Intra-subject position detection system

An intra-subject position detection system, comprising:

• a subject insertable device that is introduced into a subject and moves through the subject;
• and
• a position detecting device that is arranged outside the subject and obtains position information of the subject insertable device inside the subject,
• the subject insertable device including a magnetostatic field generator that generates a magnetostatic field, and
• the position detecting device including
• a magnetic field detector that detects a magnetic field strength,
• an alternating-current magnetic field generator that is fixed to a predetermined position relative to the subject, and outputs an alternating-current magnetic field which is used for derivation of a position of the magnetic field detector,
• a coordinate deriving unit that derives a position coordinate of the magnetic field detector based on an alternating-current magnetic field component of the magnetic field detected by the magnetic field detector,
• a distance deriving unit that derives a distance between the magnetic field detector and the subject insertable device based on a direct-current magnetic field component of the magnetic field detected by the magnetic field detector, and
• a position information deriving unit that derives the position of the subject insertable device inside the subject based on a result of derivation by the coordinate deriving unit and a result of derivation by the distance deriving unit.