Effect of Voxel Size and Computation Method on Tc-99m MAA SPECT/CT-Based Dose Estimation for Y-90 Microsphere Therapy

• Published in: IEEE transactions on medical imaging Vol. 28; no. 11; pp. 1754 - 1758
• Main Authors: Pasciak, A.S., Erwin, W.D.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01-11-2009; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Biomedical applications of radiation; Cancer; Carcinoma, Hepatocellular - radiotherapy; Computation; Computer simulation; Deposition; Distributed computing; Dosimeters; Dosimetry; Humans; Image Processing, Computer-Assisted - methods; Image reconstruction; Imaging phantoms; Liver - diagnostic imaging; Liver - pathology; Liver neoplasms; Liver Neoplasms - radiotherapy; Mathematical models; Medical treatment; Metastasis; Microsphere therapy; Microspheres; Models, Theoretical; Monte Carlo dosimetry; Monte Carlo Method; Monte Carlo methods; Phantoms, Imaging; Physics; Radiometry; Reconstruction; Studies; Technetium Tc 99m Aggregated Albumin - therapeutic use; Tomography, Emission-Computed, Single-Photon - methods; Tomography, X-Ray Computed - methods; Yttrium; Yttrium Isotopes - therapeutic use
• ISSN: 0278-0062; 1558-254X
• DOI: 10.1109/TMI.2009.2022753

The use of selective internal radiation therapy for treatment of hepatocellular carcinoma and liver metastases using Y-90 labeled microspheres has become an effective and widely used treatment regimen. However, dosimetric evaluations of this treatment are still primitive as uniform distribution models based only on injected activity are often used. This investigation attempts to quantify the effectiveness of several sophisticated patient-specific techniques which utilize the source distribution of Tc-99m MAA simulation studies to perform voxelized dosimetric computations. Among these techniques are complete Monte-Carlo radiation transport computation in patient-specific CT-based voxel phantoms, local energy deposition in patient specific phantoms and kernel transport techniques in water. Each technique was evaluated using three different phantom voxel dimensions and SPECT reconstruction matrix sizes. Dose evaluation results using all methods were compared to the exact solution, obtained using fully 3-D Monte-Carlo simulations with source distribution based not on SPECT data, but on the injected activity and exact boundaries of the anthropomorphic phantom used in the study. The results of this study show that at large voxel sizes and using SPECT reconstructions with a small matrix size (64 times 64), Monte-Carlo and local deposition methods are nearly equivalent. However, using a large SPECT reconstruction matrix (256 times 256) the local deposition method is significantly more accurate than full 3-D Monte-Carlo transport, and with a negligible computational burden.