METHODS AND DEVICES FOR DETECTING, CONTROLLING, AND PREDICTING RADIATION DELIVERY

• US 20090161827A1
• Filed: 12/18/2008
• Published: 06/25/2009
• Est. Priority Date: 12/23/2007
• Status: Active Grant

• Current Assignee: Carl Zeiss Meditec Incorporated (Carl-Zeiss-Stiftung)
• Original Assignee: Oraya Therapeutics, Inc.
• Inventors: Liang, Junzhong, Gertner, Michael, Herron, Matt, Hansen, Steven D., Chell, Erik, Koruga, Igor, Arnoldussen, Mark
• Granted Patent: US 7,792,249 B2
• Time in Patent Office: Days
• US Class Current: 378/65
• CPC Class Codes: A61F 2009/00844 Feedback systems
• CPC Class Codes: A61F 2009/00863 Retina
• CPC Class Codes: A61F 9/008 using laser
• CPC Class Codes: A61N 2005/1059 using cameras imaging the patient
• CPC Class Codes: A61N 2005/1072 taking into account movement of the target
• CPC Class Codes: A61N 2005/1091 Kilovoltage or orthovoltage range photons
• CPC Class Codes: A61N 5/1017 Treatment of the eye, e.g. for "macular degeneration"
• CPC Class Codes: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam
• CPC Class Codes: A61N 5/1067 in real time, i.e. during treatment

Abstract

Embodiments provide method and systems for determining alignment of a patient'"'"'s body part, such as an eye, in an external coordinate system of a treatment or diagnostic device, such as a radiotherapy device, so as to define a reference axis for guiding device operation. Additional embodiments provide image-based methods and systems for aligning, tracking and monitoring motion of a body part and a treatment target in relation to a radiation beam axis. Particular ophthalmic embodiments provide method and systems including an eye-contact guide device and imaging system for aligning and tracking motion of an eye and ocular treatment target in relation to an orthovoltage X-ray beam axis, so as to monitor application of radiation to a lesion, such as a macular lesion of the retina. Particular methods for controlling radiation in response to motion of the target during treatment are described, such as algorithms for gating or interrupting radiation emission, both to ensure treatment goals and to avoid exposure to sensitive structures.

Claims

1. A method of treating a lesion on or adjacent the retina of an eye of a patient with an external-beam radiation device, comprising:

(a) placing the patient'"'"'s eye in alignment with a known system axis in an external three-dimensional coordinate system, and measuring the eye'"'"'s axial length;

(b) from the known position of the system axis and from the measured axial length, determining the coordinates of the lesion to be treated in the external coordinate system;

(c) directing a collimated radiation beam along a known beam axis in the external coordinate system at the lesion to be treated;

(d) during said directing, tracking the position of the patient'"'"'s eye with respect to the known system axis, thus to track the position of the lesion to be treated in the external coordinate system; and

(e) based on the known beam axis of the collimated beam in the external coordinate system, and the instantaneous position of the lesion to be treated in the external coordinate system, as determined at least in part by the tracked position of the eye, calculating a total radiation equivalent received at the lesion to be treated during the treatment.

2. The method of claim 1, wherein:

step (b) further includes determining the coordinates of at least one radiation-sensitive structure in the external coordinate system;

step (d) further includes tracking the position of the at least one radiation-sensitive structure in the external coordinate system; and

step (e) further includes, based on the instantaneous position of the at least one radiation-sensitive structure in the external coordinate system, calculating a total radiation equivalent received at the at least one radiation-sensitive structure during the treatment;

the method further comprising the step of (f) based on the calculated radiation equivalent from step (e), controlling the radiation beam to insure that the at least one radiation-sensitive structure does not receive more than a preselected radiation equivalent during the treatment.

3. The method of claim 2, wherein step (a) includes measuring the axial length of the patient'"'"'s eye by ultrasound imaging, and step (b) includes scaling the measured axial length from step (a) to a standard human-eye model, and determining the coordinates of the lesion to be treated and the at least one radiation-sensitive structure from the eye model.

4. The method of claim 1, wherein step (a) includes determining a patient-eye geometric axis that extends through the center of the limbus and contains the corneal reflection of the patient'"'"'s eye, and aligning the geometric axis with the known system axis;

and wherein step (d) includes tracking the angular deviation of the geometric axis of the eye with the known system axis.

