低龄小儿体部64排CT低剂量扫描的探讨

Low dose Scan of 64-detector Row CT on Pediatric Body

【目的】通过动物模拟相应体质量低龄小儿,初步摸索出CT扫描显示其正常解剖结构的最低管电流,再应用于临床,避免研究中对小儿造成过度辐射。【方法】用10～12kg比格犬和18～23kg幼猪模拟<16kg和16～25kg两组低龄小儿。先行预扫描,初步确定最低管电流值后进行实验。双盲法评价图像质量。以常规剂量扫描所获图像为基础片,从①图像伪影;②质地(噪声);③组织结构的显示;④扫描脏器与周围组织的对比四个方面评价。评价结果进行多次配对设计两样本的卡方检验。得到的数据经临床随机抽取的患儿各组30例行CT扫描以验证。【结果】最终获得低龄小儿64排CT低剂量扫描的最低管电流值:<16kg者胸部为10mA、上腹部40mA、中下腹部30mA;16～25kg胸部为20mA、上腹部50mA、中下腹部40mA。【结论】64排CT低剂量扫描可获得符合临床诊断需求的图像信息,因而能应用于临床。

[Objective] To avoid the super-radiation to children caused by duplicated scanning in our research, we figured out the lowest current that could manifest the normal structure by decreasing the current step by step in animal model and could be applied in clinic. [Methods] There were two groups of animals in this study, one group was dogs （10 ~ 12 kg） who modeled children weighted 〈 16 kg, the other group was pigs （18 ±23 kg） who modeled children weighted 16 ± 25 kg. Preliminary tests were done at first. Current was decreased 10 mA from routine 100 mA step by step until the lowest dose was found, and at the same time the image quality was evaluated by two radiologists. The dogs and pigs were scanned respectively by the routine dose, the lowest dose, the dose above and below 10 mA to the lowest dose. The dogs were totally scanned 20 times in every dose, and the pigs were totally scanned 18 times in every dose. All the dogs were performed contrast scan after the abdomen plain scan. The reconstruct image quality was evaluated by two radiologists randomly with double-blind method. The image quality of plain film which was scanned by routine dose was used as the standard. The image qualities of all the films were evaluated respectively from （1）artifact; （2）noise; （3）display of structure; （4）contrast of scanning organ and adjacent structure. All the results were analyzed by Chi-square test. All these data was tested randomly by CT low dose scanning in pediatric body（30 cases in each group）. [Results] 10 mA for chest MDCT, 20 mA for mediastina MDCT, 40 mA for upper abdomen MDCT, 30 mA for middle and lower abdomen MDCT were the lowest dose for the children MDCT examination who weighed 〈 15 kg; 20 mA for chest MDCT, 30 mA for mediastina MDCT, 50 mA for upper abdomen MDCT, 40 mA for middle and lower abdomen MDCT were the lowest dose for the children MDCT examination who weighed 16 - 25 kg. [Conclusion] Low dose scan of 64-detector row CT can be used in the examination of the pediatric body in the clinic.