A Magnetic Resonance Imaging apparatus, comprising: a 3D structure having a cavity for receiving a body under examination; a pair of permanent magnets for generating a static magnetic field in said cavity and spaced from each other, so that the patient receiving cavity is interposed between said permanent magnets; coils for generating gradient magnetic fields in said cavity; an antenna for transmitting electromagnetic nuclear spin excitation pulses; an antenna for receiving the electromagnetic signals generated by nuclear spin relaxation; a respective pole piece being mounted to the side of each magnet facing towards the patient receiving cavity, each pole piece possessing a peripheral side wall protruding towards the patient receiving cavity; an end plate being provided as a gantry on the side of each of said pole pieces facing towards the patient receiving cavity; with a magnetic correction dipole locating and fixing plate being provided for at least one of said pole pieces, for locating and fixing magnetic dipoles for fine correction of magnetic field homogeneity, for the purposes of shimming; a compartment being formed between one of the pole pieces and the respective end plate, for receiving the magnetic correction dipole locating and fixing plate, with one or more of said magnetic dipoles mounted thereto; characterized in that said compartment is accessible via an opening provided inside the protruding peripheral side wall of said pole piece, the opening having a width and height suitable for insertion and removal of said magnetic correction dipole locating and fixing plate with one or more magnetic correction dipoles mounted thereto, said opening being provided underneath said antenna for transmitting electromagnetic signals and said end plate, which remain in place during insertion and removal of the magnetic dipole locating and fixing plate. a 3D structure having a cavity for receiving a body under examination; a pair of permanent magnets for generating a static magnetic field in said cavity and spaced from each other, so that the patient receiving cavity is interposed between said permanent magnets; coils for generating gradient magnetic fields in said cavity; an antenna for transmitting electromagnetic nuclear spin excitation pulses; an antenna for receiving the electromagnetic signals generated by nuclear spin relaxation; a respective pole piece being mounted to the side of each magnet facing towards the patient receiving cavity, each pole piece possessing a peripheral side wall protruding towards the patient receiving cavity; an end plate being provided as a gantry on the side of each of said pole pieces facing towards the patient receiving cavity; with a magnetic correction dipole locating and fixing plate being provided for at least one of said pole pieces, for locating and fixing magnetic dipoles for fine correction of magnetic field homogeneity, for the purposes of shimming; a compartment being formed between one of the pole pieces and the respective end plate, for receiving the magnetic correction dipole locating and fixing plate, with one or more of said magnetic dipoles mounted thereto; characterized in that said compartment is accessible via an opening provided inside the protruding peripheral side wall of said pole piece, the opening having a width and height suitable for insertion and removal of said magnetic correction dipole locating and fixing plate with one or more magnetic correction dipoles mounted thereto, said opening being provided underneath said antenna for transmitting electromagnetic signals and said end plate, which remain in place during insertion and removal of the magnetic dipole locating and fixing plate.