S-RT (a) and OD-RT (b). The grayscale is proportional to the detection probability of positron emission in various voxels for a given bin. In (a), the probability is calculated as the length of intersection between the LOR and the voxel (S-RT); in (b), as one minus the normalized perpendicular distance from the voxel to the LOR (OD-RT) [see Eq. (5)].
A 2D description of different multiray schemes and the subsampled bins for S-RT, the conventional Siddon approach (a), subsampled 4 parallel rays, S-RT-SS4 (b), and subsampled 16 parallel and crossed rays, S-RT-SS16 (c).
Modeling of the intrinsic detector response by sampling a linear function (solid line) and a Gaussian blurring (dashed line).
Tangential profiles through the sensitivity images obtained by using S-RT (hollow triangles), orthogonal distance-based ray-tracer for minimum thresholds of 0.5 (filled triangles), 0.1 (filled circles), and 0.01 (filled squares). The solid line is the theoretically calculated curve.
Iteration-dependence of CC for images reconstructed using a SRM based on the Siddon ray-tracer (hollow squares), OD-RT-01 (filled squares), and MC-SRM (small segment) methods for the CCP reconstructions.
Transverse views of the reconstructed images from HCP (left) and CCP (right) using a SRM obtained by using the S-RT (upper row), OD-RT-01 (middle row), and MC-SRM (lower row).
Contrast recovery obtained by means of the S-RT (hollow squares), the OD-RT-01 (filled squares), and MC-based SRM (small segment) for each axial cylinder of HCP (a) and CCP (b).
Tangential profiles through the sensitivity images obtained by using S-RT (hollow triangles), subsampled S-RT (hollow circles for 4 rays per detector, and hollow squares for 16 rays per detector), and OD-RT-01 (filled squares). The solid line is the theoretically calculated curve. Profiles for MC-SRM and S-RT-PSF resembled the theoretical profiles so are not shown.
Reconstructed images from experimental home-made micro-Derenzo phantom using, from left to right, S-RT, S-RT-SS4, S-RT-SS16 and S-RT-PSF (top), and OD-RT-01, OD-RT-01-G, and MC-based SRM (bottom).
Averaged spatial resolution and standard deviation.
Computation time on an Intel(R) Xeon(TM) CPU 3.20 GHz dual-processor and SRM size per subset (Mb).
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