Turbo gradient-spin-echo (GRASE): first clinical experiences with a fast T2-weighted sequence in MRI of the brain

doi:10.1016/0720-048X(94)00598-7

European Journal of Radiology

Volume 19, Issue 3, March 1995, Pages 171-176

https://doi.org/10.1016/0720-048X(94)00598-7 Get rights and content

Abstract

The aim of this study was to obtain first clinical experiences with Turbo gradient-spin-echo (TGSE). This fast MRI technique is based on the GRASE sequence which combines the gradient-echo and the spin-echo technique. In 60 patients suffering from different brain pathologies, a T2-weighted TGSE sequence was compared to a conventional spin-echo sequence. Anatomical and pathological structures were evaluated visually by three independent observers; signal and contrast behavior was assessed in regions of interest. TGSE showed reduced signal-to-noise-ratios of anatomical structures except for cerebrospinal fluid. The contrast of tumors, infarctions, and hematomas was similar in both sequence types. Small microangiopathic and inflammatory lesions as well as basal ganglia degeneration presented with diminished contrast in TGSE. The TGSE sequence can already now be used to acquire T2-weighted images in additional orientations requiring extremely short measurement time. However, further improvements of image quality are necessary for routine use of TGSE.

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Cited by (21)

Rapid whole cerebrum myelin water imaging using a 3D GRASE sequence
2012, NeuroImage
Citation Excerpt :
If MWI is to become a commonplace tool in clinical imaging or research that can be used in conjunction with other MR-imaging modalities that exhibit full brain coverage with isotropic voxel size, e.g. functional MRI, diffusion tensor imaging, magnetization transfer imaging, etc., whole brain data at reasonable spatial resolution must be acquired within clinically feasible scan durations (< 15 minutes). A combined gradient and spin echo sequence known as gradient and spin echo (GRASE) (Feinberg and Oshio, 1991) has previously been used to accelerate clinical MR acquisitions (Fellner et al., 1995, 1997; Melhelm et al., 1998; Patel et al., 1995; Rockwell et al., 1997; Umek et al., 1998). By acquiring multiple gradient echoes per refocusing pulse on either side of the spin echo, an accelerated acquisition trajectory may be realized which exhibits pure T2 weighting in the k-space centre (spin echo signal) and T2⁎ weighting in the k-space periphery (gradient echo signal).
Myelin water imaging, a magnetic resonance imaging technique capable of resolving the fraction of water molecules which are located between the layers of myelin, is a valuable tool for investigating both normal and pathological brain structure in vivo. There is a strong need for pulse sequences which improve the quality and applicability of myelin water imaging in a clinical setting. In this study, we validated the use of a fast multi echo T₂ relaxation sequence for myelin water imaging. Using a multiple combined gradient and spin echo (GRASE) technique, we attain whole cerebrum myelin water images in under 15 minutes. Region of interest analysis indicates that this fast GRASE imaging sequence produces results which are in good agreement with pure spin echo measurements (R² = 0.95, p < 0.0001). This drastic improvement in speed and brain coverage compared to current spin echo standards will allow increased inclusion of myelin water imaging in neurological research protocols and opens up the possibility of applications in a clinical setting.
Comparison of two-dimensional gradient echo, turbo spin echo and two-dimensional turbo gradient spin echo sequences in MRI of the cervical spinal cord anatomy
2001, European Journal of Radiology
The aim of this study was to assess the detectability and distinguishability of the cervical spinal cord, the anterior and posterior spinal roots and of the internal anatomy of the cord (distinction of grey and white matter). For this purpose 20 healthy volunteers were examined using a 1.5 T MR unit with 20 mT/m gradient strength and a dedicated circular polarized neck array coil. Three T2* weighted (w). 2D gradient echo sequences, two T2 w. 2D turbo spin echo (TSE) sequences and one T2 w. 2D turbo gradient spin echo (TGSE) sequence were compared. The multiecho 2D fast low angle shot (FLASH) sequence with magnetization transfer saturation pulse (me FLASH+MTS) yielded the best results for liquor/compact bone, liquor/spinal cord and grey/white matter contrast, as found with regions of interest (ROI) analysis. The single echo 2D FLASH sequence was significantly poorer than the two me FLASH+/−MTS sequences. Two-dimensional TGSE as well as 2D TSE with a 256 matrix and with a 512 matrix yielded the poorest results. In the visual analysis the contrast between liquor and compact bone, liquor and cord as well as liquor and roots was best with me FLASH+MTS, whereas grey/white matter distinction was best using me FLASH−MTS. In conclusion, we would therefore recommend the inclusion of an axial T2* w. multiecho 2D spoiled gradient echo sequence with magnetization transfer saturation pulse and gradient motion rephasing in a MR imaging protocol of the cervical spine.
Lesion load quantification on fast-flair, rapid acquisition relaxation- enhanced, and gradient spin echo brain MRI scans from multiple sclerosis patients
