剂量调制强度对成人CT辐射剂量及图像噪声的影响

Impact of dose modulation intensity on CT radiation dose and image noise in adults

目的观察不同剂量调制强度对成人头部、胸部、腹部CT辐射剂量及噪声的影响。方法采用固定毫安秒及基于CARE Dose4D技术的5种调制强度(Very Weak,Weak,Average,Strong和Very Strong)对仿真体模头部、胸部及腹部进行CT扫描。记录相应容积CT剂量指数(CTDIvol)并计算其改变量,测量各部位各层图像的标准偏差值(SD)作为图像噪声水平。分析固定毫安秒组及各调制强度组CTDIvol及其改变量,比较各组图像噪声差异。结果随调制强度增高,头部及腹部CTDIvol逐渐降低,相应CTDIvol改变量增大;胸部CTDIvol逐渐升高,相应CTDIvol改变量减小。不同调制强度下,头部及腹部图像SD值差异有统计学意义(F=9.73、45.78,P均<0.01),而胸部图像SD值差异无统计学意义(H=4.60,P=0.47)。结论随调制强度增高,仿真体模头部及腹部辐射剂量逐渐降低,图像噪声改善;胸部辐射剂量亦逐渐增加,但图像噪声无明显改变。

Objective To investigate the impact of dose modulation intensity on CT radiation dose and image noise in adults.Methods The head,chest and abdomen of phantom were scanned with fixed mAs and 5 modulation intensities(Very Weak,Weak,Average,Strong and Very Strong)based on CARE Dose4 D technology.The corresponding volume CT dose indexes(CTDIvol)were recorded,and variations were calculated.The standard deviation value(SD)of images in each layer of each position were measured and taken as the noise level.CTDIvol and changes in images of fixed mAs group and 5 modulation intensity groups were analyzed,and image noise of 6 groups were compared.Results With the increase of modulation intensity,CTDIvol of head and abdomen decreased gradually,and the corresponding change amount of CTDIvol increased.CTDIvol of chest gradually increased,but the corresponding change amount of CTDIvol decreased.There were statistical differences of SD values of head or abdomen images under different modulation intensities(F=9.73,45.78,both P<0.01),while SD values of chest images were not statistically different(H=4.60,P=0.47).Conclusion With the increase of modulation intensity,the radiation dose of head and abdomen of phantom decreased gradually,and image noise decreased,while the radiation dose of chest increased,but image noise had no significant change.