Shell-constrained localization of vasculature
Methods of and systems for reconstructing a vascular tree shape from vascular segments imaged in a single source 2-D projection image are described. A structuring shape comprising spatial positions of reference anatomical elements is defined, such as vascular segments in the definition of a 3-D surface model corresponding to a surface defined by an anatomical structure such as a body organ (e.g., heart). The 3-D surface model is used to create a 3-D model of anatomical elements (e.g., additional vascular segments of a cardiac vasculature) imaged in a source 2-D projection image, by back-projection to the 3-D surface model. The 3-D surface model is optionally aligned by first aligning the source 2-D projection image to the structuring shape. In some embodiments, the source 2-D projection image is registered to the 3-D surface model through the structuring shape by the source image's initial use in defining the structuring shape.
1. A method of reconstructing a vascular tree shape from vascular segments imaged in a source 2-D projection image using anchoring segments and reference segments, the method comprising:
receiving, by computer circuitry, a structuring shape comprising 3-D spatial positions of reference vascular segments;
extending the spatial positions to define a computer-represented surface model representing an anatomical surface along which the reference vascular segments extend;
registering, by the computer circuitry, anchoring vascular segments shown in the source 2-D projection image to the spatial positions of the reference vascular segments on the surface model; and
assigning, by the computer circuitry, 3-D positions to associated vascular segments shown in the source 2-D projection image, based on their occupation of the surface in common with the anchoring vascular segments.
2. The method of claim 1 , wherein the surface model is spatially registered to the structuring shape.
3. The method of claim 1 , further comprising defining the structuring shape using a plurality of 2-D projection images.
4. The method of claim 3 , wherein the source 2-D projection image is one of the plurality of 2-D projection images, and the registering is performed as part of the defining.
5. The method of claim 3 , wherein the defining uses convex curves defined by the extents of vascular segments visible in each of the plurality of 2-D projection images to define the surface model.
6. The method of claim 3 , wherein the assigning uses back-projection of the imaged associated vascular segments in the source 2-D projection image to the surface model, based on the registering.
7. The method of claim 6 , wherein the defining reduces errors in the back-projection using locations of at least partially-located shadow boundaries of a body organ at least partially defining the surface, imaged in the plurality of 2-D projection images.
8. The method of claim 6 , wherein:
at least one of the associated vascular segments is back-projectable based on the registering to a plurality of alternative projection regions of the surface model; and
the assigning includes selecting a selected projection region of the surface model for the at least one of the associated vascular segments.
9. The method of claim 8 , wherein the selecting is based on the proximity of a portion of the at least one of the associated vascular segments to one or more of the anchoring vascular segments.
10. The method of claim 9 , wherein the proximity is measured by distance in 3-D space.
11. The method of claim 10 , wherein the proximity is measured by distance along surfaces of the surface model.
12. The method of claim 8 , wherein the selecting is based on identification of regions where the image of at least one of the associated vascular segments changes in at least one of intensity and direction where it curves around an edge of the surface, as seen from the view point of the source 2-D projection image.
13. The method of claim 8 , wherein the selecting is based on identification of regions where the images of at least two vascular segments in the source 2-D projection image intersect, and comprises assigning intersecting vascular segments to different projection regions of the surface model in the region of the intersection.
14. The method of claim 1 , wherein the defining comprises registering a reference shape to fit a portion of the surface in a region defined by the structuring shape.
15. The method of claim 14 , wherein the reference shape comprises a shape derived from anatomical atlas data and is used as a geometrical approximation of the surface.
16. The method of claim 14 , wherein the reference shape comprises a shape derived from 3-D imaging of a body organ imaged in the source 2-D projection image.
17. The method of claim 1 , wherein the assigning comprises reducing errors in the back-projection, using as registration references locations of at least partially-determined shadow boundaries of a body organ at least partially defining the surface and imaged in the source 2-D projection image.
18. The method of claim 1 , wherein the assigning comprises reducing errors in the back-projection, using as registration references locations of at least one vascular segment comprising changes in at least one of intensity and direction where the at least one vascular segment curves around an edge of the surface, as seen from the view point of the source 2-D projection image.
19. The method of claim 1 , wherein the vascular segments are vascular segments of a coronary vasculature.
20. The method of claim 1 , wherein the surface is a surface of a heart.
21. The method of claim 1 , further comprising determining a length of at least one of the associated vascular segments based on the distance for which the 3-D positions of the associated vascular segment extend along the surface model.
22. The method of claim 1 , further comprising calculating vascular width along one of the associated vascular segments from the appearance of the associated vascular segment shown in the source 2-D projection image.
23. A system of reconstructing a vascular tree shape from vascular segments imaged in a source 2-D projection image, the system comprising computer circuitry configured to:
receive a structuring shape comprising spatial positions of reference vascular segments;
define, based on the structuring shape, a surface model representing a surface along which the reference vascular segments extend;
register anchoring vascular segments shown in the source 2-D projection image to the structuring shape; and
assign 3-D positions to associated vascular segments shown in the source 2-D projection image, based on their occupation of the surface in common with the anchoring vascular segments.
24. The system of claim 23 , wherein the computer circuitry is configured to spatially register the surface model to the structuring shape.
25. The system of claim 23 , wherein the computer circuitry is configured to define the structuring shape using a plurality of 2-D projection images.
26. The system of claim 25 , wherein the source 2-D projection image is one of the plurality of 2-D projection images, and the computer circuitry is configured to perform the registering as part of the defining.
27. The system of claim 25 , wherein the computer circuitry is configured to assign using back-projection of the imaged associated vascular segments in the source 2-D projection image to the surface model based on the registration of the vascular segments shown in the source 2-D projection image to the structuring shape.
28. The system of claim 23 , wherein the computer circuitry is configured to calculate vascular width along one of the associated vascular segments using the appearance of the associated vascular segment shown in the source 2-D projection image.