Khazaee Moghadam Maryam, Kamali Asl Alireza, Geramifar Parham, Zaidi Habib
1 Department of Radiation Medicine Engineering, Shahid Beheshti University , Tehran, Iran .
2 Research Center for Nuclear Medicine, Shariati Hospital, Tehran University of Medical Sciences , Tehran, Iran .
Cancer Biother Radiopharm. 2016 Dec;31(10):367-379. doi: 10.1089/cbr.2016.2117.
The aim of this work is to evaluate the application of tissue-specific dose kernels instead of water dose kernels to improve the accuracy of patient-specific dosimetry by taking tissue heterogeneities into consideration.
Tissue-specific dose point kernels (DPKs) and dose voxel kernels (DVKs) for yttrium-90 (Y), lutetium-177 (Lu), and phosphorus-32 (P) are calculated using the Monte Carlo (MC) simulation code GATE (version 7). The calculated DPKs for bone, lung, adipose, breast, heart, intestine, kidney, liver, and spleen are compared with those of water. The dose distribution in normal and tumorous tissues in lung, liver, and bone of a Zubal phantom is calculated using tissue-specific DVKs instead of those of water in conventional methods. For a tumor defined in a heterogeneous region in the Zubal phantom, the absorbed dose is calculated using a proposed algorithm, taking tissue heterogeneity into account. The algorithm is validated against full MC simulations.
The simulation results indicate that the highest differences between water and other tissue DPKs occur in bone for Y (12.2% ± 0.6%), P (18.8% ± 1.3%), and Lu (16.9% ± 1.3%). The second highest discrepancy corresponds to the lung for Y (6.3% ± 0.2%), P (8.9% ± 0.4%), and Lu (7.7% ± 0.3%). For Y, the mean absorbed dose in tumorous and normal tissues is calculated using tissue-specific DVKs in lung, liver, and bone. The results are compared with doses calculated considering the Zubal phantom water equivalent and the relative differences are 4.50%, 0.73%, and 12.23%, respectively. For the tumor in the heterogeneous region of the Zubal phantom that includes lung, liver, and bone, the relative difference between mean calculated dose in tumorous and normal tissues based on the proposed algorithm and the values obtained from full MC dosimetry is 5.18%.
A novel technique is proposed considering tissue-specific dose kernels in the dose calculation algorithm. This algorithm potentially enables patient-specific dosimetry and improves estimation of the average absorbed dose of Y in a tumor located in lung, bone, and soft tissue interface by 6.98% compared with the conventional methods.
本研究旨在评估应用组织特异性剂量核代替水剂量核，通过考虑组织异质性来提高患者特异性剂量测定的准确性。
使用蒙特卡罗（MC）模拟代码GATE（版本7）计算钇-90（Y）、镥-177（Lu）和磷-32（P）的组织特异性剂量点核（DPK）和剂量体素核（DVK）。将计算得到的骨、肺、脂肪、乳腺、心脏、肠道、肾脏、肝脏和脾脏的DPK与水的DPK进行比较。使用组织特异性DVK而非传统方法中的水DVK来计算祖巴尔体模肺、肝脏和骨骼中正常组织和肿瘤组织的剂量分布。对于祖巴尔体模异质区域中定义的肿瘤，使用一种考虑组织异质性的算法计算吸收剂量。该算法通过全MC模拟进行验证。
模拟结果表明，水与其他组织DPK之间的最大差异出现在骨中，Y为（12.2%±0.6%），P为（18.8%±1.3%），Lu为（16.9%±1.3%）。第二大差异对应于肺中的Y（6.3%±0.2%）、P（8.9%±0.4%）和Lu（7.7%±0.3%）。对于Y，使用肺、肝脏和骨骼中的组织特异性DVK计算肿瘤组织和正常组织中的平均吸收剂量。将结果与考虑祖巴尔体模水等效性计算的剂量进行比较，相对差异分别为4.50%、0.73%和12.23%。对于祖巴尔体模中包括肺、肝脏和骨骼的异质区域中的肿瘤，基于所提出算法计算的肿瘤组织和正常组织中的平均剂量与全MC剂量测定获得的值之间的相对差异为5.18%。
在剂量计算算法中提出了一种考虑组织特异性剂量核的新技术。与传统方法相比，该算法有可能实现患者特异性剂量测定，并将位于肺、骨和软组织界面的肿瘤中Y的平均吸收剂量估计提高6.98%。
