A system for in vivo on-demand ultra-low field Overhauser-enhanced 3D-Magnetic resonance imaging.

Development of very-low field MRI is an active area of research. It aims at reducing operating costs and improve portability. However, the signal-to-noise issue becomes prominent at ultra-low field (<1 mT), especially for molecular imaging purposes that addresses specific biochemical events.

Optically Sensitive and Magnetically Identifiable Supraparticles as Indicators of Surface Abrasion.

Identifying and ensuring the integrity of products plays an important role in today's globalized world. Miniaturized information taggants in the packaging surface are therefore required to monitor the product itself instead of applying external labels. Ideally, multiple types of information are stored in such additives.

Reversible magnetism switching of iron oxide nanoparticle dispersions by controlled agglomeration.

The controlled agglomeration of superparamagnetic iron oxide nanoparticles (SPIONs) was used to rapidly switch their magnetic properties. Small-angle X-ray scattering (SAXS) and dynamic light scattering showed that tailored iron oxide nanoparticles with phase-changing organic ligand shells agglomerate at temperatures between 5 °C and 20 °C. We observed the concurrent change in magnetic properties using magnetic particle spectroscopy (MPS) with a temporal resolution on the order of seconds and found reversible switching of magnetic properties of SPIONs by changing their agglomeration state.

Stem cell labeling with iron oxide nanoparticles: impact of 3D culture on cell labeling maintenance.

Aim: We aimed to analyze the suitability of nanoparticles (M4E) for safe human mesenchymal stem cell (hMSC) labeling and determined cell labeling maintenance in 2D and 3D culture.

Materials & Methods: We investigated cell-particle interaction and the particles' impact on cell viability, growth and proliferation. We analyzed cell labeling maintenance in 2D and 3D culture invasively and noninvasively.

Design of a mobile, homogeneous, and efficient electromagnet with a large field of view for neonatal low-field MRI.

Objective: In this work, a prototype of an effective electromagnet with a field-of-view (FoV) of 140 mm for neonatal head imaging is presented. The efficient implementation succeeded by exploiting the use of steel plates as a housing system. We achieved a compromise between large sample volumes, high homogeneity, high B0 field, low power consumption, light weight, simple fabrication, and conserved mobility without the necessity of a dedicated water cooling system.

Optimization of the AC-gradient method for velocity profile measurement and application to slow flow.

This work presents a spectroscopic method to measure slow flow. Within a single shot the velocity distribution is acquired. This allows distinguishing rapidly between single velocities within the sampled volume with a high sensitivity.

Myocardial T1: quantification by using an ECG-triggered radial single-shot inversion-recovery MR imaging sequence.

Purpose: To develop and validate a fast cardiac magnetic resonance imaging T1 mapping technique with high spatial resolution based on a radial inversion-recovery (IR) spoiled gradient-echo acquisition.

Materials And Methods: Approval for the study was granted by the local institutional review board, and all subjects gave written informed consent. An electrocardiographically triggered radial single-shot IR (TRASSI) sequence was developed in conjunction with a custom-written fitting algorithm.

MRI Meets MPI: a bimodal MPI-MRI tomograph.

While magnetic particle imaging (MPI) constitutes a novel biomedical imaging technique for tracking superparamagnetic nanoparticles in vivo, unlike magnetic resonance imaging (MRI), it cannot provide anatomical background information. Until now these two modalities have been performed in separate scanners and image co-registration has been hampered by the need to reposition the sample in both systems as similarly as possible. This paper presents a bimodal MPI-MRI-tomograph that combines both modalities in a single system.

Spatial phase encoding exploiting the Bloch-Siegert shift effect.

Objective: The present work introduces an alternative to the conventional B0-gradient spatial phase encoding technique. By applying far off-resonant radiofrequency (RF) pulses, a spatially dependent phase shift is introduced to the on-resonant transverse magnetization. This so-called Bloch-Siegert (BS) phase shift has been recently used for B1(+)-mapping.

3D gradient system for two B0 field directions in earth's field MRI.

Object: A new gradient system for earth's field magnetic resonance imaging (EFMRI) is presented that can be rotated relatively to the earth's field direction while maintaining the ability to encode images. Orthogonal components of the gradient field are exploited to reduce the number of gradient coils.

Materials And Methods: Two favorable orientations of the gradient system relative to the earth's magnetic field (parallel and perpendicular) are discussed.

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.

Rapid spectroscopic velocity quantification using periodically oscillating gradients.

In this work two spectroscopic methods are described which allow rapid flow velocity quantification in the presence of a parabolic velocity distribution. This method requires only a single excitation and is based on flow encoding by periodically oscillating gradients. In the shown spin echo variant additional refocusing pulses correct for field inhomogeneities.

Quantification and localization of contrast agents using delta relaxation enhanced magnetic resonance at 1.5 T.

Object: Delta relaxation enhanced magnetic resonance (dreMR) is a new imaging technique based on the idea of cycling the magnetic field B (0) during an imaging sequence. The method determines the field dependency of the relaxation rate (relaxation dispersion dR (1)/dB). This quantity is of particular interest in contrast agent imaging because the parameter can be used to determine contrast agent concentrations and increases the ability to localize the contrast agent.

