头部不同头围受检者CT低剂量扫描参数优化研究

摘要

Objective To explore the parameters optimization method of low-dose CT scan in head examination with different thickness, so as to reduce the radiation dose. Methods According to the thickness of head, 270 cases are devided into I, II, III three groups. Each group is randomly and equably divided into three sub-groups according to the scanning regions. After scanning each subgroup patient with regular dose 280 mA, and getting their agreements, the certain level of sub-group is scanned by dosages 240 mA, 200 mA, 160 mA, 120 mA respectively, meanwhile, SD values are measured in the image. Three physicians read slices by double blind method and S-point scoring system to calculate image numbers of 5 levels in different thickness and dosage after colligation score result, count and compare image quality score among different groups, evaluate the otherness of SD values and CTDI. Results Image numbers of every level in three groups all have significant difference(P< 0.001). Group I, compared with other groups, 120 mA, whose images show low quality, has significant difference(P < 0.001). Group II, image quality of 120 mA, 160 mA is worse than other groups(P < 0.001). Group III, images of 120 mA,160 mA and 200 mA all have low quality. Poor quality images, whose scoring average is lower than 3, SD values is higher than 4.S, could not meet diagnosis requirements. Compared with regular dose 280 mA, the difference among them has statistical significance(P < 0.05). Conclusion Group 1, 160 mA is the best scanning parameter, which could make sure image quality and the lowest dose. Its dose reduces by 42.3% than regular dose 280 mA; Group II, 200 mA is the best, the dose reduces by 27.9%; Group III, 240 mA is the best, the dose reduces by 14.3%; SD values lower than or equal to 4.5 is suitable.%目的 探讨不同头围受检者CT低剂量扫描参数的优化方法,以降低辐射剂量.方法 对270例行颅脑扫描的患者按头围大小不同均分成Ⅰ、Ⅱ、Ⅲ3个组,每组再按扫描层面不同随机均分为3个亚组,每个亚组患者行常规280mA扫描后,经患者同意,分别以240mA、200mA、160mA、120mA对每个亚组的特定层面进行扫描,同时在图像上测量SD值,由3位医师进行双盲法阅片,使用5分制评分,综合评分结果计算出不同头围、不同剂量下5等级的图像数,并统计比较各组间图像质量评分,评价SD值及剂量指数(CTDI)的差异性.结果 各等级图像数在3个组中均有显著性差异(P＜ 0.001),Ⅰ组:120mA与其余各组比较有显著性差异(P＜0.001),图像质量差；Ⅱ组:120mA、160mA与其余各组比较,图像质量差(P＜ 0.001)；Ⅲ组:120mA、160mA、200mA图像质量均差.质量差的图像评分均值均＜3分,SD＞4.5,不能达到诊断要求,与常规剂量280mA比较差异有统计学意义(P＜ 0.05).结论 Ⅰ组160mA扫描最优,即保证图像质量同时剂量最低,较常规280mA剂量降低约423％；Ⅱ组200mA扫描最优,剂量降低约27.9％；Ⅲ组240mA扫描最优,剂量降低约14.3％.SD值≤4.5为宜.