SU-D-BRA-04: Improvement of Diaphragm Motion Reproducibility in MRI Using Audiovisual Biofeedback for Lung Cancer Radiotherapy.

PURPOSE Previous studies have investigated the effect of AV biofeedback on the external respiratory signal reproducibility. This is the first study investigating the effect of AV biofeedback to improve the motion reproducibility of the internal anatomy. The aim of the project is to test the hypothesis that AV biofeedback improves the diaphragm motion reproducibility. METHODS An AV biofeedback system has been employed with MRI acquisitions. The AV biofeedback system utilized (1) the external marker position on the abdomen using an RPM system (Real-time Position Management, Varian) to audio-visually guide a human subject for regular breathing and (2) a fast Gradient-Recalled-Echo (fGRE) MR pulse sequence of 3 Tesla GE MRI (GE Healthcare) to monitor the diaphragm motion (200ms). The improvement in the diaphragm motion reproducibility using the AV biofeedback system combined with MRI has been assessed in 26 studies with 13 healthy human subjects. Each subject underwent two studies for assessment of the diaphragm motion reproducibility both with AV biofeedback and without (free breathing). The second study features a reversed order of breathing conditions. The total MRI acquisitions across the 26 studies are 202 measurements including sagittal and coronal planes. RESULTS Average RMSE (root mean square error) of diaphragm displacement obtained from MRI analysis has been reduced from 2.7mm of free breathing to 1.6mm of AV biofeedback breathing (p-value < 0.05). Additionally, the average RMSE of diaphragm motion period was reduced from 1.84s with free breathing to 0.34s with AV biofeedback breathing (p- value < 0.05). 22% of average displacement error was reduced using AV biofeedback in the first study, and 47% reduction in the second study. CONCLUSIONS The study demonstrated the improvement in the diaphragm motion reproducibility using AV biofeedback. This system can provide clinically applicable motion management of the internal anatomy in MRI and for Image Guided Radiotherapy (IGRT).