Cleveland Clinic, Imaging Institute, Cleveland, Ohio, USA.
Siemens Medical Solutions USA Inc., Malvern, Pennsylvania, USA.
Med Phys. 2024 Jan;51(1):103-112. doi: 10.1002/mp.16836. Epub 2023 Nov 14.
Studies of tin spectral filtration have demonstrated potential in reducing radiation dose while maintaining image quality for unenhanced computed tomography (CT) scans. The extent of dose reduction, however, was commonly measured using the change in the scanner's reported CTDI . This method does not account for how tin filtration affects patient organ and effective dose.
To investigate the effect of tin filtration on patient organ and effective dose for CT Lung Cancer Screening (LCS) and CT Colonography (CTC).
A previously-developed Monte Carlo program was adapted to model a 96-row CT scanner (Somatom Force, Siemens Healthineers) with tin filtration capabilities at 100 kV (100Sn) and 150 kV (150Sn). The program was then validated using experimental CTDI measurements at all available kV (70-150 kV) and tin-filtered kV options (100Sn and 150Sn). After validation, the program simulated LCS scans of the chest and CTC scan of the abdomen-pelvis for a population of 53 computational patient models from the extended cardiac-torso family. Each scan was performed using three different spectra: 120 kV, 100Sn, and 150Sn. CTDI -normalized organ doses and DLP-normalized effective doses, commonly referred to as dose conversion factors, were compared between the different spectra.
For all LCS and CTC scans, CTDI -normalized organ doses and DLP-normalized effective doses increased with increasing beam hardness (120 kV, 100Sn, 150 Sn). For LCS, relative for 120 kV, conversion factors for 100Sn produced a median increase in effective dose of 9%, with organ dose increases of 8% to lung, 5% to breast, 15% to thyroid, and 3% to skin. Conversion factors for 150Sn produced a median increase in effective dose of 20%, with organ dose increases of 16%, 18%, 26%, and 12% to these same organs, respectively. For CTC, relative for 120 kV, conversion factors for 100Sn produced a median increase in effective dose of 12%, with organ dose increases of 9% to colon, 10% to liver, 11% to stomach, and 4% to skin. Conversion factors for 150Sn produced a median increase in effective dose of 21%, with organ dose increases of 16%, 17%, 19%, and 10% to these same organs, respectively.
Results show that dose conversion factors are greater when using tin filtration and should be considered when evaluating tin's potential for dose reduction.
锡光谱滤过的研究表明，在保持非增强 CT 扫描图像质量的同时，降低辐射剂量是有潜力的。然而，剂量的减少程度通常是通过扫描器报告的 CTDI 的变化来衡量的。这种方法没有考虑到锡滤过如何影响患者的器官和有效剂量。
研究锡滤过对 CT 肺癌筛查（LCS）和 CT 结肠成像（CTC）的患者器官和有效剂量的影响。
我们对一个以前开发的蒙特卡罗程序进行了改编，以模拟一个具有锡滤过功能的 96 排 CT 扫描仪（Somatom Force，西门子医疗），其管电压为 100kV（100Sn）和 150kV（150Sn）。该程序通过在所有可用的千伏（70-150kV）和锡滤过千伏选项（100Sn 和 150Sn）下的实验 CTDI 测量进行了验证。验证后，程序模拟了胸部的 LCS 扫描和腹部-骨盆的 CTC 扫描，使用三种不同的光谱：120kV、100Sn 和 150Sn。对来自扩展心脏-胸部家族的 53 个计算患者模型的每个扫描进行了比较，比较了不同光谱之间的 CTDI 归一化器官剂量和 DLP 归一化有效剂量，通常称为剂量转换因子。
对于所有的 LCS 和 CTC 扫描，CTDI 归一化器官剂量和 DLP 归一化有效剂量随着束硬度的增加而增加（120kV、100Sn、150Sn）。对于 LCS，与 120kV 相比，100Sn 的转换因子导致有效剂量中位数增加 9%，肺、乳房、甲状腺和皮肤的器官剂量分别增加 8%、5%、15%和 3%。与 150Sn 的转换因子导致有效剂量中位数增加 20%，相应的器官剂量增加分别为 16%、18%、26%和 12%。对于 CTC，与 120kV 相比，100Sn 的转换因子导致有效剂量中位数增加 12%，结肠、肝脏、胃和皮肤的器官剂量分别增加 9%、10%、11%和 4%。与 150Sn 的转换因子导致有效剂量中位数增加 21%，相应的器官剂量增加分别为 16%、17%、19%和 10%。
结果表明，使用锡滤过时，剂量转换因子更大，在评估锡降低剂量的潜力时应予以考虑。
