RAPID FOURIER-IMAGING USING STEADY-STATE FREE PRECESSION
RAPID FOURIER-IMAGING USING STEADY-STATE FREE PRECESSION
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DOI：
10.1002/mrm.1910040103
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发表时间：
1987-01-01
影响因子：
3.3
通讯作者：
PATZ, S
中科院分区：
文献类型：
--
作者：
HAWKES, RC;PATZ, S
SSFP成像实验中读取梯度的逆转允许在.tau间隔中收集完整的自旋回波。在连续的RF脉冲之间。正交梯度脉冲用于除去并随后重述每个.tau的横向磁化。启用2D或3D傅立叶技术。 3D技术中每片的最小数据收集时间为3.1 s（128。时间256）。对于2D数据收集，使用振荡双极锯齿梯度来选择切片。每个相位码值必须在振荡切片选择梯度的等效部分上取平均值，并且该条件为2D数据收集提供25 s。在切片曲线中央叶外面的信号的不到5％的情况下，可以实现出色的切片选择。 0.14 t的图像显示可以通过更改RF脉冲角来操纵组织对比，其示例分别是在30和90.度的RF脉冲角度分别存在或不存在灰色/白质对比度。脉冲角.THETA。测量具有不同值的五个样品的依赖性，并在.theta的理论和实验之间以良好的一致性进行了测量和数值计算。 .ltoreq。 90.Degree。
Reversal of the read gradient in a SSFP imaging experiment allows a full spin echo to be collected in the interval .tau. between successive rf pulses. Orthogonal gradient pulses are used to dephase and subsequently rephase the transverse magnetization each .tau. enabling 2D or 3D Fourier techniques. The minimum data collection time per slice in the 3D technique is 3.1 s (128 .times. 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.degree., respectively. The pulse angle .theta. dependence of five samples with different values of T2/T1 was measured and numerically calculated with good agreement between theory and experiment for .theta. .ltoreq. 90.degree.