PURPOSE: To automatically correct the uniformity of a magnetic field, by calculating the intensity of the magnetic field of each specimen from the center frequency of the NMR signals from a plurality of detection coils and controlling a shim coil current so as to keep the intensity and uniformity of a main magnetic field optimum.
CONSTITUTION: NMR signals from a plurality of detection coils 101W10n having specimens each generating a nuclear spin signal received therein and arranged to the outer periphery of an imaging region are alternatively selected by a muliplexer 12 and converted by an AD converter while the digitalized signals are subjected to high speed Fourier transformation by a center frequency detection circuit 14 to calculate center frequency. The center frequency is read by CPU15 to calculate the intensity and uniformity of a main magnetic field and, on the basis of this, the drive currents and center frequencies fo of shim coils S1WSn are controlled through an externally controlled interface 16. Therefore, the uniformity of the main magnetic field hourly changed by temp. can be automatically corrected and stable magnetic field distribution can be obtained.
INOUE YUJI
IWAOKA HIDETO
YOKOGAWA MEDICAL SYST
| JPS5523499A | 1980-02-19 | |||
| JPS59230149A | 1984-12-24 | |||
| JPS60102544A | 1985-06-06 |
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