Method and apparatus for tracking an internal target region without an implanted fiducial

• US 20040092815A1
• Filed: 11/12/2002
• Published: 05/13/2004
• Est. Priority Date: 11/12/2002
• Status: Active Grant

• Current Assignee: Accuray Incorporated
• Original Assignee: Accuray Incorporated
• Inventors: Adler, John R., Schweikard, Achim
• Granted Patent: US 7,260,426 B2
• Time in Patent Office: Days
• US Class Current: 600/425
• CPC Class Codes: A61B 2034/2055 Optical tracking systems
• CPC Class Codes: A61B 2034/2072 Reference field transducer attached to an instrument or patient
• CPC Class Codes: A61B 2090/364 Correlation of different images or relation of image positions in respect to the body
• CPC Class Codes: A61B 2090/376 using X-rays, e.g. fluoroscopy
• CPC Class Codes: A61B 2090/3762 using computed tomography systems [CT]
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: A61B 6/12 Arrangements for detecting or locating foreign bodies
• CPC Class Codes: A61B 6/469 for selecting a region of interest [ROI]
• CPC Class Codes: A61B 6/541 involving acquisition triggered by a physiological signal
• CPC Class Codes: A61B 8/543 involving acquisition triggered by a physiological signal
• CPC Class Codes: A61B 90/361 Image-producing devices, e.g. surgical cameras
• CPC Class Codes: A61N 2005/1061 using an x-ray imaging system having a separate imaging source
• CPC Class Codes: A61N 2005/1062 using virtual X-ray images, e.g. digitally reconstructed radiographs [DRR]
• CPC Class Codes: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam
• CPC Class Codes: A61N 5/1064 for adjusting radiation treatment in response to monitoring
• CPC Class Codes: A61N 5/1067 in real time, i.e. during treatment

Abstract

A method and apparatus for locating an internal target region during treatment without implanted fiducials is presented. The method comprises producing a plurality of first images that show an internal volume including the internal target region, then producing a live image of the internal volume during treatment and matching this live image to one of the plurality of first images. Since the first images show the internal target region, matching the live image to one of the first images identifies the position of the target region regardless of whether the second image itself shows the position of the target region. The first images may be any three-dimensional images such as CT scans, magnetic resonance imaging, and ultrasound. The live image may be, for example, an x-ray image. The invention may be used in conjunction with a real-time sensor to track the position of the target region on a real-time basis.

Claims

1. A method for locating an internal target region during treatment, the method comprising:

generating a plurality of first images of a relevant volume of a patient, the relevant volume including a target region and each of the plurality of first images showing the target region;

generating a second image of the relevant volume at a predetermined time; and

determining a location of the target region at the predetermined time by identifying one of the plurality of first images that best matches the second image.

2. The method of claim 1, wherein the plurality of first images include one of computer tomography scans, ultrasound images, and magnetic resonance images.

3. The method of claim 1, wherein the plurality of first images are three-dimensional images.

4. The method of claim 1, wherein generating the plurality of first images comprises:

generating a first computer tomography scan taken at a first point of a respiratory cycle;

generating a second computer tomography scan taken at a second point of the respiratory cycle; and

generating at least one computer-generated intermediate three-dimensional image depicting the relevant volume at a third point between the first point and the second point.

5. The method of claim 4, wherein generating the at least one intermediate three-dimensional image comprises interpolating between the first computer tomography scan and the second computer tomography scan and modifying one of the first and the second computer tomography scans.

6. The method of claim 4, wherein generating the at least one intermediate three-dimensional image comprises continuously deforming a first three-dimensional image into a second three-dimensional image taken at a different point in time from the first three-dimensional image.

7. The method of claim 1, wherein the plurality of first images are generated at preselected points in the patient'"'"'s respiratory pattern.

8. The method of claim 1, further comprising computing a plurality of digitally reconstructed radiographs for each of the plurality of first images, wherein each of the plurality of digitally reconstructed radiographs represents the relevant volume from a particular viewing angle.

9. The method of claim 8, wherein each of the first images indicate a point in the respiratory cycle and each of the digitally reconstructed radiographs indicate a rotational and translational shift of the relevant volume.

10. The method of claim 8, wherein identifying one of the plurality of first images that best matches the second image comprises comparing the digitally reconstructed radiographs to the second image.

