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A. 몬테카를로 시뮬레이션 (ground truth), 기존의 voxel S-value 기법 (N=1), 본 연구에서 제안된 multiple voxel S-value 기법 (N=4, 6, 8, 10, 20)을 통하여 획득한 선량분포 맵.

B. 각 선량평가기법에 대한 선량 프로파일.

본 논문에서 제안한 방법이 기존의 기법에 비해 ground truth와 더 유사한 선량분포맵을 보이는 것을 확인할 수 있었습니다.

Abstract
Personalized dosimetry with high accuracy is becoming more important because of the growing interest in personalized medicine and targeted radionuclide therapy. Voxel-based dosimetry using dose point kernel or voxel S-value (VSV) convolution is available. However, these approaches do not consider the heterogeneity of the medium. Here, we propose a new method for whole-body voxel-based personalized dosimetry in heterogeneous media with nonuniform activity distributions-a method we refer to as the multiple VSV approach. Instead of using only a single VSV, as found in water, the method uses multiple numbers (N) of VSVs to cover media of various density ranges, as found in the whole body. Methods: The VSVs were precalculated using GATE Monte Carlo simulation and were convoluted with the time-integrated activity to generate density-specific dose maps. CT-based segmentation was performed to generate a binary mask image for each density region. The final dose map was acquired by the summation of N segmented density-specific dose maps. We tested several sets of VSVs with different densities: N = 1 (single water VSV), 4, 6, 8, 10, and 20. To validate the proposed method, phantom and patient studies were conducted and compared with the direct Monte Carlo approach, which was considered the ground truth. Finally, dosimetry on 10 patients was performed using the multiple VSV approach and compared with the single VSV and organ-based approaches. Errors at the voxel and organ levels were reported for 8 organs. Results: In the phantom and patient studies, the multiple VSV approach showed significant decreases in voxel-level errors, especially for the lung and bone regions. As the number of VSVs increased, voxel-level errors decreased, although some overestimations were observed at the lung boundaries. For the multiple VSVs (N = 8), we achieved a voxel-level error of 2.06%. In the dosimetry study, our proposed method showed greatly improved results compared with single VSV and organ-based dosimetry. Errors at the organ level were -6.71%, 2.17%, and 227.46% for single VSV, multiple VSV, and organ-based dosimetry, respectively. Conclusion: The multiple VSV approach for heterogeneous media with nonuniform activity distributions offers fast personalized dosimetry at the whole-body level, yielding results comparable to those of the direct Monte Carlo approach.

Author information

Lee MS1,2, Kim JH3, Paeng JC1, Kang KW1,4, Jeong JM1,2,4, Lee DS1, Lee JS5,2,4.
1
Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, Korea.
2
Interdisciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, Korea.
3
Center for Ionizing Radiation, Korea Research Institute of Standards and Sciences, Daejeon, Korea; and jaes@snu.ac.kr kimjh14@kriss.re.kr.
4
Department of Biomedical Sciences, College of Medicine, Seoul National University, Seoul, Korea.
5
Department of Nuclear Medicine, College of Medicine, Seoul National University, Seoul, Korea jaes@snu.ac.kr kimjh14@kriss.re.kr.

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