Development, integration and use of an ultra-high-strength gradient system on a human-size 3 T magnet for small animal MRI.

This study aims to integrate an ultra-high-strength gradient coil system on a clinical 3 T magnet and demonstrate its preclinical imaging capabilities. Dedicated phantoms were used to qualitatively and quantitatively assess the performance of the gradient system. Advanced MR imaging sequences, including diffusion tensor imaging (DTI) and quantitative susceptibility mapping (QSM), were implemented and executed on an ex vivo specimen as well as in vivo rats.

Increasing body mass index in an elderly cohort: Effects on the quantitative MR parameters of the brain.

Background: Body mass index (BMI) is increasing in a large number of elderly persons. This increase in BMI is known to put one at risk for many "diseases of aging," although less is known about how a change in BMI may affect the brains of the elderly.

Purpose: To investigate the relationship between BMI and quantitative water content, T , T *, and the semi-quantitative magnetization transfer ratio (MTR) of various structures in elderly brains.

Sub-millimeter T mapping of rapidly relaxing compartments with gradient delay corrected spiral TAPIR and compressed sensing at 3T.

Purpose: The TAPIR sequence is an accurate and efficient method for T mapping. It combines a slice-interleaving Look-Locker read-out with an acquisition of multiple k-space lines in 1 shot. Whereas the acquisition of multiple lines per excitation increases imaging speed, the corresponding increase in TR and TE is detrimental to the T fitting performance.

Prediction of atrial fibrillation using the recurrence complex network of body surface potential mapping signals.

Objective: Atrial fibrillation (AF) is the most common type of persistent arrhythmia. Early diagnosis and intervention of AF is essential to avert the further fatality. The technique of noninvasive electrical mapping, especially the body surface potential mapping (BSPM), has a more practical application in the study of predicting AF, when compared with the invasive electrical mapping methods such as the epicardial mapping and interventional catheter mapping.

Perfusion weighted imaging using combined gradient/spin echo EPIK: Brain tumour applications in hybrid MR-PET.

Advanced perfusion-weighted imaging (PWI) methods that combine gradient echo (GE) and spin echo (SE) data are important tools for the study of brain tumours. In PWI, single-shot, EPI-based methods have been widely used due to their relatively high imaging speed. However, when used with increasing spatial resolution, single-shot EPI methods often show limitations in whole-brain coverage for multi-contrast applications.

An MR technique for simultaneous quantitative imaging of water content, conductivity and susceptibility, with application to brain tumours using a 3T hybrid MR-PET scanner.

Approaches for the quantitative mapping of water content, electrical conductivity and susceptibility have been developed independently. The purpose of this study is to develop a method for simultaneously acquiring quantitative water content, electrical conductivity and susceptibility maps based on a 2D multi-echo gradient echo sequence. Another purpose is to investigate the changes in these properties caused by brain tumours.

O-(2-[18F]-Fluoroethyl)-L-Tyrosine (FET) in Neurooncology: A Review of Experimental Results.

In recent years, PET using radiolabelled amino acids has gained considerable interest as an additional tool besides MRI to improve the diagnosis of cerebral gliomas and brain metastases. A very successful tracer in this field is O-(2-[18F]fluoroethyl)-L-tyrosine (FET) which in recent years has replaced short-lived tracers such as [11C]-methyl-L-methionine in many neuro-oncological centers in Western Europe. FET can be produced with high efficiency and distributed in a satellite concept like 2- [18F]fluoro-2-deoxy-D-glucose.

Dynamic susceptibility contrast parametric imaging using accelerated dual-contrast echo planar imaging with keyhole.

Background: Echo planar imaging (EPI) is one of the methods of choice in dynamic susceptibility contrast MRI (DSC-MRI) because it provides a sufficient temporal resolution. However, the relatively long readout duration of EPI often imposes limitations on increased spatial coverage or the use of multiple contrasts.

Purpose: To develop a DSC-MRI method using EPIK (EPI with keyhole) to provide dual-contrast (TE and TE ) information with a higher spatial coverage than EPI.

MR-PET head motion correction based on co-registration of multicontrast MR images.

