Accelerated metallic artifact reduction imaging using spectral bin modulation of multiacquisition variable-resonance image combination selective imaging.

Objectives: To assess the clinical utility of a prototype sequence for metal artifact reduction, the multiacquisition variable-resonance image combination selective (MAVRIC-SL) at 3 T. This sequence allows a surgical prosthesis-dependent reduction in the number of spectral bins. We compared the prototype MAVRIC SL to the conventional two-dimensional fast spin-echo (FSE) sequences and MAVRIC SL images acquired with all spectral bins to those acquired with the optimized number of spectral bins.

Multispectral diffusion-weighted MRI of the instrumented cervical spinal cord: a preliminary study of 5 cases.

Purpose: Diffusion-weighted imaging has undergone substantial investigation as a potential tool for advanced assessment of spinal cord health. Unfortunately, commonly encountered surgically implanted spinal hardware has historically disrupted these studies. This preliminary investigation applies the recently developed multispectral diffusion-weighted PROPELLER technique to quantitative assessment of the spinal cord immediately adjacent to metallic spinal fusion instrumentation.

MRI of Hip Arthroplasties: Comparison of Isotropic Multiacquisition Variable-Resonance Image Combination Selective (MAVRIC SL) Acquisitions With a Conventional MAVRIC SL Acquisition.

The objective of our study was to compare the quality and diagnostic utility of the following three metal artifact reduction sequences in evaluating hip arthroplasties: conventional multiacquisition variable-resonance image combination selective (MAVRIC SL), isotropic MAVRIC SL, and reduced-TR isotropic MAVRIC SL. Ninety-three hip arthroplasties (85 total hip replacements and eight hip resurfacings [nine bilateral hips]) in 84 patients (38 men and 46 women; mean age ± SD, 69.1 ± 9.

3D-multi-spectral T mapping near metal implants.

Purpose: Due to host-mediated adverse reaction to metallic debris, there is an increasing need for noninvasive assessment of the soft tissue surrounding large joint arthroplasties. Quantitative mapping can be beneficial for tissue characterization and early diagnosis of tissue pathology but current mapping techniques lack the capability to image near metal hardware. A novel multi-spectral mapping technique is proposed to address this unmet need.

Off-resonance based assessment of metallic wear debris near total hip arthroplasty.

Purpose: The presence of metallic debris near total hip arthroplasty can have a significant impact on longitudinal patient management. Methods for magnetic resonance imaging-based quantification of metallic debris near painful total hip replacements are described and applied to cohorts of symptomatic and control subject cases.

Methods: A combination of metal artifact reduction, off-resonance mapping, off-resonance background removal, and spatial clustering methods are utilized to quantify off-resonance signatures in cases of suspected metallosis.

Multispectral diffusion-weighted imaging near metal implants.

Purpose: The need for diffusion-weighted-imaging (DWI) near metallic implants is becoming increasingly relevant for a variety of clinical diagnostic applications. Conventional DWI methods are significantly hindered by metal-induced image artifacts. A novel approach relying on multispectral susceptibility artifact reduction techniques is presented to address this unmet need.

Quantifying metal-induced susceptibility artifacts of the instrumented spine at 1.5T using fast-spin echo and 3D-multispectral MRI.

Purpose: To evaluate magnetic resonance imaging (MRI) artifacts near metallic spinal instrumentation using both conventional metal artifact reduction sequences (MARS) and 3D multispectral imaging sequences (3D-MSI).

Materials And Methods: Both MARS and 3D-MSI images were acquired in 10 subjects with titanium spinal hardware on a 1.5T GE 450W scanner.

External calibration of the spectral coverage for three-dimensional multispectral MRI.

Purpose: By combining images created at distinct frequency offsets from the Larmor frequency, three-dimensional (3D) multispectral imaging (3D-MSI) sequences help overcome the large spatial frequency dispersion caused by metal implants. This frequency dispersion, however, varies with the implant size, orientation, and composition. Using a MAVRIC 3D-MSI acquisition, we sought to prospectively calibrate the spectral coverage needed for 3D-MSI scans.

Single-breath clinical imaging of hyperpolarized (129)Xe in the airspaces, barrier, and red blood cells using an interleaved 3D radial 1-point Dixon acquisition.

Purpose: We sought to develop and test a clinically feasible 1-point Dixon, three-dimensional (3D) radial acquisition strategy to create isotropic 3D MR images of (129)Xe in the airspaces, barrier, and red blood cells (RBCs) in a single breath. The approach was evaluated in healthy volunteers and subjects with idiopathic pulmonary fibrosis (IPF).

Methods: A calibration scan determined the echo time at which (129)Xe in RBCs and barrier were 90° out of phase.

Hyperpolarized Gas MR Imaging: Technique and Applications.

Functional imaging offers information more sensitive to changes in lung structure and function. Hyperpolarized helium ((3)He) and xenon ((129)Xe) MR imaging of the lungs provides sensitive contrast mechanisms to probe changes in pulmonary ventilation, microstructure, and gas exchange. Gas imaging has shifted to the use of (129)Xe.

Dose and pulse sequence considerations for hyperpolarized (129)Xe ventilation MRI.

Purpose: The aim of this study was to evaluate the effect of hyperpolarized (129)Xe dose on image signal-to-noise ratio (SNR) and ventilation defect conspicuity on both multi-slice gradient echo and isotropic 3D-radially acquired ventilation MRI.

Materials And Methods: Ten non-smoking older subjects (ages 60.8±7.

Extending semiautomatic ventilation defect analysis for hyperpolarized (129)Xe ventilation MRI.

