Model-Based Dynamic B0 Compensation of a 0.35T MRI-Linac using Inclinometer Data

Balanced steady state free procession (bSSFP) sequences are commonly used for real-time imaging during MRI guided radiotherapy treatments (MR-IGRT). bSSFP sequences offer high temporal resolution and SNR but are sensitive to B0 fluctuations which lead to imaging artifacts during radiotherapy (RT) gantry rotatation.1 Previous work demonstrated that RT gantry rotation induced artifacts could be significantly reduced by compensating for B0 fluctuations using data from a free induction decay (FID) navigator prior to each bSSFP image.2 A model-based approach to B0 compensation using the gantry inclinometer was evaluated to reduce the SNR loss and temporal resolution associated with the navigator approach.