2014年宁夏地区放射诊疗机构辐射防护监测结果分析

目的 比较容积CT剂量指数(CTDI_vol)及体型特异性剂量估算(SSDE)在估算腹部CT扫描时患者所受辐射剂量的差异。方法 采用Philips 256螺旋CT扫描仪对180例患者进行上腹部CT增强扫描,在左肾静脉主干层面测量每位患者的左右径(LAT)、前后径(AP),计算有效直径(ED),同时记录每位被检者的CTDI_vol值及体模的扫描直径,计算SSDE。将患者按照体重指数(BMI)分为3组:A组,BMI<20 kg/m²;B组,BMI介于20～24.9 kg/m²之间;C组,BMI>24.9 kg/m²。分别比较180例被检者及不同体重指数组CTDI_vol与SSDE之间的差异。结果 180例被检者CTDI_vol和SSDE分别为(9.91±2.91)和(14.01±2.82)mGy,差异有统计学意义(t=-13.354,P=0.000)。A组CTDI_vol和SSDE分别为(7.96±1.83)和(12.83±2.52)mGy ( t=-8.417,P =0.000);B组分别为(9.28±1.76)和(13.62±2.18)mGy(t=-15.051,P=0.000);C组分别为(12.19±3.65)和(15.39±3.47)mGy(t=-4.535,P=0.000)。此外,3组SSDE分别较CTDI_vol平均增加了62.83%、 47.80%和28.40%,即CTDI_vol过低估算被检者的辐射剂量,且随着体重指数的增加,CTDI_vol与SSDE之间的差值越小。结论 SSDE能够反映特定体型的被检者进行腹部CT扫描时所接受的辐射剂量。

Analysis on monitoring results of radiation protection in radiation medical institutions of Ningxia region in 2014

Objective To compare the difference between volume computed tomography dose index (CTDI_vol) and size-specific dose estimates (SSDE) in evaluating the radiation dose of abdominal CT scan. Methods Abdominal CT scan were performed on 180 consecutive patients with a 256-slice MDCT. The anterior-posterior dimension (AP) and lateral dimension (LAT) of each patients were measured at the level of left renal vein, and the effective diameter (ED) and SSDE were calculated with recorded CTDI_vol Patients were categorized into 3 groups depend on BMI: Group A, BMI<20 kg/m²; Group B,20-24.9 kg/m²; Group C, BMI>24.9 kg/m². The differences between CTDI_vol and SSDE of 180 patients and three different BMI groups were compared respectively. Results There was a significant difference between CTDI_vol and SSDE of those 180 patients (t=-13.354, P=0.000), CTDI_vol and SSDE were (9.91±2.91) and (14.01±2.82) mGy respectively. For Group A, CTDI_vol and SSDE were (7.96±1.83) and (12.83±2.52) mGy respectively (t=-8.417, P=0.000); Group B, CTDI_vol and SSDE were (9.28±1.76) and (13.62±2.18) mGy respectively (t=-15.051, P=0.000); Group C, CTDI_vol and SSDE were (12.19±3.65) and (15.39±3.47) mGy respectively (t=-4.535, P=0.000). Besides, the mean percentage values of difference between CTDI_vol and SSDE for three group was 62.83%, 47.80%, 28.40%, respectively, which means CTDI_vol underestimates the radition dose compared to SSDE. With the BMI increasing, the values of difference between CTDI_vol and SSDE decreased. Conclusions SSDE can be used to estimate the radiation dose of abdominal CT scan for a given size person.