Dose response of a storage phosphor system for intraoral radiography

Objectives: To determine the dose response function for the Digora® (Soredex Orion Corporation, Helsinki, Finland) storage phosphor system for intra-oral radiography. Methods: Specially designed software provided by the manufacturer was used to register data from the pre-scanning that takes place prior to readout. These data contain information about the signal from the photomultiplier and the amplification that forms the basis for the AD conversion to 8 bit image data. Dose response functions were determined for different calibration settings and also combined into one single function. Results: The dose response function is linear irrespective of calibration. The gray levels of the final radiographs are directly proportional to the amplified signal. The Digora® does not fully compensate for exposure differences. Increased exposure results in slightly darker radiographs. Conclusions: Since the gray levels of the final radiographs are directly proportional to the amplified signal, the gray levels may be used as a relative measure of the exposure in the Digora® system provided that they are subtracted from the maximum value of 255.