Absolute quantitation of glutamate, GABA and glutamine using localized 2D constant-time COSY spectroscopy in vivo.

Purpose: We propose an absolute quantitation method for metabolites with strongly coupled spin systems using localized 2-dimensional (2D) constant-time correlation spectroscopy (CT-COSY). We also develop two methods for improving the quality of in vivo CT-COSY spectra.

Methods: We substituted an image selected in vivo spectroscopy (ISIS) pulse for a 180° slice pulse in the CT-COSY module to decrease the slice displacement error caused by the chemical shift difference.

A Post-processing framework for localized 2D MR spectroscopy in vivo.

Purpose: We propose a post-processing framework for localized two-dimensional (2D) magnetic resonance spectroscopy (MRS) in vivo.

Methods: Our framework consists of corrections on eddy current and subject motion along with the framework used in conventional analytical 2D nuclear magnetic resonance (NMR) spectroscopy. In the eddy current correction, the phases of the free induction decays (FIDs) of the metabolite (1)H are corrected along the t₂ direction by the phase of the FID of water (1)H.

Highly resolved two-dimensional ¹H spectroscopy of the human brain using ISIS CT-PRESS with resolution enhancement.

In constant time (CT) point-resolved spectroscopy (PRESS), echo centers shift with the fast decay of short T₂* on two-dimensional (2D) time domain (TD) data under inhomogeneous B₀ field like in vivo conditions. Though ¹H decoupling along the F₁ direction is a feature of this method, the tilted and broadened peak pattern on the F₁-F₂ plane after reconstruction causes the peaks to overlap. To enhance resolution to achieve highly resolved 2D CT-PRESS spectra in the human brain, we propose a 2-part window function that comprises an enhancement part for shifting echoes with fast decay and a conventional part, such as Lorentzian, Gaussian, or sine-bell function.

Toward understanding transverse relaxation in human brain through its field dependence.

Apparent transverse-relaxation rate constants (R₂⁺ = 1/T₂⁺) were measured in various regions of the healthy human brain using a multiecho adiabatic spin-echo sequence at five different magnetic fields, 1.5, 1.9, 3, 4.

Non-uniformity correction of human brain imaging at high field by RF field mapping of B1+ and B1-.

A new method of non-uniform image correction is proposed. Image non-uniformity is originated from the spatial distribution of RF transmission and reception fields, represented as B(1)(+) and B(1)(-), respectively. In our method, B(1)(+) mapping was performed invivo by a phase method.

Estimation of brain iron concentration in vivo using a linear relationship between regional iron and apparent transverse relaxation rate of the tissue water at 4.7T.

Maps of the apparent transverse relaxation time (T(2) were collected on a transaxial plane across the basal ganglia in 54 healthy subjects at 4.7T using a multiecho adiabatic spin-echo (MASE) imaging sequence. We attempted to quantify the nonhemin iron concentration ([Fe]) in various brain regions in vivo based on the linear relationship between the apparent relaxation rate constant (R(2) = 1/T(2) and regional [Fe], as demonstrated previously in 12 subjects.

Visualization of seminiferous tubules in rat testes in normal and diseased conditions by high-resolution MRI.

Rat seminiferous tubules were visualized for the first time using high-spatial-resolution MRI and their MRI features were investigated under normal and various kinds of pathological conditions. All testes images were obtained at 4.7 T with a dedicated quadrature surface coil.

Apparent transverse relaxation rate in human brain varies linearly with tissue iron concentration at 4.7 T.

Multiple pairs of adiabatic passage pulses were implemented in a spin-echo sequence to achieve accurate measurements of the apparent transverse relaxation time (T(2)(dagger)) in a short scan time. In experiments on agarose gel phantoms with T(2) values ranging from 30 to 105 ms, the measured T(2)(dagger) values were in good agreement with transverse relaxation times measured with a nonselective Carr-Purcell-Meiboom-Gill sequence. In experiments on normal human brain at 4.

In vivo localized 1H MR spectroscopy of rat testes: stimulated echo acquisition mode (STEAM) combined with short TI inversion recovery (STIR) improves the detection of metabolite signals.

A noninvasive NMR technique for evaluating testicular function was explored in this study. Localized in vivo 1H NMR spectroscopy was performed on rat testes using a stimulated echo acquisition mode (STEAM) sequence with a short echo time (TE). In the 1H spectra, large lipid signals dominated the chemical shift range of 0.