Castellano I A, Dance D R, Evans P M
Physics Department, The Royal Marsden NHS Foundation Trust, Fulham Road, London SW3 6JJ, UK.
Radiat Prot Dosimetry. 2005;114(1-3):321-5. doi: 10.1093/rpd/nch521.
The use of geometrical phantoms for computed tomography (CT) dosimetry can incur errors in the calculation of effective dose due to the anatomically incorrect organ shapes and distributions, and unrepresentative body dimensions. A Monte Carlo program that makes use of an anatomically correct voxel phantom has been developed to calculate effective doses in CT and to compare with conventional dosimetric techniques. The code was validated against the latter by matching the phantom dimensions and simulating whole-body irradiation; agreement to within 6% was found. Effective doses were calculated for brain, lung, abdomen and pelvis CT scans for voxel phantom sizes corresponding to those of standard-sized adult, a teenager and 10% greater than those of standard-sized adult. Errors incurred by using the conventional techniques are minimised if the scan range is set by matching the fractions of radiosensitive organs that are irradiated directly. Under these circumstances, the conventional techniques will underestimate the dose to a 15 y old by up to 22% while the dose to a large subject is overestimated by up to 11%.
由于器官形状和分布在解剖学上不正确以及身体尺寸不具有代表性，用于计算机断层扫描（CT）剂量测定的几何体模会在有效剂量计算中产生误差。现已开发出一种利用解剖学上正确的体素体模的蒙特卡罗程序，以计算CT中的有效剂量并与传统剂量测定技术进行比较。通过匹配体模尺寸并模拟全身照射，该代码相对于传统技术进行了验证，发现两者的一致性在6%以内。针对与标准尺寸成人、青少年以及比标准尺寸成人尺寸大10%的体素体模尺寸，计算了脑部、肺部、腹部和骨盆CT扫描的有效剂量。如果通过匹配直接受照射的放射敏感器官的比例来设置扫描范围，使用传统技术产生的误差将降至最低。在这种情况下，传统技术会将15岁青少年的剂量低估多达22%，而将体型较大者的剂量高估多达11%。
