Patent ID: 8854048

Claim:
A sensitivity correction method for a dose monitoring device included in a particle beam therapy system which scans a particle beam and irradiates the particle beam to an irradiation position of an irradiation subject, the sensitivity correction method comprising the steps of: measuring, by said dose monitoring device, the dose of the particle beam passing through said dose monitoring device; measuring, by a small ionization chamber that is smaller in size than said dose monitoring device, the dose of the particle beam that passes through said dose monitoring device, wherein said small ionization chamber is located upstream of said dose monitoring device with respect to the traveling direction of the particle beam; and calculating, by a calculation unit, a correction coefficient of the dose measured by said dose monitoring device corresponding to the irradiation position based on the dose of the particle beam measured by said small ionization chamber, for improving measurement deterioration due to deflection of an electrode of the dose monitoring device.