CT检查显示剂量与有效剂量的关系研究与应用评估分析

Relationship between dose and effective dose by CT examination and application analysis

目的探究建立CT扫描中设备的显示剂量与实测剂量的关系,评估不同CT显示剂量是否与实测剂量相符,为CT检测剂量快速估算方法提供有效依据。根据建立的显示剂量与实测剂量的关系,测量CT检查者所受CT及^(18)F-FDG(氟代脱氧葡萄糖)药物的辐射剂量,从而分析降低CT辐射有效剂量的可能性。方法选取两所医院不同品牌的16排和64排计算机断层扫描CT设备,使用CT剂量模体,采用笔形电离室测量不同扫描参数下头部、胸部扫描的CT剂量指数,同时记录设备显示剂量,然后计算测量剂量和显示剂量的比值。入选50例接受CT检查的患者,CT扫描的辐射有效剂量采用剂量长度乘积(DLP)值计算,^(18)F-FDG(氟代脱氧葡萄糖)辐射的有效剂量,根据ICRP推荐的方法进行计算,两剂量相加得出CT受检者所受辐射的总有效剂量。结果不同品牌的16排和64排计算机断层扫描CT设备头部扫描测量剂量是显示剂量的1.35～1.39倍和1.30～1.35倍,胸部扫描测量剂量是显示剂量的2.09～2.24倍和1.96～2.21倍,头部扫描测量剂量较胸部扫描测量剂量更接近显示剂量。结论同一品牌型号的CT设备在不同曝光条件下测量剂量与显示剂量比值一致性比较好,可以根据显示剂量估算CT检查中所受辐射剂量。CT扫描所致的有效剂量占总有效剂量一半以上,可以通过降低管电流和^(18)FI-FDG(氟代脱氧葡萄糖)有效降低CT受检者所受辐射有效剂量。

Objective To explore the relationship between the display dose of the equipment and the measured dose in CT scanning, and to evaluate whether the display dose of different CT is consistent with the measured dose, so as to provide an effective basis for the fast estimation method of CT detection dose. According to the relationship between the display dose and the measured dose, the radiation dose of CT and 18 FI-FDG (fluorodeoxyglucose) to CT examiners was measured, and the possibility of reducing the effective dose of CT radiation was analyzed. Methods CT dose indices of head and chest scans were measured with pen-shaped ionization chamber using 16-row and 64-row CT scanners of different brands in two hospitals. The display dose of the equipment was recorded at the same time. Then the ratio of the measured dose to the display dose was calculated. Fifty patients were enrolled in this study. The effective dose of CT scanning was calculated by the dose-length product (DLP) value and the effective dose of 18 FI-FDG (fluorodeoxyglucose) radiation. The total effective dose of CT patients was calculated by the method recommended by ICRP. Results The dose measured by head scan of 16-row and 64-row computed tomography CT equipments of different brands was 1.35~1.39 times and 1.30~1.35 times of the display dose. The dose measured by chest scan was 2.09~2.24 times and 1.96~2.21 times of the display dose. The dose measured by head scan was closer to the display dose than that measured by chest scan. Conclusion The ratio of the measured dose to the displayed dose of the same brand of CT equipment under different exposure conditions is in good agreement, and the radiation dose received in CT examination can be estimated according to the displayed dose. The effective dose caused by CT scanning accounts for more than half of the total effective dose. It can effectively reduce the effective dose of radiation to CT patients by reducing tube current and 18 FI-FDG (fluorodeoxyglucose).