11. The method of claim 10, wherein the comparing comprises comparing the digitally reconstructed radiographs and the second image on a pixel by pixel basis.

12. The method of claim 1, wherein the second image comprises an x-ray image.

13. The method of claim 1, wherein generating the plurality of first images is done independently of the generating of the second image.

14. The method of claim 1, wherein the plurality of first images is generated prior to treatment and the second image is a live image generated during treatment.

15. The method of claim 1, wherein the position of the internal target region is indicated in coordinates of a treatment room.

16. The method of claim 1, further comprising:

coupling a real-time sensor to an external body part of the patient, the real-time sensor being read at time interval Δ

t_sensor;

reading the signal and generating a corresponding image of the relevant volume simultaneously at a time interval Δ

t wherein Δ

t is greater than Δ

t_sensor; and

identifying one of the plurality of first images that best matches the corresponding image to generate a correlation between the position of the target region and the signal.

17. The method of claim 16, wherein generating the correlation comprises:

reading the signal and generating the corresponding image of the relevant volume at a plurality of different points in time to produce a set of signal data and a set of corresponding image data;

fitting a first curve through the set of signal data;

fitting a second curve through the set of corresponding image data; and

comparing the first curve and the second curve.

18. The method of claim 17, further comprising:

reading a signal s from the real-time sensor at a time t_sensor;

locating the signal s on the first curve; and

inferring the position of the target region at time t_sensorby identifying a point y on the second curve that corresponds to the signal s of the first curve.

19. The method of claim 17, further comprising:

periodically taking a new x-ray image of the relevant volume and simultaneously reading a corresponding signal during treatment; and

updating the correlation with the new x-ray image and the corresponding signal.

20. The method of claim 16, wherein the real-time sensor comprises one of infrared tracking, force sensors, air flow meters, strain gauges, laser range sensors, and a variety of sensors based on haptic, acoustic, ultrasound, magnetic, mechanical and optical principles.

21. The method of claim 16, wherein the real-time sensor is a first sensor, further comprising coupling one or more additional sensors to the patient'"'"'s body to track patient motion.

22. The method of claim 1, further comprising:

determining a respiratory pattern of the patient; and

predicting the location of the target region at a future point in time based on the respiratory pattern and the plurality of first images that are taken at different points in the respiratory pattern.

23. A method for obtaining an image of a patient'"'"'s internal volume, the method comprising:

determining a respiratory pattern of the patient;

selecting at least one point on the respiratory pattern; and

triggering an imaging device at the at least one point on the respiratory pattern to obtain an image at a known point on the respiratory pattern.

24. A method for locating an internal target region during treatment, the method comprising:

prior to treatment, generating a correlation of a set of bone positions with a set of target region positions; and

during treatment, producing a live image of a relevant bone and selecting one of the set of bone positions that most closely matches the live image of the relevant bone to determine a target region position at the time the live image is produced.

25. An apparatus for tracking the location of a target region inside a patient, the apparatus comprising:

an imaging device periodically generating an actual image of a relevant volume;

a memory unit storing a plurality of three-dimensional images wherein each of the three-dimensional images shows a pre-generated image of the relevant volume and the target region located in the relevant volume; and

a processor coupled to the imaging device and the memory unit, the processor including a first set of computer-readable instructions for selecting a best three-dimensional image that most closely resembles the actual image and a second set of computer-readable instructions for determining a position of the target region at the time the actual image is generated based on the best three-dimensional image.

26. The apparatus of claim 25 further comprising a plurality of digitally reconstructed radiographs stored in the memory unit, wherein each one of the plurality of digitally reconstructed radiographs is associated with one of the plurality of three-dimensional images, and wherein the processor uses the digitally reconstructed radiographs to select the best three-dimensional image.

27. The apparatus of claim 26 wherein each of the plurality of digitally reconstructed radiographs reflects a different displacement of the relevant volume that results from a patient'"'"'s shifting his body.

28. The apparatus of claim 25, wherein the plurality of three-dimensional images include one of a computer tomography scan, a magnetic resonance image, and an ultrasound image.

29. The apparatus of claim 25, wherein the plurality of three-dimensional images includes a first three-dimensional image, a second three-dimensional image, and at least one synthetic three-dimensional image generated by interpolating between the first and the second three-dimensional images and modifying one of the first and second three-dimensional images.

