肿瘤靶体积测量16层CT成像参数的选择

目的:探讨16层CT在肿瘤靶体积测量中的应用.方法:在西门子Somatom Sensation16层CT机上以不同准直宽度(0.75mm、1.5mm)和不同螺距(0.5、1.0、1.5)对埋入蜡块中的实体瘤模型进行扫描,分别获取6组原始数据,每组数据采用2、3、5、8及10mm不同的重建间隔共计5组重建不同层厚的图像,在治疗计划系统上对所获图像勾画靶区,利用TPS的州量软件测得模体的体积数据.结果:不同重建层厚(2、3、5、8和10mm)所测量模体体积之均值分别为(25.55±0.08)、(25.44±0.11)、(25.36±0.17)、(21.72±0.77)和(20.55±0.03)cm3,与实际体积值(25.62 cm3)配对t检验,2、3、5 mm相对应之P值均大于0.05,8、10mm相对应之P值均小于0.01.不同准直及不同螺距在2mm重建层厚条件下的测量结果误差的直线回归分析y=0.028x 25.55(r=1.00,P＜0.01),3、5、8、10mm重建层厚之直线回归方程的斜率分别为0.031、0.027、0.034、0.011(r=1.00,P＜0.01).结论:多层螺旋CT模拟对肿瘤靶体积的测量误差与准直宽度和螺距无关,而与重建层厚有关,且2mm、3mm和5mm的重建层厚所获之体积数据最接近实际值.

Imaging Parameter Choice of 16-slice CT Scanner in Measuring the Volume of Tumor

Objective:To explore the significance of using 16-slice CT scanner in measuring the volume of tumor.Methods:Using 16-slice CT (Siemens Somatom Sensation) to scan the solid tumor models buried in paraffin blocks under different width of collimator and pitch patterns.After acquiring 6 groups of data,we used different rebuilt intervals to reconstruct 5 groups of images with different length of slices,then contoured the tumors in the treatment planning system based on the above images.Furthermore,the volume of tumor models were measured by the software of TPS.Results:The volumes of the tumor models reconstructed under different rebuilt intervals (2mm,3mm,5mm,8mm and 10mm) were as follows:(25.55+0.08,25.44+0.11,25036+0.17,21.72+0.77 and 20.55+0.03) To contrast to the real volume,there is no significance distinction within 2,3,5 groups (P>0.05) while obvious differences are found in 8,10 groups (P<0.01).The linear regression model which data is obtained in 2 rebuilt intervals under different width of collimation and pitch patterns is y=0.028x+25.55 (r=1.00,P<0.01),and the slop rate of the linear regression model analyzed from 3,5,8,10,different are 0.031,0.027,0.034,0.011 (r=1.00,P<0.01).Conclusion:The measuring error of tumor volume acquired from multilayer spiral CT simulation shows no significant correlation with the width of collimation and pitch patterns,but the thickness of rebuilt slice do play a vital role in regulating it.Moreover,data of tumor volume obtained under 2,3,5 rebuilt layers shows the best approximation to the real volume.