5. The method of claim 2, which further includes attaching an eye guide to the patient'"'"'s eye, centered thereon so that the geometric axis of the eye corresponds approximately to the axis of the eye guide, and aligning the axis of the eye guide with the known system axis.

6. The method of claim 5, wherein step (b) includes using the measured optical length of the patient'"'"'s eye to place the patient'"'"'s in registry with the eye model, and using the coordinates of the lesion to be treated and the at least one radiation-sensitive structure in the model to determine the coordinates thereof in the external coordinate system.

7. The method of claim 6, wherein step (d) includes tracking the position of the eye guide axis with respect to the system axis, thus to track the positions of the lesion and radiation-sensitive structures in the external coordinate system.

8. The method of claim 7, wherein the eye model includes a virtual medium by which the attenuation of a radiation beam along a known path through the model can be determined;

and step (e) includes determining the spatial accumulation of radiation received at the macular region of the patient'"'"'s eye based the known intensity of the collimated beam, the instantaneous positions of the of the patient'"'"'s eye, and the attenuation of the beam through the virtual medium along known pathways within the eye.

9. The method of claim 7, wherein step (e) includes mapping a spatial quantity indicative of a distribution of total radiation onto the eye model, based on the tracked position of the patient'"'"'s eye during a period of directing a radiation beam at the retinal region of the patient'"'"'s eye.

10. The method of claim 2, wherein the lesion to be treated is the macula, the at least one radiation-sensitive structure includes at least a portion of the optic nerve or optic disk of the eye, and step (e) includes calculating the total radiation equivalent received at the macula and at the optic disk during the treatment.

11. The method of claim 2, wherein step (f) of controlling the radiation beam includes controlling the radiation beam to do one or more of:

(i) achieve a desired dose of radiation at the lesion;

(ii) avoid exceeding a selected level of radiation dose at the radiation-sensitive structure; and

(iii) avoid exceeding a selected threshold based on the spatial quantity, the threshold indicative of eye-motion-based departure of the beam axis from the selected target.

12. The method of claim 2, wherein step (e) of calculating total radiation equivalent received at the lesion to be treated and the at least one radiation-sensitive structure during the treatment;

includes determining a time-increment vector summation of a parameter indicative of an eye-motion-based departure of the beam axis from the selected target lesion to be treated.

13. The method of claim 2, wherein step (e) of calculating total radiation equivalent received at the lesion to be treated and the at least one radiation-sensitive structure during the treatment includes modulating a pre-determined radiation distribution model representing predicted radiation dose distribution to be received by tissue of the patient from the collimated radiation beam in the absence of eye motion, the modulation based tracked eye motion during treatment, so as to determine a radiation dose distribution accounting for actual eye motion during treatment.

14. The method of claim 2, wherein step (e) of calculating total radiation equivalent received at the lesion to be treated and the at least one radiation-sensitive structure during the treatment;

further includes modulating a pre-determined radiation distribution model for a plurality of successive time increments during radiation treatment so as to determine a cumulative dose distribution during the course of treatment; and

wherein step (f) includes (i) comparing the cumulative dose received by a selected non-target anatomical structure with a pre-determined dose threshold quantity to determine if the threshold has been exceeded and (ii) in the event that the threshold has been exceeded, controlling the radiation beam or beam axis to reduce or eliminate further radiation dose to the selected non-target anatomical structure.

15. The method of claim 2, wherein step (e) of calculating total radiation equivalent received at the lesion to be treated and the at least one radiation-sensitive structure during the treatment;

further includes sequentially performing the modulating a pre-determined radiation distribution model for a plurality of successive time increments during radiation treatment so as to determine a cumulative dose distribution during the course of treatment; and

wherein step (f) includes (i) comparing the cumulative dose received by a selected anatomical target region with a pre-determined dose threshold quantity to determine if the threshold has been reached, and (ii) in the event that the threshold has been reached, controlling the radiation beam or beam axis to reduce or eliminate further radiation dose to the selected anatomical target region.

16. The method of claim 2, wherein the lesion is a macular lesion, wherein the radiation beam is a collimated X-ray beam, and step (c) includes determining the position of the patient'"'"'s macula in the treatment coordinate system from the known position of the eye and the coordinates of the macula in the external coordinate system, and determining a treatment axis in the external coordinate that intersects the patient macula.

17. The method of claim 16, wherein step (c) includes directing a collimated X-ray beam along each of at least two different known treatment axes in the treatment coordinate system at a region of the macular region of the patient'"'"'s retina.