Rationale And Objectives: Clinical deployment of hyperpolarized (129)Xe magnetic resonance imaging requires accurate quantification and visualization of the ventilation defect percentage (VDP). Here, we improve the robustness of our previous semiautomated analysis method to reduce operator dependence, correct for B1 inhomogeneity and vascular structures, and extend the analysis to display multiple intensity clusters.

Materials And Methods: Two segmentation methods were compared-a seeded region-growing method, previously validated by expert reader scoring, and a new linear-binning method that corrects the effects of bias field and vascular structures.

Measuring diffusion limitation with a perfusion-limited gas--hyperpolarized 129Xe gas-transfer spectroscopy in patients with idiopathic pulmonary fibrosis.

Although xenon is classically taught to be a "perfusion-limited" gas, (129)Xe in its hyperpolarized (HP) form, when detected by magnetic resonance (MR), can probe diffusion limitation. Inhaled HP (129)Xe diffuses across the pulmonary blood-gas barrier, and, depending on its tissue environment, shifts its resonant frequency relative to the gas-phase reference (0 ppm) by 198 ppm in tissue/plasma barrier and 217 ppm in red blood cells (RBCs). In this work, we hypothesized that in patients with idiopathic pulmonary fibrosis (IPF), the ratio of (129)Xe spectroscopic signal in the RBCs vs.

Probing the regional distribution of pulmonary gas exchange through single-breath gas- and dissolved-phase 129Xe MR imaging.

Although some central aspects of pulmonary function (ventilation and perfusion) are known to be heterogeneous, the distribution of diffusive gas exchange remains poorly characterized. A solution is offered by hyperpolarized 129Xe magnetic resonance (MR) imaging, because this gas can be separately detected in the lung's air spaces and dissolved in its tissues. Early dissolved-phase 129Xe images exhibited intensity gradients that favored the dependent lung.

Quantitative analysis of hyperpolarized 129Xe ventilation imaging in healthy volunteers and subjects with chronic obstructive pulmonary disease.

In this study, hyperpolarized (129) Xe MR ventilation and (1) H anatomical images were obtained from three subject groups: young healthy volunteers (HVs), subjects with chronic obstructive pulmonary disease (COPD) and age-matched controls (AMCs). Ventilation images were quantified by two methods: an expert reader-based ventilation defect score percentage (VDS%) and a semi-automated segmentation-based ventilation defect percentage (VDP). Reader-based values were assigned by two experienced radiologists and resolved by consensus.

Effects of corticosteroid treatment on airway inflammation, mechanics, and hyperpolarized ³He magnetic resonance imaging in an allergic mouse model.

The purpose of this study was to assess the effects of corticosteroid therapy on a murine model of allergic asthma using hyperpolarized (3)He magnetic resonance imaging (MRI) and respiratory mechanics measurements before, during, and after methacholine (MCh) challenge. Three groups of mice were prepared, consisting of ovalbumin sensitized/ovalbumin challenged (Ova/Ova, n = 5), Ova/Ova challenged but treated with the corticosteroid dexamethasone (Ova/Ova+Dex, n = 3), and ovalbumin-sensitized/saline-challenged (Ova/PBS, n = 4) control animals. All mice underwent baseline 3D (3)He MRI, then received a MCh challenge while 10 2D (3)He MR images were acquired for 2 min, followed by post-MCh 3D (3)He MRI.

Chronic obstructive pulmonary disease: safety and tolerability of hyperpolarized 129Xe MR imaging in healthy volunteers and patients.

Purpose: To evaluate the safety and tolerability of inhaling multiple 1-L volumes of undiluted hyperpolarized xenon 129 ((129)Xe) followed by up to a 16-second breath hold and magnetic resonance (MR) imaging.

Materials And Methods: This study was approved by the institutional review board and was HIPAA compliant. Written informed consent was obtained.

Diffusion-weighted hyperpolarized 129Xe MRI in healthy volunteers and subjects with chronic obstructive pulmonary disease.

Given its greater availability and lower cost, (129) Xe apparent diffusion coefficient (ADC) MRI offers an alternative to (3) He ADC MRI. To demonstrate the feasibility of hyperpolarized (129) Xe ADC MRI, we present results from healthy volunteers (HV), chronic obstructive pulmonary disease (COPD) subjects, and age-matched healthy controls (AMC). The mean parenchymal ADC was 0.

Hyperpolarized Xe MR imaging of alveolar gas uptake in humans.

Background: One of the central physiological functions of the lungs is to transfer inhaled gases from the alveoli to pulmonary capillary blood. However, current measures of alveolar gas uptake provide only global information and thus lack the sensitivity and specificity needed to account for regional variations in gas exchange.

Methods And Principal Findings: Here we exploit the solubility, high magnetic resonance (MR) signal intensity, and large chemical shift of hyperpolarized (HP) (129)Xe to probe the regional uptake of alveolar gases by directly imaging HP (129)Xe dissolved in the gas exchange tissues and pulmonary capillary blood of human subjects.

Quantitative analysis of hyperpolarized 3He ventilation changes in mice challenged with methacholine.

The capability to use high-resolution (3)He MRI to depict regional ventilation changes and airway narrowing in mice challenged with methacholine (MCh) offers the opportunity to gain new insights into the study of asthma. However, to fully exploit the value of this novel technique, it is important to move beyond visual inspection of the images toward automated and quantitative analysis. To address this gap, we describe a postprocessing approach to create ventilation difference maps to better visualize and quantify regional ventilation changes before and after MCh challenge.