胸部低剂量CT中肺结节自动测量软件的体模研究

Influence of Exposure Parameters and Nodule Characteristics on Computer-assisted Lung Nodule Volumetry in Low-dose CT:a Phantom Study

目的:比较不同扫描条件下,肺结节自动测量软件的测量精度。方法:对模拟肺体模和结节进行CT图像扫描。使用肺结节专业图像分析软件,进行结节直径、体积测量。计算结节直径、体积、CT值测量的绝对错误率(APE):APE=100×(V_(测量)-V_(实际))/V_(实际)。使用单向方差分析(one-way ANOVA检验)结合StudentNewman-Keuls多重比较法来比较扫描辐射剂量、结节直径、结节密度对APE的影响。结果:将APE按照扫描辐射剂量的不同进行分组比较,发现APE_(直径)、APE_(体_(体积)、APE_(CT值)三者的P值分别为0.44、0.73、0.28;将APE按照扫描方案的不同进行分组比较,发现APE_(直径)、APE_(体积)、APE_(CT值)三者的P值分别为0.37、0.82、0.93,皆无统计学差异,说明扫描辐射剂量和扫描方案的变化对肺结节测量软件的测量结果无显著影响。研究还发现肺结节的直径越大,APE_(直径)越小。而结节直径的不同对APE_(体积)、APE_(CT值)无明显影响。肺结节的密度越小,APE_(直径)越小。不论结节的直径和密度,测量软件得出的APE_(直径)、APE_(体积)皆高于结节的实际值,但都小于25%。而测量软件得出的APE_(CT值)较大。结论:不同的扫描辐射剂量和扫描方案下,肺结节测量软件的测量结果基本一致,说明胸部低剂量CT的的低剂量扫描条件不会影响肺结节测量软件的准确率。不论结节的直径和密度,软件测量得到的直径和体积结果是可信的。

Purpose： To evaluate the effect of exposure parameters and nodule characteristics on the measurement variability of computer-aided nodule volumetry on low-dose lung CT. Methods： Twelve nodules with various sizes and attenuations were placed inside a chest phantom. CT images were obtained with various radiation dose. The nodule volumes were calculated using semiautomatic software and compared with the assumed volume from the nodules. The absolute percentage measurement error （APE） was calculated by the equation： APE = 100＊（V d-Vreal）/Vreal. The one-way ANOVA and Student- Newman-Keuls tests were used to compare the influence of scan parameters on APE. Results： There were no signifcant differences of APEdiameter APEvolume APEattcbyatuin among images of different exposure dose （p= 0.44, 0.73, 0.28） and images of different scanning protocol （P=0.37, 0.82, 0.93）. It was also proved that APEdiameter decreased with the increase of the pulmonary nodule＇ s diameter, no differences of APEvolume APEattenuation were found among nodules of different diameters. And APEdiameter decreased with the decrease of the pulmonary nodule＇ s attenuation. Regardless of nodules＇ diameter and density, APEdiamcter, APEvolume remained inferior to 25%, but the result of measured APEattenatio, was not satisfying. Conclusion： Computer-aided volumetry is robust in a wide range of exposure settings. Regardless of nodules＇ diameter and density, the measured diameter and volume values remain reliable.