High-frequency coil and a magnetic resonance imaging apparatus using the same

A technique is provided to reserve large examination space in the tunnel type MRI apparatus, without increasing production cost nor reducing significantly irradiation efficiency and homogeneity in an irradiation distribution within an imaging region. The present invention provides an RF coil unit in which four partial cylindrical coils are placed with a gap therebetween in the circumferential direction inside a cylindrical RF shield, in such a manner that two pairs of the partial cylindrical coils are opposed to each other, and magnetic fields produced by the individual partial cylindrical coils are combined, thereby producing a circularly polarized wave field or an elliptically polarized wave field. The partial cylindrical coil is provided with a partial cylindrical conductor, multiple first conductors substantially parallel with the central axis of the RF shield, multiple capacitors connecting both ends of the first conductors with the partial cylindrical conductor, and a second conductor adjacent to at least one of the ends of the first conductor. The partial cylindrical coils are respectively provided with high frequency signals having a desired amplitude ratio and phase difference, while a reference frequency thereof being identical.