Head motion is a major source of image artefacts in neuroimaging studies and can lead to degradation of the quantitative accuracy of reconstructed PET images. Simultaneous magnetic resonance-positron emission tomography (MR-PET) makes it possible to estimate head motion information from high-resolution MR images and then correct motion artefacts in PET images. In this article, we introduce a fully automated PET motion correction method, MR-guided MAF, based on the co-registration of multicontrast MR images.

Design and evaluation of a H/P double-resonant helmet coil for 3T MRI of the brain.

Proton magnetic resonance imaging (MRI) can be combined with signals from non-proton nuclei (X-nuclei) to provide metabolic information. Double-resonant coils are often used for X-nuclei MR studies where the proton element is employed for scout imaging and B shimming. This work describes the development of a new double-resonant coil capable of operating at both proton and X-nuclei frequencies.

Alternative headphones for patient noise protection and communication in PET-MR studies of the brain.

Introduction: Due to the high noise emission generated by the gradients in magnetic resonance imaging (MRI), an efficient method of noise protection is mandatory. In addition to providing hearing protection, appropriate headphone systems also serve to facilitate communication between the operator and the patient. However, in combined PET-MR devices, use of common pneumatic headphones, as delivered by the manufacturer, is problematic due to the potential generation of attenuation artefacts in the PET measurement.

Dual-contrast pCASL using simultaneous gradient-echo/spin-echo multiband EPI.

A 2D gradient-echo EPI is commonly employed for arterial spin labeling (ASL) readout to achieve fast whole brain coverage measurements. However, such a readout suffers from susceptibility artifacts induced by magnetic field inhomogeneities. To reduce these susceptibility effects, single-shot spin-echo EPI was proposed to be used for acquisitions in continuous ASL (CASL).

Quality-based UnwRap of SUbdivided Large Arrays (URSULA) for high-resolution MRI data.

In Magnetic Resonance Imaging, mapping of the static magnetic field and the magnetic susceptibility is based on multidimensional phase measurements. Phase data are ambiguous and have to be unwrapped to their true range in order to exhibit a correct representation of underlying features. High-resolution imaging at ultra-high fields, where susceptibility and phase contrast are natural tools, can generate large datasets, which tend to dramatically increase computing time demands for spatial unwrapping algorithms.

Comparison of EEG microstates with resting state fMRI and FDG-PET measures in the default mode network via simultaneously recorded trimodal (PET/MR/EEG) data.

Simultaneous trimodal positron emission tomography/magnetic resonance imaging/electroencephalography (PET/MRI/EEG) resting state (rs) brain data were acquired from 10 healthy male volunteers. The rs-functional MRI (fMRI) metrics, such as regional homogeneity (ReHo), degree centrality (DC) and fractional amplitude of low-frequency fluctuations (fALFFs), as well as 2-[18F]fluoro-2-desoxy-d-glucose (FDG)-PET standardised uptake value (SUV), were calculated and the measures were extracted from the default mode network (DMN) regions of the brain. Similarly, four microstates for each subject, showing the diverse functional states of the whole brain via topographical variations due to global field power (GFP), were estimated from artefact-corrected EEG signals.

MR-compatible, 3.8 inch dual organic light-emitting diode (OLED) in-bore display for functional MRI.

Purpose: Functional MRI (fMRI) is a well-established method used to investigate localised brain activation by virtue of the blood oxygen level dependent (BOLD) effect. It often relies on visual presentations using beam projectors, liquid crystal display (LCD) screens, and goggle systems. In this study, we designed an MR compatible, low-cost display unit based on organic light-emitting diodes (OLED) and demonstrated its performance.

A 3D two-point method for whole-brain water content and relaxation time mapping: Comparison with gold standard methods.

Quantitative imaging of the human brain is of great interest in clinical research as it enables the identification of a range of MR biomarkers useful in diagnosis, treatment and prognosis of a wide spectrum of diseases. Here, a 3D two-point method for water content and relaxation time mapping is presented and compared to established gold standard methods. The method determines free water content, H2O, and the longitudinal relaxation time, T1, quantitatively from a two-point fit to the signal equation including corrections of the transmit and receive fields.

From simultaneous to synergistic MR-PET brain imaging: A review of hybrid MR-PET imaging methodologies.

