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Short Echo Time (short + echo_time)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Diffusion-weighted spectroscopy: A novel approach to determine macromolecule resonances in short-echo time 1H-MRS

MAGNETIC RESONANCE IN MEDICINE, Issue 4 2010
N. Kunz
Abstract Quantification of short-echo time proton magnetic resonance spectroscopy results in >18 metabolite concentrations (neurochemical profile). Their quantification accuracy depends on the assessment of the contribution of macromolecule (MM) resonances, previously experimentally achieved by exploiting the several fold difference in T1. To minimize effects of heterogeneities in metabolites T1, the aim of the study was to assess MM signal contributions by combining inversion recovery (IR) and diffusion-weighted proton spectroscopy at high-magnetic field (14.1 T) and short echo time (=8 msec) in the rat brain. IR combined with diffusion weighting experiments (with ,/, = 1.5/200 msec and b -value = 11.8 msec/,m2) showed that the metabolite nulled spectrum (inversion time = 740 msec) was affected by residuals attributed to creatine, inositol, taurine, choline, N -acetylaspartate as well as glutamine and glutamate. While the metabolite residuals were significantly attenuated by 50%, the MM signals were almost not affected (<8%). The combination of metabolite-nulled IR spectra with diffusion weighting allows a specific characterization of MM resonances with minimal metabolite signal contributions and is expected to lead to a more precise quantification of the neurochemical profile. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source]

An automated quantitation of short echo time MRS spectra in an open source software environment: AQSES

NMR IN BIOMEDICINE, Issue 5 2007
Jean-Baptiste Poullet
Abstract This paper describes a new quantitation method called AQSES for short echo time magnetic resonance spectra. This method is embedded in a software package available online from www.esat.kuleuven.be/sista/members/biomed/new/ with a graphical user interface, under an open source license, which means that the source code is freely available and easy to adapt to specific needs of the user. The quantitation problem is mathematically formulated as a separable nonlinear least-squares fitting problem, which is numerically solved using a modified variable-projection procedure. A macromolecular baseline is incorporated into the fit via nonparametric modelling, efficiently implemented using penalized splines. Unwanted components such as residual water are removed with a maximum-phase FIR filter. Constraints on the phases, dampings and frequencies of the metabolites can be imposed. AQSES has been tested on simulated MR spectra with several types of disturbance and on short echo time in vivo proton MR spectra. Results show that AQSES is robust, easy to use and very flexible. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Use of tissue water as a concentration reference for proton spectroscopic imaging

MAGNETIC RESONANCE IN MEDICINE, Issue 6 2006
Charles Gasparovic
Abstract A strategy for using tissue water as a concentration standard in 1H magnetic resonance spectroscopic imaging studies on the brain is presented, and the potential errors that may arise when the method is used are examined. The sensitivity of the method to errors in estimates of the different water compartment relaxation times is shown to be small at short echo times (TEs). Using data from healthy human subjects, it is shown that different image segmentation approaches that are commonly used to account for partial volume effects (SPM2, FSL's FAST, and K-means) lead to different estimates of metabolite levels, particularly in gray matter (GM), owing primarily to variability in the estimates of the cerebrospinal fluid (CSF) fraction. While consistency does not necessarily validate a method, a multispectral segmentation approach using FAST yielded the lowest intersubject variability in the estimates of GM metabolites. The mean GM and white matter (WM) levels of N-acetyl groups (NAc, primarily N-acetylaspartate), choline (Ch), and creatine (Cr) obtained in these subjects using the described method with FAST multispectral segmentation are reported: GM [NAc] = 17.16 ± 1.19 mM; WM [NAc] = 14.26 ± 1.38 mM; GM [Ch] = 3.27 ± 0.47 mM; WM [Ch] = 2.65 ± 0.25 mM; GM [Cr] = 13.98 ± 1.20 mM; and WM [Cr] = 7.10 ± 0.67 mM. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source]

High-resolution blood flow velocity measurements in the human finger

MAGNETIC RESONANCE IN MEDICINE, Issue 4 2001
M. Klarhöfer
Abstract MR phase contrast blood flow velocity measurements in the human index finger were performed with triggered, nontriggered, and cine acquisition schemes. A strong (Gmax = 200 mT/m), small bore (inner diameter 12 cm) gradient system inserted in a whole body 3 Tesla MR scanner allowed high-resolution imaging at short echo times, which decreases partial volume effects and flow artifacts. Arterial blood flow velocities ranging from 4.9,19 cm/sec were measured, while venous blood flow was significantly slower at 1.5,7.1 cm/sec. Taking into account the corresponding vessel diameters ranging from 800 ,m to 1.8 mm, blood flow rates of 3.0,26 ml/min in arteries and 1.2,4.8 ml/min in veins are obtained. The results were compared to ultrasound measurements, resulting in comparable blood flow velocities in the same subjects. Magn Reson Med 45:716,719, 2001. © 2001 Wiley-Liss, Inc. [source]