Dosimetric study on positioning error of breast cancer VMAT plan with or without autoflash optimization

  • CHENG Xiuyan ,
  • GE Hong
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  • The Affiliated Cancer Hospital of Zhengzhou University & Henan Cancer Hospital, Zhengzhou 450008, China

Received date: 2022-10-04

  Online published: 2023-03-08

Abstract

Objective: To investigate the dosimetric effect of setting errors in different directions on the breast cancer VMAT plan when Autoflash is involved in optimization. Methods: Selected 20 patients after radical mastectomy of breast cancer who underwent VMAT technology irradiation in our hospital. The Monaco treatment planning system can choose whether to use Autoflash virtual external MLC boundary to optimize the target area during optimization, and develop a plan without Autoflash during treatment.Make a plan without Autoflash for the plan with Autoflash participating in optimization during the treatment, and vice versa.The optimization functions and conditions of the two plans remain the same. Introduce the positioning error of 3mm and 5mm in the six directions of head, foot, up and down, and left and right respectively for the prepared plan, and recalculate the dose distribution, using V100, D98, D2, Dmean of PTV, and V20, V5 of the affected lung. /Dmean, the V5 and Dmean of the contralateral lung, the Dmax of the spinal cord, and the Dmean of the heart change the range to evaluate the sensitivity of the treatment plan to setup errors. Results: for 3mm setup error, the dose deviation of PTV was less than 5 % for Auto flash-optimized VMAT in either direction, and more than 5 % for non-Auto flash-optimized VMAT in the lower direction, the rest were less than 5 % . For the setting error of 5 mm, the dose deviation of PTV in the left and lower directions of VMAT plan optimized by Auto flash is more than 5 % , and the rest is less than 5 % , no Auto flash optimization of the VMAT plan in the left and lower direction of the PTV dose deviation of more than 5 % , the rest are less than 5 % . However, in terms of the magnitude of deviation, plans with Auto flash are smaller than those without Auto flash. Conclusion: the plan with Autoflash, the dosimetric difference is smaller than the plan without Autoflash when there is a setup error, and Autoflash should be used to participate in the optimization when formulating the breast cancer plan. Both plans have the least sensitivity in the inner, upper, and first directions, and the most sensitive in the outer, lower, and rear directions, and they should be deliberately paid attention to when setting up positions.

Cite this article

CHENG Xiuyan , GE Hong . Dosimetric study on positioning error of breast cancer VMAT plan with or without autoflash optimization[J]. Journal of Baotou Medical College, 2023 , 39(3) : 74 -79 . DOI: 10.16833/j.cnki.jbmc.2023.03.016

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