The most widely used technique for double-quantum filtered (DQF) single-voxel spectroscopy (SVS) is based on a symmetric PRESS sequence with two additional spatially unselective pi/2 pulses, one of which is usually frequency selective. The actual filtering, rejecting signals from all uncoupled resonances, can be done by suitable phase cycling of the rf pulses in successive shots, but in practice gradient filtering is always used. Under usual conditions the sequence repetition time is comparable to the spin-lattice relaxation time, and a stimulated echo is formed by five out of the ten rf pulses in two consecutive shots. This echo is not filtered out by the gradients, and additional phase cycling is needed to eliminate it. Its spatial origin is the full transverse slice selected by the last pulse of the PRESS sequence. The SVS shimming procedure may create an important field variation in this slice (outside the volume of interest VOI). Water singlet signals therefore appear in a band of frequencies other than 4.7 ppm, and remain unaffected by water suppression pulses. In practice phase-alternation schemes can reduce these spurious signals by several orders of magnitude, but even then they may mask the weak metabolite signals of interest. We describe a strategy to minimize these spurious signals and propose a 16-step phase cycling scheme that attenuates the stimulated echo in every two-step subcycle.

Small animal models are widely used to study various pathologies. Magnetic resonance imaging (MRI) allows investigation of these animals in a non-invasive way. Therefore, the aim of our study was to develop and evaluate a low-cost approach to measure lung volumes in small animal MRI using a clinical scanner and a specially designed RF coil. Five mice (three of an established emphysema model and two controls) were investigated in a 1.0-T clinical scanner using a specially built small animal saddle coil and three different three-dimensional sequences; overall imaging time was approximately 16 min. Lung volumes were calculated from these images using an interactive watershed transform algorithm for semi-automatic image segmentation. The gold standard for the volume measurement was water displacement after surgical explantation. MRI measured volumes correlated significantly with ex vivo measurements on the explanted lungs (r = 0.99 to 0.89; p < 0.05). Mean lung volume in emphysema model mice was larger than in controls. High-resolution, small animal MRI using a clinical scanner is feasible for volumetric analysis and provides an alternative to a dedicated small animal scanner.

Commercially available aliquots of dairy cream are shown to have diffusion decay curves characterized by biexponential functions when studied over a wide range of b-factors. The fast and slow diffusion components responsible for the biexponential decay are attributed to water and lipid protons, respectively. The fast diffusion coefficient and relative fast and slow diffusion component fractions obtained from biexponential fits of cream phantoms over a wide range of b-factors up to 3,000 s/mm2 are similar to those obtained previously for brain. The slow diffusion coefficient from lipid protons is smaller than that found in the brain. Overall, however, the results suggest that dairy cream can serve as a widely available phantom material for testing software and hardware components designed to perform quantitative, biexponential diffusion decay studies.

To describe how the information content in a Fourier velocity encoding (FVE) scan can be transformed into a very sparse representation and to develop a method that exploits the compactness of the data to significantly accelerate the acquisition. For validation, fully sampled FVE datasets were acquired in phantom and in vivo experiments. Fivefold and eightfold acceleration was simulated by using only one fifth or one eighth of the data for reconstruction in the proposed method based on the k-t BLAST framework. Reconstructed images were compared quantitatively to those from the fully sampled data. Velocity spectra in the accelerated datasets were comparable to the spectra from fully sampled datasets. The detected peak velocities remained accurate even at eightfold acceleration, and the overall shape of the spectra was well preserved. Slight temporal smoothing was seen in the accelerated datasets. A novel technique for accelerating time-resolved FVE scan is presented. It is possible to accelerate FVE to acquisition speeds comparable to a standard time-resolved phase-contrast scan.

MRI and MRS are established techniques for the evaluation of intracranial mass lesions and cysts. The 2.03 ppm signal recorded in their (1)H-MRS spectra is often assigned to NAA from outer volume contamination, although it has also been detected in non-infiltrating tumours and large cysts. We have investigated the molecular origin of this resonance in ten samples of cystic fluids from human brain tumours. The NMR detected content of the 2.03 ppm resonance in 136 ms echo time spectra, assuming an N- CH(3) origin, was 3.19 +/- 1.01 mM. Only one third (34 +/- 12%) of the N-acetyl containing compound (NAC) signal could be extracted by perchloric acid (PCA) indicating that most of it originated in a macromolecular PCA-insoluble component. Chemical analysis of the cyst fluids showed that sialic acid bound to macromolecules would account for 64.3% and hexuronic containing compounds for 29.2% of the NMR-detectable ex vivo signal, 93.4% of the signal at TE 136 ms. Lactate content measured by NMR (6.4 +/- 4.4 mM) and the predominance of NAC originating in sialic acid point to a major origin from tumour rather than from plasma for this 2.03 ppm resonance.

