Agreement between multiparametric MRI (PIVOT), Doppler ultrasound, and near-infrared spectroscopy-based assessments of skeletal muscle oxygenation and perfusion.

Unlabelled: Skeletal muscle perfusion and oxygenation are commonly evaluated using Doppler ultrasound and near-infrared spectroscopy (NIRS) techniques. However, a recently developed magnetic resonance imaging (MRI) sequence, termed PIVOT, permits the simultaneous collection of skeletal muscle perfusion and T2* (an index of skeletal muscle oxygenation).

Purpose: To determine the level of agreement between PIVOT, Doppler ultrasound, and NIRS-based assessments of skeletal muscle perfusion and oxygenation.

Displacement current distribution on a high dielectric constant helmet and its effect on RF field at 10.5 T (447 MHz).

Purpose: Investigating the designs and effects of high dielectric constant (HDC) materials in the shape of a conformal helmet on the enhancement of RF field and reduction of specific absorption rate at 10.5 T for human brain studies.

Methods: A continuous and a segmented four-piece HDC helmet fit to a human head inside an eight-channel fractionated-dipole array were constructed and studied with a phantom and a human head model using computer electromagnetic simulations.

Diffusion tensor imaging indices of acute muscle damage are augmented after exercise in peripheral arterial disease.

Purpose: Although it is known that peripheral arterial disease (PAD) is associated with chronic myopathies, the acute muscular responses to exercise in this population are less clear. This study used diffusion tensor imaging (DTI) to compare acute exercise-related muscle damage between PAD patients and healthy controls.

Methods: Eight PAD patients and seven healthy controls performed graded plantar flexion in the bore of a 3T MRI scanner.

Renal medullary oxygenation decreases with lower body negative pressure in healthy young adults.

One in three Americans suffer from kidney diseases such as chronic kidney disease, and one of the etiologies is suggested to be long-term renal hypoxia. Interestingly, sympathetic nervous system activation evokes a renal vasoconstrictor effect that may limit oxygen delivery to the kidney. In this report, we sought to determine if sympathetic activation evoked by lower body negative pressure (LBNP) would decrease cortical and medullary oxygenation in humans.

An Electronic Aerosol Delivery System for Functional Magnetic Resonance Imaging.

Background: Public health concerns over the addictive potential of electronic cigarettes (e-cigs) have heightened in recent years. Brain function during e-cig use could provide an objective measure of the addictive potential of new vaping products to facilitate research; however, there are limited methods for delivering e-cig aerosols during functional magnetic resonance imaging (fMRI). The current study describes the development and feasibility testing of a prototype to deliver up to four different e-cig aerosols during fMRI.

The exercise pressor reflex and active O transport in peripheral arterial disease.

It is unclear if the exaggerated exercise pressor reflex observed in peripheral arterial disease (PAD) patients facilitates Oxygen (O ) transport during presymptomatic exercise. Accordingly, this study compared O transport between PAD patients and healthy controls during graded presymptomatic work. Seven PAD patients and seven healthy controls performed dynamic plantar flexion in the bore of a 3T MRI scanner.

Toward whole-cortex enhancement with an ultrahigh dielectric constant helmet at 3T.

Purpose: To present a 3T brain imaging study using a conformal prototype helmet constructed with an ultra-high dielectric constant (uHDC; ε ~ 1000) materials that can be inserted into standard receive head-coils.

Methods: A helmet conformal to a standard human head constructed with uHDC materials was characterized through electromagnetic simulations and experimental work. The signal-to-noise ratio (SNR), transmit efficiency, and power deposition with the uHDC helmet inserted within a 20-channel head coil were measured in vivo and compared with a 64-channel head coil and the 20-channel coil without the helmet.

Improvements of transmit efficiency and receive sensitivity with ultrahigh dielectric constant (uHDC) ceramics at 1.5 T and 3 T.

