Monitoring of tumor oxygenation changes in head-and-neck carcinoma patients breathing a hyperoxic hypercapnic gas mixture with a noninvasive MRI technique.

Purpose: : To implement and evaluate a noninvasive functional MRI technique for measuring tumor tissue oxygenation changes in head-and-neck carcinoma patients.

Patients And Methods: : Tissue oxygenation changes were determined quantitatively in 13 patients with head-and-neck cancer. The MR examinations were performed on a clinical MR scanner at 1.

Measurement of apparent cell radii using a multiple wave vector diffusion experiment.

It had been previously shown that an idealized version of the two-wave-vector extension of the NMR pulsed-field-gradient spin echo diffusion experiment can be used to determine the apparent radius of geometries with restricted diffusion. In the present work, the feasibility of the experiment was demonstrated in an NMR imaging experiment, in which the apparent radius of axons in white matter tissue was determined. Moreover, numerical simulations have been carried out to determine the reliability of the results.

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.

Using the GRAPPA operator and the generalized sampling theorem to reconstruct undersampled non-Cartesian data.

As expected from the generalized sampling theorem of Papoulis, the use of a bunched sampling acquisition scheme in conjunction with a conjugate gradient (CG) reconstruction algorithm can decrease scan time by reducing the number of phase-encoding lines needed to generate an unaliased image at a given resolution. However, the acquisition of such bunched data requires both modified pulse sequences and high gradient performance. A novel method of generating the "bunched" data using self-calibrating GRAPPA operator gridding (GROG), a parallel imaging method that shifts data points by small distances in k-space (with Deltak usually less than 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.

Monodisperse microisland formation on Ni/Ru(0001) monolayers.

The creation of identical microislands consisting of Ni trimers and multiples thereof on Ru(0001) induced by oxygen adsorption has been observed using scanning tunnelling microscopy. The island formation is caused by an oxygen induced expulsion of Ni atoms or trimers out of the moiré-distorted (densified) Ni monolayer. The exceptional stability of the Ni trimers is attributed to oxygen attachment, forming Ni-oxygen composites, as verified by detailed density functional theory calculations.

Lung imaging under free-breathing conditions.

Respiratory motion and pulsatile blood flow can generate artifacts in morphological and functional lung imaging. Total acquisition time, and thus the achievable signal to noise ratio, is limited when performing breath-hold and/or electrocardiogram-triggered imaging. To overcome these limitations, imaging during free respiration can be performed using respiratory gating/triggering devices or navigator echoes.

Potential of magnetization transfer MRI for target volume definition in patients with non-small-cell lung cancer.

Purpose: To develop a magnetization transfer (MT) module in conjunction with a single-shot MRI readout technique and to investigate the MT phenomenon in non-small-cell lung cancer (NSCLC) as an adjunct for radiation therapy planning.

Materials And Methods: A total of 10 patients with inoperable NSCLC were investigated using a 1.5T MR scanner.

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.

Quantitative in vivo 1H spectroscopic imaging of metabolites in the early postnatal mouse brain at 17.6 T.

Object: Early postnatal brain maturation is closely connected to local changes of metabolite levels. Spatially resolved in vivo (1)H NMR spectroscopic imaging is applied to follow absolute changes of brain metabolites in early postnatal mouse brain.

Materials And Methods: A short echo time semi LASER (localization by adiabatic selective refocusing) chemical shift imaging (CSI) sequence incorporating weighted k-space averaging was implemented at high magnetic field (17.

The mechanisms of refilling of xylem conduits and bleeding of tall birch during spring.

Seasonal variations in osmolality and components of xylem sap in tall birch trees were determined using several techniques. Xylem sap was extracted from branch and trunk sections of 58 trees using the very rapid gas bubble-based jet-discharge method. The 5-cm long wood pieces were taken at short intervals over the entire tree height.

Ex vivo expanded hematopoietic progenitor cells improve cardiac function after myocardial infarction: role of beta-catenin transduction and cell dose.

Cell-based therapy after myocardial infarction (MI) is a promising therapeutic option but the relevant cell subsets and dosage requirements are poorly defined. We hypothesized that cell therapy for myocardial infarction is improved by ex vivo expansion and high-dose transplantation of defined hematopoietic progenitor cells (HPCs). Since beta-catenin promotes self-renewal of stem cells we evaluated the therapeutic efficacy of beta-catenin-mediated ex vivo expansion of mouse HPCs in a mouse model of myocardial ischemia/reperfusion followed by intraarterial cell delivery.

Zigzag sampling for improved parallel imaging.

Conventional Cartesian parallel MRI methods are limited to the sensitivity variations provided by the underlying receiver coil array in the dimension in which the data reduction is carried out, namely, the phase-encoding directions. However, in this work an acquisition strategy is presented that takes advantage of sensitivity variations in the readout direction, thus improving the parallel imaging reconstruction process. This is achieved by employing rapidly oscillating phase-encoding gradients during the actual readout.

