Chemical shift selective MR imaging using a whole-body magnet.

Frahm, Jens; Haase, Axel; Hänicke, W.; Matthaei, D.; Bomsdorf, H.; Helzel, T.

doi:10.1148/radiology.156.2.4011907

Cited by 136 publications

(78 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…S͑x,y͒ ϭ ͓W͑x,y͒ ϩ F͑x,y͒ ⅐ e i␣ ͔ ⅐ e i ͑x,y͒ ⅐ e i 0͑x,y͒ [1] where (x,y) represents the spatial coordinates (or indices) of a pixel. W and F are in general real and nonnegative numbers representing the magnitudes of the magnetizations at a given pixel for water and fat, respectively.…”

Section: Signal Modelmentioning

confidence: 99%

“…␣ is the phase angle of fat relative to that of water due to their chemical shift difference, is the error phase due to the magnetic field inhomogeneity, and 0 is another error phase due to other system imperfections such as the spatial dependence of RF penetration and different signal time delay in the receiver chains. Figure 2 illustrates graphically the vector relationship between the various quantities in Equation [1]. In a Dixon acquisition, ⌬t, which represents changes in echo time (TE) or time shifts from a spin echo, is often introduced in a pulse sequence to effect certain desired values of ␣.…”

Section: Signal Modelmentioning

confidence: 99%

“…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. While changes in ⌬B 0 in principle affect ␣ as well, the magnitude of ⌬B 0 is much smaller than B 0 .…”

Section: Signal Modelmentioning

confidence: 99%

“…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.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Dixon techniques for water and fat imaging

2008

Magnetic Resonance Imaging

514

442

View full text Add to dashboard Cite

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...

show abstract

Section: Signal Modelmentioning

confidence: 99%

Section: Signal Modelmentioning

confidence: 99%

Section: Signal Modelmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Dixon techniques for water and fat imaging

2008

Magnetic Resonance Imaging

514

442

View full text Add to dashboard Cite

show abstract

“…An in‐house developed multiphase single‐shot fast spin echo (SSFSE) sequence was used to acquire sequential T 2 ‐weighted sagittal breast images at a single slice location with the following parameters: effective TE 58 msec, TR 4 sec, bandwidth ±83 kHz, matrix size 128 × 128, field of view (FOV) 20 cm, slice thickness 5 mm, and chemical shift selective (CHESS) fat suppression 18. A conventional T 1 ‐weighted image was also acquired at the same sagittal slice location to provide anatomical detail.…”

Section: Methodsmentioning

confidence: 99%

Detecting gas‐induced vasomotor changes via blood oxygenation level‐dependent contrast in healthy breast parenchyma and breast carcinoma

Wallace

Patterson

Abeyakoon

et al. 2016

Magnetic Resonance Imaging

View full text Add to dashboard Cite

PurposeTo evaluate blood oxygenation level‐dependent (BOLD) contrast changes in healthy breast parenchyma and breast carcinoma during administration of vasoactive gas stimuli.Materials and MethodsMagnetic resonance imaging (MRI) was performed at 3T in 19 healthy premenopausal female volunteers using a single‐shot fast spin echo sequence to acquire dynamic T 2‐weighted images. 2% (n = 9) and 5% (n = 10) carbogen gas mixtures were interleaved with either medical air or oxygen in 2‐minute blocks, for four complete cycles. A 12‐minute medical air breathing period was used to determine background physiological modulation. Pixel‐wise correlation analysis was applied to evaluate response to the stimuli in breast parenchyma and these results were compared to the all‐air control. The relative BOLD effect size was compared between two groups of volunteers scanned in different phases of the menstrual cycle. The optimal stimulus design was evaluated in five breast cancer patients.ResultsOf the four stimulus combinations tested, oxygen vs. 5% carbogen produced a response that was significantly stronger (P < 0.05) than air‐only breathing in volunteers. Subjects imaged during the follicular phase of their cycle when estrogen levels typically peak exhibited a significantly smaller BOLD response (P = 0.01). Results in malignant tissue were variable, with three out of five lesions exhibiting a diminished response to the gas stimulus.ConclusionOxygen vs. 5% carbogen is the most robust stimulus for inducing BOLD contrast, consistent with the opposing vasomotor effects of these two gases. Measurements may be confounded by background physiological fluctuations and menstrual cycle changes. J. Magn. Reson. Imaging 2016;44:335–345.

show abstract

Multinuclear Magnetic Resonance Spectroscopic Imaging

Richards¹

2000

Encyclopedia of Analytical Chemistry

View full text Add to dashboard Cite

Magnetic resonance spectroscopic imaging (MRSI) is a technique for producing spatially resolved maps or images of different chemicals that are found in the body or tissue. These chemicals may be naturally inherent or may be introduced by injection, but they must be detectable by the magnetic resonance (MR) process (i.e. they must have nuclei that have a magnetic moment, and are mobile enough to give a free‐induction decay (FID)). The MRSI technique is based on many of the same principles that are used for conventional magnetic resonance imaging (MRI) and also uses much of the same equipment as MRI. This chapter focuses on multinuclear applications of MRSI such as phosphorus‐31, carbon‐13, fluorine‐19, sodium‐23, xenon‐129, helium‐3, and boron‐11. The MRSI method is an important technique for noninvasive measurement of biochemical and physiological changes in health and disease.

show abstract

Chemical shift selective MR imaging using a whole-body magnet.

Cited by 136 publications

References 0 publications

Dixon techniques for water and fat imaging

Dixon techniques for water and fat imaging

Detecting gas‐induced vasomotor changes via blood oxygenation level‐dependent contrast in healthy breast parenchyma and breast carcinoma

Multinuclear Magnetic Resonance Spectroscopic Imaging

Contact Info

Product

Resources

About