Rapid Fourier imaging using steady-state free precession

✍ Scribed by R. C. Hawkes; S. Patz

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 875 KB
• Volume: 4
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.1910040103

✦ Synopsis

Reversal of the read gradient in a SSFP imaging experiment allows a full spin echo to be collected in the interval T between successive rfpulses. Orthogonal gradient pulses are used to dephase and subsequently rephase the transverse magnetization each T enabling 2D or 3D Fourier techniques. The minimum data collection time per slice in the 3D technique is 3.1 s (128 X 256). For a 2D data collection, an oscillating bipolar sawtooth gradient is used to select the slice. Each phase-encode value must be averaged over an equivalent portion of the oscillating slice-selection gradient and this condition gives a minimum of 25 s for 2D data collection. Excellent slice selection is achieved with less than 5% of the signal lying outside the slice profile central lobe. Images at 0.14 T show tissue contrast may be manipulated by changing the rf pulse angle, an example of which is the presence or absence of gray/white matter contrast at rf pulse angles of 30 and 90", respectively. The pulse angle 0 dependence of five samples with different values of T2/T, was measured and numerically calculated with good agreement between theory and experiment for 8 C 90".