient 15 and/or the X-ray tube 16. The position measurement device 19 comprises two light sources 20, 21 embodied as lasers to emit light and one screen mounted on the tube 16 but not shown here to reflect incident light of the light sources 20, 21. The system of the shown embodiment offers a simple possibility to execute the inventive method. In case of a pre-captured X- ray image being made with a the calibrated system 14 the acquisition of a follow up image to calculate a subtraction image is even more easy. The geometry of the system positions at the pre-captured X-ray image has to be restored or can at least serve as setting for an additional scout scan.

Figure 3 shows a top view of a 2D X-ray system and a patient. A carrier is not shown here. Instead the arrangement of the two light sources 20, 21 and the two paths of light becomes clear from Fig. 3.

Finally, Fig. 4 shows a side view of an alternative 2D X-ray system with an alternative carrier according to the invention. While Fig. 2 shows the tube carrier 18 mounted on a ceiling with the ability to move in longitudinal, transversal, and vertical direction, Fig. 4 shows the tube carrier embodied as a mobile floor stand mount 23.

It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

CLAIMS:

1. A method for the planning of 2D X-ray examinations with a 2D X-ray system (14), the method comprising the steps of: obtaining of a previous obtained 2D X-ray image (1) of a patient (2, 15) or supplying an image (3) of a pre-defined examination specific standard pose of a patient; acquiring of at least one low-dose 2D X-ray scout image (4) of the patient in a first position; automatic analysis of divergence between the image data of the previous obtained 2D X-ray image (1) or the image (4) of the pre-defined examination specific standard pose and the image data of the at least one low- dose 2D X-ray scout image (4) by an image processing algorithm (5); automatic simulation (8) of changes in said divergence due to changes of values of position data of the patient and/or position data or values of setup-parameters of the said 2D X-ray system; automatic computation (10) of correction position parameters and/or correction setup parameters, at which correction position parameters and/or correction setup parameters archived a minimum of said divergence between the previous obtained 2D X-ray image (1) of the patient (2, 15) or the image (3) of a pre-defined examination specific standard pose and a follow-up final standard dose diagnostic image (13).

2. A method according to claim 1, further comprising the step of moving at least one device (16) of the X-ray system (14) such, that position parameters of the X-ray system (14) and or the patient (15) of the previous obtained 2D X-ray image or position parameters due to the pre-defined examination standard pose are reached.

3. A method according to claim 1 or 2, further comprising the step of generating a final standard dose diagnostic image (13) using the computed correction position parameters and/or correction setup parameters.

4. The method according to one of the previous claims, wherein the automatic simulation is a 3D simulation using a geometrical anatomic model.

5. The method according to one of the previous claims, wherein an optional input of correction data of an operator is stored on storage means and used for further simulation/computation.

6. The method according to one of the previous claims, further comprising the step of displaying at least one of the said images and/or the said anatomic model.

7. The method according to one of the previous claims, further comprising the step of displaying the correction position parameters and/or correction setup parameters, particularly as reference symbols (11).

8. A clinical 2D X-ray based system (14), arranged for applying a method according to one of the previous claims, comprising the following devices: an X-ray tube (16) to emit X-rays; an X-ray detector (17) to detect X-rays.

9. A clinical 2D X-ray based system (14), according to the system claimed in claim 8, further comprising: a movable tube carrier (18) carrying the X-ray tube (16).

10. A clinical 2D X-ray based system (14), according to the system claimed in one of the previous claims, further comprising: a rotatable patient table bearing the patient (15).

11. A clinical 2D X-ray based system (14), according to the system claimed in one of the previous claims, wherein a path of ray trough a patient is modifiable by moving the X-ray tube.

12. A clinical 2D X-ray based system (14), according to the system claimed in one of the previous claims, wherein a path of X-ray trough a patient is modifiable by rotating the patient table.

13. A clinical 2D X-ray based system (14), according to the system claimed in one of the previous claims, wherein the X-ray tube (16) and/or the patient table is movable manually by an operator and/or automatically by motor control.

14. A clinical 2D X-ray based system (14), according to the system claimed in one of the previous claims, further comprising: a position measurement device (19) to measure the position of the patient and/or the X-ray tube ( 16) .

15. A clinical 2D X-ray based system (14), according to the system claimed in one of the previous claims, wherein the position measurement device (19) comprising: at least one light source (20, 21), preferably an infrared light source or laser to emit light.

16. A clinical 2D X-ray based system (14), according to the system claimed in one of the previous claims, wherein the position measurement device (19) further comprising: an image acquisition device, preferably a charge-coupled device camera, to acquire reflected light from at least one marker.

17. A software arranged for executing a method as claimed in one of the previous claims on a clinical 2D X-ray based system.