站立位全脊柱正位X线摄影的质量控制

Quality control of standing total spine orthotopic radiographs

目的探讨影响站立位全脊柱正位X线摄影质量的因素,提高图像质量。方法对77疑似脊柱侧弯畸形患者进行负重站立位全脊柱正位摄影,通过分次快速曝光获得图像后拼接成全脊柱正位图像。对图像质量进行评分,将图像分为“1-2”分和“3”分两组,统计两组患者的年龄、分段图像的mAs、曝光指数(EI)、感兴趣区(ROI)平均面积、平均标准偏差(SD)值、下肢长度百分比和空气面积百分比等并进行统计学分析。结果77例患者均进行了全脊柱正位三段摄影,并拼接成功。对所得拼接图像进行质量评分:评为“1”分的22例,约占28.57%;评为“2”分的14例,约占18.18%;评为“3”分的41例,约占53.25%。下段图像平均SD值的Welch和Brown-Forsythe检验的统计量都是48.721,P<0.001,差异具有统计学意义。下段图像的mAs、EI、下肢长度百分比和空气面积百分比等统计量的F值分别为:37.320、69.199、100.461和19.451,P<0.001,差异具有统计学意义;上段和中段图像的mAs、EI、平均ROI面积及平均SD值等统计量的P均>0.05,差异无统计学意义。线性回归方程如下:下段图像平均SD值=49.361(下肢长度百分比)+31.407(空气面积百分比)(P<0.01)。Durbin-Watson值为1.696,查询Durbin Watson表发现其在无自相关的值域之中,认定残差独立,通过检验。结论使用电离室进行全脊柱正位摄影中,精准定位,避免下肢包含过多,从而避免下段图像曝光不足,可以明显改善全脊柱正位图像的质量。

Objective To analyze the factors that affect the quality of the total spine orthophoto in standing position,to make targeted corrections to further improve the image quality.Methods Using the uDR 77io digital X-ray camera,77 patients with clinically suspected scoliosis were subjected to weight-bearing standing totalspine orthophotography,and the images were obtained by fractional rapid exposure and stitched into a total-spine orthotopic image.The image quality was graded,and the images were divided into two groups:"1-2"and"3".The age of the patients,mAs,exposure index(EI),average area of area of interest(ROI)and the average standard deviation(SD)value of segmented images,lower limb length percentage and air area percentage of patients in the two groups were calculated and statistically analyzed.Results All the 77 patients underwent three-segment radiography of the total spine,and the stitching was successful.Quality evaluation of the resulting stitched images were as follows:22 cases were rated"1",accounting for approximately 28.57%;14 cases were rated"2",accounting for approximately 18.18%;41 cases were rated"3",approximately accounting for 53.25%.The statistics of the welch and brown-forsythe test of the average SD value of the lower image were both 48.721,P<0.001,the difference was statistically significant.The F values of mAs,EI,lower limb length percentage and air area percentage in the following image were 37.320,69.199,100.461 and 19.451,respectively(P<0.001).The differences were statistically significant.The statistical values of mAs,EI,average ROI area and average SD values of the upper and middle images were all>0.05,showing no statistical significance.The linear regression equation was as follows:the average SD value of the lower image was 49.361(lower limb length percentage)+31.407(air area percentage)(P<0.01).The durbin-watson value was 1.696.A query of the Durbin Watson table showed that it happened to appear in the range without autocorrelation.The residual was determined to be independent and passed the test.Conclu-sion Using ionization chambers for totalspine orthotopic photography,accurate positioning to avoid excessive inclusion of the lower limbs,thereby avoiding underexposure of the lower seg-ment images,can significantly improve the quality of the totalspine orthotopic image.