서울의대 / 김건민, 이재성*
Abstract
Purpose: Voxel-based dosimetry is potentially accurate than organ-based dosimetry because it considers the anatomical variations in each individual and the heterogeneous radioactivity distribution in each organ. Here, voxel-based dosimetry for 177 Lu-DOTATATE therapy was performed using single and multiple voxel S-value (VSV) methods and compared with Monte Carlo simulations. To verify these methods, we adopted sequential 177 Lu-DOTATATE single-photon emission computed tomography and X-ray computed tomography (SPECT/CT) dataset acquired from Sunway Medical Centre using the major vendor's SPECT/CT scanner (Siemens Symbia Intevo).
Methods: The administered activity of 177 Lu-DOTATATE was 7.99 ± 0.36 GBq. SPECT/CT images were acquired 0.5, 4, 24, and 48 h after injection in Sunway Medical Centre. For the multiple VSV method, VSV kernels of 177 Lu in media with various densities were generated by Geant4 Application for Emission Tomography (GATE) simulation first. The second step involved the convolution of the time-integrated activity map with each kernel to produce medium-specific dose maps. Third, each medium-specific dose map was masked using binary medium masks, which were generated from CT-based density maps. Finally, all masked dose maps were summed to generate the final dose map. VSV methods with four different VSV sets (1, 4, 10, and 20 VSVs) were compared. Voxel-wise density correction for the single VSV method was also performed. The absorbed doses in the kidneys, bone marrow, and tumors were analyzed, and the relative errors between the VSV and Monte Carlo simulation approaches were estimated. Organ-based dosimetry using Organ Level INternal Dose Assessment/EXponential Modeling (OLINDA/EXM) was also compared.
Results: The accuracy of the multiple VSV approach increased with the number of dose kernels. The average dose estimation errors of a single VSV with density correction and 20 VSVs were less than 6% in most cases, although organ-based dosimetry using OLINDA/EXM yielded an error of up to 123%. The advantages of the single VSV method with density correction and the 20 VSVs over organ-based dosimetry were most evident in bone marrow and bone-metastatic tumors with heterogeneous medium properties.
Conclusion: The single VSV method with density correction and multiple VSV method with 20 dose kernels enabled fast and accurate radiation dose estimation. Accordingly, voxel-based dosimetry methods can be useful for managing administration activity and for investigating tumor dose responses to further increase the therapeutic efficacy of 177 Lu-DOTATATE.
Affiliations
Keon Min Kim 1 2 , Min Sun Lee 3 , Min Seok Suh 4 5 , Haniff Shazwan Muhd Safwan Selvam 6 , Teik Hin Tan 6 , Gi Jeong Cheon 4 5 , Keon Wook Kang 4 5 7 , Jae Sung Lee 1 2 4 5
1 Interdisciplinary Program in Bioengineering, Seoul National University Graduate School, Seoul, Korea.
2 Integrated Major in Innovative Medical Science, Seoul National University Graduate School, Seoul, Korea.
3 Korea Atomic Energy Research Institute, Daejeon, Korea.
4 Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea.
5 Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Korea.
6 Nuclear Medicine Centre, Sunway Medical Centre, Selangor, Malaysia.
7 Bio-MAX Institute, Seoul National University, Seoul, Korea.
편집위원
177Lu- DOTATATE 방사선핵종 치료 환자를 대상으로 voxel 기반 dosimetry를 SPECT/CT를 이용하여 구하는 임상연구임. 해당 연구의 결과는 voxel 기반 dosimetry기법이 방사선량을 구하기 적당한 방벙임을 확인함. 임상적 의미가 확인되며, 다양한 방사성핵종치료에 이용가능할 것으로 생각됨.
2022-05-04 16:36:27