Tracking Soft Tissue in Medical Images

Abstract

The present invention relates to a medical data processing method of determining the representation of an anatomical body part (2) of a patient (1) in a sequence of medical images, the anatomical body part (2) being subject to a vital movement of the patient (1), the method being constituted to be executed by a computer and comprising the following steps: a) acquiring advance medical image data comprising a time-related advance medical image comprising a representation of the anatomical body part (2) in a specific movement phase; b) acquiring current medical image data describing a sequence of current medical images, wherein the sequence comprises a specific current medical image comprising a representation of the anatomical body part (2) in the specific movement phase, and a tracking current medical image which is different from the specific current medical image and comprises a representation of the anatomical body part (2) in a tracking movement phase which is different from the specific movement phase; c) determining, based on the advance medical image data and the current medical image data, specific image subset data describing a specific image subset of the specific current medical image, the specific image subset comprising the representation of the anatomical body part (2); d) determining, based on the current medical image data and the image subset data, subset tracking data describing a tracked image subset in the tracking current medical image, the tracked image subset comprising the representation of the anatomical body part (2).

Claims

1. A medical data processing method of determining the representation of an anatomical body part (2) of a patient (1) in a sequence of medical images, the anatomical body part (2) being subject to a vital movement of the patient (1), the method being constituted to be executed by a computer and comprising the following steps: a) acquiring (step 3) advance medical image data comprising a time-related advance medical image comprising a representation of the anatomical body part (2) in a specific movement phase; b) acquiring current medical image data describing a sequence of current medical images, wherein the sequence comprises a specific current medical image comprising a representation of the anatomical body part (2) in the specific movement phase, and a tracking current medical image which is different from the specific current medical image and comprises a representation of the anatomical body part (2) in a tracking movement phase which is different from the specific movement phase; c) determining, (step 5) based on the advance medical image data and the current medical image data, specific image subset data describing a specific image subset of the specific current medical image, the specific image subset comprising the representation of the anatomical body part (2); characterised by d) determining (step 5), based on the current medical image data and the specific image subset data, subset tracking data describing a tracked image subset in the tracking current medical image, the tracked image subset comprising the representation of the anatomical body part (2).

2. The method according to the preceding claim, comprising a step of acquiring current movement phase data describing a current movement phase of the anatomical body part (2) in the states in which it is described by the sequence of current medical images, wherein the current movement phase data is generated based on acquiring digital signals describing the vital movement which have been generated based on tracking marker devices (4) attached to the patient's body (1) and correlating the result of the tracking with the current medical image data, wherein the specific current medical image is determined based on the current movement phase data.

3. The method according to any one of the preceding claims, wherein the specific image subset data describes the position of the specific image subset in the specific current medical image, and wherein the subset tracking data describes the position of the tracked image subset in the tracking current medical image.

4. The method according to the preceding claim as far as dependent on claim 2, comprising a step of determining, based on the current medical image data and the subset tracking data and the current movement phase data, internal breathing curve data describing a time-correlation of the image positions of the anatomical body part (2) and the sequence of current medical images.

5. The method according to any one of the preceding claims, wherein the specific image subset data is determined based on determining a corresponding representation of the anatomical body part (2) in the advance medical image and in the sequence of current medical images.

6. The method according to the preceding claim, comprising a step of acquiring current medical image user input data describing an input by a user for selecting the specific image subset from the specific current medical image wherein the image subset data is determined based on the user input data.

7. The method according to any one of claims 1 to 5, comprising a step of acquiring advance image subset data describing an advance image subset of the advance medical image comprising the representation of the anatomical body part (2), wherein the specific image subset data is determined based on the advance image subset data.

8. The method according to the preceding claim, comprising a step of acquiring advance medical image user input data describing an input by a user for selecting the advance image subset from the advance medical image, wherein the advance image subset data is determined based on the advance medical image user input data.

9. The method according to any one of the two preceding claims, wherein the specific image subset data is determined based on the result of comparing the advance image subset data to the specific current medical image.

10. The method according to any one of the preceding claims, wherein the subset tracking data is determined by determining a region in the tracking current medical image which is at least to a predetermined degree comparable to the specific image subset.

11. The method according to any one of the preceding claims, wherein the advance medical image data has been generated by applying a computed tomography imaging method to the patient's body (1), wherein the advance medical image is in particular a digitally rendered radiograph rendered from the computed tomography of the patient's body, and wherein the sequence of current medical images has been generated by applying a conventional x-ray imaging method.

12. (canceled)

13. A non-transitory computer readable program storage medium (13) on which the method according to claim 1 is stored and executed by at least one processor of a computer.

14. (canceled)

15. A treatment device, comprising: a) the computer (11) according to claim 13; b) a medical imaging device (7, 8) for acquiring the current medical image data; c) an irradiation unit (9) for emitting a treatment beam to the patient's body (1), d) wherein the computer (11) is operatively coupled to the medical imaging device (7, 8) to acquire the current medical image data and to the irradiation unit (9) to issue control signals for emitting the treatment beam.

Description

DESCRIPTION OF THE FIGURES

[0066] In the following, the invention is described with reference to the enclosed figures which represent at least preferred embodiment of the invention. The scope of the invention is however not limited to the specific features disclosed in the figures and described in connection with the figures.

