Image registration in dynamic renal MRI-current status and prospects.

Magnetic resonance imaging (MRI) modalities have achieved an increasingly important role in the clinical work-up of chronic kidney diseases (CKD). This comprises among others assessment of hemodynamic parameters by arterial spin labeling (ASL) or dynamic contrast-enhanced (DCE-) MRI. Especially in the latter, images or volumes of the kidney are acquired over time for up to several minutes.

CT and MRI compatibility of flexible 3D-printed materials for soft actuators and robots used in image-guided interventions.

Purpose: Three-dimensional (3D) printing allows for the fabrication of medical devices with complex geometries, such as soft actuators and robots that can be used in image-guided interventions. This study investigates flexible and rigid 3D-printing materials in terms of their impact on multimodal medical imaging.

Methods: The generation of artifacts in clinical computer tomography (CT) and magnetic resonance (MR) imaging was evaluated for six flexible and three rigid materials, each with a cubical and a cylindrical geometry, and for one exemplary flexible fluidic actuator.

High-gradient diffusion MRI reveals distinct estimates of axon diameter index within different white matter tracts in the in vivo human brain.

Axon diameter and density are important microstructural metrics that offer valuable insight into the structural organization of white matter throughout the human brain. We report the systematic acquisition and analysis of a comprehensive diffusion MRI data set acquired with 300 mT/m maximum gradient strength in a cohort of 20 healthy human subjects that yields distinct and consistent patterns of axon diameter index in white matter tracts of arbitrary orientation. We use a straightforward, previously validated approach to estimating indices of axon diameter and volume fraction that involves interpolating the diffusion signal perpendicular to the principal fiber orientation and fitting a three-compartment model of intra-axonal, extra-axonal and free water diffusion.

Free-Breathing Dynamic Contrast-Enhanced Imaging of the Upper Abdomen Using a Cartesian Compressed-Sensing Sequence With Hard-Gated and Motion-State-Resolved Reconstruction.

Objectives: The aim of this study was to compare a compressed-sensing free-breathing VIBE (fbVIBE) with a conventional breath-hold VIBE (bhVIBE) for dynamic contrast-enhanced imaging of the upper abdomen.

Materials And Methods: In total, 70 datasets (bhVIBE, n = 30; fbVIBE n = 40; hard-gated [hg] reconstruction, n = 30; motion-state-resolved [mr] reconstruction, n = 10) were assessed by 2 experienced readers. Both sequences were performed on 1.

Cluster analysis of time evolution (CAT) for quantitative susceptibility mapping (QSM) and quantitative blood oxygen level-dependent magnitude (qBOLD)-based oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO ) mapping.

Purpose: To improve the accuracy of QSM plus quantitative blood oxygen level-dependent magnitude (QSM + qBOLD or QQ)-based mapping of the oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO ) using cluster analysis of time evolution (CAT).

Methods: 3D multi-echo gradient echo and arterial spin labeling images were acquired in 11 healthy subjects and 5 ischemic stroke patients. DWI was also carried out on patients.

Case report: a giant arachnoid cyst masking Alzheimer's disease.

Background: Intracranial arachnoid cysts are usually benign congenital findings of neuroimaging modalities, sometimes however, leading to focal neurological and psychiatric comorbidities. Whether primarily clinically silent cysts may become causally involved in cognitive decline in old age is neither well examined nor understood.

Case Presentation: A 66-year old caucasian man presenting with a giant left-hemispheric frontotemporal cyst without progression of size, presented with slowly progressive cognitive decline.

Phase-contrast magnetic resonance imaging to assess renal perfusion: a systematic review and statement paper.

Objective: Phase-contrast magnetic resonance imaging (PC-MRI) is a non-invasive method used to compute blood flow velocity and volume. This systematic review aims to discuss the current status of renal PC-MRI and provide practical recommendations which could inform future clinical studies and its adoption in clinical practice.

Methodology: A comprehensive search of all the PC-MRI studies in human healthy subjects or patients related to the kidneys was performed.

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.

Synthesis of CT images from digital body phantoms using CycleGAN.