Purpose: Incorporating high dielectric constant (HDC) materials into radiofrequency (RF) coils has been shown to effectively improve RF coil performance at 7 and 3 T because of the induced displacement current in the high dielectric constant materials. The displacement current is proportional to the RF field frequency and permittivity of the material. The aim of this paper is to investigate the effect of high dielectric constant materials with even greater permittivity on the RF field at 1.

Muscle oxygenation during dynamic plantar flexion exercise: combining BOLD MRI with traditional physiological measurements.

Blood-oxygen-level-dependent magnetic resonance imaging (BOLD MRI) has the potential to quantify skeletal muscle oxygenation with high temporal and high spatial resolution. The purpose of this study was to characterize skeletal muscle BOLD responses during steady-state plantar flexion exercise (i.e.

Dynamic characteristics of T2*-weighted signal in calf muscles of peripheral artery disease during low-intensity exercise.

Purpose: To evaluate the dynamic characteristics of T2* -weighted signal change in exercising skeletal muscle of healthy subjects and peripheral artery disease (PAD) patients under a low-intensity exercise paradigm.

Materials And Methods: Nine PAD patients and nine age- and sex-matched healthy volunteers underwent a low-intensity exercise paradigm while magnetic resonance imaging (MRI) (3.0T) was obtained.

Complex difference constrained compressed sensing reconstruction for accelerated PRF thermometry with application to MRI-induced RF heating.

Purpose: Introduce a novel compressed sensing reconstruction method to accelerate proton resonance frequency shift temperature imaging for MRI-induced radiofrequency heating evaluation.

Methods: A compressed sensing approach that exploits sparsity of the complex difference between postheating and baseline images is proposed to accelerate proton resonance frequency temperature mapping. The method exploits the intra-image and inter-image correlations to promote sparsity and remove shared aliasing artifacts.

Measurement of SAR-induced temperature increase in a phantom and in vivo with comparison to numerical simulation.

Purpose: To compare numerically simulated and experimentally measured temperature increase due to specific energy absorption rate from radiofrequency fields.

Methods: Temperature increase induced in both a phantom and in the human forearm when driving an adjacent circular surface coil was mapped using the proton resonance frequency shift technique of magnetic resonance thermography. The phantom and forearm were also modeled from magnetic resonance image data, and both specific energy absorption rate and temperature change as induced by the same coil were simulated numerically.

Permittivity and performance of dielectric pads with sintered ceramic beads in MRI: early experiments and simulations at 3 T.

Passive dielectric materials have been used to improve aspects of MRI by affecting the distribution of radiofrequency electromagnetic fields. Recently, interest in such materials has increased with the number of high-field MRI sites. Here, we introduce a new material composed of sintered high-permittivity ceramic beads in deuterated water.

Optimization of spiral-based pulse sequences for first-pass myocardial perfusion imaging.

Although spiral trajectories have multiple attractive features such as their isotropic resolution, acquisition efficiency, and robustness to motion, there has been limited application of these techniques to first-pass perfusion imaging because of potential off-resonance and inconsistent data artifacts. Spiral trajectories may also be less sensitive to dark-rim artifacts that are caused, at least in part, by cardiac motion. By careful consideration of the spiral trajectory readout duration, flip angle strategy, and image reconstruction strategy, spiral artifacts can be abated to create high-quality first-pass myocardial perfusion images with high signal-to-noise ratio.

Fast conjugate phase image reconstruction based on a Chebyshev approximation to correct for B0 field inhomogeneity and concomitant gradients.

Off-resonance effects can cause image blurring in spiral scanning and various forms of image degradation in other MRI methods. Off-resonance effects can be caused by both B0 inhomogeneity and concomitant gradient fields. Previously developed off-resonance correction methods focus on the correction of a single source of off-resonance.

Concomitant gradient field effects in balanced steady-state free precession.

Linear magnetic field gradients spatially encode the image information in MRI. Concomitant gradients are undesired magnetic fields that accompany the desired gradients and occur as an unavoidable consequence of Maxwell's equations. These concomitant gradients result in undesired phase accumulation during MRI scans.