Detection of acute renal ischemia in swine using blood oxygen level-dependent magnetic resonance imaging.

Purpose: To determine the feasibility and sensitivity of blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) to detect acute renal ischemia, using a swine model, and to present the causes of variability and assess techniques that minimize variability introduced during data analysis.

Materials And Methods: BOLD MRI was performed in axial and coronal planes of the kidneys of five swine. Color R2* maps were calculated and mean R2* values and 95% confidence intervals (CIs) for the cortex and medulla were determined for baseline, renal artery occlusion and reperfusion conditions.

Dual-velocity continuously moving table acquisition for contrast-enhanced peripheral magnetic resonance angiography.

Acquisition of MR angiographic data of the peripheral vasculature during continuous table motion offers certain advantages over fixed station approaches, such as the elimination of wasted time moving between stations and the ability to form a seamless image of the extended field of view. However, it has recently been demonstrated that there is an approximate twofold reduction in contrast bolus velocity as it moves from the thighs to the calves. This can potentially cause a mismatch of the moving table with the contrast peak, resulting in the table outpacing the contrast bolus distally.

Floating table isotropic projection (FLIPR) acquisition: a time-resolved 3D method for extended field-of-view MRI during continuous table motion.

In this work, 3D vastly undersampled isotropic projection (VIPR) acquisition is used simultaneously with continuous table motion to extend the superior/inferior (S/I) FOV for MR angiograms. The new technique is termed floating table isotropic PR (FLIPR). The use of 3D PR in conjunction with table motion obviates the need to locate and prescribe imaging volumes containing the major blood vessels over the large superior-inferior (S/I) ranges encountered in whole-body imaging.

Myocardial delayed enhancement imaging using inversion recovery single-shot steady-state free precession: initial experience.

Purpose: To evaluate the feasibility of using an inversion recovery single-shot steady-state free precession (SS_SSFP) sequence for myocardial delayed enhancement (MDE) imaging, and to compare SS_SSFP with the conventional inversion recovery segmented fast gradient echo (IR_FGRE) technique.

Materials And Methods: Ten subjects (four volunteers and six patients with suspected or known coronary disease) were included in this study. All subjects were scanned with both IR_FGRE and SS_SSFP sequences 15-25 minutes after gadopentetate dimeglumine injection.

Correction for gradient nonlinearity in continuously moving table MR imaging.

Recently, a number of methods have been demonstrated for large field of view MR imaging using continuous table motion. As with conventional, fixed-table MRI, the spatial encoding is performed using magnetic field gradients. However, it is demonstrated in this work that as a consequence of every measurement being made at a slightly different displacement between the object and the gradient field, gradient nonlinearities are manifest as blurring in addition to spatial distortion.

Helical MR: continuously moving table axial imaging with radial acquisitions.

A technique for extended field of view MRI is presented. Similar to helical computed tomography, the method utilizes a continuously moving patient table, a 2D axial slice that remains fixed relative to the MRI magnet, and a radial k-space trajectory. A fully refocused SSFP acquisition enables spatial resolution comparable to current clinical protocols in scan times that are sufficiently short to allow a reasonable breathhold duration.

Ventilation-perfusion ratio of signal intensity in human lung using oxygen-enhanced and arterial spin labeling techniques.

This study investigates the distribution of ventilation-perfusion (V/Q) signal intensity (SI) ratios using oxygen-enhanced and arterial spin labeling (ASL) techniques in the lungs of 10 healthy volunteers. Ventilation and perfusion images were simultaneously acquired using the flow-sensitive alternating inversion recovery (FAIR) method as volunteers alternately inhaled room air and 100% oxygen. Images of the T(1) distribution were calculated for five volunteers for both selective (T(1f)) and nonselective (T(1)) inversion.