Purpose: The potential of medical image analysis with neural networks is limited by the restricted availability of extensive data sets. The incorporation of synthetic training data is one approach to bypass this shortcoming, as synthetic data offer accurate annotations and unlimited data size.

Methods: We evaluated eleven CycleGAN for the synthesis of computed tomography (CT) images based on XCAT body phantoms.

Using an artificial neural network for fast mapping of the oxygen extraction fraction with combined QSM and quantitative BOLD.

Purpose: To apply an artificial neural network (ANN) for fast and robust quantification of the oxygen extraction fraction (OEF) from a combined QSM and quantitative BOLD analysis of gradient echo data and to compare the ANN to a traditional quasi-Newton (QN) method for numerical optimization.

Methods: Random combinations of OEF, deoxygenated blood volume ( ), R , and nonblood magnetic susceptibility ( ) with each parameter following a Gaussian distribution that represented physiological gray matter and white matter values were used to simulate quantitative BOLD signals and QSM values. An ANN was trained with the simulated data with added Gaussian noise.

Cerebral sodium (Na) magnetic resonance imaging in patients with migraine - a case-control study.

Objective: Evaluation of MRI-derived cerebral Na concentrations in patients with migraine in comparison with healthy controls.

Materials And Methods: In this case-control study, 24 female migraine patients (mean age, 34 ± 11 years) were enrolled after evaluation of standardized questionnaires. Half (n = 12) of the cohort suffered from migraine, the other half was impaired by both migraine and tension-type headaches (TTH).

Quantitative Brain Sodium MRI Depicts Corticospinal Impairment in Amyotrophic Lateral Sclerosis.

Background Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that mainly affects the upper and lower motor neurons. Recent sodium (Na) MRI studies have shown that abnormal sodium concentration is related to neuronal suffering in neurodegenerative conditions. Purpose To use Na MRI to investigate abnormal sodium concentrations and map their distribution in the brains of study participants with ALS as compared with healthy control subjects.

Comparison of gradient echo and gradient echo sampling of spin echo sequence for the quantification of the oxygen extraction fraction from a combined quantitative susceptibility mapping and quantitative BOLD (QSM+qBOLD) approach.

Purpose: To compare gradient echo (GRE) and gradient echo sampling of spin echo (GESSE) sequences for the quantification of the oxygen extraction fraction (OEF) from combined quantitative BOLD and quantitative susceptibility mapping (QSM) with regard to accuracy, precision and parameter initialization.

Methods: GRE and GESSE data were acquired from 7 healthy volunteers. QSM was applied to the GRE data and used as a regularization for the single-compartment quantitative BOLD fit to the GESSE and GRE data, respectively, to quantify OEF, deoxygenated blood volume (ν), R , and non-blood susceptibility (χ ).

Resting-state connectivity alterations during transient global amnesia.

While the pathophysiology of transient global amnesia (TGA) is not understood, due to the specific nature of the clinical deficits, transient dysfunction in the medial temporal lobe, especially in the hippocampus, is assumed; however, concomitant disturbances in other brain regions and in executive function have been postulated. In this study, a cohort of 16 patients was prospectively recruited from the emergency department for resting-state functional MRI (fMRI) during the acute stage of TGA, as confirmed by a standardized neuropsychological assessment. Twenty age- and sex-matched controls, as well as twenty patients with a history of TGA, were recruited for comparison.

X-nuclei imaging: Current state, technical challenges, and future directions.

H imaging is concerned with contrast generation among anatomically distinct soft tissues. X-nuclei imaging, on the other hand, aims to reveal the underlying changes in the physiological processes on a cellular level. Advanced clinical MR hardware systems improved H image quality and simultaneously enabled X-nuclei imaging.

Volumetric brain correlates of approach-avoidance behavior and their relation to chronic back pain.

Avoiding any harm, such as painful experiences, is an important ability for our physical and mental health. This avoidance behavior might be overactive under chronic pain, and the cortical and subcortical brain volumetry, which also often changes in chronic pain states, might be a significant correlate of this behavior. In the present study, we thus investigated the association between volumetric brain differences using 3 T structural magnetic resonance imaging and pain- versus pleasure-related approach-avoidance behavior using an Approach Avoidance Task in the laboratory in chronic back pain (N = 42; mean age: 51.

