Methods, systems, and computer program products for processing three-dimensional image data to render an image from a viewpoint within or beyond an occluding region of the image data

• US 20090103793A1
• Filed: 03/15/2006
• Published: 04/23/2009
• Est. Priority Date: 03/15/2005
• Status: Active Grant

• Current Assignee: University of North Carolina At Chapel Hill (University of North Carolina System)
• Original Assignee: University of North Carolina At Chapel Hill (University of North Carolina System)
• Inventors: Clarke, John, Taylor ll, Russell M., Borland, David
• Granted Patent: US 8,150,111 B2
• Time in Patent Office: Days
• US Class Current: 382/131
• CPC Class Codes: G06T 15/08 Volume rendering

Abstract

Methods, systems, and computer program products for processing three-dimensional image data to render an image from a viewpoint within or beyond an occluding region of the image data are disclosed. According to one method, a set of three-dimensional image data is accessed. The image data includes image data for a surface of interest and image data for a region occluding the surface of interest from a desired viewpoint. The viewpoint may be within or beyond the occluding region. A plurality of rays is cast from the viewpoint to the surface. Along each ray, an occlusion determination is made independent from a volume rendering transfer function definition to render voxels within the occluding region as transparent or partially transparent. The volume rendering transfer function is applied along a portion of each ray outside of the occluding region to render voxels defining surface of interest as visible. The voxels that define the surface are displayed as visible. The voxels within the occluding region are shown in a transparent or partially transparent manner.

Claims

1. A method for processing three-dimensional image data to render an image from a viewpoint within or beyond an occluding region of the image data, the method comprising:

(a) receiving a set of three-dimensional image data including image data for a surface of interest and image data for a region occluding the surface of interest from a desired viewpoint;

(b) casting a plurality of rays from the viewpoint to the surface of interest;

(c) along each ray, making an occlusion determination independently from a volume rendering transfer function definition to render voxels within the occluding region as transparent or partially transparent;

(d) applying the volume rendering transfer function along a portion of each ray outside of the occluding region to render voxels defining the surface of interest as visible; and

(e) displaying the voxels that define the surface of interest from the viewpoint, wherein the voxels within the occluding region are shown in a transparent or partially transparent manner and wherein the voxels that define the surface of interest are shown as visible.

2. The method of claim 1 wherein accessing a set of three-dimensional image data includes accessing a set of magnetic resonance imaging (MRI) image data.

3. The method of claim 1 wherein accessing a set of three-dimensional image data includes accessing a set of computerized tomography (CT) image data.

4. The method of claim 1 wherein accessing a set of three-dimensional image data includes accessing a set of magnetic resonance imaging (MRI) and a set of computerized tomography (CT) image data of the same surface.

5. The method of claim 4 wherein making the occlusion determination includes analyzing vexel intensities along each ray in the CT image data to determine where to begin rendering the surface of interest along each ray in the MRI image data.

6. The method of claim 4 wherein making the occlusion determination includes analyzing voxel intensities along each ray in the MR image data to determine where to begin rendering the surface along each ray in the CT image data.

7. The method of claim 1 wherein accessing a set of three-dimensional image data includes accessing first and second sets of magnetic resonance imaging (MRI) images, wherein making the occlusion determination includes making the occlusion determination in the first set of MRI images, and wherein applying the transfer function includes applying the transfer function to the second set of MRI images.

8. The method of claim 1 wherein accessing a set of three-dimensional image data includes accessing first and second sets of computerized tomography (CT) images, wherein making the occlusion determination includes making the occlusion determination in the first set of CT images, and wherein applying the transfer function includes applying the transfer function to the second set of CT images.

9. The method of claim 1 wherein accessing a set of three-dimensional image data includes accessing a set of filtered image data and a set of unfiltered image data of the same surface and wherein making an occlusion determination includes analyzing voxel intensities along each ray in the filtered image data to identify locations for rendering the surface of interest along each ray in the unfiltered image data.

10. The method of claim 1 wherein making an occlusion determination includes defining a fixed voxel intensity threshold that distinguishes between voxels within the occluding region and voxels that define the surface and using the threshold to determine a location along each ray to begin accumulating voxel color and intensity for the surface of interest.

11. The method of claim 1 wherein making an occlusion determination includes calculating a voxel intensity gradient along each ray, distinguishing between voxels of the occluding object and voxels of the surface of interest based on a rate of change in voxel intensity along each ray, and identifying a location to begin rendering the voxels of the surface of interest in response to the rate of change reaching or exceeding a threshold value.

12. The method of claim 1 wherein making an occlusion determination includes:

(a) accumulating voxel color and intensity along a ray;

(b) identifying a voxel along the ray having an intensity that meets or exceeds a threshold value; and

(c) in response to identifying the voxel having an intensity that meets or exceeds the threshold value, setting intensities and colors for voxels along the ray prior to reaching the voxel having the intensity that meets or exceeds the threshold value as transparent or partially transparent.

13. The method of claim 1 wherein applying a transfer function includes setting the transfer function to begin collecting voxel intensity and color upon reaching an nth surface of a plurality of surfaces of the same or similar voxel intensities, n being an integer.

14. The method of claim 13 wherein the nth surface comprises a last surface of the plurality of surfaces.

15. The method of claim 13 wherein the nth surface comprises a surface between a first and last surface of the plurality of surfaces.

16. The method of claim 1 wherein applying a transfer function includes applying a first transfer function to render the voxels of the surface of interest as visible and applying a second transfer function different from the first transfer function to render the voxels of the occluding region as transparent or partially transparent.

