Tolerance and dosimetric study of multi-leaf collimator leaf position accuracy for dynamic intensity-modulated radiotherapy
Yang Jiming1, Ma Min2, Wu Yong3, Ren Jiangping1
1Radiotherapy and Chemotherapy Center, Ningbo First Hospital, Ningbo 315000, China; 2Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Scicences and Peking Union Medical College, Beijing 100021, China; 3Department of Radiotherapy, Xingyi People's Hospital, Xingyi 562400, China
Abstract：Objective To evaluate the dosimetric effect of multi-leaf collimator (MLC) position error on dynamic intensity-modulated radiotherapy (dMLC-IMRT), aiming to provide guidance for the establishment of MLC quality control accuracy and operation tolerance. Methods In the phantom study, the virtual water phantom established in the treatment planning system (TPS), and three dynamic sliding window test fields with gap width of 5mm, 10mm and 20mm were designed. Clinical treatment plans of 7 common tumor types were extracted, including nasopharyngeal carcinoma, glioma, lung cancer, esophageal cancer, cervical cancer, prostate cancer, and breast cancer, with 6 cases in each. MLC errors were introduced into the copy from original plan to generate the simulation plans. MLC errors included systematic open/close error, systematic deviation error and random error. The dosimetric differences between the original and simulation plans were compared. Results The phantom study showed that the symbol of dose deviation was the same as that of systematic open/close error, and the value was increased with the increase of MLC error and decreased with the increase of gap width. The results of patient study showed that the systematic open/close error had a significant effect on dosimetry, the target volume dose sensitivities of different plans were 7.258-13.743%/mm, and were negatively correlated with the average field width. The dosimetric deviation caused by the systematic shift error below 2mm was less than 2%. The dosimetric change caused by the random error below 2mm could be neglected in clinical treatment. Conclusions The minimal gap width should be limited in TPS, whereas the quality control of MLC should be strengthened. In addition, for the dynamic intensity-modulated treatment technology, 2mm random error was suggested to be the operation tolerance during treatment delivery, and 0.2mm alignment accuracy on each side (or 0.4mm unilateral) is recommended to be the MLC quality control accuracy to ensure the dose accuracy of radiotherapy for different tumors.
Yang Jiming,Ma Min,Wu Yong et al. Tolerance and dosimetric study of multi-leaf collimator leaf position accuracy for dynamic intensity-modulated radiotherapy[J]. Chinese Journal of Radiation Oncology, 2021, 30(11): 1167-1172.
[1] 李明辉,马攀,田源等. 基于IAEA 483号报告的小野射野输出因子测量及修正方法[J]. 中华放射肿瘤学杂志,2019, 28(6):452-456. DOI:10.3760/cma.j.issn.1004-4221.2019.06.013. Li MH, Ma P, Tian Y, et al. Small field output factor measurement and correction method based on IAEA report No.483[J]. Chin J Radiat Oncol, 2019,28(6):452-456. DOI:10.3760/cma.j.issn.1004-4221.2019.06.013. [2] Das IJ, Ding GX, Ahnesjö A. Small fields:nonequilibrium radiation dosimetry[J]. Med Phys, 2008, 35(1):206-215. DOI:10.1118/1.2815356. [3] 程燕铭,胡彩容,阴晓娟,等. 鼻咽癌IMRT和VMAT计划对机器跳数和MLC误差剂量学敏感度对比研究[J]. 