1200例肿瘤患者CT检查辐射剂量的调查研究

Survey of CT radiation dose to 1200 cancer patients

目的 调查当前肿瘤患者CT检查的辐射剂量,与国家新标准给出的诊断学参考水平进行对比分析.方法 应用标准模体测量5台不同类型CT在典型扫描条件下的加权CT剂量指数（CTDIw）,并回顾统计900例成年肿瘤患者及300例儿童肿瘤患者的CT检查剂量参数,包括平均容积CT剂量指数（CTDIvol）、剂量长度乘积（DLP）、75％分位DLP值,估算有效剂量.结果 成人头部的CTDIw测量值与参考值处于同一水平,腰椎及腹部的CTDIw测量值小于参考值.对于成年患者,脑血管增强扫描的DLP最高,而腹部增强扫描的有效剂量最大.对于儿童患者,不同年龄段的DLP无明显差别.结论 CTDI虽然可以反映CT断层平面的剂量状况,但不能反映患者检查的总剂量水平.对于需要多次重复扫描的检查,因为有可能造成患者个体的高辐射剂量,国家标准应给出以DLP为单位的诊断学参考水平作为对照.应用个体化的扫描方案是降低儿童剂量的有效手段.

Objective To survey the CT radiation dose to cancer patients, and to compare it with diag- nostic reference level （DRL） provided by newly issued national standard. Methods Computed tomography dose index weighted （ CTD[w ） of 5 CT equipments was measured by the standard phantom with typical scanning protocol and radiation dose parameters including average computed tomography dose index volume （CTDIvol ） , dose length product （DLP）, 75% DLP with 900 adult and 300 pediatric cancer patients were collected. According to age stage, effective dose was estimated. Results The measured CTDIw for head scanning was on the same level with DRL, while lumbar vertebra and abdominal scanning were lower than DRL. To adults, DLP of cerebrovascular enhanced scanning and effective dose of abdominal enhanced scanning were the highest. To pediatric patients, there was no significant difference in DLP among different ages. Conclusion CTDI only reflects the dose contribution from a slice, but do not reflect the cumulative dose. For the patients need multi- phase scanning, because they may be exposed to high dose, national standard should provide DLP value as the diagnostic reference level. Using individual scanning protocol is an effective method to reduce radiation dose of pediatric patient.