Helping You Find Full Text Journal Articles

Search Results:

Author: Matthew D Robson (137)


Feb
2018

Imaging studies have relied on the 'overall' volumetric quantification of perivascular adipose tissue. We sought to assess the relationship of circumferential distribution between perivascular adipose tissue and adjacent wall thickness of carotid and aortic arteries using dedicated magnetic resonance imaging sequences.
Vessel wall and perivascular adipose tissue were acquired using magnetic resonance imaging (1.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
2017

To establish a cardiac signal from scattering matrix or scattering coefficient measurements made on a 7T 8-channel parallel transmit (pTx) system, and to evaluate its use for cardiac gating.
Measurements of the scattering matrix and scattering coefficients were acquired using a monitoring pulse sequence and during a standard cine acquisition, respectively. Postprocessing used an independent component analysis and gating feature identification.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

Cardiac phosphorus magnetic resonance spectroscopy (31P-MRS) provides unique insight into the mechanisms of heart failure. Yet, clinical applications have been hindered by the restricted sensitivity of the surface radiofrequency-coils normally used. These permit the analysis of spectra only from the interventricular septum, or large volumes of myocardium, which may not be meaningful in focal disease.

View Full Text PDF Listings View primary source full text article PDFs.

Sep
2017

Novel low-energy defibrillation therapies are thought to be driven by virtual-electrodes (VEs), due to the interaction of applied monophasic electric shocks with fine-scale anatomical structures within the heart. Significant inter-species differences in the cardiac (micro)-anatomy exist, however, particularly with respect to the degree of endocardial trabeculations, which may underlie important differences in response to low-energy defibrillation protocols. Understanding the interaction of monophasic electric fields with the specific human micro-anatomy is therefore imperative in facilitating the translation and optimisation of these promising experimental therapies to the clinic.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

In vivo magnetic resonance spectroscopy provides insight into metabolism in the human body. New acquisition protocols are often proposed to improve the quality or efficiency of data collection. Processing pipelines must also be developed to use these data optimally.

View Full Text PDF Listings View primary source full text article PDFs.

Aug
2017

CMR T1 mapping is a quantitative imaging technique allowing the assessment of myocardial injury early after ST-segment-elevation myocardial infarction. We sought to investigate the ability of acute native T1 mapping to differentiate reversible and irreversible myocardial injury and its predictive value for left ventricular remodeling.
Sixty ST-segment-elevation myocardial infarction patients underwent acute and 6-month 3T CMR, including cine, T2-weighted (T2W) imaging, native shortened modified look-locker inversion recovery T1 mapping, rest first pass perfusion, and late gadolinium enhancement.

View Full Text PDF Listings View primary source full text article PDFs.

Apr
2018

To evaluate the use of radiofrequency scattering of a parallel transmit coil to track diaphragm motion.
Measurements made during radiofrequency excitation on an 8-channel parallel transmit coil by the directional couplers of the radiofrequency safety monitor were combined and converted into diaphragm position. A 30-s subject-specific calibration with an MRI navigator was used to determine a diaphragm estimate from each directional-coupler measure.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

Techniques to stratify subgroups of patients with asymptomatic carotid artery disease are urgently needed to guide decisions on optimal treatment. Reliance on estimates of % luminal stenosis has not been effective, perhaps because that approach entirely disregards potentially important information on the pathological process in the wall of the artery.
Since plaque lipid is a key determinant of plaque behaviour we used a newly validated, high-sensitivity T2-mapping MR technique for a systematic survey of the quantity and distribution of plaque lipid in patients undergoing endarterectomy.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
2017

Phosphorus (P) metabolites are emerging liver disease biomarkers. Of particular interest are phosphomonoester and phosphodiester (PDE) "peaks" that comprise multiple overlapping resonances inP spectra. This study investigates the effect of improved spectral resolution at 7 Tesla (T) on quantifying hepatic metabolites in cirrhosis.

View Full Text PDF Listings View primary source full text article PDFs.

