CT扫描所致受检者器官剂量的体模实验研究

Organ dose evaluation for CT scans based on in-phantom measurements

目的了解不同部位X射线CT扫描所致受检者器官或组织的吸收剂量及其分布。方法实测体模中重要组织器官的CT值，并转换成线性吸收系数与人体正常值进行比较；在体模中布放光致辐射发光玻璃剂量计，分别模拟测量头部、胸部、腹部和盆腔CT扫描所致受检者主要器官或组织的吸收剂量。结果实验用仿真人体模具有良好的组织等效性。头部扫描吸收剂量最大的器官是大脑，胸部扫描吸收剂量较大的器官是甲状腺、乳腺、肺和食道，腹部扫描吸收剂量较大的器官是肝、胃、结肠和肺，单次盆腔扫描体所致骨表面和结肠的吸收剂量可达50mGy以上。结论X射线CT扫描所致受检者的器官剂量及其分布随扫描部位的不同而异。盆腔扫描时结肠、红骨髓、性腺和膀胱等主要器官的吸收剂量较大，应引起注意。

Objective To explore the organ doses and their distributions in different projections of CT scans. Methods The CT values were measured and the linear absorption coefficients were derived for the main organs of the anthropomorphic phantom to compare with the normal values of human beings. The radiophotoluminescent glass dosimeters were set into various tissues or organs of the phantom for mimic measurements of the organ doses undergoing the head, chest, abdomen and pelvis CT scans, respectively. Results The tissue equivalence of the phantom used in this study was good. The brain had the largest organ dose undergoing the head CT scan. The organ doses in thyroid, breast, lung and oesophagus were relatively large in performing the chest CT scan, while the liver, stomach, colon and lung had relatively large organ doses in abdomen CT practice. The doses in bone surface and colon exceeded by 50 mGy in a single pelvis CT scan. Conclusions The organ doses and their distributions largely vary with different projections of CT scans. The organ doses of colon, bone marrow, gonads and bladder are fairly large in performing pelvis CT scan, which should be paid attention in the practice.