RF circuit, MRI apparatus, and method of monitoring RF pulse power

According to one embodiment, an RF circuit includes a directional coupler, processing circuitry, and an adjuster. The directional coupler includes a first port for outputting at least a part of a traveling wave and a second port for outputting at least a part of a reflected wave. The processing circuitry is configured to calculate impedance of a load side that is viewed from the directional coupler, by using a voltage standing wave ratio based on respective outputs from the first port and the second port and a phase of the reflected wave based on an output from the second port. The adjuster is configured to adjust an output from at least one of the first port and the second port based on the impedance calculated by the processing circuitry.