Gating with anatomically varying durations
A method for reconstructing a radioactive emission image of an overall volume having first and second volumetric regions, each volumetric region having respectively independent dynamic characteristics. The method comprises the following steps: a) obtaining radioactive emissions from the overall volume, including the volumetric regions, b) reconstructing an initial radioactive emission image of the volumetric region according to the radioactive emissions, c) segmenting the initial radioactive emission image to delineate the first and second volumetric regions, and d) separately reconstructing the first and the second volumetric regions according to the respectively independent dynamic characteristics.
1. A method for reconstructing a radioactive emission image of an overall volume in a human body having first and second volumetric regions, each volumetric region having respectively independent dynamic characteristics, the method comprising:
a) obtaining a structural image of the overall volume in the human body, including said volumetric regions;
b) delineating said structural image of the overall volume including said first and second volumetric regions, to delineate said first and second volumetric regions-;
c) obtaining radioactive emissions from the overall volume in the human body, including said volumetric regions and including timing data, using a plurality of detectors each performing oscillatory motion;
d) reconstructing, using said radioactive emissions, a series of 3D images with time by:
separately reconstructing said first volumetric region and said second volumetric region
using said timing data, where different gating is employed for said first and said second volumetric regions, said different gating according to said respectively independent dynamic characteristics; and
using a model for at least one of said volumetric regions, said model describing a relationship, with time, for said at least one volumetric region, between radioactive emission intensities and one or more of: concentration of radioactive tracer in the blood, uptake time constant of the tissue and washout time constant of the tissue.
2. The method of claim, 1 wherein said separately reconstructing is an iterative process including using object implantation for refining reconstruction of at least one of the first and second volumetric regions.
3. The method of claim 2 , wherein at least one of the volumetric regions comprises at least a part of a body organ or other body portion; and
wherein said object implantation includes:
providing a model of only a part of said overall volume in the human body, said model comprising a general location and shape of, and expected number of photons emitted from, said body organ or said at least part of body portion;
replacing, at a general location in said initial radioactive emission image corresponding to said model general location, initial radioactive emission image voxels with said model general shape and initial radioactive emission image voxel photon counts, based on said expected number of photons from said model, where said replacing is one or more times during said iterative process, each time for providing a better starting point for performing next iteration of said reconstruction of at least one of the first and second volumetric regions.
4. The method of claim 1 , wherein said obtaining radioactive emissions further includes obtaining timing data by a method selected from the group consisting of time stamping, time binning, and a combination thereof.
5. The method of claim 4 , wherein said separately reconstructing includes separately reconstructing said first and second volumetric regions according to said respectively independent dynamic characteristics of said timing data.
6. The method of claim 4 ,
wherein said timing data comprises first timing data for said first volumetric region and second timing data for said second volumetric region;
wherein said separately reconstructing comprises: reconstructing said first volumetric region using said first timing data; and reconstructing said second volumetric region using said second timing data.
7. The method of claim 6 , including:
obtaining a second set of radioactive emissions from the overall volume in the human body, including said volumetric regions, after the reconstructing the initial radioactive emission image, the second set including timing data,
wherein said separately reconstructing includes separately reconstructing said first and second volumetric regions according to said respectively independent dynamic characteristics, from said second set.
8. The method of claim 7 , wherein said first and second volumetric regions have higher dynamic activity than surrounding tissue;
wherein obtaining a second set of radioactive emissions, further includes independently directing detecting resources to said first and second volumetric regions, so as to concentrate detecting resources on the volumetric region of greater dynamic activity.
9. The method of claim 1 , wherein separately reconstructing further includes independently carrying reconstruction of said first and second volumetric regions, to different levels of accuracy, so as to concentrate reconstruction resources on a volumetric region of greater dynamic activity.
10. The method of claim 1 , wherein said first volumetric region confines a human heart.
11. The method of claim 1 , wherein said volumetric regions comprises independent sub-volumetric regions, wherein during said separately reconstructing, each one of said independent sub-volumetric regions is reconstructed separately.
12. The method of claim 1 , wherein said radioactive emissions are obtained using a single photon emission computed tomography (SPECT) camera.
13. The method of claim 12 , wherein said SPECT camera comprises a plurality of detecting units.
14. The method of claim 13 , wherein time binning is independently enabled to each detecting unit from said plurality of detecting units.
15. The method of claim 13 , wherein time binning is independently enabled to one or more sub-groups of said plurality of detecting units from said plurality of detecting units.
16. The method of claim 13 , wherein each said detecting unit includes:
a single-pixel detector, for detecting radioactive emissions; and
a dedicated collimator, attached to the single-pixel detector, at the proximal end thereof, for defining a solid collection angle δ for the detecting unit.
17. The method of claim 1 , wherein said separately reconstructing comprises reconstructing an initial radioactive emission image which is represented by a system of voxels.
18. The method of claim 17 , further comprising:
constructing an anatomical construction of voxels, for said system of voxels, in which voxel boundaries are aligned with boundaries of structural objects of said first volumetric region, based on said structural image,
said separately reconstructing being based on said anatomical construction of voxels.
19. The method of claim 18 , wherein the anatomical construction of voxels includes voxels of varying volumetric regions, depending on their anatomic position and relevance.
20. The method of claim 1 , wherein said structural image is provided by a source, selected from the group consisting of 2-D ultrasound, 3-D ultrasound, planner x-rays, CT x-rays, MRI, and an anatomical atlas.
21. The method of claim 1 , wherein said obtaining radioactive emissions comprises time binning said radioactive emissions using different time bin lengths for said first and said second volumetric regions.
22. The method of claim 1 , wherein said obtaining a structural image of the overall volume includes obtaining the structural image of the overall volume, including the separate volumetric regions, wherein the first volumetric region has a first amount of dynamic activity and the second volumetric region has a second amount of dynamic activity, and wherein the first volumetric region moves in the overall volume relative to the second volumetric region.
23. The method of claim 1 comprising, after said separately reconstructing, repeating said separately reconstructing until a desired quality of reconstruction of the overall volume has been reached.
24. The method of claim 23 , wherein it is determined that the desired quality of reconstructions of the overall volume has been reached when a number of gated voxels with activity is above a predefined threshold.
25. The method of claim 1 , wherein said separately reconstructing includes separately reconstructing said first volumetric region and reconstructing said second volumetric region according to said respectively independent dynamic characteristics of said respective first and second volumetric regions;
wherein said method further includes combining said first and second reconstructed volumetric regions into a single image.
26. The method of claim 1 , wherein said separately reconstructing comprises using at least two different said models for different portions of said at least one of said volumetric regions.
27. The method of claim 1 , wherein said structural image is a first reconstruction based on said radioactive emissions of said overall volume.
28. The method of claim 1 , wherein said model describes a relationship, between radioactive emission intensities and concentration of radioactive tracer in the blood, uptake time constant of the tissue, and washout time constant of the tissue.
29. The method of claim 1 , wherein said using said model comprises generating, for said at least one volumetric region, a three dimensional relationship with time between said radioactive emission intensities and said one or more of: concentration of radioactive tracer in the blood, uptake time constant of the tissue and washout time constant of the tissue.