31P NMR表面线圈探头射频场B1的空间分布特性研究

对本实验室自制的³¹P表面线圈探头的射频场B₁强度的空间分布和脉冲宽度进行了初步研究.结果表明该表面线圈中心的90°脉冲约为10μs.得到的信号主要是线圈圆周内射频场B₁作用的结果,在垂直线圈平面的方向上随距离增加,信号迅速减弱.因此该表面线圈射频场B₁有效的作用范围在一个近半圆球体内,底面积半径约为线圈外半径,有效作用深度约为线圈半径.

SPATIAL DISTRIBUTION OF RADIOFREQUENCY FIELD B 1 PRODUCED BY 31 P NMR SURFACE COIL PROBE

Spatial distribution of radiofrequency field B₁ produced by self-made ³¹P NMR surfacecoil probe was studied.The results show ed that 90° pulse width at the center of the coil was 10μs, and that radiofrequency field B₁ contributing to the signals was limited within the circumference of the coil, and that along the axis perpendicular to the surface coil the intensity of B₁ decreased sharply with the increase of the distance from the coil.Simply speaking, the spatial distribution of effective B₁ of this surface coil can be considered as a sub-hemisphere, which has a bottom radius nearly equal to the coil radius and a maximum depth of action of about the coil radius.