Analysis of unsharpness evaluation method in radiographic testing by numerical simulation

Unsharpness is an important parameter to evaluate image quality in radiographic testing, especially for digital radiography. In practice, duplex wire image quality indicator (IQI) is often used to measure unsharpness value of radiography, however, contents of the measurement method in current standards need to be clarified or modified. To investigate principle behind duplex wire IQI and the relation between unsharpness value and response from the IQI, imaging models of duplex wire IQI and edge tool were established. By numerical simulation method, response curves of the test took at certain testing parameters of x-ray source and testing arrangement were obtained, and then unsharpness values were analyzed contrastively. The results show that image of the IQI corresponding to a nominal unsharpness value will show different identity because of different focus intensity distribution, but 20% modulation in response curve from the IQI can be used as a quantitative criterion to calculate the resolution capability nevertheless. (author)