Whole‐Body Oxygen‐Enhanced MRI of Tumor‐Bearing Mice Under Hyperbaric Oxygenation

Purpose Oxygen‐enhanced MRI (OE‐MRI) enables noninvasive assessment of tissue oxygenation by exploiting the paramagnetic effect of molecular oxygen on longitudinal relaxation. The purpose of this study was to evaluate whether whole‐body oxygen‐enhanced MRI (OE‐MRI) can be performed under hyperbaric oxygen (HBO) conditions and to assess its utility for detecting oxygenation changes in a small‐animal tumor model using a clinical 3 T scanner. Methods A fully MRI‐compatible HBO chamber was built for imaging mice and installed in a 3 T clinical scanner. SCC7‐tumor‐bearing C3H mice underwent whole‐body OE‐MRI with variable flip‐angle T 1 mapping. Longitudinal relaxation‐rates ( R 1 ) and Δ R 1 were measured while the animals breathed 21% O 2 at 1 ATA, 21% O 2 at 2 ATA, 100% O 2 at 1 ATA, and 100% O 2 at 2 ATA. Δ R 1 was quantified in tumor, brain, and heart regions. Results High‐quality OE‐MRI was obtained under all hyperbaric conditions. Normal tissues (brain, heart) showed uniform, pressure‐dependent increases in Δ R 1 with higher inspired oxygen fractions. Tumors displayed pronounced spatial heterogeneity: many voxels responded robustly, while others showed little or no Δ R 1 change even at 2 ATA 100% O 2 . The proportion of oxygen‐responsive tumor voxels rose with increasing pressure, yet non‐responsive regions persisted. Conclusion Whole‐body pre‐clinical OE‐MRI on a clinical 3 T system is feasible and sensitive under hyperbaric oxygenation, capturing both tissue‐level pressure effects and heterogeneous tumor oxygen responses. This non‐invasive HBO‐OE‐MRI platform provides a valuable pre‐clinical tool for assessing oxygen delivery and identifying oxygen‐refractory tumor zones, supporting oxygen‐guided therapeutic strategies.