Particle beam irradiation apparatus and particle beam therapy system utilizing a beam position monitor to provide feedback adjustments based on the beam position

A particle beam irradiation apparatus that irradiates a charged particle beam accelerated by an accelerator onto an irradiation subject, the particle beam irradiation apparatus comprising:

• a scanning electromagnet configured to scan the charged particle beam in a direction that is perpendicular to a beam axis;
• a position monitor that (i) is disposed such that the relative position thereof to the scanning electromagnet in the beam axis direction is changeable to a desired position and (ii) is configured to detect a passing position of the charged particle beam;
• a distance sensor configured to detect a changing beam-axis direction position of the position monitor from at least a first beam-axis direction position to at least a second beam axis direction position when irradiation is performed onto the irradiation subject;
• and
• an irradiation control apparatus configured to
• calculate, based on a signal received from the distance sensor regarding the changing beam-axis direction position information of the position monitor, position monitor distance information, which includes a beam-axis-direction distance from an irradiation plane on the irradiation subject to the position monitor,
• calculate a beam irradiation position on the irradiation subject, based on (i) a detection signal, including information on the passing position of the charged particle beam, from the position monitor and (ii) the calculated position monitor distance information, which includes information on a changed beam-axis direction position of the position monitor, and
• control irradiation of the charged particle beam, wherein
• the irradiation control apparatus includes a position calculation apparatus configured to calculate the beam irradiation position, on the irradiation plane, that is expressed based on a distance from an intersection point of the beam axis with the irradiation plane, said position calculation apparatus calculates the beam irradiation position based on (i) a beam position detected by the position monitor, (ii) scanning starting point distance information that includes a distance from the irradiation plane of the irradiation subject to a scanning starting point, of the charged particle beam, in the scanning electromagnet, and (iii) the position monitor distance information, which includes information on a changed beam-axis direction position of the position monitor.