Method for correcting position deviation due to static magnetic field change in NMR imaging device

In an NMR imaging device comprising mean for applying a static magnetic field to an object to be examined, means for applying to the object a gradient magnetic field in a slice direction, a gradient magnetic field in a phase encode direction and a magnetic field in a frequency encode direction, means for applying radio frequency pulses to the object to cause nuclear magnetic resonance (NMR) in atomic nuclei of atoms constituting tissues of the object, means for detecting the NMR signals thus generated, and means for Fourier-transforming the NMR signals to reconstruct an NMR image, a method for correcting deviation of a static magnetic field intensity comprising the steps of:

• a first step of placing the object in the static magnetic field;
• a second step of applying 90 degree and 180 degree radio frequency pulses at a preset center frequency of .omega..sub.0 at predetermined time intervals;
• a third step of detecting an NMR signal thus produced;
• a fourth step of Fourier-transforming said NMR signal to provide a peak frequency .omega..sub.1 of the resultant frequency spectrum;
• and
• a sixth step of obtaining the deviation difference between .omega..sub.0 and .omega..sub.1 and adding it to the frequency .omega..sub.0.

An NMR imaging device comprising:

• means for applying a static magnetic field to an object to be examined;
• means for applying gradient magnetic fields to the object;
• means for applying radio frequency pulses to the object to cause nuclear magnetic resonance (NMR) in atomic nuclei of atoms constituting tissues of the object;
• means for detecting the NMR signals thus generated;
• means for Fourier-transforming the NMR signals to reconstruct an NMR image;
• said means for applying gradient magnetic fields to the object applying only a gradient magnetic field in a slice direction but not applying a gradient magnetic field in a frequency encode direction and a gradient magnetic field in a phase encode direction;
• said means for applying radio frequency pulses to the object irradiating 90 degree and 180 degree pulses to the object at predetermined time intervals;
• said means for detecting the NMR signals comprising means for detecting the NMR signals and detecting the static magnetic field intensity from the spectrum of the NMR signals, which is provided by said Fourier transforming means, and means for suitably correcting a parameter for imaging, thereby providing the NMR image free from any position deviation.