18. The method of claim 17, wherein step (f) includes controlling the X-ray beam to deliver approximately equal doses of radiation at the patient'"'"'s macula along each of the different known treatment axes.

19. The method of claim 14, wherein step (f) includes turning off the beam being directed onto the patient'"'"'s eye when the position of the patient'"'"'s macula, as tracked in step (c), relative to the axis of the beam, is greater than a predetermined threshold distance.

20. The method of claim 14, wherein step (f) includes directing the beam against the patient'"'"'s macular region until the spatial accumulation of radiation mapped at the macula of the eye model reaches a predetermined dose level.

21. A system for treating a target area in a patient with an irradiation beam, comprising:

(a) a tracking assembly for tracking the position of a patient body region containing the target area and at least one radiation-sensitive area with respect to a known reference axis in an external coordinate system;

(b) a beam source for directing an irradiation beam at the patient target area along a known treatment axis in the external coordinate system; and

(c) a processor operatively connected to the tracking device and beam source, and operable to;

(i) determine, from the known position of body region in the external coordinate system, the coordinates of the target area to be treated and the coordinates of the at least one radiation-sensitive patient structure;

(ii) during a period when the irradiation beam is being directed along the treatment axis at the target area, and based on information received from the tracking device, track the positions of the target area to be treated and the at least one radiation-sensitive structure;

(iii) based on the known beam axis of the collimated beam in the external coordinate system, and the instantaneous positions of the target area to be treated and the at least one radiation-sensitive structure, calculate a total radiation equivalent received at the target area and at least one radiation-sensitive structure; and

(iv) based on the calculated radiation equivalents from step (iii), control the irradiation beam to insure that the at least one radiation-sensitive structure does not receive more than a preselected radiation equivalent during the treatment.

22. The system of claim 21, wherein

the tracking assembly includes (i) an imaging device for recording an image of a region of the patient'"'"'s body that contains natural or fiducial landmarks that define a geometric axis of the imaged region and (ii) an image detector operably connected to the imaging device for converting the recorded image to a digital image made up of known-coordinate pixels, and

the processor is operably connected to said detector for determining pixel coordinates of the geometric axis of the body region and step (ii) of the processor operation includes using the pixel coordinates of the geometric axis, relative to known pixel coordinates of the reference axis, to track the position of the patient body region relative to the reference axis.

23. The system of claim 21, for use in treating an ocular lesion, wherein the body region includes the patient eye, the target area includes the ocular lesion, the at least one radiation-sensitive structure includes the optic disc of the eye, the natural landmarks of the eye that define its geometric axis are the center of the limbus and a first corneal reflection, and the beam source produces a collimated x-ray beam.

24. The system of claim 21, for use in treating an ocular lesion, wherein the body region includes the patient eye, the target area includes the ocular lesion, the at least one radiation-sensitive structure includes the optic disc of the eye, and the natural landmarks of the eye that define its geometric axis are the center of the limbus and a first corneal reflection, which further includes

an eye guide adapted to be placed on the patient'"'"'s eye, centered thereon so that the geometric axis of the eye corresponds approximately to the axis of the eye guide, and a detector for determining the coordinates of the axis of the eye guide in the external coordinate system, and

the processor is operably connected to said detector for determining the coordinates of the eye guide axis and step (ii) of the processor operation includes using the coordinates of the eye-guide axis, relative to the known coordinates of the reference axis, to track the position of the patient'"'"'s eye relative to the reference axis.

25. The system of claim 21, wherein said tracking system is operable to capture a plurality of time-sequenced images of the body region and its landmarks during the treatment method, and said processor is operable to determine the coordinates of the body region geometric axis for each of the plurality of images, and in step (ii) to determine a time-dependent change in the coordinates of the target area to be treated and the at least one radiation-sensitive structure.

26. The system of claim 25, wherein the processor is operable to carry out, in step (iii) generating a map of total equivalent radiation covering the target area and the at least one radiation-sensitive area in the patient body region, and in step (iii), to determine from the total equivalent radiation map, the radiation equivalent received at any time during treatment by the target area and at least one radiation-sensitive area.

27. The system of claim 26, for use in treating an ocular lesion, wherein the body region includes the patient eye, the target area includes the ocular lesion, the at least one radiation-sensitive structure includes the optic disc of the eye, and the processor is operable, to carry out in step (iii) generating a map of total equivalent radiation covering the target area and the at least one radiation-sensitive area in the patient body region, and in step (iii), determining from the total equivalent radiation map, the radiation equivalent received at any time during treatment by ocular lesion and at least one radiation-sensitive area.

