A novel saturation transfer contrast method for 3D time‐of‐flight magnetic resonance angiography: A slice‐selective off‐resonance sinc pulse (SORS) technique

Abstract

Saturation transfer contrast (STC) techniques have been employed to decrease the signal intensity of observed water by saturating a broad proton component. The STC pulse, generally spatially nonselective, reduces the signal of brain background tissues as well as inflowing blood in 3D time-of-flight (TOF) angiography. We present a novel technique, a slice-selective off-resonance sinc pulse (SORS), which is employed to enhance inflowing blood and to suppress the signal of stationary background tissues. The STC effects of the SORS and other spatially nonselective methods influencing inflowing blood is discussed in detail. Angiograms using the SORS method are also presented to demonstrate improved vessel conspicuity. In addition, the SORS method is applicable to imagers with a whole-body RF transmitter system.

Visualization of Neuromelanin in the Substantia Nigra and Locus Ceruleus at 1.5T Using a 3D-gradient Echo Sequence with Magnetization Transfer Contrast

“…Not only the signal contrast ratio (blood/background), but also the reduction of the signal intensity of the brain background was largest when using the SORS method. 6 We used an MTC pulse of 5009because in our clinical MRA protocol, although an MTC pulse of 3609was applied and SNc was often identiˆed, we felt that it was not enough to visualize the LC by this protocol. Edelman and colleagues reported that larger MTC pulse permitted substantial improvement in small vessel conspicuity in time-of‰ight MR angiography, 11 so we selected the larger 5009pulse.…”

“…We consider 2 possible reasons for ourˆndings. First, we selected a SORS-STC pulse 6 that generated MTC, which enhances in‰owing blood and suppresses the signals of stationary background tissues and veins by applying a slice-selective pulse above the in‰ow-ing blood and maintaining the MTC on the stationary background. In the present study, there was an apparent diŠerence between images taken with and without SORS-STC.…”

“…), 2-mm slice thickness, and 56 slices. We applied a slice-selective oŠ-resonance sinc pulse-saturation transfer contrast (SORS-STC) pulse, a sinc pulse with a 5009 FA, to generate MTC 6 and performed this scan twice, once with and once without use of SORS-STC. In either case, acquisition time was 8 min 20 s. We set the slab prudentially in the oblique axial plane perpendicular to the ‰oor of the fourth ventricle, extending coverage from the medulla oblongata to the midbrain.…”

Time‐resolved three‐dimensional magnetic resonance digital subtraction angiography without contrast material in the brain: Initial investigation

“…Imaging parameters of TOF-MRA were as follows: TR/TE ϭ 30/6.8 msec, flip angle ϭ 20°, field of view ϭ 180 ϫ 180mm, matrix size ϭ 512 ϫ 512, partition thickness/gap ϭ 1/0 mm, pixel bandwidth ϭ 122 Hz. Magnetization transfer technique was used for suppress background signal on the TOF-MRA (18).…”

Improved Visualization of Intracranial Vessels by Gradient Moment Nulling in Hybrid of Opposite-contrast Magnetic Resonance Angiography (HOP MRA)

“…We did not use MTC pulses 12 in the sequence because MTC reduced the CNR of the blood vessels in the second echo. The reduction of TR shortened acquisition time.…”