MRI: Use of the inversion recovery pulse sequence

Gm, Bydder; Hajnal, Joseph V.; Young, I. R.

doi:10.1016/s0009-9260(98)80096-2

Cited by 159 publications

(175 citation statements)

References 81 publications

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“…Optimized 3D MPRAGE sequences yield higher white matter to gray matter signal-to-noise ratios than do optimized 3D FLASH sequences. 91 IR sequences 92 provide high contrast images of the brain and more consistent hippocampal measurements. 85 SE sequences are commonly used in neuroradiology, and provide excellent anatomic detail at the expense of longer scan times.…”

Section: Discussionmentioning

confidence: 99%

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

2004

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The advance of neuroimaging techniques has resulted in a burgeoning of studies reporting abnormalities in brain structure and function in a number of neuropsychiatric disorders. Measurement of hippocampal volume has developed as a useful tool in the study of neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. From this database, the methodology of all original manual tracing protocols were studied. These protocols differed in a number of important factors for accurate hippocampal volume determination including magnetic field strength, the number of slices assessed and the thickness of slices, hippocampal orientation correction, volumetric correction, software used, inter-rater reliability, and anatomical boundaries of the hippocampus. The findings are discussed in relation to optimizing determination of hippocampal volume.

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Section: Discussionmentioning

confidence: 99%

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

2004

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“…Several comments need to be made regarding Equations [1][2][3]. First, W, F, , and 0 in Equation [1] and ⌬B 0 in Equation [3] are all spatially dependent and thus may vary from pixel to pixel.…”

Section: Signal Modelmentioning

confidence: 99%

“…Thus, ␣ can be considered spatially invariant and depends only on ⌬t and the chemical shift of fat (see Eq. [2]), which is a constant. When multiple receiver coils are used, W and F may be weighted by each coil's spatial sensitivity and 0 is usually also coil dependent.…”

Section: Signal Modelmentioning

confidence: 99%

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Dixon techniques for water and fat imaging

2008

Magnetic Resonance Imaging

513

442

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In 1984, Dixon published a first paper on a simple spectroscopic imaging technique for water and fat separation. The technique acquires two separate images with a modified spin echo pulse sequence. One is a conventional spin echo image with water and fat signals in-phase and the other is acquired with the readout gradient slightly shifted so that the water and fat signals are 180°out-of-phase. Dixon showed that from these two images, a water-only image and a fat-only image can be generated. The wateronly image by the Dixon's technique can serve the purpose of fat suppression, an important and widely used imaging option for clinical MRI. Additionally, the availability of both the water-only and fat-only images allows direct imagebased water and fat quantitation. These applications, as well as the potential that the technique can be made highly insensitive to magnetic field inhomogeneity, have generated substantial research interests and efforts from many investigators. As a result, significant improvement to the original technique has been made in the last 2 decades. The following article reviews the underlying physical principles and describes some major technical aspects in the development of these Dixon techniques. MR IMAGES ACQUIRED IN VIVO usually contain signals from both water and fat. In many pulse sequences, fat appears hyperintense. However, the contribution from water is often of the primary interest for many practical applications. Without suppression, the bright fat signal may result in aggravated motion-related artifacts and, more importantly, reduce the underlying lesion conspicuity. Because of its chemical shift, fat is also responsible for the well-known spatial misregistration artifacts, which can appear both along the frequency encode direction and along the slice select direction. For a few other applications such as diagnosis of bone marrow diseases or hepatic steatosis, detection rather than suppression of the fat signal can also be valuable.Several approaches have been proposed and developed for achieving fat suppression. Perhaps the most popular is the chemical shift selective saturation (1) or its variants. In this approach, a frequency selective radiofrequency (RF) pulse and a spoiler gradient pulse are used in conjunction to first excite and then saturate the fat magnetization before water is excited for imaging. Alternatively, a frequency selective RF pulse can be used to directly excite only the water magnetization and leave the fat magnetization alone along the longitudinal axis. These techniques, particularly the selective saturation technique, are easy to implement and have been widely used with great success. However, both selective saturation pulses and selective excitation pulses increase the scan time. Another limitation for fat suppression by the selective saturation pulses is that it typically requires an accurate 90°flip angle, and as a result, its performance can be dependent on B1 homogeneity. Perhaps most importantly, fat suppression using the frequency selective approach...

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“…FLAIR is an imaging modality that suppresses the signal from CSF (5)(6)(7)(8). All images were taken with 5-mm thick, contiguous coronal slices, with 24-cm FOV and a frequency ϫ phase matrix of 256 ϫ 192 (CSE) or 256 ϫ 256 (FSE, FF).…”

Section: Studies In Phantoms and Normal Hippocampimentioning

confidence: 99%

A fast FLAIR dual‐echo technique for hippocampal T2 relaxometry: First experiences in patients with temporal lobe epilepsy

Woermann

Steiner

Barker

et al. 2001

Magnetic Resonance Imaging

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To evaluate the use of cerebrospinal fluid (CSF) signal nulling in MR T2 measurements of the hippocampus in normal control subjects and patients with temporal lobe epilepsy (TLE), dual-echo acquisitions covering the whole brain were used. T2 relaxation times were estimated in 12 standard Eurospin II MR test objects and in the hippocampi of 10 control subjects, using T2 maps constructed from conventional spin-echo (CSE), fast spin-echo (FSE), and fast FLAIR (FF) dual-echo sequences on a 1.5-T MR scanner. Hippocampal T2 values (HCT2) were measured on contiguous coronal 5-mm slices throughout the antero-posterior extent of each hippocampus in the 10 controls and 12 TLE patients, using both CSE and FF. Scan-rescan reproducibility in Eurospin II standard MR test objects was high for all sequences. There was a good correlation between T2 values from CSE, FF, and FSE sequences in test objects and in control hippocampi. In controls, the coefficient of variation of mean HCT2 values differed between slice positions, but was lowest for FF, followed by CSE data. The intrarater coefficient of reliability between repeated measurements in control subjects was lowest for FF HCT2, at 2.3%. The interrater coefficient of reliability for CSE HCT2 measurements in controls (4.8%) was slightly lower than the interrater coefficient for FF HCT2 (5.4%). HCT2 measurement with both CSE and FF identified abnormal values in the same 10 hippocampi of 12 patients. Hippocampal dualecho T2 relaxometry using CSF nulling is reliable in control subjects, and identifies the abnormal hippocampi in patients with TLE. The increases in hippocampal T2 signal demonstrated using FF HCT2 measurements are unlikely to be partial volume effects from CSF. J. Magn. Reson. Imaging 2001;13:547-552.

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MRI: Use of the inversion recovery pulse sequence

Cited by 159 publications

References 81 publications

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

Dixon techniques for water and fat imaging

A fast FLAIR dual‐echo technique for hippocampal T2 relaxometry: First experiences in patients with temporal lobe epilepsy

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