| 摘要 |
<p>In an open magnetic resonance system, pole pieces (16,18) on opposite sides of an imaging region (10) are supported by a ferrous flux return path (20). During normal operation, environmental disturbances that cause low frequency vertical vibrations in the floor cause corresponding fluctuations in the main field of the magnet. A spacing between the pole pieces (16, 18) expands and contracts with the vibration causing a strength of the main field to fluctuate. A force transducer (60) under the magnet assembly measures the magnitude of the vibrations. A vibration analyzer (62) analyzes the vibrations waveform and calculates compensation for the changes in the interpole spacing. The vibration analyzer (62) controls one or more of a shim coil (70) which produces a field equal and opposite to the main field fluctuations, a reconstruction processor (52) to compensate for magnetic field resonance frequency fluctuations attributable to the main field fluctuations, and gradient magnetic fields applied by gradient field coils (22, 24). <IMAGE></p> |
