^(31)P NMR表面线圈探头射频场B1的空间分布特性研究

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

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 self made 31 P NMR surface coil probe was studied. The results showed that 90° pulse width at the center of the coil was 10μs, and that radiofrequency field B 1 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 B 1 decreased sharply with the increase of the distance from the coil. Simply speaking, the spatial distribution of effective B 1 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.