A Novel Portable Unilateral Magnetic Resonance Magnet for Noninvasive Quantification of Human Liver Fat

Fatty liver disease has become one of the common liver diseases seriously affecting people's health and quality of life. Existing means to quantify liver fat content are usually invasive and high-cost. Our research aims to design a single-sided magnet to develop a low-cost, noninvasive, and lightweight unilateral magnetic resonance (UMR) system that can satisfy the needs for fatty liver screening and diagnosis. A novel single-sided permanent magnet with a pear-shaped magnetic field iso-surface was designed to avoid the excitation of subcutaneous tissue in the human body. The weight of the magnet was optimized to 12.9 kg, and the mean magnetic field strength of the region of interest (ROI) was 0.07 T. The radio frequency (RF) coil set, the pulse sequence, and the modeling method for measuring proton density fat fraction (PDFF) were also introduced. Experiments for phantoms and volunteers were carried out by the UMR system to verify the performance of detection. The phantom detection results show that the UMR system can effectively avoid the influence of the subcutaneous tissue part on PDFF detection, with reasonable accuracy (around 5% fat fraction error) and robustness (within 10% relative error). Compared with a conventional magnetic resonance imaging (MRI) scanner, measurement results of volunteers (around 3% fat fraction error) show the effectiveness of the UMR system for screening fatty liver diseases. The UMR system developed based on the proposed portable single-sided magnet could be a low-cost and reliable diagnostic tool for noninvasive fatty liver disease diagnosis.