The assessment of functional liver tissue is of growing clinical importance in predicting post-operative outcomes and optimizing liver-directed therapies. Quantitative Blood Oxygen Level Dependent (qBOLD) imaging offers a non-invasive MRI-based method to measure tissue oxygenation via the R2′ relaxation parameter. R2′ is defined as the difference between R2* and R2, and reflects magnetic field inhomogeneities caused by deoxyhemoglobin, among other factors.

This research explores the feasibility of estimating R2′ in the liver using a multiparametric qBOLD (MqBOLD) approach under free-breathing conditions. Two MRI sequences, one for R2 and one for R2* mapping, were optimized and applied at 1.5 T and 3 T. A cohort of five healthy volunteers was scanned to evaluate image quality and relaxation rates across field strengths and breathing techniques.

Results showed that R2′ mapping is feasible using an MqBOLD approach under predominantly free-breathing conditions, without apparent motion artifacts. The mean R2′ values in homogeneous liver parenchyma were 12.7 ± 2.8 s⁻¹ at 1.5 T and 24.6 ± 4.8 s⁻¹ at 3 T. Both 1.5 T and 3 T proved suitable for R2′ mapping. While 1.5 T offered better image quality, 3 T provided more reliable quantitative results and greater patient comfort.

As a proof of concept, the MqBOLD protocol was successfully integrated into a routine clinical liver MRI scan protocol for a patient with neuroendocrine liver metastasis. The additional scan time was under three minutes, and the resulting relaxation maps showed contrast between tumor and healthy liver tissue.

In conclusion, this research establishes the feasibility of R2′ mapping in the liver using a multiparametric MRI approach under mostly free-breathing conditions. It presents a foundation for non-invasive liver oxygenation imaging, with the potential to evolve into a clinically applicable tool for functional liver assessment.