Fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths MR elastography.

PURPOSE: To design a new 2D gradient recalled echo MR elastography (MRE) pulse sequence with inflow saturation for measuring liver stiffness in half the breath-hold time compared to standard of care (SC) 2D GRE MRE sequences. METHODS: FASTWALTZ (fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths) MRE employs an interleaved dual TR strategy with wave amplitude labeling and compressed SENSE undersampling to reduce breath-hold time while incorporating inflow saturation to suppress flow artifacts. The sequence was implemented and compared with SC MRE both in phantoms and in vivo in 5 asymptomatic volunteers. Stiffness values, region of interest size, and breath-hold times were compared between sequences. RESULTS: Stiffness values were comparable between FASTWALTZ and SC MRE for both phantoms and in-vivo data. In volunteers, the group mean stiffness values at 60 Hz and region of interest size were 1.96 ± 0.30 kilopascals and 2279 ± 516 mm2 for SC MRE, and 1.95 ± 0.29 kilopascals and 2061 ± 464 mm2 for FASTWALTZ. Breath-hold duration for FASTWALTZ was 6.3 s compared to 13.3 s for SC MRE. CONCLUSION: FASTWALTZ provides comparable stiffness values in half the breath-hold time compared to SC MRE and may have clinical benefits in patients with limited breath-holding capacity.

A Novel Approach to Evaluate Brain Activation for Lower Extremity Motor Control.

BACKGROUND AND PURPOSE: The purpose of this study was to assess the consistency of a novel MR safe lower extremity motor control neuroimaging paradigm to elicit reliable sensorimotor region brain activity. METHODS: Participants completed multiple sets of unilateral leg presses combining ankle, knee, and hip extension and flexion movements against resistance at a pace of 1.2 Hz while lying supine in a 3T MRI scanner. Regions of Interest (ROI) consisted of regions primarily involved in lower extremity motor control (right and left primary motor cortex, primary somatosensory cortex, premotor cortex, secondary somatosensory cortex, basal ganglia, and the cerebellum). RESULTS: The group analysis based on mixed effects paired samples t-test revealed no differences for brain activity between sessions (P > .05). Intraclass correlation coefficients in the sensorimotor regions were good to excellent for average percent signal change (.621 to .918) and Z-score (.697 to .883), with the exception of the left secondary somatosensory cortex percent signal change (.165). CONCLUSIONS: These results indicate that a loaded lower extremity force production and attenuation task that simulates the range of motion of squatting, stepping, and landing from a jump is reliable for longitudinal neuroimaging applications and support the use of this paradigm in further studies examining therapeutic interventions and changes in dynamic lower extremity motor function.