Parametric Assessment of the Effect of Cochlear Implant Positioning on Brain MRI Artefacts at 3 T.

Background: Brain magnetic resonance imaging in patients with cochlear implants (CIs) is impacted by image artefacts.

Hypothesis: The optimal positioning of the CI to minimize artefacts is unknown. This study aimed to characterize the dependence of the extent and distribution of the artefact on CI positioning.

Clinical Validation of a 3-Dimensional Ultrafast Cardiac Magnetic Resonance Protocol Including Single Breath-Hold 3-Dimensional Sequences.

Objectives: This study sought to clinically validate a novel 3-dimensional (3D) ultrafast cardiac magnetic resonance (CMR) protocol including cine (anatomy and function) and late gadolinium enhancement (LGE), each in a single breath-hold.

Background: CMR is the reference tool for cardiac imaging but is time-consuming.

Methods: A protocol comprising isotropic 3D cine (Enhanced sensitivity encoding [SENSE] by Static Outer volume Subtraction [ESSOS]) and isotropic 3D LGE sequences was compared with a standard cine+LGE protocol in a prospective study of 107 patients (age 58 ± 11 years; 24% female).

Dissolved hyperpolarized xenon-129 MRI in human kidneys.

Purpose: To assess the feasibility of using dissolved hyperpolarized xenon-129 ( Xe) MRI to study renal physiology in humans at 3 T.

Methods: Using a flexible transceiver RF coil, dynamic and spatially resolved Xe spectroscopy was performed in the abdomen after inhalation of hyperpolarized Xe gas with 3 healthy male volunteers. A transmit-only receive-only RF coil array was purpose-built to focus RF excitation and enhance sensitivity for dynamic imaging of Xe uptake in the kidneys using spoiled gradient echo and balanced steady-state sequences.

Exercise cardiac MRI unmasks right ventricular dysfunction in acute hypoxia and chronic pulmonary arterial hypertension.

Coupling of right ventricular (RV) contractility to afterload is maintained at rest in the early stages of pulmonary arterial hypertension (PAH), but exercise may unmask depleted contractile reserves. We assessed whether elevated afterload reduces RV contractile reserve despite compensated resting function using noninvasive exercise imaging. Fourteen patients with PAH (mean age: 39.

Event-related dynamics of glutamate and BOLD effects measured using functional magnetic resonance spectroscopy (fMRS) at 3T in a repetition suppression paradigm.

Proton MR spectroscopy ((1)H-MRS) complements other brain research methods by providing measures of neurometabolites noninvasively in a localized brain area. Improvements in MR scanner technologies, and data acquisition and analysis methods should allow functional (1)H-MRS (fMRS) to measure neurometabolite concentration changes during task-induced brain activation. The aim of the current study was to further develop event-related fMRS at 3T to investigate glutamate dynamics in response to repetition suppression.

Noninvasive in vivo magnetic resonance measures of glutathione synthesis in human and rat liver as an oxidative stress biomarker.

Unlabelled: Oxidative stress (OS) plays a central role in the progression of liver disease and in damage to liver by toxic xenobiotics. We have developed methods for noninvasive assessment of hepatic OS defenses by measuring flux through the glutathione (GSH) synthesis pathway. (13) C-labeled GSH is endogenously produced and detected by in vivo magnetic resonance after administration of [2-(13) C]-glycine.

Sodium ((23)Na) ultra-short echo time imaging in the human brain using a 3D-Cones trajectory.

Object: Sodium magnetic resonance imaging ((23)Na-MRI) of the brain has shown changes in (23)Na signal as a hallmark of various neurological diseases such as stroke, Alzheimer's disease, Multiple Sclerosis and Huntington's disease. To improve scan times and image quality, we have implemented the 3D-Cones (CN) sequence for in vivo (23)Na brain MRI.

Materials And Methods: Using signal-to-noise (SNR) as a measurement of sequence performance, CN is compared against more established 3D-radial k-space sampling schemes featuring cylindrical stack-of-stars (SOS) and 3D-spokes kooshball (KB) trajectories, on five healthy volunteers in a clinical setting.

High-resolution imaging of magnetisation transfer and nuclear Overhauser effect in the human visual cortex at 7 T.

