Indirect H-[C] MRS of the human brain at 7 T using a C-birdcage coil and eight transmit-receive H-dipole antennas with a 32-channel H-receive array.

The neuronal tricarboxylic acid and glutamate/glutamine (Glu/Gln) cycles play important roles in brain function. These processes can be measured in vivo using dynamic H-[C] MRS during administration of C-labeled glucose. Proton-observed carbon-edited (POCE) MRS enhances the signal-to-noise ratio (SNR) compared with direct C-MRS.

Amide proton transfer weighted imaging in pediatric neuro-oncology: initial experience.

Amide proton transfer weighted (APTw) imaging enables in vivo assessment of tissue-bound mobile proteins and peptides through the detection of chemical exchange saturation transfer. Promising applications of APTw imaging have been shown in adult brain tumors. As pediatric brain tumors differ from their adult counterparts, we investigate the radiological appearance of pediatric brain tumors on APTw imaging.

The use of variable delay multipulse chemical exchange saturation transfer for separately assessing different CEST pools in the human brain at 7T.

Purpose: Current challenges of in vivo CEST imaging include overlapping signals from different pools. The overlap arises from closely resonating pools and/or the broad magnetization transfer contrast (MTC) from macromolecules. This study aimed to evaluate the feasibility of variable delay multipulse (VDMP) CEST to separately assess solute pools with different chemical exchange rates in the human brain in vivo, while mitigating the MTC.

No need to detune transmitters in 32-channel receiver arrays at 7 T.

Ultrahigh field magnetic resonance imaging facilitates high spatiotemporal resolution that benefits from increasing the number of receiver elements. Because high-density receiver arrays have a relatively small element size compared with the transmitter, a side effect is that such setups cause low flux coupling between the transmitter and receiver. Moreover, when transmitters are designed in a multitransmit configuration, their relative size is much smaller than the sample, reducing coupling to the sample and thereby potentially also the coupling to the receivers.

The YOUth cohort study: MRI protocol and test-retest reliability in adults.

The YOUth cohort study is a unique longitudinal study on brain development in the general population. As part of the YOUth study, 2000 children will be included at 8, 9 or 10 years of age and planned to return every three years during adolescence. Magnetic resonance imaging (MRI) brain scans are collected, including structural T1-weighted imaging, diffusion-weighted imaging (DWI), resting-state functional MRI and task-based functional MRI.

Validation of multiparametric MRI by histopathology after nephrectomy: a case study.

Objectives: Renal multiparametric MRI (mpMRI) is a promising tool to monitor renal allograft health to enable timely treatment of chronic allograft nephropathy. This study aims to validate mpMRI by whole-kidney histology following transplantectomy.

Materials And Methods: A patient with kidney transplant failure underwent mpMRI prior to transplantectomy.

Multiparametric Renal MRI: An Intrasubject Test-Retest Repeatability Study.

Background: Renal multiparametric magnetic resonance imaging (MRI) is a promising tool for diagnosis, prognosis, and treatment monitoring in kidney disease.

Purpose: To determine intrasubject test-retest repeatability of renal MRI measurements.

Study Type: Prospective.

Decreased native renal T up to one week after gadobutrol administration in healthy volunteers.

Background: Gadolinium-based contrast agents (GBCAs) are widely used in MRI, despite safety concerns regarding deposition in brain and other organs. In animal studies gadolinium was detected for weeks after administration in the kidneys, but this has not yet been demonstrated in humans.

Purpose: To find evidence for the prolonged presence of gadobutrol in the kidneys in healthy volunteers.

Volume increase in the dentate gyrus after electroconvulsive therapy in depressed patients as measured with 7T.

Electroconvulsive therapy (ECT) is the most effective treatment for depression, yet its working mechanism remains unclear. In the animal analog of ECT, neurogenesis in the dentate gyrus (DG) of the hippocampus is observed. In humans, volume increase of the hippocampus has been reported, but accurately measuring the volume of subfields is limited with common MRI protocols.

