Rippke Carolin, Renkamp C Katharina, Attieh Charbel, Schlüter Fabian, Buchele Carolin, Debus Jürgen, Alber Markus, Klüter Sebastian
Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Baden-Württemberg, Germany.
Heidelberg Institute of Radiation Oncology (HIRO), National Center for Radiation Oncology (NCRO), Heidelberg, Baden-Württemberg, Germany.
Phys Imaging Radiat Oncol. 2023 Aug 10;27:100477. doi: 10.1016/j.phro.2023.100477. eCollection 2023 Jul.
In online adaptive stereotactic body radiotherapy treatments, linear accelerator delivery accuracy is essential. Recently introduced double stack multileaf collimators (MLCs) have new facets in their calibration. We established a radiation-based leaf-individual calibration (LIMCA) method for double stack MLCs.
MLC leaf positions were evaluated from four cardinal angles with test patterns at measurement positions throughout the radiation field on EBT3 radiochromic film for each single stack. The accuracy of the method and repeatability of the results were assessed. The effect of MLC positioning errors was characterized for a measured output factor curve and a clinical patient plan.
All positions in the motor step - position calibration file were optimized in the established LIMCA method. The resulting double stack mean accuracy for all angles was 0.2 ± 0.1 mm for X1 (left bank) and 0.2 ± 0.2 mm for X2 (right bank). The accuracy of the leaf position evaluation was 0.2 mm (95% confidence level). The MLC calibration remained stable over four months. Small MLC leaf position errors (e.g. 1.2 mm field size reduction) resulted in important dose errors (-5.8 %) for small quadratic fields of 0.83 × 0.83 cm. Single stack position accuracy was essential for highly modulated treatment plans.
LIMCA is a new double stack MLC calibration method that increases treatment accuracy from four angles and for all moving leaves.
在在线自适应立体定向体部放射治疗中，直线加速器的投照精度至关重要。最近引入的双层多叶准直器（MLC）在其校准方面有新的特点。我们为双层MLC建立了一种基于辐射的叶片个体校准（LIMCA）方法。
在EBT3放射变色胶片上，针对每个单层，在整个辐射野的测量位置用测试图案从四个基本角度评估MLC叶片位置。评估了该方法的准确性和结果的可重复性。针对测量的输出因子曲线和临床患者计划，表征了MLC定位误差的影响。
在已建立的LIMCA方法中，电机步长 - 位置校准文件中的所有位置均得到优化。对于X1（左岸），所有角度的双层平均精度为0.2±0.1毫米，对于X2（右岸）为0.2±0.2毫米。叶片位置评估的精度为0.2毫米（95%置信水平）。MLC校准在四个月内保持稳定。对于0.83×0.83厘米的小方形野，小的MLC叶片位置误差（例如射野尺寸缩小1.2毫米）会导致重要的剂量误差（-5.8%）。单层位置精度对于高度调强治疗计划至关重要。
LIMCA是一种新的双层MLC校准方法，可从四个角度提高所有移动叶片的治疗精度。
