加速器机架角度对多叶准直器叶片到位精度的影响

Impact of accelerator＇s gantry angle on multi-leaf collimator position accuracy

目的测量加速器机架角度对多叶准直器叶片到位精度的影响。方法用柯达xomat—V胶片进行测量，选定合适叶片位置和机架角度，保证精确摆位，用RITll3胶片分析软件对曝光的胶片做分析。结果在所有测量情况下，绝大部分叶片到位偏差都〈0．5mm，只有在机架角270°、叶片从左向右运动情况下有2对叶片到位偏差〉1mm。结论机架角度即重力对多叶准直器叶片到位精度确有影响，精确摆位对测量工作至关重要。

Objective To study the impact of accelerator＇s gantry angle on MLC position accuracy. Methods Kodak X-omat-V Films were used, appropriate multi-leaf collimator positions and gantry angles were chosen , precise setup was needed , and the exposal films were analyzed by RIT 1 1 3 software. Results At all conditions, most of the leaf position errors were less than 0.5 ram. There were 2 pairs of leaf position errors larger than 1 mm when the gantry angle was 270° and the leaves moved from left to right. Conclu- sions Gantry angle can affect the accuracy of multi-leaf collimator position. Gravity and inertia increase the uncertainty of leaf position accuracy. Pricise setup is critical for the dose measurement.