Origin of a Signal Intensity Loss Artifact in Fat-Saturation MR Imaging

Axel, Leon; Kolman, Louis; Charafeddine, Riad; Hwang, Scott N.; Stolpen, Alan H.

doi:10.1148/radiology.217.3.r00dc43911

Cited by 17 publications

(9 citation statements)

References 5 publications

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“…Conventional fatsaturation RF pulses cause selective saturation of the magnetization of the fat so that the fat signal is suppressed in the imaging [14]. An alternative method for stationary background and fatty tissue suppression is the selective water excitation in which only water protons will be excited [10].…”

Section: Discussionmentioning

confidence: 99%

3D time-of-flight MR angiography of the intracranial vessels: optimization of the technique with water excitation, parallel acquisition, eight-channel phased-array head coil and low-dose contrast administration

Özsarlak

Goethem

Parizel³

2004

Eur Radiol

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The aim of this study is three folds: to compare the eight-channel phased-array and standard circularly polarized (CP) head coils in visualisation of the intracranial vessels, to compare the three-dimensional (3D) time-of-flight (TOF) MR angiography (MRA) techniques, and to define the effects of parallel imaging in 3D TOF MRA. Fifteen healthy volunteers underwent 3D TOF MRA of the intracranial vessels using eight-channel phased-array and CP standard head coils. The following MRA techniques were obtained on each volunteer: (1) conventional 3D TOF MRA with magnetization transfer; (2) 3D TOF MRA with water excitation for background suppression; and (3) low-dose (0.5 ml) gadolinium-enhanced 3D TOF MRA with water excitation. Results are demonstrating that water excitation is a valuable background suppression technique, especially when applied with an eight-channel phased-array head coil. For central and proximal portions of the intracranial arteries, unenhanced TOF MRA with water excitation was the best technique. Low-dose contrast enhanced TOF MRA using an eight-channel phased-array head coil is superior in the evaluation of distal branches over the standard CP head coil. Parallel imaging with an acceleration factor of two allows an important time gain without a significant decrease in vessel evaluation. Water excitation allows better background suppression, especially around the orbits and at the periphery, when compared to conventional acquisitions.

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Section: Discussionmentioning

confidence: 99%

3D time-of-flight MR angiography of the intracranial vessels: optimization of the technique with water excitation, parallel acquisition, eight-channel phased-array head coil and low-dose contrast administration

Özsarlak

Goethem

Parizel³

2004

Eur Radiol

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“…A major limitation of NC‐MRA is its sensitivity to off‐resonance (e.g., signal loss of great vessel origins) (28). Local shimming of the ascending aorta and arch region has been reported to be useful (6).…”

Section: Discussionmentioning

confidence: 99%

Single breathhold noncontrast thoracic MRA using highly accelerated parallel imaging with a 32‐element coil array

Xu¹,

McGorty²,

Lim³

et al. 2011

Magnetic Resonance Imaging

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OBJECTIVE To evaluate the feasibility of performing single breath-hold 3D thoracic non-contrast magnetic resonance angiography (NC-MRA) using highly-accelerated parallel imaging. MATERIALS AND METHODS We developed a single breath-hold NC MRA pulse sequence using balanced steady state free precession (SSFP) readout and highly-accelerated parallel imaging. In 17 subjects, highly-accelerated non-contrast MRA was compared against electrocardiogram (ECG)-triggered contrast-enhanced MRA. Anonymized images were randomized for blinded review by two independent readers for image quality, artifact severity in 8 defined vessel segments and aortic dimensions in 6 standard sites. NC-MRA and CE-MRA were compared in terms of these measures using paired sample t and Wilcoxon tests. RESULTS The overall image quality (3.21±0.68 for NC-MRA vs. 3.12±0.71 for CE-MRA) and artifact (2.87±1.01 for NC-MRA vs. 2.92±0.87 for CE-MRA) scores were not significantly different, but there were significant differences for the great vessel and coronary artery origins. NC-MRA demonstrated significantly lower aortic diameter measurements compared to CE-MRA; however, this difference was not considered clinically relevant (>3 mm difference) for less than 12% of segments, most commonly at the sinotubular junction. Mean total scan time was significantly lower for NC-MRA compared to CE-MRA (18.2 ± 6.0s vs. 28.1 ± 5.4s, respectively; p < 0.05). CONCLUSION Single breath-hold NC-MRA is feasible and can be a useful alternative for evaluation and follow-up of thoracic aortic diseases.

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“…It should be noted that off‐resonance effects can also affect the SPIR implementation of fat suppression, and reduce the signal intensity, if the frequency of the off‐resonant water signal falls within the bandwidth of the fat‐selective RF pulse (20).…”

Section: Discussionmentioning

confidence: 99%

Efficient fat suppression by slice‐selection gradient reversal in twice‐refocused diffusion encoding

Nagy

Weiskopf

2008

Magnetic Resonance in Med

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Most diffusion imaging sequences rely on single-shot echoplanar imaging (EPI) for spatial encoding since it is the fastest acquisition available. However, it is sensitive to chemical-shift artifacts due to the low bandwidth in the phase-encoding direction, making fat suppression necessary. Often, spectral-selective RF pulses followed by gradient spoiling are used to selectively saturate the fat signal. This lengthens the acquisition time and increases the specific absorption rate (SAR). However, in pulse sequences that contain two slice-selective 180°refo-cusing pulses, the slice-selection gradient reversal (SSGR) method of fat suppression can be implemented; i.e., using sliceselection gradients of opposing polarity for the two refocusing pulses. We combined this method with the twice-refocused spin-echo sequence for diffusion encoding and tested its performance in both phantoms and in vivo. Unwanted fat signal was entirely suppressed with this method without affecting the water signal intensity or the slice profile. Magn Reson Med 60: 1256 -1260, 2008.

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Origin of a Signal Intensity Loss Artifact in Fat-Saturation MR Imaging

Cited by 17 publications

References 5 publications

3D time-of-flight MR angiography of the intracranial vessels: optimization of the technique with water excitation, parallel acquisition, eight-channel phased-array head coil and low-dose contrast administration

3D time-of-flight MR angiography of the intracranial vessels: optimization of the technique with water excitation, parallel acquisition, eight-channel phased-array head coil and low-dose contrast administration

Single breathhold noncontrast thoracic MRA using highly accelerated parallel imaging with a 32‐element coil array

Efficient fat suppression by slice‐selection gradient reversal in twice‐refocused diffusion encoding

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