Nov
2017

Hepatic iron content (HIC) quantification via transverse relaxation rate (R2*)-MRI using multi-gradient echo (mGRE) imaging is compromised toward high HIC or at higher fields due to the rapid signal decay. Our study aims at presenting an optimized 2D ultrashort echo time (UTE) sequence for R2* quantification to overcome these limitations.
Two-dimensional UTE imaging was realized via half-pulse excitation and radial center-out sampling.

View Full Text PDF Listings View primary source full text article PDFs.

Nov
2017

Phosphorus magnetic resonance spectroscopy (P-MRS) provides a unique tool for assessing cardiac energy metabolism, often quantified using the phosphocreatine (PCr)/adenosine triphosphate (ATP) ratio. Surface coils are typically used for excitation forP-MRS, but they create an inhomogeneous excitation field across the myocardium, producing undesirable, spatially varying partial saturation. Therefore, we implemented adiabatic excitation in a 3D chemical shift imaging (CSI) sequence for cardiacP-MRS at 7 Tesla (T).

View Full Text PDF Listings View primary source full text article PDFs.

View Full Text PDF Listings View primary source full text article PDFs.

Jul
2017

The diagnosis of non-alcoholic steatohepatitis and fibrosis staging are central to non-alcoholic fatty liver disease assessment. We evaluated multiparametric magnetic resonance in the assessment of non-alcoholic steatohepatitis and fibrosis using histology as standard in non-alcoholic fatty liver disease.
Seventy-one patients with suspected non-alcoholic fatty liver disease were recruited within 1 month of liver biopsy.

View Full Text PDF Listings View primary source full text article PDFs.

Nov
2016

Purpose To test whether the increased signal-to-noise ratio of phosphorus 31 (P) magnetic resonance (MR) spectroscopy at 7 T improves precision in cardiac metabolite quantification in patients with dilated cardiomyopathy (DCM) compared with that at 3 T. Materials and Methods Ethical approval was obtained, and participants provided written informe consent. In a prospective study,P MR spectroscopy was performed at 3 T and 7 T in 25 patients with DCM.

View Full Text PDF Listings View primary source full text article PDFs.

Jul
2017

The aim of this study was to: 1) provide tissue validation of quantitative Tmapping to measure plaque lipid content; and 2) investigate whether this technique could discern differences in plaque characteristics between symptom-related and non-symptom-related carotid plaques.
Noninvasive plaque lipid quantification is appealing both for stratification in treatment selection and as a possible predictor of future plaque rupture. However, current cardiovascular magnetic resonance (CMR) methods are insensitive, require a coalesced mass of lipid core, and rely on multicontrast acquisition with contrast media and extensive post-processing.

View Full Text PDF Listings View primary source full text article PDFs.

Oct
2016

Evidence suggests that interleukin (IL)-1β is important in the pathogenesis of atherosclerosis and its complications and that inhibiting IL-1β may favorably affect vascular disease progression.
The goal of this study was to evaluate the effects of IL-1β inhibition with canakinumab versus placebo on arterial structure and function, determined by magnetic resonance imaging.
Patients (N = 189) with atherosclerotic disease and either type 2 diabetes mellitus or impaired glucose tolerance were randomized to receive placebo (n = 94) or canakinumab 150 mg monthly (n = 95) for 12 months.

View Full Text PDF Listings View primary source full text article PDFs.

Aug
2017

A novel method for quantitative measurement of myocardial blood flow (MBF) using arterial spin labeling (ASL) in a single breath-hold is presented, evaluated by simulations, phantom studies and in vivo studies and tested for reproducibility and variability.
A flow-sensitive alternating inversion recovery (FAIR) ASL method with Look-Locker readout (LL-FAIR-ASL) was implemented at 3 tesla. Scans were performed on 10 healthy volunteers and MBF measured in three slices.

View Full Text PDF Listings View primary source full text article PDFs.