中华放射肿瘤学杂志,2017,26(10):1199-1203. DOI:10.3760/cma.j.issn.1004-4221.2017.10.019. Cheng YM, Hu CR, Yin XJ, et al. Dosimetric sensitivity with MU and MLC errors in IMRT versus VMAT plan for nasopharyngeal carcinoma[J]. Chin J Radiat Oncol, 2017, 26(10):1199-1203. DOI:10.3760/cma.j.issn.1004-4221.2017.10.019. [4] 叶淑敏,滕建建,石锦平,等. MLC叶片系统误差对鼻咽癌VMAT和IMRT计划剂量影响的比较[J]. 中国医学物理学杂志,2019, 36(10):1139-1144. DOI:10.3969/j.issn.1005-202X.2019.10.005. Ye SM, Teng JJ, Shi JP, et al. Comparison of dosimetric impacts of MLC systematic errors on VMAT and IMRT plans for nasopharyngeal carcinoma[J]. Chin J Med Phys, 2019, 36(10):1139-1144. DOI:10.3969/j.issn.1005-202X.2019.10.005. [5] Rangel A, Dunscombe P. Tolerances on MLC leaf position accuracy for IMRT delivery with a dynamic MLC[J]. Med Phys, 2009, 36(7):3304-3309. DOI:10.1118/1.3134244. [6] 李光俊,李衍龙,袁青青,等. 加速器运行误差对宫颈癌容积旋转调强放疗的剂量学影响[J]. 中华放射医学与防护杂志,2018, 38(11):824-829. DOI:10.3760/cma.j.issn.0254-5098.2018.11.005. Li GJ, Li YL, Yuan QQ, et al. The dosimetric impacts of accelerator operation error on the volumetric m odulated arc therapy for cervical cancer[J]. Chin J Radiol Med Protect, 2018, 38(11):824-829. DOI:10.3760/cma.j.issn.0254-5098.2018.11.005. [7] Arnfield MR, Wu Q, Tong S, et al. Dosimetric validation for multileaf collimator-based intensity-modulated radiotherapy:a review[J]. Med Dosim, 2001, 26(2):179-188. DOI:10.1016/s0958-3947(01)00058-9. [8] Mu G, Ludlum E, Xia P. Impact of MLC leaf position errors on simple and complex IMRT plans for head and neck cancer[J]. Phys Med Biol, 2008, 53(1):77-88. DOI:10.1088/0031-9155/53/1/005. [9] Luo W, Li J, Price RA Jr, et al. Monte Carlo based IMRT dose verification using MLC log files and R/V outputs[J]. Med Phys, 2006, 33(7):2557-2564. DOI:10.1118/1.2208916. [10] LoSasso T, Chui CS, Ling CC. Physical and dosimetric aspects of a multileaf collimation system used in the dynamic mode for implementing intensity modulated radiotherapy[J]. Med Phys, 1998, 25(10):1919-1927. DOI:10.1118/1.598381. [11] LoSasso T, Chui CS, Ling CC. Comprehensive quality assurance for the delivery of intensity modulated radiotherapy with a multileaf collimator used in the dynamic mode[J]. Med Phys, 2001, 28(11):2209-2219. DOI:10.1118/1.1410123. [12] Arnfield MR, Otto K, Aroumougame VR, et al. The use of film dosimetry of the penumbra region to improve the accuracy of intensity modulated radiotherapy[J]. Med Phys, 2005, 32(1):12-18. DOI:10.1118/1.1829246. [13] Van Esch A, Bohsung J, Sorvari P, et al. Acceptance tests and quality control (QC) procedures for the clinical implementation of intensity modulated radiotherapy (IMRT) using inverse planning and the sliding window technique:experience from five radiotherapy departments[J]. Radiother Oncol, 2002, 65(1):53-70. DOI:10.1016/S0167-8140(02)00174-3. [14] Losasso T. IMRT delivery performance with a varian multileaf collimator[J]. Int J Radiat Oncol Biol Phys, 2008, 71(1 suppl):S85-S88. DOI:10.1016/j.ijrobp.2007.06.082. [15] Surendran S, Rao DP. Dynamic MLC-QA based on portal dosimetry[J]. Int J Engin Res Appl, 2014, 4(5):134-137. [16] 张朋,闫冰,薛旭东,等. 不同三维探测器对鼻咽癌VMAT计划MLC位置误差探测灵敏度的研究[J]. 中华放射肿瘤学杂志,2019, 28(7):527-531. DOI:10.3760/cma.j.issn.1004-4221.2019.07.011. Zhang P, Yan B, Xue XD, et al. Study on the sensitivity of different 3D detectors to MLC positioning errors in volumetric modulated arc therapy (VMAT) plan for nasopharyngeal carcinoma[J]. Chin J Radiat Oncol, 2019, 28(7):527-531. DOI:10.3760/cma.j.issn.1004-4221.2019.07.011.
2021, Vol. 30 
