Free-Breathing Hepatic Oxygen Extraction Fraction (OEF) Mapping Using Radial GESSE.
Authors
Affiliations (9)
Affiliations (9)
- Department of Diagnostic and Interventional Radiology, Heidelberg University Hospital, Heidelberg, Germany.
- Translational Lung Research Center (TLRC), German Center for Lung Research (DZL), Heidelberg, Germany.
- Department of Diagnostic and Interventional Radiology With Nuclear Medicine, Thoraxklinik at Heidelberg University Hospital, Heidelberg, Germany.
- Divison of Radiology, German Cancer Research Center, Heidelberg, Germany.
- Division of Neuroradiology, Geneva University Hospitals, Geneva, Switzerland.
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China.
- Division of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany.
- Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany.
- Faculty of Medicine, Heidelberg University, Heidelberg, Germany.
Abstract
Noninvasive assessment of hepatic oxygenation is relevant for evaluating liver both in acute and long-term liver pathologies. However, existing methods are limited to single-slice acquisitions and require breath-holding. This study aims to develop and evaluate a motion-robust technique for whole-liver oxygen extraction fraction (OEF) mapping using a radial gradient-echo sampling of spin-echo (rGESSE) sequence in combination with an artificial neural network (ANN) for quantification. Seven healthy volunteers were scanned using a 1.5 T MRI system with an 18-channel body coil. A multi-slice rGESSE sequence with radial sampling was employed under free-breathing conditions to acquire volumetric liver data. Signal processing included bias-field correction and 3D median filtering. OEF, deoxygenated blood volume (DBV), and transverse relaxation rate (R<sub>2</sub>) were estimated using a trained feedforward ANN based on simulated qBOLD signal models. Whole-liver OEF maps were successfully obtained in all volunteers under free-breathing. Representative parameter maps showed consistent spatial patterns and anatomical correspondence. The mean hepatic OEF across subjects was 55.75% ± 6.88%, and the mean DBV was 0.568 ± 0.039. Comparison with literature values suggested a systematic overestimation, likely arising from a combination of model approximations, residual B<sub>0</sub> inhomogeneity, motion effects, and acquisition-specific sensitivities. ANN-based fitting outperformed standard least-squares regression in terms of stability and artifact suppression. This study demonstrates the feasibility of using rGESSE combined with ANN analysis for free-breathing, whole-liver OEF mapping. The proposed approach allows for noninvasive, volumetric hepatic oxygenation assessment with improved motion robustness, offering potential for clinical application in liver disease diagnosis and monitoring.