STUDY OF γ-RAY YIELDS USING A NaI DETECTOR FROM PION ABSORPTION WITH APPLICATION TO PION THERAPY

抄録

The yields of gamma-rays have been measured for stopping pions in water and polyethylene using a NaI detector. Nal detectors have the application to externally monitor the stopping region of negative pions within a patient undergoing therapy. Negative n mesic X-rays, r-rays and neutrons are emitted from the region at which ir mesons stop and produce stars. These radiations can be detected outside the exposed patient. A water phantom was exposed tormesons at various depths. The resulting T-ray yields were determined by counting the r-rays in coincidence with incident n mesons using a sodium iodide (Nal) detector. This type of T-ray measurement can assure that the depth-dose distribution in the patient is situated exactly at the desired location during irradiation. A direct-reading instrument such as the scintillation camera with multihole collimator is suggested as a powerful and convenient tool to ascertain the twodimensional position of the peak region in the patient.