PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 10374658

Fast magnetic resonance imaging techniques.

Q Chen·K W Stock·P V Prasad·H Hatabu
View original source ↗Export metadata ↓

Abstract

This article reviews fast magnetic resonance (MR) techniques currently used for body imaging. Improvements in gradient performance have made very short repetition and echo times on clinical scanners feasible, thus enabling subsecond image acquisition. The article provides a fundamental overview of the technical aspects from the concept of k-space and k-space segmentation technique, fast MR imaging techniques including fast spin echo, fast gradient echo with or without magnetization preparation to echo planar and hybrid techniques. The article also addresses the use of different fat suppression techniques in MR imaging of the body and improvements in coil technology to obtain faster images and higher signal-to-noise.

Explore related subjects

Echo-Planar ImagingHumansMagnetic Resonance ImagingJournal ArticleReview

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Q Chen, K W Stock, P V Prasad, H Hatabu. 1999. Fast magnetic resonance imaging techniques.. https://doi.org/10.1016/s0720-048x(98)00172-7

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2006

[Fundamental study of turbo spin echo sequence with driven equilibrium pulse].

UNLABELLED: When MR images are obtained with the turbo spin echo (TSE) sequence, DRIVE can be used as a sequence in which the driven equilibrium pulse (DE pulse), a reset pulse, is applied at the TSE echo train to accelerate relaxation time and return to the equilibrium of Mz magnetization. In this study, we examined the extent to which TR could be shortened in DRIVE and how the other parameters of the turbo spin echo sequence influence it. RESULTS: 1) DRIVE is effective when the T2 value is long. 2) It is necessary to set TR at 1000 ms or more to obtain image contrast with free water and fat in T2-weighted images for which a conventional turbo spin echo sequence using DRIVE is employed in clinical examination. 3) It is not necessary to consider the influence of the TSE factor when using DRIVE.

Echo-Planar Imaging↗
PubMed2006

Spatial and temporal characteristics of physiological noise in fMRI at 3T.

RATIONALE AND OBJECTIVES: Physiological noise in blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) has been shown to have characteristics similar to the BOLD signal itself, suggesting that it may have a vascular dependence. In this study, we evaluated the influence of physiological noise in fMRI as revealed by the differences in vasculature sensitivity of gradient-echo echo-planar imaging (GE-EPI) and spin-echo EPI (SE-EPI). MATERIALS AND METHODS: The contribution of physiological noise to the fMRI signal during activation of the visual cortex was assessed by comparing its temporal characteristics with respect to echo time (TE), using both GE-EPI and SE-EPI. The correlation of the noise in fMRI with apparent diffusion coefficient (ADC) and the number of components required to describe its variance, as determined by principal-component analysis (PCA), were also assessed. RESULTS: The SE-EPI data were less affected by a TE-dependence of noise, in contrast to the apparent physiological noise in GE-EPI. Voxel-wise analysis revealed that total apparent noise increased as ADC values increased, and the relationship was different for GE-EPI and SE-EPI. PCA revealed that while the number of components characterizing the noise in SE-EPI data increased in a TE-dependent manner, approaching that of white noise at long echo time, the number of components from GE-EPI data was TE-independent. CONCLUSIONS: The difference in sensitivities to physiological noise between SE-EPI and GE-EPI suggests that extravascular BOLD processes around draining veins contribute significantly to physiological noise in BOLD fMRI, and the suppression of this noise component may enhance SE-EPI BOLD sensitivity at higher fields.

Echo-Planar Imaging↗
PubMed2005

[Basis examination of image contrast in fluid attenuated inversion recovery balanced turbo field echo (FLAIR-B-TFE)].

PURPOSE: We have made clinical use of FLAIR-B-TFE, where an image is taken at the null point (NP) of water with the addition of inversion pulse to B-TFE, and obtained highly effective results in many areas. Changes in NP and image contrast were reviewed to optimize this sequence. MATERIALS AND METHODS: Oil, water, and venous blood before and after Gd-DTPA dispensation as well as diluted (by 500/4000 times) Gd-DTPA solution were designated as the standard phantoms wherein shot intervals (SI), scan modes, k-space ordering, TFE factor, dummy pulse, and presence or absence of IR pulses were changed. RESULTS: What affects the NP of water most is the SI, and unless SI is long enough so that the longitudinal magnetization of water can recover to the full, NP will change. There is little difference in image contrast between the NP of water and that of blood, and a sluggish blood signal ascendance will necessitate intentional blood signal ascendance by contrast-enhancement. The signal intensity of blood after the angiographies will almost reach a plateau at an SI level of more than 2000 ms. Therefore, it is appropriate to apply SI 2000 ms, in view of the time necessary for contrast-enhancement.

Echo-Planar Imaging↗