应用统计学体模评价CR乳腺摄影影像的探讨

目的应用ALVIM统计学体模TRM,探讨乳腺计算机X线摄影(CR)获得尺寸最小的Al2O3斑点(钙化灶)和尼龙纤维(肿块灶)信号的能力。方法将具有各5种大小不同Al2O3斑点和尼龙纤维组成的ALVIM统计学体模TRM置于成像板(IP)上,用钼靶X线机26kV,调节毫安量,选择适当图像处理参数,获得一张密度值D=0·70±0·05的实验照片,用5值判断法取得每一行由5个信号和噪声所组成的10行信号的记分总值,用ALVIM统计学体模的计算公式计算出一组真阳性概率P(S/s)和假阳性概率P(S/n)值,绘制ROC曲线,并计算出每种信号的判断概率值Pdet,再用SPSS10·0统计学单因素方差分析软件处理数据,获得尺寸最小的钙化灶和软组织肿块灶。结果用概率统计方法获得制作ROC曲线的数据和判断概率平均值Pdet,5种大小不同的Al2O3斑点(钙化灶)中,0·20mm的Pdet=0·6250最小,0·55mm的Pdet=0·9000最大,而0·20mm与0·25mm的Pdet差异无统计学意义,与其他的差异有统计学意义;5种大小不同的尼龙纤维(肿块灶)中,0·45mm的Pdet=0·5313最小,1·00mm的Pdet=0·8813最大,而0·45mm的与0·60mm的差异无统计学意义,0·45mm与其他的差异有统计学意义。结论应用ALVIM统计学体模TRM制作ROC曲线和获得判断概率值Pdet的计算简单、快捷,宜于日常临床工作开展的评价影像质量控制,值得推广。

Evaluation of the image in mammography application of ALVIM statistics phantom using computed radiography(CR)

Objective To evaluate the minimal Al₂O₃ mottle (calcification)and nylon fiber signal(tumor) in mammography application of ALVIM statistics phantom by computed radiography(CR). Methods ALVIM statistics phantom consists of five Al₂O₃ mottles(calcification) and five nylon fiber signals(tumor) various in size and was placed on the imaging plate(IP),test image with a density of D=0.70±0.05 was obtained by molybdenum target X-ray equipment with a voltage of 26 kV and by adjusting exposure and selecting appropriate image processing parameter.Four observers gave it the total points of the ten lines each line consisting of five signals and five noise applying of the method of five values estimation,then according to the formula of ALVIM statistics phantom figuring out a set of true positive probabilities P(S/s) and false positive probabilities P(S/n) to drawing the ROC curve and figuring out each signals probabilities P det,at last processing data using SPSS 10.0 statistics analysis software to acquire the smallest calcification and parenchyma tumor. Results After acquiring the data and judging probability average value P det of the ROC curves statistics,five Al₂O₃ mottle (calcification) equal to 0.6250 of 0.22 mm is minimal, and P det equal to 0.9000 of 0.55 mm was maximal. There was no significant variation in size P det difference between P det of 0.20 mm and of 0.25 mm but there was among others.Among the five varying nylon fibers size P det equal to 0.5313 was minimal and P det equal to 0.8813 of 1.00 mm was maximal.There was no significant difference between P det of 0.45 mm and of 0.60 mm while significant difference was found between 0.45 and others. Conclusion The method of plotting ROC curve using ALVIM statistics phantom and getting the judging probability P det was easy,fast and suitable to evaluate image quality control in daily clinic and popularized easily.