Cerebral metabolic changes that concur to motor and/or cognitive disorders in actively drinking alcoholics are not well established. We tested the hypothesis that chronic alcoholics exhibit profound alterations in the cerebral metabolism of scyllo-inositol. Brain metabolism was explored in nine actively drinking and 11 recently detoxified chronic alcoholics by in vivo brain (1)H-MRS and in vitro(1)H-MRS of blood serum and cerebrospinal fluid. The cohort was composed of individuals with acute, subacute or chronic encephalopathy or without any clinical encephalopathy. Chronic alcoholism is associated with a hitherto unrecognized accumulation of brain scyllo-inositol. Our results suggest that scyllo-inositol is produced within the central nervous system and shows a diffuse but heterogenous distribution in brain where it can persist several weeks after detoxification. Its highest levels were observed in subjects with a clinically symptomatic alcohol-related encephalopathy. When detected, brain scyllo-inositol takes part in a metabolic encephalopathy since it is associated with reduced N-acetylaspartate and increased creatine. High levels of cerebral scyllo-inositol are correlated with altered glial and neuronal metabolism. Our findings suggest that the accumulation of scyllo-inositol may precede and take part in the development of symptomatic alcoholic metabolic encephalopathy.

The purpose of this paper is to present a new pulse sequence for visualizing slow flow. The new sequence consists of an initial Stejskal-Tanner flow sensitization part followed by a DEFT pulse and a spoiler gradient. A single-shot TSE readout train is then applied to sample the NMR signal. The sequence was initially tested using a simple flow phantom. To verify potential clinical use, both flow-sensitive MRCP and cerebrospinal fluid (CSF) images were produced. The phantom study proved the sequence sensitivity to flow in the range 0-1 cm/s. bVE-factors 1.5, 3, 6 and 12 were chosen. Within this flow velocity range, the signal dropped as predicted theoretically. This indicates that the method can be used to quantify flow. All anatomical features seen in a standard MRCP sequence were identified and the methods sensitivity to CSF flow was demonstrated by sagital images of the head. A new pulse sequence sensitive to slow flow has been developed.

Cardiac MR cine imaging during breath hold is a compromise between spatial and temporal resolution and duration of breath hold. Especially for sick patients who have problems holding their breath, a short acquisition time is mandatory for all sequences. A combination of Auto-SENSE parallel imaging and view-sharing was implemented for fast cine imaging of the human heart and applied to healthy volunteers. Compared to conventional Fourier imaging, data acquisition could be accelerated by a factor of 3.6. Neither a pre-scan nor additional lines in k-space are required to generate the sensitivity maps in Auto-SENSE.

To evaluate the effect of a new oral manganese contrast agent (CMC-001) on magnetic resonance imaging (MRI) intensities at different magnetic field strengths. Twelve healthy volunteers underwent abdominal MRI 1 week before and within 2.5-4.5 h after CMC-001 (MnCl(2) and absorption promoters dissolved in water) intake at three different MR scanners of 0.23, 0.6 and 1.5 T. Image contrast and intensity enhancement of liver and pancreas were analysed relatively to muscle and fat intensities. Manganese blood levels were followed for 24 h. Whole-blood manganese concentration levels stayed within the normal range. The liver intensities on T2w images decreased about 10% for the 1/2 contrast dose and about 20% for the full contrast dose independent of the field strength. The liver intensities on T1w images increased more than 30% for 1/2 contrast dose and over 40% for full contrast dose. The maximum T1 enhancement was achieved at the highest field. Pancreas intensities were not affected. Contrast between liver, muscle and fat intensities increased with magnetic field, as well as standard errors of the volunteer-averaged intensities. Oral intake of CMC-001 influences liver intensities and does not affect pancreas intensities at different magnetic field strengths.

High-speed switching of current in gradient coils within high magnetic field strength magnetic resonance imaging (MRI) scanners results in high acoustic sound pressure levels (SPL) in and around these machines. To characterize the vibration properties as well as the acoustic noise properties of the gradient coil, a finite-element (FE) model was developed using the dimensional design specifications of an available gradient-coil insert and the concentration of the copper windings in the coil. This FE model was then validated using experimentally collected vibration data. A computational acoustic noise model was then developed based on the validated FE model. The validation of the finite-element analysis results was done using experimental modal testing of the same gradient coil in a free-free state (no boundary constraints). Based on the validated FE model, boundary conditions (supports) were added to the model to simulate the operating condition when the gradient-coil insert is in place in an MRI machine. Vibration analysis results from the FE model were again validated through experimental vibration testing with the gradient-coil insert installed in the MRI scanner and excited using swept sinusoidal time waveforms. The simulation results from the computational acoustic noise model were also validated through experimental noise measurement from the gradient-coil insert in the MRI scanner using swept sinusoidal time waveform inputs. Comparisons show that the FE model predicts the vibration properties and the computational acoustic noise model predicts the noise characteristic properties extremely accurately.