Calibrating imaging devices

• US 20060036170A1
• Filed: 07/19/2005
• Published: 02/16/2006
• Est. Priority Date: 07/20/2004
• Status: Active Grant

• Current Assignee: Elekta Ltd. (Elekta AB)
• Original Assignee: Elekta Ltd. (Elekta AB)
• Inventors: Falco, Tony, Lachaine, Martin, Huang, Xing, Audet, Veronique
• Granted Patent: US 8,000,442 B2
• Time in Patent Office: Days
• US Class Current: 600/437
• CPC Class Codes: A61B 2090/364 Correlation of different images or relation of image positions in respect to the body
• CPC Class Codes: A61B 8/00 Diagnosis using ultrasonic, sonic or infrasonic waves imaging of objects using sonar G01S15/00
• CPC Class Codes: A61B 8/4209 by using holders, e.g. positioning frames
• CPC Class Codes: A61B 8/4245 involving determining the position of the probe, e.g. with respect to an external reference frame or to the patient
• CPC Class Codes: A61B 8/587 Calibration phantoms models for medical purposes G09B23/28
• CPC Class Codes: G01S 15/8936 using transducers mounted for mechanical movement in three dimensions
• CPC Class Codes: G01S 7/5205 Means for monitoring or calibrating

Abstract

Methods and apparatus for calibrating images and imaging devices to common coordinate systems utilize, in some embodiments, rods that detectably reflect an acoustic signal regardless of the incidence angle of the signal with respect to the rods. Typically, the rods are disposed within a “phantom” at known positions with respect to a room coordinate system. Images of the cylindrical rods may be obtained from different directions, allowing the imaging device to be calibrated to the room coordinate system.

Claims

1. A method for calibrating an imaging device to a reference coordinate system, the method comprising:

locating a plurality of elongated members that detectably reflect an acoustic signal regardless of incidence angle of the signal with respect to the members at known positions with respect to a reference coordinate system;

obtaining a plurality of images taken from different directions with respect to the elongated members and comprising representations of the elongated members; and

calibrating the imaging device to the reference coordinate system based in part on the plurality of images.

2. The method of claim 1 wherein the elongated members are rods.

3. The method of claim 2 wherein the rods are cylindrical.

4. The method of claim 2 wherein the rods have a diameter of at least about 3 mm.

5. The method of claim 1 wherein the shape of the elongated member is such that cross-sectional images of the member are concentric regardless of sectional angle.

6. The method of claim 1 wherein the reference coordinate system is a three-dimensional reference coordinate system.

7. The method of claim 6 wherein the three-dimensional reference coordinate system is defined by a series of lasers disposed about a room.

8. The method of claim 6 wherein the three-dimensional reference coordinate system is defined by the physical orientation of a treatment device.

9. The method of claim 6 wherein the three-dimensional reference coordinate system is defined by the physical orientation of an imaging device.

10. The method of claim 1 wherein the plurality of images are two-dimensional ultrasound images.

11. The method of claim 10 wherein the two-dimensional ultrasound images are taken from different angles with respect to the cylindrical rods.

12. The method of claim 11 wherein the angles are orthogonal to the cylindrical rods.

13. The method of claim 11 wherein the angles are oblique to the cylindrical rods.

14. The method of claim 1 wherein the calibration step further comprises determining the centers of one or more of the rods within each representation.

15. The method of claim 14 wherein the calibration step further comprises relating the coordinates of the rods to the reference coordinate system based on the determined centers.

16. The method of claim 1 wherein the calibration step comprises relating the plurality of images to a coordinate system of the device, and relating the coordinate system of the device to the reference coordinate system.

17. The method of claim 1 further comprising recalibrating the imaging device to the reference coordinate system in response to images taken at an image depth different from that of the obtained plurality of images.

18. A system for calibrating an imaging device to a reference coordinate system, the system comprising:

a register for receiving a plurality of images imaged from a plurality of locations, the images comprising representations of a plurality of elongated members having known positions with respect to a reference coordinate system and that detectably reflect an acoustic signal regardless of incidence angle of the signal with respect to the members; and

a processor, responsive to the images, for calibrating the imaging device to the reference coordinate system.

19. The system of claim 18 wherein the elongated members are rods.

20. The system of claim 19 wherein the rods are cylindrical.

21. The system of claim 19 wherein the rods have a diameter of at least about 3 mm.

22. The system of claim 18 wherein the shape of the elongated members is such that cross-sectional images of any one of the member are concentric regardless of sectional angle.

