流动质子NMR信号强度与梯度回波中翻转角间的关系

THE RELATIONSHIP BETWEEN SIGNAL INTENSITY OF FLOWING PROTONS AND FLIP ANGLE IN FLASH

梯度回波脉冲序列对血流分布和血管结构极其敏感。当脉冲序列中的参数发生变化时 ,血流的NMR(NuclearMagneticResonance)信号也发生改变。本文阐述了流动质子NMR信号强度与FLASH(fastlowangleshot)序列中的射频翻转角间的关系。并通过模拟实验验证了此关系的有效性。这种关系对在临床应用NMR血管成像时选取梯度回波脉冲序列有一定的指导意义。

Gradient echoes techniques have become increasingly popular in clinical practice. The relationship between signal intensity of flowing protons and flip angle in FLASH sequence is described in this paper. Experimental measurements have been performed on a flow phantom in a whole-body NMR imaging system operating at 1.0 T with different radiofrequency pulse flip angles and flow rates. The result indicates that the flowing NMR signal decreases as stimulating flip angle increases in the low velocity ranging up to the maximum intensity at V=L/TR. This relationship is very important in clinic.