A comparison of the response of storage phosphor and film radiography to small variations in X-ray exposure

Objective: To determine the response to small repeated variations in X-ray exposure of storage phosphor (SP) plates compared with Ektaspeed Plus dental film. Methods: Exposure of SP plates and Ektaspeed Plus dental him was varied within a small range [8.62 mu C kg(-1) to 9.03 mu C kg(-1), (5%)]. Radiographs were digitized and SP plates read with a laser-based scanner. Nested analysis of variance, analysis of covariance, and regression analysis were used to test the relationship between exposure and the resulting signal. Results: The relationship between exposure and signal for digital images of film radiographs was not significant whereas the corresponding relationship for SP images was highly significant (P<0.001, R-2 = 0.34). Conclusions: Over the narrow range of X-ray exposures studied there was a significant direct linear relationship between exposure and digital gray-scare values for SP images but not for digital images of Ektaspeed Plus films.