Comparing R2* and QSM at 9.4T for the ability to detect increased deoxyhemoglobin (hypoxia) in the mouse brain

Motivation: Investigating R2* and QSM for deoxyhemoglobin detection is vital for diagnosing and understanding diseases where tissue oxygenation is frequently compromised. Goal(s): To evaluate R2* against QSM for their ability to detect deoxyhemoglobin changes in a controlled hypoxic environment using a mouse model. Approach: Employ a graded hypoxia protocol in naïve, female C57Bl/6 mice, capturing 3D MGE images at various oxygen levels (30%, 15% and 10%) to measure R2* and QSM responses. Results: R2* demonstrated significant sensitivity to hypoxia in brain regions, particularly the hippocampus, unlike QSM, suggesting its potential as a superior hypoxia biomarker. Impact: This study reveals R2* relaxometry's superior sensitivity to the detection of changes in deoxyhemoglobin over QSM, potentially improving early detection and monitoring of hypoxia-related diseases, such as Multiple Sclerosis, and informing future clinical imaging protocols.