The aim of this study was to optimise a pulse sequence for high-resolution imaging sensitive to the effects of conventional macromolecular magnetisation transfer (MT(m)) and nuclear Overhauser enhancement (NOE), and to use it to investigate variations in these parameters across the cerebral cortex. A high-spatial-resolution magnetisation transfer-prepared turbo field echo (MT-TFE) sequence was designed to have high sensitivity to MT(m) and NOE effects, whilst being robust to B0 and B1 inhomogeneities, and producing a good point spread function across the cortex. This was achieved by optimising the saturation and imaging components of the sequence using simulations based on the Bloch equations, including exchange and an image simulator.

Simultaneous imaging of lung structure and function with triple-nuclear hybrid MR imaging.

Purpose: To re-engineer a standard clinical magnetic resonance (MR) imaging system to enable the acquisition, in the same breath hold, of lung images from two hyperpolarized gases (helium 3 [(3)He] and xenon 129 [(129)Xe]) with simultaneous registered anatomic proton (hydrogen 1 [(1)H]) MR images of lung structure.

Materials And Methods: Studies with (3)He and (129)Xe were performed with National Research Ethics Committee approval, with informed consent from the volunteer. (1)H-(3)He-(129)Xe MR imaging was achieved in the same breath by using mutually decoupled nested radiofrequency coil hardware capable of transmit and receive on each respective nucleus without power cross talk.

Quantification of venous vessel size in human brain in response to hypercapnia and hyperoxia using magnetic resonance imaging.

Hypercapnia and hyperoxia give rise to vasodilation and vasoconstriction, respectively. This study investigates the influence of hypercapnia and hyperoxia on venous vessel size in the human brain. Venous vessel radii were measured in response to hypercapnia and hyperoxia.

Magnetic resonance imaging of the mean venous vessel size in the human brain using transient hyperoxia.

Vessel size imaging is an emerging magnetic resonance imaging (MRI) technique which has been demonstrated to provide clinically relevant information about microvascular morphology. While previous studies of vessel size in humans relied on MRI contrast agents or hypercapnia-induced changes in blood oxygenation, the technique described here uses transient hyperoxia to alter the venous blood oxygenation. The experimental paradigm consisted of two 3-minute intervals of breathing 100% O(2) interleaved with three 2-minute intervals of breathing room air.

Susceptibility effects in hyperpolarized (3)He lung MRI at 1.5T and 3T.

Purpose: To compare susceptibility effects in hyperpolarized (3)He lung MRI at the clinically relevant field strengths of 1.5T and 3T.

Materials And Methods: Susceptibility-related B(0) inhomogeneity was evaluated on a macroscopic scale by B(0) field mapping via phase difference.

A functional-magnetic-resonance-imaging investigation of cortical activation from moving vibrotactile stimuli on the fingertip.

Using a 100-element tactile stimulator on the fingertip during functional-magnetic-resonance imaging, brain areas were identified that were selectively activated by a moving vibrotactile stimulus (the sensation of a moving line being dragged over the fingertip). Activation patterns elicited by tactile motion, contrasted to an equivalent stationary stimulus, were compared in six human subjects with those generated by a moving visual stimulus, contrasted to an equivalent stationary stimulus. Results provide further evidence for a neuroanatomical convergence of tactile-motion processing and visual-motion processing in humans.

Cadaveric and MRI study of the musculotendinous contributions to the capsule of the symphysis pubis.

Objective: The purpose of this article is to define the relations of the symphysis pubis and capsular tissues to the adductor and rectus abdominis soft-tissue attachments on cadaver dissection and correlate with MRI of the anterior pelvis.

Subjects And Methods: Seventeen cadavers (8 males and 9 females; mean age, 80 years) were dissected bilaterally. Rectus abdominis and adductor muscles were traced to the pubis and further attachments to the pubic symphysis were defined.

Delayed hypothermia prevents decreases in N-acetylaspartate and reduced glutathione in the cerebral cortex of the neonatal pig following transient hypoxia-ischaemia.

The effects of normothermia and delayed hypothermia on the levels of N-acetylaspartate (NAA), reduced glutathione (GSH) and the activities of mitochondrial complex I, II-III, IV and citrate synthase were measured in brain homogenates obtained from anaesthetized neonatal pigs following transient in vivo hypoxia-ischaemia. In the normothermic animals there was a significant decrease in complex I activity and in the levels of GSH and NAA when compared to the controls. Delayed hypothermia preserved NAA and GSH at control levels and enhanced the rate of complex II-III activity.