Toward Hypoxia Imaging for Adaptive Dose Painting: Optimization of MP2RAGE for T1 Mapping in a Low-Field 0.35T MR-Linac (MRL)

Motivation: Stereotactic MR-guided Adaptive Radiation Therapy (SMART) ‘dose painting’ for hypoxia can improve treatment outcomes, but implementation on MR-Linac (MRL) faces low-field SNR challenges. Optimization of T1-to-noise ratio at 0.35T will enable clinical implementation of oxygen-enhanced (OE)-MRI. Goal(s): Develop and validate an optimized MP2RAGE sequence for low-field T1 mapping, establish feasibility and evaluate reproducibility in phantoms and healthy subjects. Approach: We optimized and validated an MP2RAGE sequence with simulations and a ground-truth phantom. T1 mapping feasibility was established in healthy subjects, variability and reproducibility was assessed. Results: A clinically feasible optimized low-field MP2RAGE protocol was developed, yielding accurate and reproducible T1 mapping. Impact: This work builds a foundation towards clinically feasible hypoxia imaging for low-field MRL. This would facilitate a paradigm shift toward MR-guided biological adaptation and dose painting, leveraging the spatial distribution of hypoxia, and improving patient outcomes in conventionally challenging-to-treat cancers.