Aaron T. Hess
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View article: Comparison of cardiac diffusion MRI using multiple prospective respiratory motion correction techniques
Comparison of cardiac diffusion MRI using multiple prospective respiratory motion correction techniques Open
Purpose A novel prospective motion correction control system with slice tracking (MNav‐CoS) was compared with three other prospective respiratory motion correction techniques in performing free‐breathing cardiovascular diffusion tensor ima…
View article: Investigating motion-induced signal corruption in steady-state diffusion MRI
Investigating motion-induced signal corruption in steady-state diffusion MRI Open
Purpose Diffusion-weighted steady-state free precession (DW-SSFP) is a diffusion imaging sequence achieving high SNR efficiency and strong diffusion-weighting. A key challenge for in vivo DW-SSFP is the sequence’s severe motion sensitivity…
View article: <scp>SNR</scp> ‐efficient whole‐brain pseudo‐continuous arterial spin labeling perfusion imaging at 7 T
<span>SNR</span> ‐efficient whole‐brain pseudo‐continuous arterial spin labeling perfusion imaging at 7 T Open
Purpose To optimize pseudo‐continuous arterial spin labeling (PCASL) parameters to maximize SNR efficiency for RF power constrained whole brain perfusion imaging at 7 T. Methods We used Bloch simulations of pulsatile laminar flow to optimi…
View article: GABAergic inhibition in the visual cortex of children before and after amblyopia therapy
GABAergic inhibition in the visual cortex of children before and after amblyopia therapy Open
Amblyopia is the most common vision disorder in children. It is marked by chronically reduced vision in one eye, possibly due to abnormal visual suppression. We aim to test whether GABAergic inhibition in the visual cortex is involved in a…
View article: SNR-Efficient Whole-Brain Pseudo-Continuous Arterial Spin Labeling Perfusion Imaging at 7 Tesla
SNR-Efficient Whole-Brain Pseudo-Continuous Arterial Spin Labeling Perfusion Imaging at 7 Tesla Open
Purpose To optimize pseudo-continuous arterial spin labeling (PCASL) parameters to maximize SNR efficiency for RF power constrained whole brain perfusion imaging at 7 T. Methods We used Bloch simulations of pulsatile laminar flow to optimi…
View article: Simulation‐based optimization and experimental comparison of intracranial T2‐weighted DANTE‐SPACE vessel wall imaging at 3T and 7T
Simulation‐based optimization and experimental comparison of intracranial T2‐weighted DANTE‐SPACE vessel wall imaging at 3T and 7T Open
Purpose T2‐weighted DANTE‐SPACE (Delay Alternating with Nutation for Tailored Excitation — Sampling Perfection with Application optimized Contrasts using different flip angle Evolution) sequences facilitate non‐invasive intracranial vessel…
View article: Accelerated <scp>3D</scp> multi‐channel B1+ mapping at <scp>7 T</scp> for the brain and heart
Accelerated <span>3D</span> multi‐channel B1+ mapping at <span>7 T</span> for the brain and heart Open
Purpose To acquire accurate volumetric multi‐channel maps in under 14 s whole‐brain or 23 heartbeats whole‐heart for parallel transmit (pTx) applications at 7 T. Theory and Methods We evaluate the combination of three recently proposed tec…
View article: An extended phase graph‐based framework for <scp>DANTE‐SPACE</scp> simulations including physiological, temporal, and spatial variations
An extended phase graph‐based framework for <span>DANTE‐SPACE</span> simulations including physiological, temporal, and spatial variations Open
Purpose The delay alternating with nutation for tailored excitation (DANTE)–sampling perfection with application‐optimized contrasts (SPACE) sequence facilitates 3D intracranial vessel wall imaging with simultaneous suppression of blood an…
View article: Head‐and‐neck multichannel <scp>B1</scp><sup>+</sup> mapping and <scp>RF</scp> shimming of the carotid arteries using a <scp>7T</scp> parallel‐transmit head coil
Head‐and‐neck multichannel <span>B1</span><sup>+</sup> mapping and <span>RF</span> shimming of the carotid arteries using a <span>7T</span> parallel‐transmit head coil Open
Purpose Neurovascular MRI suffers from a rapid drop in B 1 + into the neck when using transmit head coils at 7 T. One solution to improving B 1 + magnitude in the major feeding arteries in the neck is to use custom RF shims on parallel‐tra…
View article: An Extended Phase Graph-based framework for DANTE-SPACE simulations including physiological, temporal, and spatial variations
An Extended Phase Graph-based framework for DANTE-SPACE simulations including physiological, temporal, and spatial variations Open
