A comparison of gas-free MRI methods for CMRO2 quantification in primary brain tumour

Motivation: Several MRI techniques have been proposed for quantification of cerebral metabolic rate of oxygen consumption (CMRO2), each with its own assumptions and limitations. Their relative performance in pathology has not been previously characterised. Goal(s): To compare the performance of three gas-free methodologies for mapping CMRO2 in brains with significantly altered physiology. Approach: Patients with glioma were scanned with qBOLD, breath-hold calibrated fMRI (bhc-fMRI), and QSM mapping of macrovascular oxygenation. Results: CMRO2 estimates from QSM and bhc-fMRI were in good agreement across GM, WM, oedema and enhancing tumour. CMRO2 estimates from qBOLD were elevated in enhancing tumour and had increased variability. Impact: Common implementations for gas-free CMRO2 quantification do not account for non-blood susceptibility sources. This is demonstrated to be problematic for an R2' based qBOLD implementation in primary brain tumour, where haemorrhage and iron deposition can occur concurrently with metabolic changes.