Enhancing quality and speed in database-free neural network reconstructions of undersampled MRI with SCAMPI.

Purpose: We present SCAMPI (Sparsity Constrained Application of deep Magnetic resonance Priors for Image reconstruction), an untrained deep Neural Network for MRI reconstruction without previous training on datasets. It expands the Deep Image Prior approach with a multidomain, sparsity-enforcing loss function to achieve higher image quality at a faster convergence speed than previously reported methods.

Methods: Two-dimensional MRI data from the FastMRI dataset with Cartesian undersampling in phase-encoding direction were reconstructed for different acceleration rates for single coil and multicoil data.

Remineralization of Artificially Demineralized Human Enamel and Dentin Samples by Zinc-Carbonate Hydroxyapatite Nanocrystals.

(1) Background: Decalcified enamel and dentin surfaces can be regenerated with non-fluoride-containing biomimetic systems. This study aimed to investigate the effect of a zinc carbonate-hydroxyapatite-containing dentifrice on artificially demineralized enamel and dentin surfaces. (2) Methods: Human enamel and dentin discs were prepared and subjected to surface demineralization with 30% orthophosphoric acid for 60 s.

2D Projection Maps of WSS and OSI Reveal Distinct Spatiotemporal Changes in Hemodynamics in the Murine Aorta during Ageing and Atherosclerosis.

Growth, ageing and atherosclerotic plaque development alter the biomechanical forces acting on the vessel wall. However, monitoring the detailed local changes in wall shear stress (WSS) at distinct sites of the murine aortic arch over time has been challenging. Here, we studied the temporal and spatial changes in flow, WSS, oscillatory shear index (OSI) and elastic properties of healthy wildtype (WT, = 5) and atherosclerotic apolipoprotein E-deficient (, = 6) mice during ageing and atherosclerosis using high-resolution 4D flow magnetic resonance imaging (MRI).

Simultaneous measurements of 3D wall shear stress and pulse wave velocity in the murine aortic arch.

Purpose: Wall shear stress (WSS) and pulse wave velocity (PWV) are important parameters to characterize blood flow in the vessel wall. Their quantification with flow-sensitive phase-contrast (PC) cardiovascular magnetic resonance (CMR), however, is time-consuming. Furthermore, the measurement of WSS requires high spatial resolution, whereas high temporal resolution is necessary for PWV measurements.

Evaluation of Plaque Characteristics and Inflammation Using Magnetic Resonance Imaging.

Atherosclerosis is an inflammatory disease of large and medium-sized arteries, characterized by the growth of atherosclerotic lesions (plaques). These plaques often develop at inner curvatures of arteries, branchpoints, and bifurcations, where the endothelial wall shear stress is low and oscillatory. In conjunction with other processes such as lipid deposition, biomechanical factors lead to local vascular inflammation and plaque growth.

Wall shear stress analysis using 17.6 Tesla MRI: A longitudinal study in ApoE-/- mice with histological analysis.

This longitudinal study was performed to evaluate the feasibility of detecting the interaction between wall shear stress (WSS) and plaque development. 20 ApoE-/- mice were separated in 12 mice with Western Diet and 8 mice with Chow Diet. Magnetic resonance (MR) scans at 17.

Fast self-navigated wall shear stress measurements in the murine aortic arch using radial 4D-phase contrast cardiovascular magnetic resonance at 17.6 T.

Purpose: 4D flow cardiovascular magnetic resonance (CMR) and the assessment of wall shear stress (WSS) are non-invasive tools to study cardiovascular risks in vivo. Major limitations of conventional triggered methods are the long measurement times needed for high-resolution data sets and the necessity of stable electrocardiographic (ECG) triggering. In this work an ECG-free retrospectively synchronized method is presented that enables accelerated high-resolution measurements of 4D flow and WSS in the aortic arch of mice.

Assessment of local pulse wave velocity distribution in mice using k-t BLAST PC-CMR with semi-automatic area segmentation.

Background: Local aortic pulse wave velocity (PWV) is a measure for vascular stiffness and has a predictive value for cardiovascular events. Ultra high field CMR scanners allow the quantification of local PWV in mice, however these systems are yet unable to monitor the distribution of local elasticities.

