Howard Stephanie A, Rosenthal Michael H, Qin Lei, Matalon Shanna A, Bernard Brandon D, Beard Clair J, Sweeney Christopher J
Dana Farber Cancer Institute.
Brigham and Women's Hospital.
Am J Clin Oncol. 2018 Oct;41(10):949-952. doi: 10.1097/COC.0000000000000399.
Upgrading computerized tomography (CT) scanners to iterative reconstruction techniques (IRT) decreases radiation dose. This reduction, combined with changes in surveillance protocols in clinical stage I testicular cancer (CS1TC) measurably decrease the lifetime attributable risk (LAR) of dying of radiation-associated cancer.
This IRB-approved study enrolled 24 CS1TC patients who had CT scans on the same Toshiba Aquilion 64 CT before and after IRT software installation. Dose-length product and CT dose index volume were recorded. A physicist calculated effective doses. Radiation doses were compared using the Wilcoxon signed rank test. Median effective dose per scan was multiplied by scan number based on 16 versus 7 scans in 5-year AS protocols to calculate estimated cumulative dose (ECD). LAR of dying of radiation-associated solid tumor was estimated using ECD for a single exposure at age 35 with the excess absolute risk transport model from the BEIR VII analysis of long-term atomic bomb survivors.
Median preupgrade and postupgrade effective doses were 12.5 and 7.7 mSv, respectively (P<0.0001). A linear regression model with a constrained zero intercept fit to the data found that IRT dose was estimated as 61% of filtered back projection dose (95% confidence interval, 0.56-0.66). The IRT upgrade reduced the LAR of the 16-scan protocol 35%. Combination of IRT upgrade and 7-scan protocol reduced surveillance LAR 72%.
Modern CT technology combined with reduced scanning strategies can markedly decrease lifetime radiation exposure, further lowering the already small potential mortality of imaging-associated cancers.
将计算机断层扫描（CT）扫描仪升级为迭代重建技术（IRT）可降低辐射剂量。这种剂量降低，再加上临床I期睾丸癌（CS1TC）监测方案的改变，可显著降低死于辐射相关癌症的终生归因风险（LAR）。
这项经机构审查委员会批准的研究纳入了24例CS1TC患者，这些患者在安装IRT软件前后，在同一台东芝Aquilion 64 CT上进行了CT扫描。记录剂量长度乘积和CT剂量指数容积。由一名物理学家计算有效剂量。使用Wilcoxon符号秩检验比较辐射剂量。根据5年AS方案中16次扫描与7次扫描，将每次扫描的中位有效剂量乘以扫描次数，以计算估计累积剂量（ECD）。使用ECD，通过BEIR VII对长期原子弹幸存者分析的超额绝对风险转移模型，估计35岁时单次暴露死于辐射相关实体瘤的LAR。
升级前和升级后的中位有效剂量分别为12.5 mSv和7.7 mSv（P<0.0001）。对数据拟合的具有受限零截距的线性回归模型发现，IRT剂量估计为滤波反投影剂量的61%（95%置信区间，0.56 - 0.66）。IRT升级使16次扫描方案的LAR降低了35%。IRT升级与7次扫描方案相结合使监测LAR降低了72%。
现代CT技术与减少扫描策略相结合，可显著降低终生辐射暴露，进一步降低成像相关癌症本就较小的潜在死亡率。