Purpose: The DANTE-SPACE sequence facilitates three-dimensional intracranial vessel wall imaging with simultaneous suppression of blood and cerebrospinal fluid (CSF). However, the achieved image contrast depends closely on the selected seq…
View article: A temperature‐controlled cooling system for accurate quantitative post‐mortem <scp>MRI</scp>
A temperature‐controlled cooling system for accurate quantitative post‐mortem <span>MRI</span> Open
Purpose To develop a temperature‐controlled cooling system to facilitate accurate quantitative post‐mortem MRI and enable scanning of unfixed tissue. Methods A water cooling system was built and integrated with a 7T scanner to minimize tem…
View article: Reduced Left Atrial Rotational Flow Is Independently Associated With Embolic Brain Infarcts
Reduced Left Atrial Rotational Flow Is Independently Associated With Embolic Brain Infarcts Open
Reduced LA flow vorticity is significantly and independently associated with embolic brain infarcts. Imaging LA flow characteristics may aid identification of individuals who would benefit from anticoagulation for embolic stroke prevention…
View article: Novel insights into diminished cardiac reserve in non-obstructive hypertrophic cardiomyopathy from four-dimensional flow cardiac magnetic resonance component analysis
Novel insights into diminished cardiac reserve in non-obstructive hypertrophic cardiomyopathy from four-dimensional flow cardiac magnetic resonance component analysis Open
Aims Hypertrophic cardiomyopathy (HCM) is characterized by hypercontractility and diastolic dysfunction, which alter blood flow haemodynamics and are linked with increased risk of adverse clinical events. Four-dimensional flow cardiac magn…
View article: Effect of subject‐specific head morphometry on specific absorption rate estimates in parallel‐transmit <scp>MRI</scp> at <scp>7 T</scp>
Effect of subject‐specific head morphometry on specific absorption rate estimates in parallel‐transmit <span>MRI</span> at <span>7 T</span> Open
Purpose To assess the accuracy of morphing an established reference electromagnetic head model to a subject‐specific morphometry for the estimation of specific absorption rate (SAR) in 7T parallel‐transmit (pTx) MRI. Methods Synthetic T 1 …
View article: Head-and-neck multi-channel B1+ mapping and carotid arteries RF shimming using a parallel transmit head coil
Head-and-neck multi-channel B1+ mapping and carotid arteries RF shimming using a parallel transmit head coil Open
Purpose: Neurovascular MRI suffers from a rapid drop in B1+ into the neck when using transmit head coils at 7T. One solution to improving B1+ magnitude in the major feeding arteries in the neck is to use custom RF shims on parallel transmi…
View article: Rapid 3D absolute B<sub>1</sub><sup>+</sup> mapping using a sandwiched train presaturated TurboFLASH sequence at 7 T for the brain and heart
Rapid 3D absolute B<sub>1</sub><sup>+</sup> mapping using a sandwiched train presaturated TurboFLASH sequence at 7 T for the brain and heart Open
Purpose To shorten the acquisition time of magnetization‐prepared absolute transmit field (B 1 + ) mapping known as presaturation TurboFLASH, or satTFL, to enable single breath‐hold whole‐heart 3D B 1 + mapping. Methods SatTFL is modified …
View article: External Hardware and Sensors, for Improved<scp>MRI</scp>
External Hardware and Sensors, for Improved<span>MRI</span> Open
Complex engineered systems are often equipped with suites of sensors and ancillary devices that monitor their performance and maintenance needs. MRI scanners are no different in this regard. Some of the ancillary devices available to suppo…
View article: Left atrial vorticity is independently associated with embolic brain infarcts and represents a promising imaging biomarker of cardioembolism in sinus rhythm and atrial fibrillation
Left atrial vorticity is independently associated with embolic brain infarcts and represents a promising imaging biomarker of cardioembolism in sinus rhythm and atrial fibrillation Open
Background Atrial fibrillation (AF) is associated with embolic stroke, but risk scores such as CHA2DS2-VASc perform only modestly (C statistics 0.6–0.7). Meanwhile, up to 25% of embolic strokes in patients without AF have no identifiable c…
View article: E Reduced left atrial rotational flow is independently associated with the risk of embolic brain infarcts
E Reduced left atrial rotational flow is independently associated with the risk of embolic brain infarcts Open
Introduction Atrial fibrillation (AF) is a major risk factor for ischaemic stroke. Low blood flow velocities within the fibrillating left atrium (LA) are thought to predispose to activation of the coagulation cascade (1) and local thrombus…
View article: Optimization of undersampling parameters for <scp>3D</scp> intracranial compressed sensing <scp>MR</scp> angiography at 7 T
