Free-breathing abdominal T mapping using an optimized MR fingerprinting sequence.

In this work, we propose a free-breathing magnetic resonance fingerprinting (MRF) method that can be used to obtain B -robust quantitative T maps of the abdomen in a clinically acceptable time. A three-dimensional MRF sequence with a radial stack-of-stars trajectory was implemented, and its k-space acquisition ordering was adjusted to improve motion-robustness in the context of MRF. The flip angle pattern was optimized using the Cramér-Rao Lower Bound, and the encoding efficiency of sequences with 300, 600, 900 and 1800 flip angles was evaluated.

Dynamic P-MRI and P-MRS of lower leg muscles in heart failure patients.

Impaired oxidative metabolism is one of multi-variate factors leading to exercise intolerance in heart failure patients. The purpose of the study was to demonstrate the use of dynamic P magnetic resonance spectroscopy (MRS) and P magnetic resonance imaging (MRI) techniques to measure PCr resynthesis rate post-exercise as a biomarker for oxidative metabolism in skeletal muscle in HF patients and controls. In this prospective imaging study, we recruited six HF patients and five healthy controls.

Improved whole-brain SNR with an integrated high-permittivity material in a head array at 7T.

Purpose: To demonstrate that strategic use of materials with high electric permittivity along with integrated head-sized coil arrays can improve SNR in the entire brain.

Methods: Numerical simulations were used to design a high-permittivity material (HPM) helmet for enhancing SNR throughout the brain in receive arrays of 8 and 28 channels. Then, two 30-channel head coils of identical geometry were constructed: one fitted with a prototype helmet-shaped ceramic HPM helmet, and the second with a helmet-shaped low-permittivity shell, each 8-mm thick.

Fast, regional three-dimensional hybrid (1D-Hadamard 2D-rosette) proton MR spectroscopic imaging in the human temporal lobes.

H-MRSI is commonly performed with gradient phase encoding, due to its simplicity and minimal radio frequency (RF) heating (specific absorption rate). Its two well-known main problems-(i) "voxel bleed" due to the intrinsic point-spread function, and (ii) chemical shift displacement error (CSDE) when slice-selective RF pulses are used, which worsens with increasing volume of interest (VOI) size-have long become accepted as unavoidable. Both problems can be mitigated with Hadamard multislice RF encoding.

A guideline for 3D printing terminology in biomedical research utilizing ISO/ASTM standards.

First patented in 1986, three-dimensional (3D) printing, also known as additive manufacturing or rapid prototyping, now encompasses a variety of distinct technology types where material is deposited, joined, or solidified layer by layer to create a physical object from a digital file. As 3D printing technologies continue to evolve, and as more manuscripts describing these technologies are published in the medical literature, it is imperative that standardized terminology for 3D printing is utilized. The purpose of this manuscript is to provide recommendations for standardized lexicons for 3D printing technologies described in the medical literature.

Measurement of Three-Dimensional Internal Dynamic Strains in the Intervertebral Disc of the Lumbar Spine With Mechanical Loading and Golden-Angle Radial Sparse Parallel-Magnetic Resonance Imaging.

Background: Noninvasive measurement of internal dynamic strain can be potentially useful to characterize spine intervertebral disc (IVD) in the setting of injury or degenerative disease.

Purpose: To develop and demonstrate a noninvasive technique to quantify three-dimensional (3D) internal dynamic strains in the IVD using a combination of static mechanical loading of the IVD using a magnetic resonance imaging (MRI)-compatible ergometer.

Study Type: Prospective.

The variability of MR axon radii estimates in the human white matter.

The noninvasive quantification of axonal morphology is an exciting avenue for gaining understanding of the function and structure of the central nervous system. Accurate non-invasive mapping of micron-sized axon radii using commonly applied neuroimaging techniques, that is, diffusion-weighted MRI, has been bolstered by recent hardware developments, specifically MR gradient design. Here the whole brain characterization of the effective MR axon radius is presented and the inter- and intra-scanner test-retest repeatability and reproducibility are evaluated to promote the further development of the effective MR axon radius as a neuroimaging biomarker.

Simultaneous T , T , and T relaxation mapping of the lower leg muscle with MR fingerprinting.

