Development and evaluation of physical properties for digital intra-oral radiographic system

As a part of the development of a dental digital radiographic (DDR) system using a CMOS sensor, we developed hardware and software based on a graphical user interface (GUI) to acquire and display intra-oral images. The aims of this study were to develop the DDR system and evaluate its physical properties. Electric signals generated from the CMOS sensor were transformed to digital images through a control computer equipped with a USB board. The distance between the X-ray tube and the CMOS sensor was varied between 10-40 cm for optimal image quality. To evaluate the image quality according to dose variance, phantom images (60 kVp, 7 mA) were obtained at 0.03, 0.05, 0.08, 0.10, and 0.12 s of exposure time and signal-to-noise ratio (SNR) was calculated form the phantom image data. The modulation transfer function (MTF) was obtained as the Fourier transform of the line spread function (LSF), a derivative of the edge spread function (ESF) of sharp edge images acquired at exposure conditions of 60 kVp and 0.56 mA. The most compatible contrast and distinct focal point length was recorded at 20 cm. The resolution of the DDR system was approximately 6.2 line pair per mm. The developed DDR system could be used for clinical diagnosis with improvement of acquisition time and resolution. Measurement of other physical factors such as detected quantum efficiency (DQE) would be necessary to evaluate the physical properties of the DDR system.