| 摘要 |
PURPOSE:To correct the irregularity of a static magnetic field, to perform magnetic resonance image pickup operation under invariably uniform condition, and to improve spatial resolution by detecting the decay time T2 of a magnetic resonance echo by using only a gradient magnetic field perpendicular to an object surface of image pickup operation and making an adjustment so that the length of the T2 is longest. CONSTITUTION:Air-core magnetic field coil systems 4A and 4B are excited by a static magnetic field power source 13 to apply a static field H0 to an object body P and also to superpose a Z-directional gradient magnetic field GZ perpendicular to a tomographic surface (X-Y plane) upon the H0 by a coil 5 and apply select pulses SEP to the object body P through a transmitter and a coil system 7. Then, a gradient magnetic field GXY is superposed upon the H0 by a coil system 6. Nonselection pulses are applied through the coil system 7 after the application, the GZ is superposed upon the H0, and then the GXY is superposed upon the H0; and the coil system 7 receives an MR echo signal, which is added and averaged 11 through a phase detecting device 8 and an AD converter 10 and Fourier-transformed 12 to reconstruct 15 an image, which is displayed 16. A gradient magnetic field controller 14 calculates such an offset voltage that the decay time T2 is longest and supplies the voltage to a coil system 5.
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