SU1823194A1 - Method of determination of dose distribution in object - Google Patents

Abstract

FIELD: medical equipment, and namely, in radiology for determination of dose distribution in object. SUBSTANCE: a number of nominal electron acceleration energies, higher and lower than the nominally preset one, is set, at which the range of deviations of actual electron energies from the nominal energies at different time moments overlap one another; at each nominal energy an electron beam is directed to the phantom and irradiates it, during phantom irradiation the actual electron energy in the beam is being continuously measured, and compliance of actual energy with one of the narrow and energy bands, whose width is less than the actual energy instability range at each nominal energy, is determined; at the same time doses in phantom parts with different coordinates and the mean dose according to the gas volume of the ionization chamber - dose monitor, spatially fixed relative to the phantom surface irradiated region, are determined. Doses are determined as a set of separate dose contributions created by beam electrons with measured energies of individual separated narrow bands; dose contributions, created in phantom by electrons with energies from each narrow band, are normalized into the respective dose contributions to the gas volume of the ionization chamber - dose monitor. Then the preset nominal energy of electrons in the beam is set, the beam is directed to the patient's organ and irradiates it. During irradiation of the patient's organ the electron energy in the beam in different time intervals of irradiation is being continuously measured, the actual electron energy in different time intervals corresponding to one of the narrow energy bands is determined, the mean dose according to the gas volume of the ionization chamber - dose monitor, spatially fixed relative to the irradiated surface of the patient, is determined in the same may as at irradiation of phantom relative to the irradiated region of the phantom surface. Dose is determined as a set of separate dose contributions created by beam electrons with measured energies of similar separate narrow bands of energies that were liberated at irradiation of phantom; dose distribution in the irradiated organ is being continuously determined according to normalized distributions of dose in phantom, corresponding to narrow electron energy bands, and according to separate dose contributions created in the process of irradiation of the organ in liberated gas object by electrons with energies from separate narrow bands; and irradiation is stopped at an equality of dose in the preset part of the volume of the irradiated organ of the preset dose. EFFECT: enhanced accuracy of determination of dose in different regions of the irradiated organ at employment of a relatively low-stable accelerator. 2 cl, 2 dwg