Improvement of precision in quantitative measurements of radioactivity with an imaging plate

To obtain a high precision in radiation or radioactivity measurements with an imaging plate, the photo-stimulated luminescence intensity must be large. To get the highest intensity, we reread an imaging plate repeatedly and summed each intensity for the purpose of reducing the variation of the measured intensities. A great improvement of the precision in the measurement was achieved with the method of repeated readings when the time interval between each reading is more than about 1 h.