Contrast agent derived determination of the total circulating blood volume using magnetic resonance.

Object: Knowledge of the total circulating blood volume (TCBV) is essential for the treatment of a variety of medical conditions and blood disorders. To date, blood volume analysis is rarely carried out due to the disadvantages of available methods. Our aim was to develop a widely available, simple, fast, yet accurate method for the determination of the total circulating blood volume.

Feasibility of contrast-enhanced and nonenhanced MRI for intraprocedural and postprocedural lesion visualization in interventional electrophysiology: animal studies and early delineation of isthmus ablation lesions in patients with typical atrial flutter.

Background: Imaging of myocardial ablation lesions during electrophysiology procedures would enable superior guidance of interventions and immediate identification of potential complications. The aim of this study was to establish clinically suitable MRI-based imaging techniques for intraprocedural lesion visualization in interventional electrophysiology.

Methods And Results: Interventional electrophysiology was performed under magnetic resonance guidance in an animal model, using a custom setup including magnetic resonance-conditional catheters.

Feasibility of real-time MRI with a novel carbon catheter for interventional electrophysiology.

Background: Cardiac MRI offers 3D real-time imaging with unsurpassed soft tissue contrast without x-ray exposure. To minimize safety concerns and imaging artifacts in MR-guided interventional electrophysiology (EP), we aimed at developing a setup including catheters for ablation therapy based on carbon technology.

Methods And Results: The setup, including a steerable carbon catheter, was tested for safety, image distortion, and feasibility of diagnostic EP studies and radiofrequency ablation at 1.

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.

Investigating the locomotion of the sandfish in desert sand using NMR-imaging.

The sandfish (Scincus scincus) is a lizard having the remarkable ability to move through desert sand for significant distances. It is well adapted to living in loose sand by virtue of a combination of morphological and behavioural specializations. We investigated the bodyform of the sandfish using 3D-laserscanning and explored its locomotion in loose desert sand using fast nuclear magnetic resonance (NMR) imaging.

Spatial distribution of RF-induced E-fields and implant heating in MRI.

The purpose of this study was to assess the distribution of RF-induced E-fields inside a gel-filled phantom of the human head and torso and compare the results with the RF-induced temperature rise at the tip of a straight conductive implant, specifically examining the dependence of the temperature rise on the position of the implant inside the gel. MRI experiments were performed in two different 1.5T MR systems of the same manufacturer.

MRI thermometry: Fast mapping of RF-induced heating along conductive wires.

Conductive implants are in most cases a strict contraindication for MRI examinations, as RF pulses applied during the MRI measurement can lead to severe heating of the surrounding tissue. Understanding and mapping of these heating effects is therefore crucial for determining the circumstances under which patient examinations are safe. The use of fluoroptic probes is the standard procedure for monitoring these heating effects.

Quantitative regional oxygen transfer imaging of the human lung.

Purpose: To demonstrate that the use of nonquantitative methods in oxygen-enhanced (OE) lung imaging can be problematic and to present a new approach for quantitative OE lung imaging, which fulfills the requirements for easy application in clinical practice.

Materials And Methods: A total of 10 healthy volunteers and three non-small-cell lung cancer (NSCLC) patients were examined using a 1.5T scanner.

Sequential changes of myocardial function during acute myocardial infarction, in the early and chronic phase after coronary intervention described by ultrasonic strain rate imaging.

Objective: The aim of this prospective clinical study was to follow up patients with acute myocardial infarction from the ischemic event, over the primary coronary intervention (PCI), up to the chronic phase after survived myocardial infarction by noninvasive strain rate (SR) imaging and to determine its role in the assessment of transmurality of infarction.

Methods: In all, 41 patients with acute S-T elevation infarction were examined immediately before, 3 days after, and 5 months after PCI. Regional myocardial function was assessed by the use of ultrasonic SR imaging and peak systolic SR and systolic strain were extracted.

Myocardial perfusion measurements by spin-labeling under different vasodynamic states.

In this study absolute myocardial perfusion was determined using a spin-labeling magnetic resonance imaging (MRI) technique at 2 Tesla. The technique was applied to 16 healthy volunteers at resting conditions, adenosine-induced stress, and oxygen breathing. Overall myocardial quantitative perfusion was determined as 2.

Quantitative assessment of myocardial perfusion with a spin-labeling technique: preliminary results in patients with coronary artery disease.

Purpose: To determine perfusion and coronary reserve in human myocardium without contrast agent using a spin labeling technique.

Materials And Methods: Assessment of myocardial perfusion is based on T1 measurements after global and slice-selective spin preparation. This magnetic resonance imaging (MRI) technique was applied to 12 healthy volunteers and 16 patients with suspected coronary artery disease under resting conditions and adenosine-induced vasodilatation.

Microscopic spin tagging (MiST) for flow imaging.

In this study, a new strategy for slow flow imaging is proposed. The basic idea is to generate flow contrast on a microscopic level below the spatial resolution of an imaging experiment. Since a microscopic spin tagging scheme is used, this concept is called MiST (Microscopic Spin Tagging).