(Sunday, 7/14/2019) 2:00 PM - 3:00 PM
Room: 301
Purpose: Convolution-based radionuclide dose calculations require energy deposition kernels of appropriate size and resolution. The purpose of this work was to demonstrate a method for efficient and accurate resampling of publicly available energy deposition kernels from the pre-tabulated radial coordinates to the Cartesian image domain.
Methods: Kernels from a previously described library (Graves et al., AAPM, 2018) were sampled onto a Cartesian matrix, consisting of voxels sized smaller than the image data by an integer multiplier (resample factor – rf). The energy contained within the center voxel in this high-resolution matrix was calculated by integrating the radial dose point kernel to a volume equal to the volume of the center voxel. To enforce the requirement that activity is uniformly distributed within a voxel in the image domain, this high-resolution kernel was convolved with a rectangular function equal to the size of an image voxel. The result of this convolution was down-sampled to the target image resolution, and scaled to conserve energy.
Results: Kernel generation (25x25x25 voxels; rf=8) was complete within ~3.2 seconds on a workstation grade CPU in MatLab. With a peak memory allocation of <200 MB, this process appears feasible on standard clinical workstations. Computation time did not depend significantly on voxel-size, and diminishing returns on spatial accuracy were observed for rf > 8. The resulting kernels compared favorably against literature kernels that were generated natively in a Cartesian geometry. For accurate incorporation of photon dose it was found desirable to generate a larger low-resolution photon-only kernel. This two-kernel approach accelerates the subsequent dose calculation, potentially increasing collapsed cone-type calculation speed.
Conclusion: It is feasible to rapidly and accurately compute a custom radionuclide dose kernel from publicly available radial energy deposition kernels. These methods expand calculation flexibility in voxelwise targeted radiopharmaceutical dosimetry.
Keywords
Nuclear Medicine, Radial Dose Function, Radiation Dosimetry
Taxonomy
IM/TH- Radiopharmaceutical therapy: Non I-131 MIRD/analytical dose estimation
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