28. The system of claim 21, for use in treating an ocular lesion, wherein the body region includes the patient eye, the target area includes the ocular lesion, the at least one radiation-sensitive structure includes the optic disc of the eye, and said processor includes a model of the human eye by which the coordinates of the lesion to be treated and the at least one radiation-sensitive structure can be determined, when the patient'"'"'s eye is superimposed on the eye model.

29. The system of claim 28, wherein the eye model in the processor includes a virtual medium by which the attenuation of a radiation beam along a known path through the model can be determined, and the processor is operable to determine from the known intensity of the beam and the length of the radiation path through the virtual medium within the eye model, the amount of radiation that is received by the retina in the eye model.

30. The system of claim 21, for use in treating an ocular lesion, wherein the body region includes the patient eye, the target area includes the ocular lesion, the at least one radiation-sensitive structure includes the optic disc of the eye, wherein said processor is operable, by determining the position of the ocular lesion in the external coordinate system, to determine a treatment axis in the treatment coordinate system that intersects the lesion.

31. The system of claim 30, wherein said processor is operable to determine at least two different treatment axes in the treatment coordinate system, and to control the radiation beam to deliver approximately equal doses of radiation at the lesion along each of the different known axes.

32. The system of claim 31, wherein said processor is operable to turn off the beam being directed onto the patient'"'"'s eye when the distance between the position of the patient'"'"'s lesion, as determined in operation (d)(ii), and the intersection of the axis of the beam on the retina, is greater than a predetermined threshold distance.

33. The system of claim 21, wherein said processor is operable to direct the beam against the patient'"'"'s retinal region until the spatial accumulation of radiation mapped at the lesion of the eye model reaches a predetermined dose level.

34. Machine-readable code operable on an electronic computer, in monitoring the total radiation dose received at a target site during the course of treatment in which the target site is irradiated with a collimated x-radiation, to perform the steps comprising:

(a) defining, in an external coordinate system, coordinates for (i) a reference axis, (ii) a radiation-beam axis, and (iii) the target site which, when a body axis having a known relationship to the target site is aligned with the reference axis, places the radiation beam at the center of the target area,

(b) receiving from a body tracking device, ongoing information during the course of radiation treatment on the position of the body axis with respect to the reference axis,

(c) from the information received in step (b), and from the known intensity of the beam at the radiation beam, calculating the spatial distribution of radiation received in the region of the target site over the course of the treatment, and

(d) using the spatial distribution of radiation calculated in step (c) to monitor the total radiation dose at the target site over the course of the treatment.

35. The code of claim 34, wherein the treatment method is intended to treat an ocular lesion, the target area includes the ocular lesion, the body axis is the geometric axis of the eye, and information received from a body tracking device is in the form of ocular images from which the geometric axis of the eye can be determined.

36. The code of claim 34, wherein the treatment method is intended to treat an ocular lesion, the target area includes the ocular lesion, the body axis is the geometric axis of the eye, and the eye is irradiated during the course of treatment by an a collimated x-radiation beam directed at the target site along at least two different beam axes.

37. The code of claim 36, wherein an eye guide is centered on the eye such that an eye guide axis corresponds approximately to the geometric axis of the eye, and the information received from a body tracking device is in the form of information on the position of the eye guide.

38. The code of claim 34, which are further operable, in step (a) to determine the coordinates, in the external coordinate system, of the optic disc of the patient'"'"'s eye, based on a known spatial relationship between the lesion of the optic disc, and further operable in step (d) to use the spatial distribution of radiation calculated in step (c) to monitor the total radiation dose at the optic disc during the course of treatment.

39. Machine readable code operable on an electronic computer, in controlling the treatment of an ocular lesion by exposing the lesion to a collimated x-radiation beam, to perform the steps comprising:

(a) using information received from a eye-tracking system to determine a geometric axis of the eye in an external coordinate system,

(b) with the geometric axis of the eye placed in alignment with a reference axis, determining the coordinates of the lesion in an external coordinate system,

(c) from the coordinates of the ocular lesion determined in step (b), determining a beam axis that intersects the lesion with the patient eye in an defined position with respect to the reference axis, and

(d) controlling the position of an x-ray beam source to position the beam along the beam axis determined in step (d).