Methods: In the present study we provide a new accelerated method to quantify local aortic PWV in mice with phase-contrast cardiovascular magnetic resonance imaging (PC-CMR) at 17.

MRI-based quantification of renal perfusion in mice: Improving sensitivity and stability in FAIR ASL.

Purpose: The importance of the orientation of the selective inversion slice in relation to the anatomy in flow-sensitive alternating inversion recovery arterial spin labeling (FAIR ASL) kidney perfusion measurements is demonstrated by comparing the standard FAIR scheme to a scheme with an improved slice selective control experiment.

Methods: A FAIR ASL method is used. The selective inversion preparation slice is set perpendicular to the measurement slice to decrease the unintended labeling of arterial spins in the control experiment.

Local versus global aortic pulse wave velocity in early atherosclerosis: An animal study in ApoE-/--mice using ultrahigh field MRI.

Increased aortic stiffness is known to be associated with atherosclerosis and has a predictive value for cardiovascular events. This study aims to investigate the local distribution of early arterial stiffening due to initial atherosclerotic lesions. Therefore, global and local pulse wave velocity (PWV) were measured in ApoE-/- and wild type (WT) mice using ultrahigh field MRI.

Self-navigation under non-steady-state conditions: Cardiac and respiratory self-gating of inversion recovery snapshot FLASH acquisitions in mice.

Purpose: An algorithm is presented to enable cardiac and respiratory self-gating in combination with Inversion Recovery Look-Locker read-outs.

Methods: A radial inversion recovery snapshot FLASH sequence was adapted for retrospective cardiac T measurements in mice. Cardiac and respiratory data were extracted from the k-space center of radial projections and an adapted method for retrospective cardiac synchronization is introduced.

Targeting P-selectin by gallium-68-labeled fucoidan positron emission tomography for noninvasive characterization of vulnerable plaques: correlation with in vivo 17.6T MRI.

Objective: Nuclear imaging of active plaques still remains challenging. Advanced atherosclerotic plaques have a strong expression of P-selectin by the endothelium overlying active atherosclerotic plaques, but not on the endothelium overlying inactive fibrous plaques. We proposed a new approach for noninvasive in vivo characterization of P-selectin on active plaques based on (68)Ga-Fucoidan, which is a polysaccharidic ligand of P-selectin with a nanomolar affinity.

Local arterial stiffening assessed by MRI precedes atherosclerotic plaque formation.

Background: Atherosclerosis is known to impair vascular function and cause vascular stiffening. The aim of this study was to evaluate the potential predictive role of vascular stiffening in the early detection of atherosclerosis. Therefore, we investigated the time course of early functional and morphological alterations of the vessel wall in a murine atherosclerosis model.

Fast retrospectively triggered local pulse-wave velocity measurements in mice with CMR-microscopy using a radial trajectory.

Background: The aortic pulse-wave velocity (PWV) is an important indicator of cardiovascular risk. In recent studies MRI methods have been developed to measure this parameter noninvasively in mice. Present techniques require additional hardware for cardiac and respiratory gating.

Visualization of vascular inflammation in the atherosclerotic mouse by ultrasmall superparamagnetic iron oxide vascular cell adhesion molecule-1-specific nanoparticles.

Objective: Noninvasive imaging of atherosclerosis remains challenging in clinical applications. Here, we applied noninvasive molecular imaging to detect vascular cell adhesion molecule-1 in early and advanced atherosclerotic lesions of apolipoprotein E-deficient mice.

Methods And Results: Ultrasmall superparamagnetic iron oxide particles functionalized with (P03011) or without (P3007) vascular cell adhesion molecule-1-binding peptide were visualized by ultra high-field (17.

Reducing RF-related heating of cardiac pacemaker leads in MRI: implementation and experimental verification of practical design changes.

There are serious concerns regarding safety when performing magnetic resonance imaging in patients with implanted conductive medical devices, such as cardiac pacemakers, and associated leads, as severe incidents have occurred in the past. In this study, several approaches for altering an implant's lead design were systematically developed and evaluated to enhance the safety of implanted medical devices in a magnetic resonance imaging environment. The individual impact of each design change on radiofrequency heating was then systematically investigated in functional lead prototypes at 1.

Plaque imaging in murine models of cardiovascular disease.

