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肺部肿瘤会随着人的呼吸运动而运动,为研究肿瘤运动周期内运动时段的不同对锥形束CT(CBCT)确定肿瘤靶区的影响,应用CIRS008胸部运动模体,取直径分别为1cm和3cm的球形靶模拟肺部肿瘤的正弦运动,然后在振幅不变的情况下改变靶运动在近呼气端与近吸气端时间的比值(E/I)进行CBCT扫描。提取靶运动方向中心线上每个像素的CT值分析图像中靶区对比度的变化,应用区域生长的方法自动勾画靶区,并与根据小球运动轨迹计算的运动体积进行比较。结果显示随着E/I的增大,近呼气端对比度升高而近吸气端对比度降低。勾画的靶区体积随着E/I的增大而减小,当E/I=4,振幅A=1cm时,直径分别为1cm和3cm的小球,体积分别减小了48.2%和22.7%;研究表明E/I增大时CBCT不能完整的反映靶的运动范围,CBCT可能会低估肺部肿瘤的内靶区。
In order to study the effect of different exercise periods on the CBCT in determining the tumor target area, the lung tumor was moved along with the respiratory movement of human. CIRS008 chest motility was used to measure the diameter of the tumor. And 3 cm spherical targets to simulate the sinus motion of the lung tumor and then CBCT scans were performed with varying amplitude (E / I) of the target motion at the near-expiratory to near-aspiration end. The CT value of each pixel in the centerline of the target motion direction was extracted to analyze the contrast of the target area. The target area was automatically delineated by the method of area growth and compared with the motion volume calculated from the trajectory of the ball. The results show that with the increase of E / I, near expiratory contrast increased near the suction side of the contrast decreased. The volume of the target plotted decreases with the increase of E / I. When E / I = 4 and amplitude A = 1cm, the diameters of 1cm and 3cm beads decrease by 48.2% and 22.7% ; Studies have shown that CBCT does not fully reflect the range of motion of the target when the E / I increases. CBCT may underestimate the target area of the lung tumor.