[0067] FIG. 1 shows a treatment device usable for conducting the invention;

[0068] FIG. 2 is a flow diagram showing the functionality of the method in accordance with the invention; and

[0069] FIGS. 3A to 3C show screenshots from a prototype software application implementing the disclosed method.

[0070] According to FIG. 1, the treatment device (which can be a radiotherapy or radiosurgery device) comprises at least a patient support device embodied by a treatment table 5, an imaging unit comprising an x-ray tube 8 and an x-ray detector 7, and a treatment unit embodied by a linear accelerator 9 which is configured to emit a treatment beam comprising ionizing treatment radiation onto the anatomical body part represented by the patient's lung 2. A patient 1 having the anatomical body part is placed on the patient support device embodied by the treatment table 5 which can be moved by a moving unit embodied by an electric motor 6. The treatment table 5 is placed under the treatment unit. The curved arrow indicates that the linear accelerator 9 can be rotated around the patient's longitudinal axis. A headrest 3 made from a carbon material is placed adjacent to (in particular under) the patient's head in order to support the patient's head. The base plate of the headrest 3 is shown in FIG. 1 out of perspective and merely for reasons of illustration. A marker device (for example in the shape of a frame or a belt) comprising a plurality of markers 4 is disposed on the patient's thorax, in the case of FIG. 1 three markers 4a are used. The spatial relationship between the markers 4 and the headrest 3 is known and fixed. The treatment device also comprises a computer 11 which is part of a navigation system 10. The computer 11 comprises a volatile memory such as a RAM 14, a non-volatile memory embodied by a hard disc 13 and a processing unit embodied by microprocessor 12. Furthermore, the computer 11 is operatively coupled to an input unit embodied by a keyboard 15 and a visual output unit such as a monitor 16. The navigation system also comprises a transmitter of the navigation system embodied by infrared transmitters 17 and a receiver embodied by infrared-sensitive stereoscopic camera 18 which are both operatively coupled to the computer 11. The computer 11 is also configured to control the other parts of the treatment device such as the imaging unit and the treatment unit and the moving unit. The treatment unit is operatively coupled to the computer 11 in order to receive, from the computer 11, control signals for activating the treatment beam in dependence on the current movement phase data as explained above.

[0071] FIG. 2 shows a flow diagram comprising exemplary steps of the above-described data processing method.

[0072] In the flow diagram of FIG. 2 and the screenshots of FIGS. 3A to C, the anatomical body part is a lung tumour and the vital movement is the breathing movement of the patient's thorax.

[0073] In particular, steps 1) and 2) relate to generating and acquiring the advance medical image data embodied by a stereo-fluoro-sequence (i.e. sequence of pairs of fluoroscopic images which have been taken in particular in directions which—in three-dimensional space—are perpendicular to each other). In step 1), retroreflective markers are attached to the patient's chest and tracked using an infrared tracking camera 18 to produce a breathing curve for the patient 1. In step 2), the stereo-fluoro-sequence is taken prior to the treatment. Time-stamp synchronization is used to time-correlate the current medical image data embodied by the fluoro-sequence. Thereby, the fluoro-sequence is registered to the breathing curve.

[0074] In step 3), the advance medical image data is acquired. In the case of FIG. 2, a planning CT of only one specific respiratory state (i.e. specific movement phase) is used as the advance medical image. From the planning CT, a pair of digitally radiographs (DRRs) of the target region and/or indicators for the position of the target region are rendered. These DRRs are fused in step 4) to that x-ray image pair in the stereo-fluoro-sequence (which embodies the sequence of current medical images) which originates from the at least substantially same respiratory state as the respiratory with which the planning CT is associated. Step 5) encompasses determination of the specific image subset data and the subset tracking data by using a matched counterpart embodied by two selections, e.g. cutouts (clippings), from the x-ray image pair for mono-modal detection of the target position (i.e. of the position of the target region) in the remaining image pairs (i.e. in the remaining current medical images), in particular in the at least one tracking current medical image of the sequence of current medical images embodied by the fluoro-sequence.

[0075] Optional step 6) relates to building a correlation model between the external breathing curve generated for generating the advance medical image data (the planning CT and the internal position of the target region which may be embodied by the anatomical body part). Thus, an internal breathing curve can be established. Such an internal breathing curve may serve as a basis for issuing the control signals to the treatment unit for activating or de-activating the treatment beam.

[0076] FIGS. 3A to 3C are screenshots gathered from a prototype software application for implementing the disclosed data processing method. FIG. 3A shows in its left half three views from three different spatial directions in which the specific image subset is defined for example by manually clipping a rectangular region in the centre of one of the views, i.e. by user input. The application automatically clips a corresponding region in the two other views by transformation of the coordinates from the manually edited view into the coordinates of the other two views. The three views shown in FIG. 3A are the axial, the coronal and the sagittal view of the planning CT of the tumour. In the right half of FIG. 3A, a preview of a pair of DRRs is given which show a stereo-imaging view of the image region selected (clipped) in one of the views in the left half of FIG. 3A.

[0077] FIG. 3B shows a fusion of the DRRs generated as explained with regard to FIG. 3A with the x-ray image pair which has been determined as the specific current medical image. Based on comparing the DRRs to the x-ray image pair, the region in the x-ray image pair representing the specific image subset can be determined and highlighted by placing a rectangular frame around it as shown in FIG. 3C. The rectangular frame shown in FIG. 3C therefore is an example of the above-described graphical feature defined by the display marking data.