Comprehensive imaging of the cardiovascular system of murine models of atherosclerosis requires high spatial and temporal resolution as well as a high soft tissue contrast. High-field (≥7 T) experimental magnetic resonance imaging can provide noninvasive, high-resolution images of the murine cardiovascular system. High-field scanners, however, require special equipment and imaging protocols.

Regional in vivo transit time measurements of aortic pulse wave velocity in mice with high-field CMR at 17.6 Tesla.

Background: Transgenic mouse models are increasingly used to study the pathophysiology of human cardiovascular diseases. The aortic pulse wave velocity (PWV) is an indirect measure for vascular stiffness and a marker for cardiovascular risk.

Results: This study presents a cardiovascular magnetic resonance (CMR) transit time (TT) method that allows the determination of the PWV in the descending murine aorta by analyzing blood flow waveforms.

Impact of imaging landmark on the risk of MRI-related heating near implanted medical devices like cardiac pacemaker leads.

Implanted medical devices such as cardiac pacemakers pose a potential hazard in magnetic resonance imaging. Electromagnetic fields have been shown to cause severe radio frequency-induced tissue heating in some cases. Imaging exclusion zones have been proposed as an instrument to reduce patient risk.

Quantification of dental erosion--a comparison of stylus profilometry and confocal laser scanning microscopy (CLSM).

Objectives: Since stylus profilometry applies a force on the sample surface, it is logical to hypothesize that the profilometer penetrates the surface of the enamel softened by acid solutions. The aims of the present study were, therefore, to test the hypothesis that surface profilometry measurements of eroded enamel alter the surface of the enamel, to quantify the potential effect of the surface alteration (scratches) on the measured values of enamel erosion by atomic force microscopy and to compare the values of enamel loss caused by erosion as measured by profilometry and non-contact confocal laser scanning microscopy (CLSM).

Methods: Enamel samples, cut from unerupted human third molars were treated with Volvic Mineral Water and citric acid solutions of different pH values.

In vivo measurement of local aortic pulse-wave velocity in mice with MR microscopy at 17.6 Tesla.

Transgenic mouse models of human diseases have gained increasing importance in the pathophysiology of cardiovascular diseases (CVD). As an indirect measure of vascular stiffness, aortic pulse-wave velocity (PWV) is an important predictor of cardiovascular risk. This study presents an MRI approach that uses a flow area method to estimate local aortic pulse-wave velocity at different sites in the murine aorta.

Murine atherosclerotic plaque imaging with the USPIO Ferumoxtran-10.

In this study we intended to image plaque inflammation in a murine model of atherosclerosis with MRI and Ferumoxtran-10 (Sinerem, Guerbet, France). 8 apoE-/- mice were injected 500 micromol Fe/kg or 1000 micromol Fe/kg Ferumoxtran-10. 2 apoE-/- mice were injected NaCl.

In vivo comparison of atherosclerotic plaque progression with vessel wall strain and blood flow velocity in apoE(-/-) mice with MR microscopy at 17.6 T.

Object: At present, in vivo plaque characterization in mice by MRI is typically limited to the visualization of vascular lesions with no accompanying analysis of vessel wall function. The aim of this study was to analyze the influence of atherosclerotic plaque development on the morphological and mechanical characteristics of the aortic vessel wall in a pre-clinical murine model of atherosclerosis.

Materials And Methods: Groups of apolipoprotein E-deficient (apoE(-/-)) and C57BL/6J control mice fed a high-fat diet were monitored over a 12-week time period by high-field MRI.

Measuring RF-induced currents inside implants: Impact of device configuration on MRI safety of cardiac pacemaker leads.

Radiofrequency (RF)-related heating of cardiac pacemaker leads is a serious concern in magnetic resonance imaging (MRI). Recent investigations suggest such heating to be strongly dependent on an implant's position within the surrounding medium, but this issue is currently poorly understood. In this study, phantom measurements of the RF-induced electric currents inside a pacemaker lead were performed to investigate the impact of the device position and lead configuration on the amount of MRI-related heating at the lead tip.

Structure-specific magnetic field inhomogeneities and its effect on the correlation time.

We describe the relationship between the correlation time and microscopic spatial inhomogeneities in the static magnetic field. The theory takes into account diffusion of nuclear spins in the inhomogeneous field created by magnetized objects. A simple general expression for the correlation time is obtained.