利用仿真头模进行机载影像系统质控的探讨

目的 探讨利用人体仿真头模对瓦里安直线加速器机载影像系统进行质控的方法.方法 将人体仿真头模按常规方法进行CT模拟、计划设计、治疗摆位、锥形束CT扫描和千伏特正交片位置验证等过程,1次/d,连续10 d并对位置偏差的结果进行分析.结果 连续10次锥形束CT验证模拟靶在纵、垂直、横、旋转方向的误差分别为(0.06±0.11)、(0.03±0.05)、(0.07±0.07)、(0.03±0.10)cm,连续10次千伏特正交片验证的分别为(0.04±0.010)、(0.03±0.05)、(0.08±0.06)、(0.05±0.05)cm,两种方法验证结果显示差异无统计学意义(纵向比t=0.44,P=0.667;垂直向比t=0.00,P=1.000;横向比t=0.34,P=0.735;旋转向比t=0.58,P=0.568).结论 研究之加速器机载影像系统稳定可靠,状态良好.利用人体仿真头模模拟实际治疗过程对机载影像系统进行质控,是一种简便易行、结果可靠的有效方法,具有推广应用价值.

Phantom test for daily quality assurance of on board image system

Objective To study the method of using phantom test for daily quality assurance of on board image(OBI) system. Methods The routine procedures of radiotherapy, including CT simulation, planning,setup,cone beam CT(CBCT) scan and kilovolt X-ray orthogonal film were carried out on a head phantom. The procedures repeated once a day in the following 10 days. The geometric errors of the phantom were recorded. Results The geometric errors of the phantom by CBCT were 0.06±0.11] cm, 0.03±0.05] cm, 0.07±0.07] cm and 0.03±0.10] cm in longitudinal, vertical, lateral and rotation directions, respectively. The geometric errors of the phantom by kilovolt X-ray orthogonal film were 0.04±0.10] cm, 0.03±0.05] cm, 0.08±0.06] cm and 0.05±0.05] cm, respectively. The differences of geometric errors of the phantom by CBCT and kilovolt X-ray orthogonal film were not significant(t = 0.44,P=0.667 in longitudinal direction ; t=0.00, P=1.060 in vertical direction ; t=0.34, P=0.735 in lateral direction; t=0.58,P=0.568 in rotation direction). Conclusions The OBI system of our accelerator is reliable and at excellent performance status. The method by using phantom test for the daily quality assurance of OBI system is easy and reliable.