17. The method of claim 1 wherein the three-dimensional image data comprises medical image data.

18. The method of claim 1 wherein the three-dimensional image data comprises non-medical image data.

19. The method of claim 1 wherein the surface of interest comprises a surface having a predetermined property and being surrounded by another surface and wherein displaying the surface of interest as visible includes displaying the surrounding surface as transparent or partially transparent and displaying the surface of interest in a color different from colors of surfaces that do not have the property.

20. The method of claim 1 wherein rendering the surface of interest as visible includes rendering a region that includes the surface of interest as visible.

21. The method of claim 1 wherein the viewpoint is within the occluding region.

22. The method of claim 1 wherein the viewpoint is beyond the occluding region.

23. A system for processing three-dimensional image data to render an image from a viewpoint within or beyond an occluding region of the image data, the method comprising:

(a) a surface rendering module for accessing a set of three-dimensional image data including image data for a surface of interest and image data for a region occluding the surface of interest from a desired viewpoint and for;

(i) casting a plurality of rays from the viewpoint to the surface of interest;

(ii) along each ray, making an occlusion determination independently from a volume rendering transfer function definition to render voxels within the occluding region as transparent or partially transparent; and

(iii) applying the volume rendering transfer function along a portion of each ray outside of the occluding region to render voxels defining the surface of interest as visible; and

(b) a display module for displaying the voxels that define the surface of interest from the viewpoint as visible and for displaying the voxels within the occluding region as transparent or partially transparent.

24. The system of claim 23 wherein the surface rendering module is adapted to access a set of magnetic resonance imaging (MRI) image data.

25. The system of claim 23 wherein the surface rendering module is adapted to access a set of computerized tomography (CT) image data.

26. The system of claim 23 wherein the surface rendering module is adapted to access a set of magnetic resonance imaging (MRI) and a set of computerized tomography (CT) image data of the same surface.

27. The system of claim 26 wherein the surface rendering module is adapted to analyze voxel intensities along rays cast from the viewpoint to the surface in the CT image data to determine where to begin rendering the surface of interest along each ray in the MRI image data.

28. The system of claim 26 wherein the surface rendering module is adapted to analyze voxel intensities along rays case form the viewpoint in the MRI image data to determine where to begin rendering the surface along each ray in the CT image data.

29. The system of claim 23 wherein the surface rendering module is adapted to access first and second sets of magnetic resonance imaging (MRI) images, to make the occlusion determination using the first set of MRI images, and to apply the transfer function to the second set of MRI images.

30. The system of claim 23 wherein the surface rendering module is adapted to access first and second sets of computerized tomography (CT) images, to make the occlusion determination using the first set of CT images, and to apply the transfer function to the second set of CT images.

31. The system of claim 23 wherein the surface rendering module is adapted to access a set of filtered image data and a set of unfiltered image data of the same surface, to identify a location of the surface of interest along each ray using the filtered image data, and to render the surface in the unfiltered image data based on the locations identified using the filtered image data.

32. The system of claim 23 wherein surface rendering module is adapted to define a fixed voxel intensity threshold that distinguishes between voxels within the occluding region and voxels that define the surface and to use the threshold to determine a location along each ray to begin accumulating voxel color and intensity for the surface of interest.

33. The system of claim 23 wherein the surface rendering module is adapted to calculate a voxel intensity gradient along each ray, to distinguish between voxels of the occluding region and voxels of the surface of interest based on a rate of change in voxel intensity along each ray, and to begin rendering the voxels of the surface of interest when the rate of change reaches or exceeds a threshold value.

34. The system of claim 23 wherein the surface rendering module is adapted to:

(a) accumulate voxel color and intensity along a ray;

(b) identify a voxel along the ray having an intensity that meets or exceeds a threshold value;

(c) in response to identifying the voxel having an intensity that meets or exceeds the threshold value, set intensities and colors for voxels along the ray prior to reaching the voxel having the intensity that meets or exceeds the threshold value as transparent or partially transparent; and

(d) accumulate intensity and color for voxels on a far side of the voxel having the intensity that meets or exceeds the threshold.

35. The system of claim 23 wherein the surface rendering module is adapted to set the transfer function to begin collecting voxel intensity and color upon reaching an nth surface of a plurality of surfaces of the same or similar voxel intensities, n being an integer.

36. The system of claim 23 wherein the surface rendering module is adapted to apply a first transfer function to render the voxels of the surface of interest as visible and to apply a second transfer function different from the first transfer function to render the voxels of the occluding region as transparent or semi-transparent.

37. The system of claim 23 wherein the three-dimensional image data comprises medical image data.

38. The system of claim 23 wherein the three-dimensional image data comprises non-medical image data.

39. The system of claim 23 wherein the surface of interest comprises a surface having a predetermined property and being surrounded by another surface and wherein the display module is adapted to display the surrounding surface as transparent or partially transparent and to display the surface of interest in a color different from colors of surfaces that do not have the property.

40. The system of claim 23 wherein rendering the surface of interest as visible includes rendering a region that includes the surface of interest as visible.

41. The system of claim 23 wherein the viewpoint is within the occluding region.

42. The system of claim 23 wherein the viewpoint is beyond the occluding region.

43. A computer program product comprising computer-executable instructions embodied in a computer-readable medium for performing steps comprising:

(a) receiving a set of three-dimensional image data including image data for a surface of interest and image data for a region occluding the surface of interest from a desired viewpoint;

(b) casting a plurality of rays from the viewpoint to the surface of interest;

(c) along each ray, making an occlusion determination independently from a volume rendering transfer function definition to render voxels within the occluding region as transparent or partially transparent;

(d) applying the volume rendering transfer function along a portion of each ray outside of the occluding region to render voxels defining the surface of interest as visible; and

(e) displaying the voxels that define the surface of interest from the viewpoint, wherein the voxels within the occluding region are shown in a transparent or partially transparent manner and wherein the voxels that define the surface of interest are shown as visible.