Multiecho Fat-Water Spiral MR Elastography With Distributed Encoding for Simultaneously Imaging Brain and Skull Displacement

Purpose: To introduce a novel multiecho, multishot spiral MR elastography (MRE) sequence to image brain and skull displacement simultaneously using a joint fat-water image reconstruction and distributed motion encoding. Methods: Multiple echo times were implemented into a high-resolution multishot spiral MRE sequence to capture water-based brain signal and fat-based skull signal in a single acquisition. A joint fat-water reconstruction was optimized for brain-skull imaging, and a distributed motion encoding technique was incorporated to reduce acquisition time. This work demonstrates the feasibility of this sequence to quantify relative brain-skull displacement and brain tissue mechanical properties. Results: Brain and skull displacement were successfully imaged in a single acquisition. This technique was validated through comparison to a reference EPI MRE scan in which no significant differences were found in mechanical properties derived from each scan. A preliminary analysis of brain and skull displacement over time revealed that relative brain-skull displacement was variable across the surface of the brain, with a higher amplitude of brain displacement at the anterior of the head. Conclusion: The proposed multiecho fat-water spiral MRE sequence is a promising technique for quantifying brain-skull displacement in vivo to improve computational modeling of traumatic brain injury.