Abstract：Objective To analyze the influence between the mean aperture area (MAA) and the multi-leaf collimator error
(MLCerror) for nasopharyngeal carcinoma volumetric modulated arc therapy. Methods 30 patients diagnosed with postoperative
nasopharyngeal carcinoma were selected as the study objects. Every original plan for each patient was exported and compiled
using Python. Six modified plans were generated by different MLCerror (±0.2 mm, ±0.5 mm, ±1.0 mm). The dosimetry
parameters and passing rate of the original and modified plan were compared and the relationship among MLCerror , and
MAA was analyzed. Among them, the planned target volume (PTV) of nasopharyngeal tumor and the target area of cervical
metastatic lymph node tumor were integrated into PTV69 by Boolean operation. Results The corresponding variation of PTV69,
planning clinical target volume 1 and planning clinical target volume 2 due to MLCerror (-1-1 mm) were 6.1 %/mm, 6.0 %/mm
and 6.3 %/mm (P<0.05). The dose gradient of the organs at risk (OAR) was higher than that of the target area. The dose falloff
were 10.6 %/mm, 10.5 %/mm, 12.3 %/mm, 12.0 %/mm, 8.1 %/mm and 11.2 %/mm in spinal-cord, brainstem, parotid-L,
parotid-R, oral and larynx (P<0.05). With the increase of MLCerror, the passing rate difference of different MAA plan showed
an increasing trend. When the MLCerror reached ±1.0 mm, the discrepancy of different MAA plan was largest (51.7%-90.2%).
Conclusion It is more beneficial for limiting MLCerror value to protect OAR than target. For the complicated nasopharyngeal
carcinoma, less than 0.5 mm MLCerror is suggested to be the operation tolerance and decreasing the the small segment is
recommended to protect OAR and ensure the dose accuracy.
贾晓斌，岳堃. MLC运动误差对不同射野面积的鼻咽癌
容积调强计划的影响[J]. 中国医疗设备, 2024, 39(3): 68-72.
JIA Xiaobin, YUE Kun. Impacts of MLCerror on the Different Beam Area of Volumetric Arc Therapy for
Nasopharyngeal Carcinoma. China Medical Devices, 2024, 39(3): 68-72.
