Fallahmohammadi Gholamreza, Nodeh Zeinab Kordzini, Mahdavi Mohammad
Department of Radiology, Faculty of Allied Medicine, Mazandaran University of Medical Sciences, Sari, Iran.
Department of Physics, University of Mazandaran, Babolsar, Iran.
J Med Signals Sens. 2024 Apr 18;14:11. doi: 10.4103/jmss.jmss_53_22. eCollection 2024.
Computed tomography (CT) imaging has a large portion in the dose of patients from radiological procedures; therefore, accurate calculation of radiation risk estimation in this modality is inevitable. In this study, a method for determining the patient-specific effective dose using the dose-length product (DLP) index in lung CT scan using Monte Carlo (MC) simulation is introduced.
EGSnrc/BEAMnrc MC code was used to simulate a CT scanner. The DOSxyznrc simulation code was used to simulate a specific voxelized phantom from the patient's lungs and irradiate it according to X-ray parameter of routing lung CT scan, and dose delivered to thorax organs was calculated. Three types of phantoms were simulated according to three different body habits (slim, standard, and fat patients) in two groups of men and women. A factor was used to convert the relative dose per particle in MC code to the absolute dose. The dose was calculated in all lung organs, and the effective dose was calculated for all three groups of patient body habits. DLP index and volume CT dose index (CTDIvol) were extracted from the patient's dose report in the CT scanner. The DLP to effective dose conversion factor (k-factor) for patients with different body habitus was calculated.
Lung radiation dose in slim, standard, and fat patients in men was 0.164, 0.103, and 0.078 mGy/mAs and in women was 0.164, 0.105, and 0.079 mGy/mAs, respectively. The k-factor in the group of slim patients, especially in women, was higher than in other groups.
CT scan dose indexes for slim patients are reported to be underestimated in studies. The dose report in CT scan systems should be modified in proportion to the patient's body habitus, to accurately estimate the radiation risk.
在放射检查中，计算机断层扫描（CT）成像占患者所受辐射剂量的很大一部分；因此，准确计算这种检查方式中的辐射风险评估是必不可少的。在本研究中，介绍了一种使用蒙特卡罗（MC）模拟，通过剂量长度乘积（DLP）指数来确定肺部CT扫描中患者特异性有效剂量的方法。
使用EGSnrc/BEAMnrc MC代码模拟CT扫描仪。使用DOSxyznrc模拟代码从患者肺部模拟特定的体素化体模，并根据常规肺部CT扫描的X射线参数对其进行照射，计算胸部器官的剂量。根据男性和女性两组中三种不同体型（瘦、标准和胖患者）模拟三种类型的体模。使用一个因子将MC代码中每个粒子的相对剂量转换为绝对剂量。计算所有肺部器官的剂量，并计算所有三组患者体型的有效剂量。从CT扫描仪中的患者剂量报告中提取DLP指数和容积CT剂量指数（CTDIvol）。计算不同体型患者的DLP至有效剂量转换因子（k因子）。
男性瘦、标准和胖患者的肺部辐射剂量分别为0.164、0.103和0.078 mGy/mAs，女性分别为0.164、0.105和0.079 mGy/mAs。瘦患者组，尤其是女性的k因子高于其他组。
研究报告称，瘦患者的CT扫描剂量指数被低估。CT扫描系统中的剂量报告应根据患者的体型进行调整，以准确估计辐射风险。