Repeatability and reproducibility of cerebral Na imaging in healthy subjects.

Background: Initial reports of Na magnetic resonance imaging (MRI) date back to the 1970s. However, methodological challenges of the technique hampered its widespread adoption for many years. Recent technical developments have overcome some of these limitations and have led to more optimal conditions for Na-MR imaging.

Feasibility study of a double resonant 8-channel H/ 8-channel Na receive-only head coil at 3 Tesla.

Sodium (Na) magnetic resonance imaging (MRI), especially brain applications are increasingly interesting since sodium MRI can provide additional information about tissue viability and vitality. In order to include sodium MRI in the clinical routine, a single RF setup is preferable which provides high sodium sensitivity and full proton performance in terms of signal-to-noise ratio (SNR) and parallel imaging performance. The aim of this work was to evaluate the feasibility of a double resonant receive (Rx) coil array for proton and sodium head MRI.

Feasibility of quantitative MR-perfusion imaging to monitor treatment response after uterine artery embolization (UAE) in symptomatic uterus fibroids.

Introduction: In 25% of women, symptomatic uterus myomas are diagnosed with clinical and functional impairment ranging from abdominal and pelvic pain to dys- and hypermenorrhea, dyspareunia, pollakiuria and infertility. Women undergoing a treatment increasingly prefer nowadays minimal invasive, uterus preserving therapies like uterine artery embolization (UAE) over surgical hysterectomy, nowadays. To emphasize the efficacy of UAE as a uterus preserving treatment with targeted therapy of myomas only, analysis of tissue perfusion pre and post embolization is required.

Simulation-based deep artifact correction with Convolutional Neural Networks for limited angle artifacts.

Non-conventional scan trajectories for interventional three-dimensional imaging promise low-dose interventions and a better radiation protection to the personnel. Circular tomosynthesis (cTS) scan trajectories yield an anisotropical image quality distribution. In contrast to conventional Computed Tomographies (CT), the reconstructions have a preferred focus plane.

Feasibility study of a double resonant (H/Na) abdominal RF setup at 3T.

Sodium magnetic resonance imaging (MRI) of the human abdomen is of increasing clinical interest for e.g. kidney, intervertebral disks, prostate and tumor monitoring examinations in the abdomen.

Na Triple-quantum signal of in vitro human liver cells, liposomes, and nanoparticles: Cell viability assessment vs. separation of intra- and extracellular signal.

Background: Triple-quantum (TQ) filtered sequences have become more popular in sodium MR due to the increased usage of scanners with field strengths exceeding 3T. Disagreement as to whether TQ signal can provide separation of intra- and extracellular compartments persists.

Purpose: To provide insight into TQ signal behavior on a cellular level.

Temporal evolution of acute multiple sclerosis lesions on serial sodium (Na) MRI.

Background: Several studies have reported the characteristics of acute multiple sclerosis (MS) lesions on diffusion-weighted magnetic resonance imaging (DWI MRI). Current publications reported a transient reduction of the apparent diffusion coefficient (ADC) delineating an early phase of lesion evolution, before increased diffusion occurs in parallel to blood-brain-barrier (BBB) breakdown. Sodium MRI might provide another perspective on lesion development, but clinical applications have been limited to high field MR systems.

Sensitivity analysis of neurodynamic and electromagnetic simulation parameters for robust prediction of peripheral nerve stimulation.

Peripheral nerve stimulation (PNS) has become an important limitation for fast MR imaging using the latest gradient hardware. We have recently developed a simulation framework to predict PNS thresholds and stimulation locations in the body for arbitrary coil geometries to inform the gradient coil optimization process. Our approach couples electromagnetic field simulations in realistic body models to a neurodynamic model of peripheral nerve fibers.

Risk assessment of copper-containing contraceptives: the impact for women with implanted intrauterine devices during clinical MRI and CT examinations.

Objectives: To assess the risks for implant users with copper-containing intrauterine devices (IUDs) during MR and CT examinations.

Methods: A tissue-mimicking phantom suitable for all experiments within this study was developed. Seven different types of copper IUDs were evaluated.