慢速CT扫描用于肺肿瘤三维适形放疗的可行性研究

A feasibility study of slow CT scan technique using in three-dimensional conformal radiotherapy for lung tumor

目的 研究在三维适形放疗中应用慢速CT扫描技术更合理的确定肺肿瘤靶区的可行性。方法 用直径2 .5、5 cm的小球模拟肺肿瘤,在不同移动距离下行常规CT扫描(螺旋扫描每层扫描时间2秒)和慢速CT扫描(轴层扫描每层扫描时间5秒)。测定各CT扫描序列的小球体积作为大体肿瘤体积(Gross target volume,GTV)。两次相同方式下扫描均捕获到的GTV为共同体积即V共同,两次相同方式下扫描一起确定的GTV即V总。用比值R1(R1=V共同/ GTV)和R2 (R2 =V共同/ V总)评价常规扫描和慢速扫描的重复性。结果 慢速CT扫描确定的GTV大于常规CT扫描确定的GTV ,经统计学处理,P <0 .0 1。常规扫描的R1、R2比值为6 7.4 4 %～93.88%(80 .5 9%±9.5 8% )和4 3.30 %～93.10 % (70 .0 7%±14 .2 8% ) ,慢速扫描的R1、R2比值为80 .4 3%～97.4 9% (90 .81%±4 .18% )和6 9.6 0 %～88.4 0 % (82 .2 4 %±5 .90 % ) ,P均<0 .0 1。结论 慢速扫描CT技术较常规CT定位方法能捕获到更多的肿瘤运动信息,有更好的定位重复性,可以更合理的确定肺肿瘤三维适形放疗的靶区。

Objective To investigate the feasibility of achieving more accurate target volume definition of moving lung tumor using slow scan technique for three-dimensional conformal radiotherapy.Methods To mimic lung tumors,two spheres of 2.5cm and 5cm in diameter were imaged while moving varies distances with conventional CT scan mode(spiral scan,2s/slice)and slow CT scan mode(axial scan,5s/slice).The imaged ball volumes of all CT series defined as GTV were estimated.The common component of the GTV covered by two scans using certain CT technique was defined as V_ com.The total volume enveloped by GTVs from both scans of a specific technique was defined as V_ total.The reproducibility of conventional scan technique and slow scan technique was evaluated using two ratios,R1(R1=V_ com/GTV)and R2(R2=V_ com/V_ total).Results The GTV imaged with slow scan technique was larger than that with conventional scan mode,P<0.01.The R1 and R2 obtained with conventional mode were 67.44%~93.88%(80.59%±9.58%) and 43.30%~93.10%(70.07%±14.28%), 80.43%~97.49%(90.81%±4.18%) and 69.60%~88.40%(82.24%±5.90%) with slow scan,P<0.01.Conclusions Compared with conventional method,slow scan technique used in CT can capture more information about moving tumor and have better reproducibility.