Magnetic resonance imaging apparatus

Abstract

A magnetic resonance imaging apparatus uses an NMR phenomenon, and includes a number of imaging elements. A made magnet generates a uniform static magnetic field in an imaging space, and first, second and third gradient field coils are provided. These field coils are mounted on the main magnet, and generate three gradient field pulses with magnetic strength varying in three orthogonal directions in the imaging space. An RF coil is provided for transmitting an RF signal to an examinee, and for detecting an NMR signal generated therein. A gradient field control device is connected the gradient field coils for causing the gradient field coils to generate a plurality of gradient field pulses. A first pulse sequence is generated and repeated, while a phase-encoding gradient field pulse is varied. An RF control device is connected to the RF coil for causing the RF coil, in each pulse sequence, to transmit the RF signal and to apply to the RF signal a magnetization transfer contrast pulse having a frequency slightly offset from a resonance frequency of free water protons. The RF control device controls irradiation strength of the MTC pulse based upon variations in the strength of the phase-encoding gradient field pulse, such that the irradiation strength is decreased when a phase-encoding amount is small, and decreased when the phase-encoding amount is large. A data processing device collect data from the NMR signal and reconstruct a sectional image therefrom.