Simultaneous Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) scanning is a recent major development in biomedical imaging. The full integration of the PET detector ring and electronics within the MR system has been a technologically challenging design to develop but provides capacity for simultaneous imaging and the potential for new diagnostic and research capability. This article reviews state-of-the-art MR-PET hardware and software, and discusses future developments focusing on neuroimaging methodologies for MR-PET scanning.

Relaxometry and quantification in simultaneously acquired single and triple quantum filtered sodium MRI.

Purpose: Sodium imaging delivers valuable information about in vivo metabolism and pathophysiology. Image quantification can benefit the diagnosis and characterization of existing pathologies and the clinical course of a disease. An enhanced SISTINA sequence is proposed for sodium imaging and for the estimation of sodium tissue parameters for a 2-compartment model of the brain, such as relaxation times in intracellular space and tissue, intracellular volume fraction, and intracellular molar fraction.

Olfactory functioning in adults with Tourette syndrome.

Tourette syndrome is a chronic tic disorder characterized by motor and vocal tics. Comorbidities such as attention deficit hyperactivity disorder and obsessive compulsive disorder can be found. The overlap between neuroanatomical regions and neurotransmitter systems in the olfactory system and the pathophysiology of Tourette syndrome let us hypothesize altered olfactory performance in Tourette syndrome.

A novel analytical description of periodic volume coil geometries in MRI.

MRI volume coils can be represented by equivalent lumped element circuits and for a variety of these circuit configurations analytical design equations have been presented. The unification of several volume coil topologies results in a two-dimensional gridded equivalent lumped element circuit which compromises the birdcage resonator, its multiple endring derivative but also novel structures like the capacitive coupled ring resonator. The theory section analyzes a general two-dimensional circuit by noting that its current distribution can be decomposed into a longitudinal and an azimuthal dependency.

9.4 T small animal MRI using clinical components for direct translational studies.

Background: Magnetic resonance is a major preclinical and clinical imaging modality ideally suited for longitudinal studies, e.g. in pharmacological developments.

Design and use of a folded four-ring double-tuned birdcage coil for rat brain sodium imaging at 9.4 T.

A folded four-ring quadrature birdcage coil was designed and constructed with a double-tune configuration of an outer high-pass coil for H (400 MHz) and inner low-pass coil for Na (105.72 MHz at 9.4 T).

Simultaneous trimodal PET-MR-EEG imaging: Do EEG caps generate artefacts in PET images?

Trimodal simultaneous acquisition of positron emission tomography (PET), magnetic resonance imaging (MRI), and electroencephalography (EEG) has become feasible due to the development of hybrid PET-MR scanners. To capture the temporal dynamics of neuronal activation on a millisecond-by-millisecond basis, an EEG system is appended to the quantitative high resolution PET-MR imaging modality already established in our institute. One of the major difficulties associated with the development of simultaneous trimodal acquisition is that the components traditionally used in each modality can cause interferences in its counterpart.

Microstructure-informed slow diffusion tractography in humans enhances visualisation of fibre pathways.

Conventional fibre tractography methods based on diffusion tensor imaging exploit diffusion anisotropy and directionality in the range of low diffusion weightings (b-values). High b-value Biexponential Diffusion Tensor Analysis reported previously has demonstrated that fractional anisotropy of the slow diffusion component is essentially higher than that of conventional diffusion tensor imaging whereas popular compartment models associate this slow diffusion component with axonal water fraction. One of the primary aims of this study is to elucidate the feasibility and potential benefits of "microstructure-informed" whole-brain slow-diffusion fibre tracking (SDIFT) in humans.

Methods for molecular imaging of brain tumours in a hybrid MR-PET context: Water content, T, diffusion indices and FET-PET.

The aim of this study is to present and evaluate a multiparametric and multi-modality imaging protocol applied to brain tumours and investigate correlations between these different imaging measures. In particular, we describe a method for rapid, non-invasive, quantitative imaging of water content of brain tissue, based on a single multiple-echo gradient-echo (mGRE) acquisition. We include in the processing a method for noise reduction of the multi-contrast data based on Principal Component Analysis (PCA).