Jul
2017

We present a new Bloch-Siegert four Angle Saturation Transfer (BOAST) method for measuring the creatine kinase (CK) first-order effective rate constant kin human myocardium at 7 tesla (T). BOAST combines a variant of the four-angle saturation transfer (FAST) method using amplitude-modulated radiofrequency pulses, phosphorus Bloch-Siegert B1+-mapping to determine the per-voxel flip angles, and nonlinear fitting to Bloch simulations for postprocessing.
Optimal flip angles and repetition time parameters were determined from Monte Carlo simulations.

View Full Text PDF Listings View primary source full text article PDFs.

Feb
2017

To propose a simple multicompartment model of the liver and use Bloch-McConnell simulations to demonstrate the effects of iron and fibrosis on shortened-MOLLI (shMOLLI) Tmeasurements. Liver Tvalues have shown sensitivity to inflammation and fibrosis, but are also affected by hepatic iron content. Modified Look-Locker inversion recovery (MOLLI) Tmeasurements are biased by the lower Tassociated with high iron.

View Full Text PDF Listings View primary source full text article PDFs.

May
2016

Pheochromocytoma is associated with catecholamine-induced cardiac toxicity, but the extent and nature of cardiac involvement in clinical cohorts is not well-characterized.
This study characterized the cardiac phenotype in patients with pheochromocytoma using cardiac magnetic resonance (CMR).
A total of 125 subjects were studied, including patients with newly diagnosed pheochromocytoma (n = 29), patients with previously surgically cured pheochromocytoma (n = 31), healthy control subjects (n = 51), and hypertensive control subjects (HTN) (n = 14), using CMR (1.

View Full Text PDF Listings View primary source full text article PDFs.

Mar
2017

To present a framework in which time-varying gradients are applied with RF spoiling to reduce unwanted signal, particularly at high flip angles.
A time-varying gradient spoiler scheme compatible with RF spoiling is defined, in which spoiler gradients cycle through the vertices of a hexagon, which we call hexagonal spoiling. The method is compared with a traditional constant spoiling gradient both in the transition to and in the steady state.

View Full Text PDF Listings View primary source full text article PDFs.

Feb
2016

UK Biobank's ambitious aim is to perform cardiovascular magnetic resonance (CMR) in 100,000 people previously recruited into this prospective cohort study of half a million 40-69 year-olds.
We describe the CMR protocol applied in UK Biobank's pilot phase, which will be extended into the main phase with three centres using the same equipment and protocols. The CMR protocol includes white blood CMR (sagittal anatomy, coronary and transverse anatomy), cine CMR (long axis cines, short axis cines of the ventricles, coronal LVOT cine), strain CMR (tagging), flow CMR (aortic valve flow) and parametric CMR (native T1 map).

View Full Text PDF Listings View primary source full text article PDFs.

Jan
2016

The authors sought to generate a synthetic extracellular volume fraction (ECV) from the relationship between hematocrit and longitudinal relaxation rate of blood.
ECV quantification by cardiac magnetic resonance (CMR) measures diagnostically and prognostically relevant changes in the extracellular space. Current methodologies require blood hematocrit (Hct) measurement-a complication to easy clinical application.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

To characterize the effect of fat on modified Look-Locker inversion recovery (MOLLI) T1 maps of the liver. The balanced steady-state free precession (bSSFP) sequence causes water and fat signals to have opposite phase when repetition time (TR) = 2.3 msec at 3T.

View Full Text PDF Listings View primary source full text article PDFs.

Jan
2017

To demonstrate the feasibility of imaging a bolus of co-polarized [1-C]pyruvate andC-urea to simultaneously assess both metabolism and perfusion in the rodent heart.
Copolarized [1-C]pyruvate andC-urea was imaged using a multi-echo, flow-sensitized spiral pulse sequence. Healthy rats were scanned in a two-factor factorial design (n = 12 total; metabolism: overnight fasting versus fed with dichloroacetate injection; perfusion: rest versus adenosine stress-induced hyperemia).

