Initial Experience of Applying TWIST-Dixon With Flexible View Sharing in Breast DCE-MRI.

Introduction: We developed a new fast imaging technique with flexible time-resolved angiography with stochastic trajectories (TWIST) view sharing to achieve variable temporal resolution and with flexible echo time Dixon to achieve robust fat suppression and to evaluate its application in breast dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI).

Materials And Methods: The TWIST-Dixon technique was improved with more flexible view sharing and echo times (TWIST-Dixon-Flex). In a dynamic series, each measurement can be separately prescribed as "full," "partial," or "center-only.

Free-breathing variable flip angle balanced SSFP cardiac cine imaging with reduced SAR at 3T.

Purpose: To develop a free-breathing variable flip angle (VFA) balanced steady-state free precession (bSSFP) cardiac cine imaging technique with reduced specific absorption rate (SAR) at 3 Tesla.

Methods: Free-breathing VFA (FB-VFA) images in the short-axis and four-chamber views were acquired using an optimal VFA scheme, then compared with conventional breath-hold constant flip angle (BH-CFA) acquisitions. Two cardiac MRI experts used a 5-point scale to score images from healthy subjects (N = 10).

Clinical evaluation of CAIPIRINHA: comparison against a GRAPPA standard.

Purpose: To evaluate image quality when using a CAIPIRINHA sampling pattern in comparison to a standard GRAPPA sampling pattern in patients undergoing a routine three-dimensional (3D) breathheld liver exam. CAIPIRINHA uses an optimized phase encoding sampling strategy to alter aliasing artifacts in 3D acquisitions to improve parallel imaging reconstruction.

Materials And Methods: Twenty patient volunteers were scanned using a 3D VIBE acquisition with an acceleration factor of four using a CAIPIRINHA and standard GRAPPA sampling pattern.

Application of time-resolved angiography with stochastic trajectories (TWIST)-Dixon in dynamic contrast-enhanced (DCE) breast MRI.

Purpose: To evaluate a magnetic resonance imaging (MRI) technique that integrates time-resolved angiography with stochastic trajectories (TWIST) view sharing and Dixon for a breast dynamic contrast-enhanced (DCE)-MRI application.

Materials And Methods: Simulation study: K-space data at six timepoints (1 pre-, 5 postcontrast) were generated by performing Fourier transform on a digital "phantom" with 3-9 mm enhancing lesions and three types of enhancement curves (persistent, plateau, washout). Images were reconstructed with and without TWIST.

High spatial and temporal resolution dynamic contrast-enhanced magnetic resonance angiography using compressed sensing with magnitude image subtraction.

Purpose: We propose a compressed-sensing (CS) technique based on magnitude image subtraction for high spatial and temporal resolution dynamic contrast-enhanced MR angiography (CE-MRA).

Methods: Our technique integrates the magnitude difference image into the CS reconstruction to promote subtraction sparsity. Fully sampled Cartesian 3D CE-MRA datasets from 6 volunteers were retrospectively under-sampled and three reconstruction strategies were evaluated: k-space subtraction CS, independent CS, and magnitude subtraction CS.

CAIPIRINHA-Dixon-TWIST (CDT)-volume-interpolated breath-hold examination (VIBE): a new technique for fast time-resolved dynamic 3-dimensional imaging of the abdomen with high spatial resolution.

Purpose: The purpose of this study was to assess the feasibility and image quality of a novel, highly accelerated T1-weighted sequence for time-resolved imaging of the abdomen during the first pass of contrast media transit using controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) under sampling, view-sharing techniques, and Dixon water-fat separation (CAIPRINHA-Dixon-time-resolved imaging with interleaved stochastic trajectories-volumetric interpolated breath-hold examination [CDT-VIBE]).

Materials And Methods: In this retrospective, institutional review board-approved study, 47 patients (median age, 62 years; 25 men, 22 women) scanned on a 3.0-T magnetic resonance system (Skyra; Siemens) were included.