Implications of Extracranial Distortion in Ultra-High-Field Magnetic Resonance Imaging for Image-Guided Cranial Neurosurgery.

Background: Ultra-high-field magnetic resonance imaging (MRI) of the brain is attractive for image guidance during neurosurgery because of its high tissue contrast and detailed vessel visualization. However, high-field MRI is prone to distortion artifacts, which may compromise image guidance. Here we investigate intra- and extracranial distortions in 7-T MRI scans.

Analysis of chemical exchange saturation transfer contributions from brain metabolites to the Z-spectra at various field strengths and pH.

Chemical exchange saturation transfer (CEST) exploits the chemical exchange of labile protons of an endogenous or exogenous compound with water to image the former indirectly through the water signal. Z-spectra of the brain have traditionally been analyzed for two most common saturation phenomena: downfield amide proton transfer (APT) and upfield nuclear Overhauser enhancement (NOE). However, a great body of brain metabolites, many of interest in neurology and oncology, contributes to the downfield saturation in Z-spectra.

Phase matched RF pulse design for imaging a reduced field of excitation with a fast TSE acquisition.

A method is described to design parallel transmit (PTX) excitation pulses that are compatible with turbo spin echo (TSE) sequences, based on information available from conventional per-channel B mapping. The excitation phase of PTX pulses that generate a reduced field of excitation (rFOX) is matched to the phase the quadrature mode of a PTX coil. This enables TSE imaging of a PTX-enabled rFOX excitation combined with standard nonselective refocusing pulses transmitted in the quadrature mode.

Whole-brain 3D FLAIR at 7T using direct signal control.

Purpose: Image quality obtained for brain imaging at 7T can be hampered by inhomogeneities in the static magnetic field, B , and the RF electromagnetic field, B . In imaging sequences such as fluid-attenuated inversion recovery (FLAIR), which is used to assess neurological disorders, these inhomogeneities cause spatial variations in signal that can reduce clinical efficacy. In this work, we aim to correct for signal inhomogeneities to ensure whole-brain coverage with 3D FLAIR at 7T.

Establishing upper limits on neuronal activity-evoked pH changes with APT-CEST MRI at 7 T.

Purpose: To detect neuronal activity-evoked pH changes by amide proton transfer-chemical exchange saturation transfer (APT-CEST) MRI at 7 T.

Methods: Three healthy subjects participated in the study. A low-power 3-dimensional APT-CEST sequence was optimized through the Bloch-McConnell equations.

Fast quantitative MRI as a nonlinear tomography problem.

Quantitative Magnetic Resonance Imaging (MRI) is based on a two-steps approach: estimation of the magnetic moments distribution inside the body, followed by a voxel-by-voxel quantification of the human tissue properties. This splitting simplifies the computations but poses several constraints on the measurement process, limiting its efficiency. Here, we perform quantitative MRI as a one step process; signal localization and parameter quantification are simultaneously obtained by the solution of a large scale nonlinear inversion problem based on first-principles.

Relation between brown adipose tissue and measures of obesity and metabolic dysfunction in patients with cardiovascular disease.

Purpose: To evaluate whether brown adipose tissue (BAT) is present in middle-aged patients with cardiovascular comorbidities and to quantify how BAT presence associates with obesity and metabolic dysfunction.

Materials And Methods: Supraclavicular and subcutaneous adipose tissue fat-signal-fraction (FF) was determined with 1.5T water-fat magnetic resonance imaging (MRI) in 50 patients with coronary artery disease, cerebrovascular disease, or peripheral artery disease.

On the transmit field inhomogeneity correction of relaxation-compensated amide and NOE CEST effects at 7 T.

High field MRI is beneficial for chemical exchange saturation transfer (CEST) in terms of high SNR, CNR, and chemical shift dispersion. These advantages may, however, be counter-balanced by the increased transmit field inhomogeneity normally associated with high field MRI. The relatively high sensitivity of the CEST contrast to B inhomogeneity necessitates the development of correction methods, which is essential for the clinical translation of CEST.

Is there any difference in Amide and NOE CEST effects between white and gray matter at 7T?