View Full Text PDF Listings View primary source full text article PDFs.

Jan
2016

The aim of this study was to evaluate the potential of T1 mapping at rest and during adenosine stress as a novel method for ischemia detection without the use of gadolinium contrast.
In chronic coronary artery disease (CAD), accurate detection of ischemia is important because targeted revascularization improves clinical outcomes. Myocardial blood volume (MBV) may be a more comprehensive marker of ischemia than myocardial blood flow.

View Full Text PDF Listings View primary source full text article PDFs.

Jan
2016

To investigate the relationship between hepatic fat content, circulating triglyceride levels and aortic stiffness in adult and childhood obesity.
Seventy-seven adults and 18 children across a wide range of body mass index (18.5-52.

View Full Text PDF Listings View primary source full text article PDFs.

Oct
2016

Phosphorus MR spectroscopy ((31) P-MRS) is a powerful tool for investigating tissue energetics in vivo. Cardiac (31) P-MRS is typically performed using surface coils that create an inhomogeneous excitation field across the myocardium. Accurate measurements of B1+ (and hence flip angle) are necessary for quantitative analysis of (31) P-MR spectra.

View Full Text PDF Listings View primary source full text article PDFs.

Feb
2016

Multiparametric magnetic resonance (MR) imaging has been demonstrated to quantify hepatic fibrosis, iron, and steatosis. The aim of this study was to determine if MR can be used to predict negative clinical outcomes in liver disease patients.
Patients with chronic liver disease (n=112) were recruited for MR imaging and data on the development of liver related clinical events were collected by medical records review.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
2016

Patients with type 2 diabetes mellitus (T2DM) are known to have impaired resting myocardial energetics and impaired myocardial perfusion reserve, even in the absence of obstructive epicardial coronary artery disease (CAD). Whether or not the pre-existing energetic deficit is exacerbated by exercise, and whether the impaired myocardial perfusion causes deoxygenation and further energetic derangement during exercise stress, is uncertain.
Thirty-one T2DM patients, on oral antidiabetic therapies with a mean HBA1c of 7.

View Full Text PDF Listings View primary source full text article PDFs.

Aug
2015

T1-mapping using the Shortened Modified Look-Locker Inversion Recovery (ShMOLLI) technique enables non-invasive assessment of important myocardial tissue characteristics. However, tachyarrhythmia may cause mistriggering and inaccurate T1 estimation. We set out to test whether systolic T1-mapping might overcome this, and whether T1 values or data quality would be significantly different compared to conventional diastolic T1-mapping.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
1969

Parallel transmission (PTx) requires knowledge of the B1+ produced by each element. However, B1+ mapping can be challenging when transmit fields exhibit large dynamic range. This study presents a method to produce high quality relative B1+ maps when this is the case.

View Full Text PDF Listings View primary source full text article PDFs.

Apr
2016

To demonstrate the feasibility of imaging the first passage of a bolus of hyperpolarized (13)C urea through the rodent heart using flow-sensitizing gradients to reduce signal from the blood pool.
A flow-sensitizing bipolar gradient was optimized to reduce the bright signal within the cardiac chambers, enabling improved contrast of the agent within the tissue capillary bed. The gradient was incorporated into a dynamic golden angle spiral (13)C imaging sequence.

View Full Text PDF Listings View primary source full text article PDFs.

Mar
2016

The translation of sophisticated phosphorus MR spectroscopy ((31)P-MRS) protocols to 7 Tesla (T) is particularly challenged by the issue of radiofrequency (RF) heating. Legal limits on RF heating make it hard to reliably suppress signals from skeletal muscle that can contaminate human cardiac (31)P spectra at 7T. We introduce the first surface-spoiling crusher coil for human cardiac (31)P-MRS at 7T.

View Full Text PDF Listings View primary source full text article PDFs.