Steady-state first-pass perfusion (SSFPP): a new approach to 3D first-pass myocardial perfusion imaging.

Purpose: To describe and characterize a new approach to first-pass myocardial perfusion utilizing balanced steady-state free precession acquisition without the use of saturation recovery or other magnetization preparation.

Theory: The balanced steady-state free precession sequence is inherently sensitive to contrast agent enhancement of the myocardium. This sensitivity can be used to advantage in first-pass myocardial perfusion imaging by eliminating the need for magnetization preparation.

Development and evaluation of TWIST Dixon for dynamic contrast-enhanced (DCE) MRI with improved acquisition efficiency and fat suppression.

Purpose: To develop a new pulse sequence called time-resolved angiography with stochastic trajectories (TWIST) Dixon for dynamic contrast enhanced magnetic resonance imaging (DCE-MRI).

Materials And Methods: The method combines dual-echo Dixon to generate separated water and fat images with a k-space view-sharing scheme developed for 3D TWIST. The performance of TWIST Dixon was compared with a volume interpolated breathhold examination (VIBE) sequence paired with spectrally selective adiabatic inversion Recovery (SPAIR) and quick fat-sat (QFS) fat-suppression techniques at 3.

Automatic view planning for cardiac MRI acquisition.

Conventional cardiac MRI acquisition involves a multi-step approach, requiring a few double-oblique localizers in order to locate the heart and prescribe long- and short-axis views of the heart. This approach is operator-dependent and time-consuming. We propose a new approach to automating and accelerating the acquisition process to improve the clinical workflow.

Optimal k-space sampling for dynamic contrast-enhanced MRI with an application to MR renography.

For time-resolved acquisitions with k-space undersampling, a simulation method was developed for selecting imaging parameters based on minimization of errors in signal intensity versus time and physiologic parameters derived from tracer kinetic analysis. Optimization was performed for time-resolved angiography with stochastic trajectories (TWIST) algorithm applied to contrast-enhanced MR renography. A realistic 4D phantom comprised of aorta and two kidneys, one healthy and one diseased, was created with ideal tissue time-enhancement pattern generated using a three-compartment model with fixed parameters, including glomerular filtration rate (GFR) and renal plasma flow (RPF).

Time-resolved MR angiography with generalized autocalibrating partially parallel acquisition and time-resolved echo-sharing angiographic technique for hemodialysis arteriovenous fistulas and grafts.

Purpose: To evaluate the imaging of hemodialysis arteriovenous (AV) fistulas and grafts with use of magnetic resonance (MR) angiography with generalized autocalibrating partially parallel acquisition (GRAPPA) and time-resolved echo-sharing angiographic technique (TREAT) and compare the findings with those of digital subtraction angiography (DSA).

Materials And Methods: The vascular tree directly related to AV fistulas and grafts was divided into nine segments. Images of each segment obtained on GRAPPA MR angiography were evaluated for the presence of stenosis, occlusion, and any other disease (eg, pseudoaneurysm) by two independent observers and compared with a consensus reading of the same segments on DSA imaging.

Time-resolved contrast-enhanced three-dimensional magnetic resonance angiography of the chest: combination of parallel imaging with view sharing (TREAT).

Rationale And Objectives: In view sharing, some parts of k-space are updated more often than others, leading to an effective shortening of the total acquisition time. Undersampling of high-frequency k-space data, however, can result in artifacts at the edges of blood vessels, especially during the rapid signal intensity changes. The objective of this study was to evaluate a new time-resolved echo-shared angiographic technique (TREAT) combining parallel imaging with view sharing.

Thorax: low-dose contrast-enhanced three-dimensional MR angiography with subsecond temporal resolution--initial results.

The purpose of the study was to implement a three-dimensional (3D) magnetic resonance (MR) angiographic technique with acquisition times on the order of 800 msec with use of a spoiled gradient-echo pulse sequence (repetition time, 1.60 msec; echo time, 0.65 msec) and bolus intravenous injection of contrast material doses as small as 6 mL.