Simultaneous, multidirectional acquisition of displacement fields in magnetic resonance elastography of the in vivo human brain

Purpose—To implement a multidirectional motion encoding scheme for magnetic resonance elastography (MRE) of the human brain with reduced acquisition time, and investigate its performance relative to a conventional MRE scheme. Materials and Methods—The sample interval modulation (SLIM) scheme was implemented in a multishot, variable density spiral MRE sequence. The brains of seven healthy volunteers were investigated with both SLIM-MRE and conventional MRE acquisitions in a single imaging session on a clinical 3 T MRI scanner with 50 Hz vibration. Following extraction of displacement fields, complex shear modulus property maps were estimated for each encoding acquisition. Results—The SLIM-MRE and conventional MRE acquisitions produced deformation fields that were nearly identical and exhibited an average correlation coefficient of 0.95 (all p < 0.05). Average properties of white matter differed between the two acquisitions by less than 5% for all volunteers, which is better than reproducibility estimates for conventional MRE alone. Conclusions—The use of SLIM provides very similar quantitative property estimates compared to the conventional MRE encoding scheme. The SLIM acquisition is 2.5 times faster than the conventional acquisition, and may improve the adoption of MRE in clinical settings.