May
2015

The goal of this study was to assess the diffuse myocardial fibrosis and edema in rheumatoid arthritis (RA) using multiparametric cardiac magnetic resonance (CMR) and the association of myocardial T1 and extracellular volume (ECV) with disease activity, duration, and cardiac function.
RA is a connective tissue disorder, with frequent cardiovascular disease. Myocardial inflammation and diffuse fibrosis can be detected noninvasively by using native T1 mapping and ECV quantification on CMR.

View Full Text PDF Listings View primary source full text article PDFs.

Feb
2016

Combining spectra from receive arrays, particularly X-nuclear spectra with low signal-to-noise ratios (SNRs), is challenging. We test whether data-driven combination methods are better than using computed coil sensitivities.
Several combination algorithms are recast into the notation of Roemer's classic formula, showing that they differ primarily in their estimation of coil receive sensitivities.

View Full Text PDF Listings View primary source full text article PDFs.

View Full Text PDF Listings View primary source full text article PDFs.

Dec
2014

Cardiovascular magnetic resonance (CMR) derived native myocardial T1 is decreased in patients with Fabry disease even before left ventricular hypertrophy (LVH) occurs and may be the first non-invasive measure of myocyte sphingolipid storage. The relationship of native T1 lowering prior to hypertrophy and other candidate early phenotype markers are unknown. Furthermore, the reproducibility of T1 mapping has never been assessed in Fabry disease.

View Full Text PDF Listings View primary source full text article PDFs.

Jun
2015

To explore the use and reproducibility of magnetic resonance-derived myocardial T1 mapping in patients with iron overload.
The research received ethics committee approval and all patients provided written informed consent. This was a prospective study of 88 patients and 67 healthy volunteers.

View Full Text PDF Listings View primary source full text article PDFs.

Jun
2015

Ultra-high field (UHF) MR scanning in the body requires novel coil designs due to B1 field inhomogeneities. In the transverse electromagnetic field (TEM) design, maximum B1 transmit power can only be achieved if each individual transmit element is tuned and matched for different coil loads, which requires a considerable amount of valuable scanner time.
An integrated system for autotuning a multichannel parallel transmit (pTx) cardiac TEM array was devised, using piezoelectric actuators, power monitoring equipment and control software.

View Full Text PDF Listings View primary source full text article PDFs.

May
2015

To investigate for the first time the feasibility of aortic four-dimensional (4D) flow at 7T, both contrast enhanced (CE) and non-CE. To quantify the signal-to-noise ratio (SNR) in aortic 4D flow as a function of field strength and CE with gadobenate dimeglumine (MultiHance).
Six healthy male volunteers were scanned at 1.

View Full Text PDF Listings View primary source full text article PDFs.

Nov
2014

To prospectively compare the black-blood ( BB black blood ) imaging efficiency of a delay alternating with nutation for tailored excitation ( DANTE delay alternating with nutation for tailored excitation ) preparation module with conventional double inversion-recovery ( DIR double inversion recovery ) and motion-sensitive driven equilibrium ( MSDE motion-sensitive driven equilibrium ) preparation modules and to introduce a new three-dimensional ( 3D three-dimensional ) T1-weighted magnetic resonance (MR) imaging sequence.
Carotid artery wall imaging was performed in 10 healthy volunteers and 15 patients in accordance with an institutional review board-approved protocol. Two-dimensional ( 2D two-dimensional ) turbo spin-echo ( TSE turbo spin echo ) and 3D three-dimensional fast low-angle shot ( FLASH fast low-angle shot ) sequences served as readout modules.

View Full Text PDF Listings View primary source full text article PDFs.

May
2014

Acute myocarditis can be diagnosed on cardiovascular magnetic resonance (CMR) using multiple techniques, including late gadolinium enhancement (LGE) imaging, which requires contrast administration. Native T1-mapping is significantly more sensitive than LGE and conventional T2-weighted (T2W) imaging in detecting myocarditis. The aims of this study were to demonstrate how to display the non-ischemic patterns of injury and to quantify myocardial involvement in acute myocarditis without the need for contrast agents, using topographic T1-maps and incremental T1 thresholds.

