Evaluation of Dose Distribution in Intensity Modulated Radiosurgery for Lung Cancer under Condition of Respiratory Motion.

Myung Ha Yoon ,Jae‐Uk Jeong ,Sung‐Ja Ahn ,Woong‐Ki Chung ,Taek‐Keun Nam ,Jong Tae Song

doi:10.1371/journal.pone.0163112

Abstract

The dose of a real tumor target volume and surrounding organs at risk (OARs) under the effect of respiratory motion was calculated for a lung tumor plan, based on the target volume covering the whole tumor motion range for intensity modulated radiosurgery (IMRS). Two types of IMRS plans based on simulated respiratory motion were designed using humanoid and dynamic phantoms. Delivery quality assurance (DQA) was performed using ArcCHECK and MapCHECK2 for several moving conditions of the tumor and the real dose inside the humanoid phantom was evaluated using the 3DVH program. This evaluated dose in the tumor target and OAR using the 3DVH program was higher than the calculated dose in the plan, and a greater difference was seen for the RapidArc treatment than for the standard intensity modulated radiation therapy (IMRT) with fixed gantry angle beams. The results of this study show that for IMRS plans based on target volume, including the whole tumor motion range, tighter constraints of the OAR should be considered in the optimization process. The method devised in this study can be applied effectively to analyze the dose distribution in the real volume of tumor target and OARs in IMRT plans targeting the whole tumor motion range.

Highlights

Radiosurgery for lung cancer can deliver higher dose per treatment than conventional radiotherapy, thereby reducing the number of days required for treatment
The applications are increasing with the development of accurate treatment equipment such as a linear accelerator (LINAC) that has a high dose rate photon beam and micro multi-leaf collimator (MMLC) [1,2,3]
One of its limitations is that, the intensity modulated radiation therapy (IMRT) plan does not calculate the real volume of the tumor target and organs at risk (OARs), and it is difficult to evaluate the real delivered dose under the moving condition

Summary

Introduction

Radiosurgery for lung cancer can deliver higher dose per treatment than conventional radiotherapy, thereby reducing the number of days required for treatment. The applications are increasing with the development of accurate treatment equipment such as a linear accelerator (LINAC) that has a high dose rate photon beam and micro multi-leaf collimator (MMLC) [1,2,3]. Intensity modulated radiosurgery (IMRS) adopting the intensity modulated radiation therapy (IMRT) technique that minimizes the side effects of the organs at risk (OARs) surrounding the tumor target has been applied effectively to clinical lung cancer treatment [4,5,6,7]. The effect of respiratory motion should be considered in the treatment plan for lung tumors, as this can introduce significant dosimetric errors in the radiosurgery process. The first is to reduce the treated volume by PLOS ONE | DOI:10.1371/journal.pone.0163112 September 20, 2016

Methods

Results

Discussion

Conclusion