30. The apparatus of claim 25, wherein the imaging device comprises at least one x-ray generator and the actual image is a stereo x-ray image.

31. The apparatus of claim 30 further comprising a sensing system coupled to the processor, the sensing system reading a movement of an external body part at the same time that the imaging device generates an actual image so that the processor generates a correlation between the movement of the external body part and the position of the target region.

32. The apparatus of claim 31, wherein the sensing system comprises one of infrared tracking, force sensors, air flow meters, strain gauges, laser range sensors, and a variety of sensors based on haptic, acoustic, ultrasound, magnetic, mechanical and optical principles.

33. The apparatus of claim 25 further comprising a respiratory pattern of the patient stored in the memory unit, wherein processor comprises a third set of computer-readable instructions for generating a three-dimensional image of the relevant volume at one or more preselected points in the respiratory pattern.

34. The apparatus of claim 25 further comprising a beaming device directing a treatment beam to the location of the target region in response to a processor command.

35. The apparatus of claim 25 wherein the plurality of three-dimensional images comprises at least one of a computer tomography scan, a magnetic resonance image, or an ultrasound image.

36. A method for locating an internal target region during treatment, the method comprising:

prior to treatment, generating a correlation of a set of bone positions with a set of target region positions; and

during treatment, producing an image of a relevant bone and selecting one of the set of bone positions that most closely matches the image of the relevant bone to determine the target region position.

37. An apparatus for tracking the location of a target region inside a patient, the apparatus comprising:

means for generating a plurality of first images of a relevant volume inside the patient, the relevant volume including a target region and each of the plurality of first images showing the target region;

means for generating a second image of the relevant volume at a predetermined time; and

means for determining a location of the target region at the predetermined time by identifying one of the plurality of first images that best matches the second image.

38. The apparatus of claim 37, wherein the means for generating the plurality of first images comprises:

means for generating a first computer tomography scan taken at a first point of a respiratory cycle;

means for generating a second computer tomography scan taken at a second point of the respiratory cycle; and

means for generating at least one computer-generated intermediate three-dimensional image depicting the relevant volume at a third point between the first point and the second point.

39. The apparatus of claim 38, wherein the means for generating the at least one intermediate three-dimensional image comprises means for interpolating between the first computer tomography scan and the second computer tomography scan and modifying one of the first and the second computer tomography scans.

40. The apparatus of claim 37, further comprising means for computing a plurality of digitally reconstructed radiographs for each of the three-dimensional images, wherein each of the plurality of digitally reconstructed radiographs is a representation of the relevant volume from a particular viewing angle.

41. The apparatus of claim 40, wherein the means for identifying one of the plurality of first images comprises means for comparing the digitally reconstructed radiographs to the second image.

42. The apparatus of claim 37, further comprising:

means for sensing a movement of an external body part of the patient, the means for sensing emitting a signal at time interval Δ

t_sensor;

means for reading the signal and generating a corresponding image of the relevant volume simultaneously at a time interval Δ

t wherein Δ

t is greater than Δ

t_sensor; and

means for identifying one of the plurality of first images that best matches the corresponding image to generate a correlation between the position of the target region and the signal.

43. The apparatus of claim 42, wherein the means for identifying comprises:

means for reading the signal and generating the corresponding image of the relevant volume at a plurality of different points in time to produce a set of signal data and a set of corresponding image data;

means for fitting a first curve through the set of signal data;

means for fitting a second curve through the set of corresponding image data; and

means for comparing the first curve and the second curve.

44. The apparatus of claim 43, further comprising:

means for reading a signal s from the real-time sensor at a time t_sensor;

means for locating the signal s on the first curve; and

means for inferring the position of the target region at time t_sensor or by identifying a point y on the second curve that corresponds to the signal s of the first curve.

45. The apparatus of claim 43, further comprising:

means for periodically taking a new x-ray image of the relevant volume and simultaneously reading a corresponding signal during treatment; and

means for updating the correlation with the new x-ray image and the corresponding signal.

46. The apparatus of claim 37, further comprising means for determining a respiratory pattern of the patient wherein the plurality of first images are generated at preselected points of the respiratory pattern.