Development of dosimetry using detectors of diagnostic digital radiography systems

Dosimetry using an imaging plate (IP) of computed radiography (CR) systems was developed for quality control of output of the x-ray equipment. Sensitivity index, or the S number, of the CR systems was used for estimating exposure dose under the routine condition: exposure dose from 1.0 to 1.0 x 10(2) microC kg(-1), tube voltages from 50 to 120 kV, and added filtration from 0 to 4.0 mm Al. The IP was calibrated by using a 6 cc ionization chamber having traceability to the National Standard Ionization Chamber. The uncertainty concerning the fading effect was suppressed less than 1.9% by reading the latent image 4 min+/-5 s after irradiation at the room temperature 25.9+/-1.0 degrees C. The S number decreased linearly on the logarithmic graph regardless of the beam quality as exposure dose increased. The relationship between the exposure dose (E) and the S number was fitted by the equation E=a' X S(-b). The coefficient a' decreased when the added filtration and the tube voltage were increased. The coefficient b was 0.977+/-0.007 in all beam qualities. The dosimetry using the IP and the equation can estimate the exposure dose in a range from 9.0 x 10(-2) to 5.0 microC kg(-1) within an uncertainty of +/-5% required by the Japanese Industry Standard. This dose range partially included the doses under routine condition. The doses between 1.0 and 1.0 x 10(2) microC kg(-1) under the routine condition can be shifted to the 5% region by using an absorber. The IP dosimetry is applicable to the quality control of the CR systems.