Magnetic resonance imaging system

Claim 1

A magnetic resonance imaging system comprising: static magnetic field application means (2, 3) for applying a uniform static magnetic field to an object to be examined; excitation means (5, 6, 8) for applying a radio-frequency magnetic field for exciting a magnetic resonance phenomenon to said object to be examined; gra­dient field application means (18-21) for applying, to said object to be examined, a first gradient field which has a magnetic gradient along a first direction and is used for determining a slice to be imaged in which the magnetic resonance phenomenon is excited, a second gra­dient field which has a magnetic gradient along a second direction perpendicular to the first direction and is used for phase-encoding echo data based on the magnetic resonance phenomenon, and a third gradient field which has a magnetic gradient along a third direction perpen­dicular to the first and second directions, and is used for reading out the echo data based on the magnetic re­sonance phenomenon; control means (4, 17) for controlling said excitation means (5, 6, 8) and said gradient field application means (18-21) so as to apply the pulsed radio-frequency magnetic field and the pulsed first to third gradient fields in accordance with a predetermined sequence; signal acquisition means (8-15) for acquiring an echo signal based on the magnetic resonance phenome­non generated in the object to be examined; and image reconstruction means (15) for obtaining an image of magnetic resonance data from the echo signal, said control means (4, 17) comprising first echo control means for alternately and repe­titively executing a first operation for applying the third gradient field while repetitively inverting it so as to produce the echo signal, and a second operation for applying, as the radio-frequency magnetic field, a 180° pulse which can compensate for an echo signal phase error due to a nonuniformity and offset of the static magnetic field so as to generate the echo signal, and second echo control means for inverting the second gradient field each time the 180° pulse is applied.