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.

Magnetic resonance of mouse models of cardiac disease.

In recent years magnetic resonance imaging (MRI) has become the noninvasive standard for the quantitative evaluation of cardiac function, masses, and infarct size. Wall motion analysis is used to display myocardial dysfunction and microcirculatory deficits can be displayed by perfusion imaging and quantification of the myocardial regional blood volume. Magnetic resonance spectroscopy (MRS) also provides quantitative information on cardiac energetics and, in combination with MRI, insights into cardiac structure and function.

Frequency autocorrelation function of stochastically fluctuating fields caused by specific magnetic field inhomogeneities.

Signal formation in NMR is due to incoherent dephasing of nuclear spins. Of particular practical importance is the situation of nuclear spins undergoing independent stochastic motion in inhomogeneous local magnetic fields, e.g.

Short-echo spectroscopic imaging combined with lactate editing in a single scan.

A short-echo spectroscopic imaging sequence extended with a frequency-selective multiple-quantum- coherence technique (Sel-MQC) is presented. The method enables acquisition of a complete water-suppressed proton spectrum with a short echo time and filtering of the J-coupling metabolite, lactate, from co-resonant lipids in one scan. The purpose of the study was to validate this combined pulse sequence in vitro and in vivo.

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.

Reconstruction of undersampled non-Cartesian data sets using pseudo-Cartesian GRAPPA in conjunction with GROG.

Most k-space-based parallel imaging reconstruction techniques, such as Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA), necessitate the acquisition of regularly sampled Cartesian k-space data to reconstruct a nonaliased image efficiently. However, non-Cartesian sampling schemes offer some inherent advantages to the user due to their better coverage of the center of k-space and faster acquisition times. On the other hand, these sampling schemes have the disadvantage that the points acquired generally do not lie on a grid and have complex k-space sampling patterns.

Self-calibrating GRAPPA operator gridding for radial and spiral trajectories.

Self-calibrating GRAPPA operator gridding (GROG) is a method by which non-Cartesian MRI data can be gridded using spatial information from a multichannel coil array without the need for an additional calibration dataset. Using self-calibrating GROG, the non-Cartesian datapoints are shifted to nearby k-space locations using parallel imaging weight sets determined from the datapoints themselves. GROG employs the GRAPPA Operator, a special formulation of the general reconstruction method GRAPPA, to perform these shifts.

Diffusion generated T1 and T2 contrast.

In MR images of porous organic samples (such as roots or wood) in water media, the sample is often surrounded by a bright ring, with a corresponding decreased T1 value in T1 maps. When the medium is removed, or contrast agents are added, the ring disappears, indicating that the signal does not originate in the outer layers of the sample, but from the medium itself. It can be shown that this "bright ring effect" is only observed when the medium experiences a reduction in T1 when permeating the sample.

Foliar water supply of tall trees: evidence for mucilage-facilitated moisture uptake from the atmosphere and the impact on pressure bomb measurements.

The water supply to leaves of 25 to 60 m tall trees (including high-salinity-tolerant ones) was studied. The filling status of the xylem vessels was determined by xylem sap extraction (using jet-discharge, gravity-discharge, and centrifugation) and by (1)H nuclear magnetic resonance imaging of wood pieces. Simultaneously, pressure bomb experiments were performed along the entire trunk of the trees up to a height of 57 m.

Iron oxide labelling of human mesenchymal stem cells in collagen hydrogels for articular cartilage repair.

For the development of new therapeutical cell-based strategies for articular cartilage repair, a reliable cell monitoring technique is required to track the cells in vivo non-invasively and repeatedly. We present a systematic and detailed study on the performance and biological impact of a simple and efficient labelling protocol for human mesenchymal stem cells (hMSCs). Commercially available very small superparamagnetic iron oxide particles (VSOPs) were used as magnetic resonance (MR) contrast agent.

T1 mapping of the entire lung parenchyma: Influence of respiratory phase and correlation to lung function test results in patients with diffuse lung disease.

The T(1) values of lung parenchyma of 25 patients with fibrosis and emphysema were measured in the entire lung, and the effect of inspiration and expiration was investigated. T(1) map acquisition was based on a snapshot-fast low-angle shot (FLASH) sequence. Lung function and blood gas tests were measured.

Males of a solitary wasp possess a postpharyngeal gland.

The postpharyngeal gland has long been thought to occur only in ants. Here we characterize, by use of light and electron microscopy as well as 3D reconstruction based on nuclear magnetic resonance (NMR) imaging data, a large cephalic gland reservoir of males of a solitary digger wasp, the European beewolf, Philanthus triangulum. Several lines of evidence suggest that this reservoir is a postpharyngeal gland.