Magnetic Resonance Fingerprinting for Rapid Quantitative Imaging of the Liver
This work presents developments in and applications of quantitative magnetic resonance imaging (qMRI) of the liver. Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent pathology whose pathogenesis and longitudinal behavior is not entirely understood. There is currently no non-invasive diagnostic test sensitive to all the stages of NAFLD progression, but several qMRI metrics such as fat signal fraction, water T1, and water T2 correlate with different liver histopathological states related to NAFLD. The abdomen is a challenging site for qMRI because of its large size, anatomical heterogeneity, and respiratory motion. These challenges affect the practicality of using qMRI in the abdomen to determine their relationship with NALFD histopathology. A recent development in qMRI called magnetic resonance fingerprinting (MRF) permits simultaneous estimation of multiple MRI parameters in scan times ≲ 20 s. However, the original form of this technique was not sensitive to partial volumes of fat and was generally not tailored for use in the abdomen. The following presents developments and applications towards unbiased and repeatable MRF parameter estimation in the liver for NAFLD study. These developments and applications include: blurring correction from off-resonance and chemical shift effects; fat-water separation with MRF with inline estimation of off-resonance frequency; expansion of extended phase graph modeling to address slice-profile effects; and evaluation of these technical advances in a repeatability study of MRF T1 and T2 estimation in the liver. We also demonstrate that MRF with fat-water separation may be deployed in NAFLD subjects.