Optimization of undersampling parameters for <span>3D</span> intracranial compressed sensing <span>MR</span> angiography at 7 T Open
Purpose 3D time‐of‐flight MRA can accurately visualize the intracranial vasculature but is limited by long acquisition times. Compressed sensing reconstruction can be used to substantially accelerate acquisitions. The quality of those reco…
View article: Tuning-free multi-coil compressed sensing MRI with Parallel Variable Density Approximate Message Passing (P-VDAMP)
Tuning-free multi-coil compressed sensing MRI with Parallel Variable Density Approximate Message Passing (P-VDAMP) Open
Magnetic Resonance Imaging (MRI) has excellent soft tissue contrast but is hindered by an inherently slow data acquisition process. Compressed sensing, which reconstructs sparse signals from incoherently sampled data, has been widely appli…
View article: The impact of atrial fibrillation and stroke risk factors on left atrial blood flow characteristics
The impact of atrial fibrillation and stroke risk factors on left atrial blood flow characteristics Open
Aims Altered left atrial (LA) blood flow characteristics account for an increase in cardioembolic stroke risk in atrial fibrillation (AF). Here, we aimed to assess whether exposure to stroke risk factors is sufficient to alter LA blood flo…
View article: Accelerated calibrationless parallel transmit mapping using joint transmit and receive low‐rank tensor completion
Accelerated calibrationless parallel transmit mapping using joint transmit and receive low‐rank tensor completion Open
Purpose To evaluate an algorithm for calibrationless parallel imaging to reconstruct undersampled parallel transmit field maps for the body and brain. Methods Using a combination of synthetic data and in vivo measurements from brain and bo…
View article: Optimization of Undersampling Parameters for 3D Intracranial Compressed\n Sensing MR Angiography at 7 Tesla
Optimization of Undersampling Parameters for 3D Intracranial Compressed\n Sensing MR Angiography at 7 Tesla Open
Purpose: 3D Time-of-flight (TOF) MR Angiography (MRA) can accurately\nvisualize the intracranial vasculature, but is limited by long acquisition\ntimes. Compressed sensing (CS) reconstruction can be used to substantially\naccelerate acquis…
View article: Optimization of Undersampling Parameters for 3D Intracranial Compressed Sensing MR Angiography at 7 Tesla
Optimization of Undersampling Parameters for 3D Intracranial Compressed Sensing MR Angiography at 7 Tesla Open
Purpose: 3D Time-of-flight (TOF) MR Angiography (MRA) can accurately visualize the intracranial vasculature, but is limited by long acquisition times. Compressed sensing (CS) reconstruction can be used to substantially accelerate acquisiti…
View article: Left atrial 4D flow cardiovascular magnetic resonance: a reproducibility study in sinus rhythm and atrial fibrillation
Left atrial 4D flow cardiovascular magnetic resonance: a reproducibility study in sinus rhythm and atrial fibrillation Open
View article: Matlab code for retrospective MRA undersampling optimization for Compressed Sensing reconstruction
Matlab code for retrospective MRA undersampling optimization for Compressed Sensing reconstruction Open
View article: Assessment of radio-frequency heating of a parallel transmit coil in a phantom using multi-echo proton resonance frequency shift thermometry
Assessment of radio-frequency heating of a parallel transmit coil in a phantom using multi-echo proton resonance frequency shift thermometry Open
We propose a workflow for validating parallel transmission (pTx) radio-frequency (RF) magnetic field heating patterns using Proton-Resonance Frequency shift (PRF)-based MR thermometry. Electromagnetic (EM) and thermal simulations of a 7 T …
View article: An Approximate Message Passing Algorithm For Rapid Parameter-Free Compressed Sensing MRI
An Approximate Message Passing Algorithm For Rapid Parameter-Free Compressed Sensing MRI Open
For certain sensing matrices, the Approximate Message Passing (AMP) algorithm efficiently reconstructs undersampled signals. However, in Magnetic Resonance Imaging (MRI), where Fourier coefficients of a natural image are sampled with varia…
View article: An investigation into the minimum number of tissue groups required for 7T in‐silico parallel transmit electromagnetic safety simulations in the human head
An investigation into the minimum number of tissue groups required for 7T in‐silico parallel transmit electromagnetic safety simulations in the human head Open
Purpose Safety limits for the permitted specific absorption rate (SAR) place restrictions on pulse sequence design, especially at ultrahigh fields (≥ 7 tesla). Due to intersubject variability, the SAR is usually conservatively estimated ba…