Magnetic resonance diagnostic apparatus

Abstract

A magnetic resonance imaging apparatus generates a radiofrequency magnetic field to excite magnetization spins of a subject placed in a static magnetic field, and which receives magnetic resonance signals generated from the excited magnetization spins so as to generate an image of the subject based on the received magnetic resonance signals. A superconducting coil carries out at least one of generation of the radiofrequency magnetic field and a reception of the magnetic resonance signals. A cryostat has a refrigerant container therein. The refrigerant container contains refrigerant and the superconducting coil. A flow space is formed between the refrigerant container and a surface of the cryostat. Fluid having appropriate temperature and amount of supply is made to flow to the flow space, thereby temperature of a surface of the cryostat can be maintained in a predetermined range. The subject is directly placed on the surface of the cryostat. Since the temperature of the surface of the cryostat is maintained in the predetermined range, the subject can lay on the surface of the cryostat for a relatively long period of time. Thus, time for photographing is not limited. It is necessary to sufficiently thicken insulating material to maintain the temperature of the surface of the cryostat with insulating material. However, the thickness of the insulting material results in separating the subject from the superconducting coil and reducing sensitivity of receiving the magnetic resonance signals. According to the present invention, the superconducting coil can be made closer to the subject, so that reduction of the sensitivity of receiving can be restrained.