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 graphical user interface (GUI) to acquire and display readily intra-oral images from the prototype DDR system. The aims of this study were to develop the DDR system using a CMOS sensor and evaluate the physical properties of it. Electric signals generated from the CMOS sensor were transformed to digital images through control computer equipped with USB board. The distance between the X-ray tube and the CMOS sensor was varied between 10-40 cm to be optimal image quality. To evaluate the image quality according to dose variances, phantom images (60 kVp, 7 mA) were obtained at 0.03, 0.05, 0.08, 0.10, and 0.12 sec of exposure time and signal-to-noise ratio (SNR) was calculated form the this phantom image data. Modulation transfer function (MTF) was yielded by the fourier transform of the line spread function (LSF) which was derivative of the edge spread function (ESF) of sharp edge image acquired at the exposure condition of 60 kVp and 0.56 mAs. The most compatible contrast and distinct focal point length was recorded at 20 cm. The mean intensity value of pixels was irregular, so the result of SNR didn't have meaning. The result of MTF showed that the resolution of the DDR system was approximately 6.2 fine pair per mm. Prototypic DDR system was sufficient to use in intra-oral radiography in aspect of physical property even if pre-processing was not performed. The developed DDR system could be used for clinical diagnosis with the improvement of acquisition time and resolution. The measurement of another physical factors such as detected quantum efficiency (DQE) and other method signal-to-noise ratio (SNR) should be necessary to evaluate the physical properties of DDR system.