Purpose: To develop a novel MR-fingerprinting (MRF) pulse sequence that is insensitive to and B imperfections for simultaneous T , T , and T relaxation mapping.

Methods: We implemented a totally balanced spin-lock (TB-SL) module to encode T relaxation into an existing MRF framework that encoded T and T . The spin-lock module used two 180° pulses with compensatory phases to reduce T sensitivity to B and B inhomogeneities.

Bilateral gradient-echo spectroscopic imaging with correction of frequency variations for measurement of fatty acid composition in mammary adipose tissue.

Purpose: To develop a simultaneous dual-slab three-dimensional gradient-echo spectroscopic imaging (GSI) technique with frequency drift compensation for rapid (<6 min) bilateral measurement of fatty acid composition (FAC) in mammary adipose tissue.

Methods: A bilateral GSI sequence was developed using a simultaneous dual-slab excitation followed by 128 monopolar echoes. A short train of navigator echoes without phase or partition encoding was included at the beginning of each pulse repetition time period to correct for frequency variation caused by respiration and heating of the cryostat.

Effect of radiofrequency shield diameter on signal-to-noise ratio at ultra-high field MRI.

Purpose: In this work, we investigated how the position of the radiofrequency (RF) shield can affect the signal-to-noise ratio (SNR) of a receive RF coil. Our aim was to obtain physical insight for the design of a 10.5T 32-channel head coil, subject to the constraints on the diameter of the RF shield imposed by the head gradient coil geometry.

Clinical feasibility of 2D dynamic sagittal HASTE flexion-extension imaging of the cervical spine for the assessment of spondylolisthesis and cervical cord impingement.

Purpose: To assess the utility of a 2D dynamic HASTE sequence in assessment of cervical spine flexion-extension, specifically (1) comparing dynamic spondylolisthesis to radiographs and (2) assessing dynamic contact upon or deformity of the cord.

Methods: Patients with a dynamic flexion-extension sagittal 2D HASTE sequence in addition to routine cervical spine sequences were identified. Static and dynamic listhesis was first determined on flexion-extension radiographs reviewed in consensus.

Early life stress causes sex-specific changes in adult fronto-limbic connectivity that differentially drive learning.

It is currently unclear whether early life stress (ELS) affects males and females differently. However, a growing body of work has shown that sex moderates responses to stress and injury, with important insights into sex-specific mechanisms provided by work in rodents. Unfortunately, most of the ELS studies in rodents were conducted only in males, a bias that is particularly notable in translational work that has used human imaging.

Evaluation of metronomic chemotherapy response using diffusion and dynamic contrast-enhanced MRI.

Purpose: To investigate the feasibility of using diffusion MRI (dMRI) and dynamic contrast-enhanced (DCE) MRI to evaluate the treatment response of metronomic chemotherapy (MCT) in the 4T1 mammary tumor model of locally advanced breast cancer.

Methods: Twelve Balb/c mice with metastatic breast cancer were divided into treated and untreated (control) groups. The treated group (n = 6) received five treatments of anti-metabolite agent 5-Fluorouracil (5FU) in the span of two weeks.

Musculoskeletal MR Imaging Applications at Ultra-High (7T) Field Strength.

Regulatory approval of ultrahigh field (UHF) MR imaging scanners for clinical use has opened new opportunities for musculoskeletal imaging applications. UHF MR imaging has unique advantages in terms of signal-to-noise ratio, contrast-to-noise ratio, spectral resolution, and multinuclear applications, thus providing unique information not available at lower field strengths. But UHF also comes with a set of technical challenges that are yet to be resolved and may not be suitable for all imaging applications.

Global brain volume and N-acetyl-aspartate decline over seven decades of normal aging.

We characterize the whole-brain N-acetyl-aspartate (WBNAA) and brain tissue fractions across the adult lifespan and test the hypothesis that, despite age-related atrophy, neuronal integrity (reflected by WBNAA) is preserved in normal aging. Two-hundred-and-seven participants: 133 cognitively intact older adults (73.6 ± 7.

Detection of Cerebrovascular Loss in the Normal Aging C57BL/6 Mouse Brain Using Contrast-Enhanced Magnetic Resonance Angiography.

