摘要目的 评价低剂量CT检查诊断肋骨骨折的可行性及图像质量.方法 25例胸部外伤行CT检查的患者,采用64层螺旋CT自动曝光控制技术,于吸气末屏气对整个胸廓以噪声指数(NI)11、21进行2次扫描,2次扫描的其他参数均保持一致.记录每次扫描的平均管电流、CT容积剂量指数(CTDIvol)和有效剂量(ED).由2名放射诊断医师埘每次扫描所见的肋骨骨折按Ⅰ、Ⅱ、Ⅲ度进行统计,以Wilcoxon配对符号秩和检验比较其差异;以5分制对图像诊断的接受率及主观噪声进行评价.采用Kappa-致性检验评价2名医师评定结果 的一致性.结果 NI为11时,平均CTDIvol、ED分别为(13.88±5.17)mGy、(8.14 4-3.21)mSv;NI为21时,分别为(3.91±1.57)mGy、(2.31±0.97)mSv.NI为21的辐射剂量较NI为11者下降了72%.NI为11的平均管电流为(195.88±69.33)mAs、NI为21的平均管电流为(54.56±21.54)mAs.NI为21时扫描能检出NI为11时扫描所发现的全部Ⅱ度、Ⅲ度骨折及绝大部分Ⅰ度骨折.NI为11时骨窗的图像诊断接受率评分及主观噪声评分2名医师分别为(4.9±0.2)、(4.6±0.5)分;NI为21时平均为(3.5±0.5)、(3.3±0.5)分.2名医师对肋骨骨折的检出、图像诊断接受率及主观噪声的评定结果 Kappa值分别为0.876、0.820和0.792(P值均<0.01).结论 NI为21的低剂量CT扫描能满足临床对肋骨骨折诊断的要求.

abstractsObjective To evaluate images quality and diagnostic feasibility of low-dose CT in patients with traumatic rib fractures.Methods Twenty-five patients presented with thoracic iniury were underwent 64-slice spiral CT scanning in inspiration breath-hold technique.Two scan protocols were performed.In one scan protocol noise index(NI)is 11,and in another NI is 21,but the other scan parameters were no difference.The mean value of tube current,the volume CT dose index(CTDIvol),and effective dose(ED)were recorded.Image quality was scored by 2 experienced radiologists using the 5-points scale.The numbers and degrees of rib fractures were recorded.The data were tested by using the Wilcoxon signed rank sum test.The differences of the inter-observer were determined by Kappa statistics.Results The mean CTDIvol and ED in scan protocol with NI of 11 were(13.88±5.17)mGy and(8.14±3.21)mSv,and that with NI of 21 were(3.91±1.57)mGy and(2.31±0.97)mSv.Compared the scan with NI of 11.there was 72%intrinsie dose reduction in the scan with NI of 21.The mean value of tube current in scan with NI of 11 and 21 were(195.88±69.33)mAs and(54.56±21.54)mAs.AIl patients with 11 and Ⅲ degree and most patients with I degree rib fractures that identified by the scan with NT of 11 were detected by the scan with NI of 21.There were no statistical difference between two scaus with the Wilcoxon signed rank sum test.The diagnostic acceptability and image noise score in the scan with NI of 11 were 4.9±0.2 and 4.6±0.5.and that with NI=21 were 3.5±0.5 and 3.3±0.5.There was prefect concordante in the inter-observers in diagnostic acceptability on finding of rib fractures.diagnostic acceptability and image noise(Kappa=0.876,0.820,0.792,P<0.01)between two scan protocols.Conclusion Rib fractures can be diagnosed by the low-dose CT using the scan protocol with NI of 21.