View Full Text PDF Listings View primary source full text article PDFs.

May
2014

Diffusion tensor cardiac magnetic resonance (DT-CMR) enables probing of the microarchitecture of the myocardium, but the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) reported in healthy volunteers have been inconsistent. The aim of this study was to validate a stimulated-echo diffusion sequence using phantoms, and to assess the intercentre reproducibility of in-vivo diffusion measures using the sequence.
A stimulated-echo, cardiac-gated DT-CMR sequence with a reduced-field-of-view, single-shot EPI readout was used at two centres with 3 T MRI scanners.

View Full Text PDF Listings View primary source full text article PDFs.

Apr
2014

Left ventricular (LV) hypertrophy in aortic stenosis (AS) is characterized by reduced myocardial perfusion reserve due to coronary microvascular dysfunction. However, whether this hypoperfusion leads to tissue deoxygenation is unknown. We aimed to assess myocardial oxygenation in severe AS without obstructive coronary artery disease, and to investigate its association with myocardial energetics and function.

View Full Text PDF Listings View primary source full text article PDFs.

Apr
2015

To investigate whether saturation using existing methods developed for 3T imaging is feasible for clinical perfusion imaging at 7T, and to propose a new design of saturation pulse train for first-pass myocardial perfusion imaging at 7T.
The new design of saturation pulse train consists of four hyperbolic-secant (HS8) radiofrequency pulses, whose peak amplitudes are optimized for a target range of static and transmit field variations and radiofrequency power deposition restrictions measured in the myocardium at 7T. The proposed method and existing methods were compared in simulation, phantom, and in vivo experiments.

View Full Text PDF Listings View primary source full text article PDFs.

Mar
2015

To demonstrate the feasibility of accelerating measurements of cardiac fiber structure using simultaneous multislice (SMS) imaging.
SMS excitation with a blipped controlled aliasing (CAIPI) readout was incorporated into a diffusion-encoded stimulated echo pulse sequence to obtain diffusion measurements in three separate slices of the heart (8-mm thickness, 12-mm gap). A novel image entropy-based method for removing image ghosts in blipped CAIPI acquisitions is also introduced that enables SMS imaging of closely spaced slices in the heart.

View Full Text PDF Listings View primary source full text article PDFs.

Mar
2014

Systemic sclerosis (SSc) is characterised by multi-organ tissue fibrosis including the myocardium. Diffuse myocardial fibrosis can be detected non-invasively by T1 and extracellular volume (ECV) quantification, while focal myocardial inflammation and fibrosis may be detected by T2-weighted and late gadolinium enhancement (LGE), respectively, using cardiovascular magnetic resonance (CMR). We hypothesised that multiparametric CMR can detect subclinical myocardial involvement in patients with SSc.

View Full Text PDF Listings View primary source full text article PDFs.

May
2014

Cardiac magnetic resonance (CMR) imaging is a well-established noninvasive imaging modality in clinical cardiology. Its unsurpassed accuracy in defining cardiac morphology and function and its ability to provide tissue characterization make it well suited for the study of patients with cardiac diseases. Late gadolinium enhancement was a major advancement in the development of tissue characterization techniques, allowing the unique ability of CMR to differentiate ischemic heart disease from nonischemic cardiomyopathies.

View Full Text PDF Listings View primary source full text article PDFs.

Feb
2014

The aims of the study were to explore the ability of native myocardial T1 mapping by cardiac magnetic resonance to: 1) detect cardiac involvement in patients with transthyretin amyloidosis (ATTR amyloidosis); 2) track the cardiac amyloid burden; and 3) detect early disease.
ATTR amyloidosis is an underdiagnosed cause of heart failure, with no truly quantitative test. In cardiac immunoglobulin light-chain amyloidosis (AL amyloidosis), T1 has high diagnostic accuracy and tracks disease.

View Full Text PDF Listings View primary source full text article PDFs.

Back to top