23. The system of claim 18 wherein the processor, in calibrating the imaging device, further determines the centers of one or more of the elongated members within the representations and relates the coordinates of the rods to the reference coordinate system based on the determined centers.

24. The system of claim 18 wherein the reference coordinate system is a three-dimensional reference coordinate system.

25. The system of claim 24 wherein the three-dimensional reference coordinate system is defined by a series of lasers disposed about a room.

26. The system of claim 24 wherein the three-dimensional reference coordinate system is defined by the physical orientation of a treatment device.

27. The system of claim 24 wherein the three-dimensional reference coordinate system is defined by the physical orientation of an imaging device.

28. The system of claim 18 wherein the plurality of images are two-dimensional ultrasound images.

29. The system of claim 18 wherein the processor recalibrates the imaging device to the reference coordinate system in response to a second set of images taken at an image depth different from that of the received plurality of images.

30. An apparatus for calibrating an imaging device to a reference coordinate system, the apparatus comprising:

a first housing comprising a plurality of elongated members disposed at fixed positions within the first housing, the fixed positions being registerable to a reference coordinate system, and

a second housing displaced upon the first housing, the second housing comprising a plurality of target areas disposed about the second housing for placement of an imaging device such that images taken by the imaging device, when placed at the target areas, comprise representations of the elongated members within the first housing.

31. The apparatus of claim 30 wherein the elongated members detectably reflect an acoustic signal regardless of incidence angle of the signal with respect to the members.

32. The apparatus of claim 30 wherein the elongated members are rods.

33. The apparatus of claim 32 wherein the rods are cylindrical.

34. The apparatus of claim 32 wherein the rods have a diameter of at least about 3 mm.

35. The apparatus of claim 30 wherein the shape of the elongated members is such that cross-sectional images of any one of the members are concentric regardless of sectional angle.

36. The apparatus of claim 30 wherein the target areas comprise one or more of apertures, slots, and recesses.

37. The apparatus of claim 36 wherein the target areas comprise recesses, and an imaging device is received in close-fitting relation to one or more of the recesses.

38. The apparatus of claim 36 wherein the target areas comprise recesses, and the imaging device is repositionable in more than one orientation within the recess.

39. The apparatus of claim 38 wherein the position of the imaging device is indexable.

40. The apparatus of claim 38 wherein the imaging device is rotatable about an axis passing through the imaging device.

41. The apparatus of claim 38 wherein the imaging device is rotatable about an axis external to the imaging device.

42. The apparatus of claim 30 further comprising one or more support arms temporarily mated to the second housing.

43. The apparatus of claim 42 further comprising one or more openings displaced about the second housing for receiving one of the one or more support arms.

44. The apparatus of claim 42 wherein the imaging device is temporarily mated to the support arm.

45. The apparatus of claim 30 wherein the first housing and second housing are integral.

46. A method for calibrating an imaging device to a reference coordinate system, the method comprising:

locating, at known positions with respect to a reference coordinate system, one or more objects that diffusely reflect an acoustic signal from an imaging device;

applying an acoustic signal to the objects to obtain a plurality of images thereof based on diffuse reflection of the signal; and

calibrating the imaging device to the reference coordinate system based at least in part on the plurality of images.

47. The method of claim 46 wherein the imaging device is an ultrasound probe.

48. The method of claim 46 wherein the reference coordinate system is a three-dimensional reference coordinate system.

49. The method of claim 48 wherein the three-dimensional reference coordinate system is defined by the physical orientation of a treatment device.

50. The method of claim 48 wherein the three-dimensional reference coordinate system is defined by the physical orientation of an imaging device.

51. An apparatus for obtaining ultrasonic images, the apparatus comprising:

a probe comprising an elongated handle;

a faceplate attached to the probe and at least partially surrounding the handle; and

a plurality of signal emitters dispersed about the faceplate.

52. The apparatus of claim 51 wherein the probe houses an ultrasound imaging device.

53. The apparatus of claim 51 wherein the signal emitters are infrared emitters.

54. The apparatus of claim 53 wherein the infrared emitters are in communication with a reference coordinate system positioning device, whereby images can be obtained from multiple locations about a patient while the infrared emitters communicate with the positioning device.

55. The apparatus of claim 51 wherein the faceplate is curved.