Oscillating gradient spin echo diffusion time effects implicate variations in neurite beading for the heterogeneous reduced diffusion in human acute ischemic stroke lesions.

Purpose: Monte Carlo simulations and short diffusion time measurements have suggested neurite beading and swelling as the underlying mechanism of reduced diffusion in acute stroke, although the observed diffusion time dependence is often heterogeneous and not yet fully understood. This study aimed to investigate the heterogeneity of diffusion time effects in ischemic lesions and explore the potential microstructural basis with Monte Carlo simulations.

Methods: Pulsed gradient spin echo (PGSE, diffusion time 40 ms) and oscillating gradient spin echo (OGSE 40 Hz, diffusion time ˜5.

Magnetization transfer MRI of third trimester fetal brain: a pilot of gestational myelin imaging.

Background: Magnetic resonance imaging (MRI) is commonly used as a tool for confirming a fetal brain abnormality suspected on ultrasound. Common clinical MRI sequences typically only reveal changes in the brain once there are gross abnormalities. Detection of more minute changes in brain tissue microstructure could permit earlier detection of complications, allowing for potentially more timely, effective interventions.

Sodium MRI of the skin using a surface coil to investigate and reduce signal loss and bias.

Purpose: The purpose was to improve sodium MRI of human skin using a surface coil and twisted projection imaging with smaller, reshaped voxels.

Methods: Calf skin sodium images were acquired in 14 healthy adults using twisted projection imaging with short TE ˜ 0.1 ms, first with a volume coil and voxels (1.

Dynamic changes in lung water density and volume following supine body positioning.

Purpose: Measure the changes in relative lung water density (rLWD), lung volume, and total lung water content as a function of time after supine body positioning.

Methods: An efficient ultrashort-TE pulse sequence with a yarnball k-space trajectory was used to measure water density-weighted lung images for 25 min following supine body positioning (free breathing, 74-s acquisitions, 3D images at functional residual capacity, 18 time points) in 9 healthy volunteers. Global and regional (10 chest-to-back positions) rLWD, lung volume, and total lung water volume were measured in all subjects at all time points.

Diffusion time dependency along the human corpus callosum and exploration of age and sex differences as assessed by oscillating gradient spin-echo diffusion tensor imaging.

Conventional diffusion imaging uses pulsed gradient spin echo (PGSE) waveforms with diffusion times of tens of milliseconds (ms) to infer differences of white matter microstructure. The combined use of these long diffusion times with short diffusion times (<10 ​ms) enabled by oscillating gradient spin echo (OGSE) waveforms can enable more sensitivity to changes of restrictive boundaries on the scale of white matter microstructure (e.g.

Radiofrequency excitation-related Na MRI signal loss in skeletal muscle, cartilage, and skin.

Purpose: To assess the sodium MRI signal loss resulting from typically used RF excitation pulses in human skeletal muscle, patellar cartilage, and skin.

Methods: A double flip-angle experiment was performed 3 times on the knees of 5 healthy volunteers with prescribed ω = γB of 1.67 kHz, 0.