Boron Neutron Capture Therapy (BNCT) is an emerging radiotherapy technique. However, respiratory motion has a critical impact on the dose accuracy in BNCT treatment of lung cancer.

This study aims to quantify the dosimetric impact caused by respiratory motion during BNCT treatment of lung cancer.

This study adopted the Monte Carlo simulation method was adopted to develop a dynamic model that captured the spatiotemporal variations of tumors and organs caused by respiratory motion during lung cancer treatment, and performed dose calculations for BNCT. Firstly, the Multi-function and Generalized Intelligent Code-bench based on Monte Carlo method (MagicMC) was employed to model the adult male phantom provided by Oak Ridge National Laboratory (ORNL). Then, a dynamic dose calculation model was established by incorporating high-order cosine functions that described respiratory motion. Finally, MagicMC was applied to the calculation of the dose errors in tumors and organs resulting from respiratory motion in different directions within three-dimensional space.

The results indicate that during a respiratory cycle, the tumor in all three motion directions exhibits the largest percentage dose difference at the 50% phase. In the left-right direction (LR), it is 0.310%; in the anterior-posterior direction (AP), it is 5.830%; and in the superior-inferior direction (SI), it is -2.852%. The closer healthy tissues are to the irradiation field, the higher the dose rate they receive. The maximum percentage dose difference for the heart in the LR direction is 2.070%, and the maximum percentage dose differences for the right lung in the AP and SI directions are 4.128% and -11.962%, respectively. During BNCT treatment irradiation, organ motion in the AP direction has the greatest impact on tumor dose, resulting in a dose error of 1.644%. For healthy tissues, the dose errors induced by motion in all three directions remain within ±4%.

The study demonstrates that organ respiratory motion during BNCT treatment for lung cancer affects the doses received by tumors and healthy tissues, the calculation results can provide a reference for precise dose calculation and clinical irradiation dose correction in BNCT treatment of lung cancer.