40. The code of claim 39, wherein the information received from the eye tracking system is an ocular image from which the geometric axis can be determined by determining the center of the sclera and a corneal reflection from the ocular image.

41. The code of claim 39, wherein an eye guide is centered on the eye such that an eye guide axis corresponds approximately to the geometric axis of the eye, and the information received from a body tracking device is in the form of information on the position of the eye guide.

42. The code of claim 39, wherein step (c) includes determining two or more beam axes that intersect the lesion with the patient eye in an defined position with respect to the reference axis.

43. The code of claim 42, wherein the computer is operably connected to a beam-source robotic device for position the beam along a selected beam axis, and step (d) includes acting on the robotic device to shift the beam axis during the course of treatment, from one beam axis to another determined in step (c).

44. Machine-readable code operable on an electronic computer in a treatment system for treating a lesion of a patient'"'"'s eye by directing a collimated radiation beam along a beam path to the lesion and including, operably connected to an eye-tracking device, the eye tracking device including an eye-contact member configured to engage the eye and having visible fiducials, and a camera configured to capture an electronic image of the eye, to execute instructions effective to perform the steps comprising:

(a) aligning the camera to a known position and/or orientation with respect to a treatment system coordinate system (system coordinates) wherein the camera is directed to the eye as engaged with the contact member;

(b) capturing an image of the eye as engaged with the contact member;

(c) identifying one or more pixels of the image representing the location of an axis of the contact member;

(d) determining from image data that the eye-guide axis is aligned to a known position and/or orientation with respect to the system coordinates;

(e) determining from image data the location of the center of limbus in the system coordinates; and

(f) determining a deviation of the location of the center of limbus to a known position and/or orientation of the eye-guide.

45. The code of claim 44, wherein the step (e) of determining the location of the center of limbus includes:

(i) determine a portion of the image including all or a portion of the exposed portion of the limbus boundary, and identifying the locations in the image corresponding to the limbus boundary image;

(ii) determining a mathematical representation of a “

best fit”

shape corresponding to the limbus boundary locations; and

(iii) calculate a center of “

best fit”

shape so as to determine the location of the limbus center.

46. The code of claim 44, further including the steps:

(g) registering the positions and/or orientations determined in steps (a-d) of one or both of contact member and limbus in a virtual computer eye model.

(h) calculating the position of an anatomical eye structure in the system coordinates based on the registered eye model

(i) controlling the at least one operational aspect of the collimated radiation beam in response to the calculated the position of the anatomical eye structure.

47. A computer-executed method for use in a radiation treatment device including a computer processor and a body-part motion tracking device operably connected to the computer processor, the tracking device including an body-contact member configured to engage the surface of a body part of the patient which includes a radiation treatment target, and a camera configured to capture an electronic image of the body part, the processor effective to execute instructions to perform the steps comprising:

(a) determining an initial position and orientation of the body part, based on;

(i) determining the alignment of the contact member as engaged with the body so as to have a known orientation relative to an anatomical axis of the body part and a known position relative to the contacted body surface; and

(ii) determining the alignment of the contact member as engaged with the body with the radiation treatment device so as to have a known initial position and orientation in a coordinate system of radiation treatment device;

(b) determining an initial position of the treatment target in the coordinate system of radiation treatment device, based on determining the relative position of the treatment target to the contact member;

(c) electronically capturing a plurality of time-sequenced images including the contact member while engaged with the body during the administration of radiation treatment;

(d) processing the images in the computer processor so as to determine one or both of an orientation and a position of the contact member in a coordinate system of the radiation treatment device at the time of capture of each image; and

(e) determining for each image, from the orientation and/or position of the contact member at the time of capture of the image, the change from the initial orientation and/or position of the contact member in the coordinate system of radiation treatment device; and

(f) determining for each image, the change from the initial position of the treatment target in the coordinate system of radiation treatment device, so as to track the sequential motion of the treatment target; and

(g) controlling at least one aspect of the radiation treatment based on the tracking of the sequential motion of the treatment target.

48. The computer-executed method of claim 47, wherein the body part is an eye, wherein the treatment target includes a portion of the retina, and wherein the contact member includes a lens element contacting the surface of the eye.

49. The computer-executed method of claim 47, wherein the body part includes a treatment target is selected from the group consisting essentially of a portion of the brain, spine, a breast, musculoskeletal tissue, vasculature, abdominal and gastrointestinal lesions.