1999, Magnetic Resonance Imaging
Previous studies have addressed the issue of the usefullness of fast fluid-attenuated (fast-FLAIR), rapid acquisition relaxation-enhanced (RARE), and gradient spin echo (GRASE) sequences in small groups of patients with multiple sclerosis (MS). The aim of this study was to assess and compare the lesion volumes and the intra-rater reproducibility of such measurements using fast-FLAIR, dual echo RARE, and dual echo GRASE brain scans from a large sample of MS patients. Using a 1.5 Tesla scanner, fast-FLAIR, dual echo RARE, and dual echo GRASE scans (24 axial, 5-mm thick contiguous interleaved slices) of the brain were obtained from 50 MS patients. Total lesion loads (TLL) were assessed twice using a semi-automated local thresholding segmentation technique by the same rater from the scans obtained with the three techniques. Mean TLL were 20.3 mL for fast-FLAIR, 16.6 mL for RARE, and 17.6 mL for GRASE sequences. Mean TLL detected by the three techniques were significantly heterogeneous (p < 0.001); at post-hoc analysis, the mean lesion volume detected on fast-FLAIR images was significantly higher than that on both RARE and GRASE images (p < 0.001) and the mean TLL on GRASE scans was significantly higher than that on RARE scans (p = 0.001). The mean values of intra-observer coefficient of variation for TLL measurements were similar for the three techniques (2.69% for fast-FLAIR, 2.33% for RARE, and 2.65% for GRASE). Our results confirm that fast-FLAIR sequences detect higher lesion volumes than those detected by other magnetic resonance imaging (MRI) sequences with shorter acquisition times. However, the reproducibility of TLL measurements is comparable among fast-FLAIR, RARE, and GRASE. This suggests that when assessing MS disease burden with MRI, the choice of the pulse sequence to be used should be dictated by the clinical setting.
Fast magnetic resonance imaging techniques
1999, European Journal of Radiology
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.
Fast spin-echo (FSE) and gradient- and spin-echo (GRASE) in fast MRI of the pelvis
1997, Magnetic Resonance Imaging
In this prospective study two different T2-weighted fast spin-echo (FSE) sequences and a gradient- and spin-echo (GRASE) sequence were compared in 20 consecutive patients undergoing clinical pelvic MR examinations. A GRASE and two FSE sequences were applied, whereby the FSE sequences differed from each other by altered echo spacings (15.0 and 22.5 ms) and T2 contrast. Quantitative image analysis included ROI evaluation of different $S N$ and $C N$ values. Visual image analysis was performed by two independent readers using a standardized score sheet for anatomic and pathologic findings. Overall image quality was significantly better in both FSE sequences. GRASE and FSE_22.5 were superior in delineation of most of anatomic and pathologic structures due to intermediate to hypointense contrast behavior of pelvic fat compared to FSE_15.0 in which fat was bright. Therefore, FSE_15.0 was optimal for low intensity lesions. Short acquisition times of FSE and GRASE sequences allow application of two different techniques—fat hypointense respectively bright—for excellent lesion visualisation. This study demonstrates the usefulness of contrast manipulation in fast T2-weighted MRI techniques without special techniques, such as fat saturation.
Fast flair imaging of the brain using the fast spin-echo and gradient spin-echo technique
1997, Magnetic Resonance Imaging
The purpose of this study was to compare the gradient spin-echo (GRASE) to the fast spin-echo (FSE) implementation of fast fluid-attenuated inversion recovery (FLAIR) sequences for brain imaging. Thirty patients with high signal intensity lesions on T₂-weighted images were examined on a 1.5 T MR system. Scan time-minimized thin-section FLAIR-FSE and FLAIR-GRASE sequences were obtained and compared side by side. Image assessment criteria were lesion conspicuity, contrast between different types of normal tissue, image quality, and artifacts. In addition, contrast ratios and contrast-to-noise ratios were determined. Compared to FSE, the GRASE technique allowed a 17% reduction in scan time but conspicuity of small lesions in particular was significantly lower on FLAIR-GRASE images because of higher image noise and increased artifacts. Gray-white differentiation was slightly worse on FLAIR-GRASE. Physiological ferritin deposition appeared slightly darker on FLAIR-GRASE images and susceptibility artifacts were stronger. Fatty tissue was less bright with FLAIR-GRASE. With current standard hardware equipment, the GRASE technique is not an adequate alternative to FSE for the implementation of fast FLAIR sequences in routine clinical MR brain imaging.

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View full text

Turbo gradient-spin-echo (GRASE): first clinical experiences with a fast T2-weighted sequence in MRI of the brain

Abstract

Multi-planar image formation using NMR spin-echoes

J Phys

RARE imaging: a fast imaging method for clinical MR

Magn Reson Med

GRASE (gradient- and spin-echo) imaging: a novel fast MRI technique

Magn Reson Med

GRASE (gradient- and spin-echo) MR imaging

True proton density and T2-weighted turbo spin-echo sequences for routine MR imaging of the brain

Neuroradiology