The present invention provides a quality assurance method of three-dimensional isocenters of diagnostic and treatment devices using radiation. The method comprises the steps of: in a device including a gantry having a space spaced apart from a rotation axis and being rotatable about the rotation axis, inserting, into a radiation irradiation unit rotatable with the gantry, a first isocenter measuring module for measuring a first isocenter representing a rotation center of the gantry； determining the first isocenter by photographing the first isocenter measuring module with a camera unit while rotating the gantry； arranging a second isocenter measuring module for measuring a second isocenter representing a center to which radiation is irradiated at a laser isocenter indicated by a laser beam at a center of the gantry； inserting a collimator into the radiation irradiation unit； determining the second isocenter by irradiating radiation while rotating the gantry and the collimator； obtaining a two-dimensional projection image of at least a part of the second isocenter measuring module using an imaging device, and determining a third isocenter representing an isocenter of an image reconstructed by the imaging device； and determining whether the first isocenter, the second isocenter, the third isocenter, and the laser isocenter are located within a specified distance.La présente invention concerne un procédé d'assurance qualité d'isocentres tridimensionnels de dispositifs de diagnostic et de traitement utilisant un rayonnement. Le procédé comprend les étapes consistant à: insérer, dans un dispositif comprenant un portique ayant un espace espacé d'un axe de rotation et pouvant tourner autour de l'axe de rotation, dans une unité d'irradiation de rayonnement pouvant tourner avec le portique, un premier module de mesure d'isocentre pour mesurer un premier isocentre représentant un centre de rotation du portique； déterminer le premier isocentre en photographiant le premier modu