Microvascular rarefaction, or the decrease in vascular density, has been described in the cerebrovasculature of aging humans, rats, and, more recently, mice in the presence and absence of age-dependent diseases. Given the wide use of mice in modeling age-dependent human diseases of the cerebrovasculature, visualization, and quantification of the global murine cerebrovasculature is necessary for establishing the baseline changes that occur with aging. To provide whole-brain imaging of the cerebrovasculature in aging C57BL/6 mice longitudinally, contrast-enhanced magnetic resonance angiography (CE-MRA) was employed using a house-made gadolinium-bearing micellar blood pool agent.

Performance Comparison of Compressed Sensing Algorithms for Accelerating T Mapping of Human Brain.

Background: 3D-T mapping is useful to quantify various neurologic disorders, but data are currently time-consuming to acquire.

Purpose: To compare the performance of five compressed sensing (CS) algorithms-spatiotemporal finite differences (STFD), exponential dictionary (EXP), 3D-wavelet transform (WAV), low-rank (LOW) and low-rank plus sparse model with spatial finite differences (L + S SFD)-for 3D-T mapping of the human brain with acceleration factors (AFs) of 2, 5, and 10.

Study Type: Retrospective.

Rapid mono and biexponential 3D-T mapping of knee cartilage using variational networks.

In this study we use undersampled MRI acquisition methods to obtain accelerated 3D mono and biexponential spin-lattice relaxation time in the rotating frame (T) mapping of knee cartilage, reducing the usual long scan time. We compare the accelerated T maps obtained by deep learning-based variational network (VN) and compressed sensing (CS). Both methods were compared with spatial (S) and spatio-temporal (ST) filters.

MRI guided procedure planning and 3D simulation for partial gland cryoablation of the prostate: a pilot study.

Purpose: This study reports on the development of a novel 3D procedure planning technique to provide pre-ablation treatment planning for partial gland prostate cryoablation (cPGA).

Methods: Twenty men scheduled for partial gland cryoablation (cPGA) underwent pre-operative image segmentation and 3D modeling of the prostatic capsule, index lesion, urethra, rectum, and neurovascular bundles based upon multi-parametric MRI data. Pre-treatment 3D planning models were designed including virtual 3D cryotherapy probes to predict and plan cryotherapy probe configuration needed to achieve confluent treatment volume.

The present and the future of microstructure MRI: From a paradigm shift to normal science.

The aspiration of imaging tissue microstructure with MRI is to uncover micrometer-scale tissue features within millimeter-scale imaging voxels, in vivo. This kind of super-resolution has fueled a paradigm shift within the biomedical imaging community. However, what feels like an ongoing revolution in MRI, has been conceptually experienced in physics decades ago; from this point of view, our current developments can be seen as Thomas Kuhn's "normal science" stage of progress.

Approximating anatomically-guided PET reconstruction in image space using a convolutional neural network.

In the last two decades, it has been shown that anatomically-guided PET reconstruction can lead to improved bias-noise characteristics in brain PET imaging. However, despite promising results in simulations and first studies, anatomically-guided PET reconstructions are not yet available for use in routine clinical because of several reasons. In light of this, we investigate whether the improvements of anatomically-guided PET reconstruction methods can be achieved entirely in the image domain with a convolutional neural network (CNN).

The clinical utility of proton magnetic resonance spectroscopy in traumatic brain injury: recommendations from the ENIGMA MRS working group.

Proton (H) magnetic resonance spectroscopy provides a non-invasive and quantitative measure of brain metabolites. Traumatic brain injury impacts cerebral metabolism and a number of research groups have successfully used this technique as a biomarker of injury and/or outcome in both pediatric and adult TBI populations. However, this technique is underutilized, with studies being performed primarily at centers with access to MR research support.

Visceral adipose tissue in patients with COVID-19: risk stratification for severity.

Purpose: To assess visceral (VAT), subcutaneous (SAT), and total adipose tissue (TAT) estimates at abdominopelvic CT in COVID-19 patients with different severity, and analyze Body Mass Index (BMI) and CT estimates of fat content in patients requiring hospitalization.

Methods: In this retrospective IRB approved HIPPA compliant study, 51 patients with SARS-CoV-2 infection with abdominopelvic CT were included. Patients were stratified based on disease severity as outpatient (no hospital admission) and patients who were hospitalized.