Measurement of Chemical Exchange Saturation Transfer (CEST) is providing tissue physiology dependent contrast, e.g. by looking at Amide and NOE (Nuclear Overhauser Enhancement) effects.

Combining a reduced field of excitation with SENSE-based parallel imaging for maximum imaging efficiency.

Purpose: To show that a combination of parallel imaging using sensitivity encoding (SENSE) and inner volume imaging (IVI) combines the known benefits of both techniques. SENSE with a reduced field of excitation (rFOX) is termed rSENSE.

Theory And Methods: The noise level in SENSE reconstructions is reduced by removing voxels from the unfolding process that are rendered silent by using rFOX.

Comparison of pulsed three-dimensional CEST acquisition schemes at 7 tesla: steady state versus pseudosteady state.

Purpose: To compare two pulsed, volumetric chemical exchange saturation transfer (CEST) acquisition schemes: steady state (SS) and pseudosteady state (PS) for the same brain coverage, spatial/spectral resolution and scan time.

Methods: Both schemes were optimized for maximum sensitivity to amide proton transfer (APT) and nuclear Overhauser enhancement (NOE) effects through Bloch-McConnell simulations, and compared in terms of sensitivity to APT and NOE effects, and to transmit field inhomogeneity. Five consented healthy volunteers were scanned on a 7 Tesla Philips MR-system using the optimized protocols at three nominal B amplitudes: 1 μT, 2 μT, and 3 μT.

Surgical Accuracy of 3-Tesla Versus 7-Tesla Magnetic Resonance Imaging in Deep Brain Stimulation for Parkinson Disease.

Background: In deep brain stimulation (DBS), accurate placement of the lead is critical. Target definition is highly dependent on visual recognition on magnetic resonance imaging (MRI). We prospectively investigated whether the 7-T MRI enabled better visualization of targets and led to better placement of leads compared with the 1.

Quantitative T1 mapping under precisely controlled graded hyperoxia at 7T.

Increasing the concentration of oxygen dissolved in water is known to increase the recovery rate (R1 = 1/T1) of longitudinal magnetization (T1 relaxation). Direct T1 changes in response to precise hyperoxic gas challenges have not yet been quantified and the actual effect of increasing arterial oxygen concentration on the T1 of brain parenchyma remains unclear. The aim of this work was to use quantitative T1 mapping to measure tissue T1 changes in response to precisely targeted hyperoxic respiratory challenges ranging from baseline end-tidal oxygen (PetO) to approximately 500 mmHg.

The BOLD cerebrovascular reactivity response to progressive hypercapnia in young and elderly.

Blood Oxygenation Level Dependent (BOLD) imaging in combination with vasoactive stimuli can be used to probe cerebrovascular reactivity (CVR). Characterizing the healthy, age-related changes in the BOLD-CVR response can provide a reference point from which to distinguish abnormal CVR from the otherwise normal effects of ageing. Using a computer controlled gas delivery system, we examine differences in BOLD-CVR response to progressive hypercapnia between 16 young (28±3years, 9 female) and 30 elderly subjects (66±4years, 13 female).

Improving peak local SAR prediction in parallel transmit using in situ S-matrix measurements.

Purpose: Peak local specific absorption rate (pSAR10g) is an important parameter used to determine patient safety during radiofrequency transmission. pSAR10g predictions for parallel transmit MRI are affected by the level of coupling exhibited by a modeled array in the simulation environment. However, simulated array coupling is rarely equal to the physical array coupling.

Amide proton transfer (APT) imaging of brain tumors at 7 T: The role of tissue water T -Relaxation properties.

Purpose: To provide insight into the effect of water T relaxation (T ) on amide proton transfer (APT) contrast in tumors. Three different metrics of APT contrast-magnetization transfer ratio (MTR ), relaxation-compensated MTR (AREX), and traditional asymmetry (MTR )-were compared in normal and tumor tissues in a variety of intracranial tumors at 7 Tesla (T).

Methods: Six consented intracranial tumor patients were scanned using a low-power, three-dimensional (3D) APT imaging sequence.