Analysis of MTF in digital radiography using linear detector array

Abstract Background: Nowadays, digital radiography is widely utilized in non-destructive testing. However, some issues concerning this new technique need to be addressed properly, and some key parameters of the imaging system need to be quantified by some measurement methods. Purpose: To evaluate a digital radiography system using linear detector array quantitatively and efficiently, and optimize the testing parameters accordingly, modulation transfer function (MTF) of the imaging system was calculated and analyzed. Methods: Edge tool, duplex wire image quality indicator (IQI) and resolution test card were used to measure MTF of the system under different testing parameters, which include focus size, magnification and object orientation. Results: Results show that the contrast transfer function (CTF) measured by duplex IQI and resolution test card is almost identical, while signals from duplex IQI are easier to analyze quantitatively. CTF from duplex IQI is approximately a curve of second order, and the CTF can be used to transform to MTF, but the values are higher than that from edge tool, as movement during image acquisition process is unstable. Conclusion: After analysis, we find that the system performance is affected by many factors together, but MTF can be used to evaluate these factors perfectly, thus to find out equivalent parameters combination or determine the optimum testing parameters. (authors)