Noninvasive Mechanical Ventilation Is a Promising Way to Improve Lung Cancer Radiation Therapy

Abstract

Purpose: Accurate radiation therapy (RT) for lung cancer is challenging because of the respiratory motion of the tumor and surrounding organs at risk. Recently, non-invasive mechanical ventilation (NIMV) has been investigated as a novel respiratory motion management strategy. Using NIMV, respiratory motion can be minimized, while a larger lung volume yields less overall lung dose. The purpose of this study was to determine the potential benefit of NIMV to improve lung cancer RT using magnetic resonance imaging (MRI) data of healthy volunteers. Methods and Materials: Twelve healthy volunteers practiced NIMV at 60 breaths per minute (NIMV60) with added positive end-expiratory pressure (PEEP) in 2 sessions and subsequently underwent NIMV60 in 2 MRI sessions. We acquired single-slice sagittal 2-dimensional MRI images at 2.6 Hz for 6 minutes during free breathing and NIMV60. We quantified the motion of all visible cross-sections of lung arteries, as a surrogate for lung tumors, in cranio-caudal and anterior-posterior directions using deformable image registration, distinguishing between 4 quadrants in the lungs (posterior-cranial, posterior-caudal, anterior-caudal, and anterior-cranial). Also, we analyzed average lung area, as a surrogate for lung volume, on the sagittal images using automatic segmentation. Results: All volunteers were successfully trained to be ventilated with NIMV60, and completed all sessions. The reduction of the median lung artery motion in each of the quadrants varied from 61% to 67% (from 10.7-29.9 to 3.8-11.7 mm) in cranio-caudal direction and from 51% to 68% (from 8.0-13.7 to 3.0-5.1 mm) in anterior-posterior direction using NIMV60. NIMV60 increased the sagittal lung area by 35% compared with free breathing. Conclusions: NIMV60 with added PEEP is a promising way to improve lung cancer RT because of reduced respiratory motion and increased lung area compared with free breathing.