A dynamic tumor radiation treatment program for causing a computer to function. The program includes detecting an annihilation gamma ray with a gamma ray detector, storing the threshold of counting rate in a displacement threshold memory, computing the counting rate according to the detection signal of an annihilation gamma ray with a gamma ray counting rate computer, comparing the counting rate of annihilation gamma rays acquired from the gamma ray counting rate computer with the threshold of the counting rate acquired from the displacement threshold storage memory by means of a threshold comparator, judging whether or not the tumor is displaced out of the radiation irradiation spot by means of a tumor position judging unit, and making a control to stop radiation irradiation or outputting a stop command signal by means of an irradiation controller.
