Antenna device and magnetic resonance imaging device

An RF antenna device of an MRI apparatus used for transmission and/or reception of a signal, comprising:

• a cylindrical conductor having a cylindrical shape;
• a ribbon-shaped conductor having a length longer than the circumference of the cylindrical conductor;
• and
• a cable connected to the cylindrical conductor and the ribbon-shaped conductor, which transmits and receives signals to and from the RF antenna device, wherein
• the ribbon-shaped conductor is disposed on a cylindrical surface inside of the cylindrical conductor in the form of a loop so as to generate a magnetic field having a component perpendicular to a central axis of the cylindrical conductor in the inside of the cylindrical conductor,
• the ribbon-shaped conductor comprises:
• a plurality of first portions having a component parallel to the central axis direction of the cylindrical conductor, and
• a plurality of second portions having a component in the circumferential direction of the cylindrical conductor connecting the first portions, wherein
• the first portions are disposed so that a component along the circumferential direction of the cylindrical conductor of one first portion does not overlap with a component along the circumferential direction of the cylindrical conductor of an adjacent first portion, and
• where a number of the first portions of the ribbon-shaped conductor is represented as 2N (where N is equal to a wavenumber of an electromagnetic wave to be transmitted or received), a length of the ribbon-shaped conductor is represented as L, and a specific propagation velocity ratio of the whole propagation line of the ribbon-shaped conductor with the cylindrical conductor as a ground plane, with respect to the velocity of light in a vacuum, is represented as A, a value obtained by dividing the length L by the specific propagation velocity ratio A is substantially equal to (N−1) or (N+1) times the wavelength of an electromagnetic wave in a vacuum that resonates with the antenna device.