Читать книгу Essentials of MRI Safety - Donald W. McRobbie - Страница 15

Image formation is achieved by varying the value of magnetic field in the z‐ or B₀ direction. The field variation is applied by passing electrical pulses through one or more sets of gradient coils, forming the gradient pulses. The gradients, known as G_x, G_y, G_z, are designed to produce linear variations in the z‐component of the magnetic field with respect to the x, y, and z axes (Figure 1.5). In terms of their function in image formation they are known as slice‐select (G_SS), phase‐encode (G_PE), or frequency‐encode (G_FE).

Figure 1.5 B_z from magnetic field gradients G_x and G_y.