| 摘要 |
A magnetic resonance imaging apparatus and method having a magnet assembly, which provides substantially flat surfaces of constant magnetic field outside the assembly and a set of magnetic field gradient coils. One-, two-, and three-dimensional images are rendered. The static magnetic field is virtually uniform within horizontal degrees of freedom and decreases monotonically in a direction away from the surface of magnetic assembly. An RF probe, located adjacent to the surface, produces a field substantially perpendicular to the static magnetic field. Magnetic field gradient coils are set to horizontally scan a given level within the sensitive volume. Received magnetic resonance signals are detected by the coil for a depth corresponding to the excitation frequency. As the tuning frequency and excitation frequency are switched to lower values, signals are generated for layers progressively farther from the surface. The RF probe is automatically tuned. Depth profiles are rendered by concatenating the signals collected at various frequencies. Horizontal resolution is attained by the use of controlled magnetic field gradients. |
