PSI - Issue 33

Dionysios Linardatos et al. / Procedia Structural Integrity 33 (2021) 304–311 Linardatos / Structural Integrity Procedia 00 (2021) 000 – 000

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determined by the intrinsic phosphor material properties and by the screen thickness of the imaging system. In thick screens, the lateral light trajectories are very long, causing a large fraction of the laterally directed photons to be absorbed before reaching the screen output. The practical value of the IC is that it defines an imaging performance index that evaluates image information quantity by a single numerical value. Information capacity is not expressed for specific frequency values, since it is the outcome of integration over the spatial frequency bandwidth (Michail et al., 2014). Thus, IC is significantly affected by the maximum frequency contained in the signal, i.e., the frequency bandwidth over which integration is performed. Thin screens exhibit a larger bandwidth, something that can cause an increase in IC values. In addition to this, the information capacity is calculated using spatial frequency as a factor, which multiplies the logarithmic term containing the SNR. As the allowed spatial frequency region is enlarged to include higher and higher spatial frequencies, the information capacity slightly increases at fixed SNR. This affects IC in a sense that it may be preferably emphasized by high frequency information content, i.e., the kind of information that is expressed by spatial resolution and sharpness, which is better displayed by thin screens. 4. Conclusion In the present study, the image information content of a 1650 x 1246 pixels at 20 μm pitch NDT CMOS sensor was investigated in terms of the information capacity, which is based on Shannon’s mathematical communication theory. The determination of the IC was based on the measurement of the noise equivalent quanta under radiographic conditions. Results showed that the information capacity values of the CMOS APS sensor under investigation were found comparable to those of a previously studied CMOS sensor of different dimensions, coupled to various scintillating screens under similar exposure conditions. References Anastasiou, A., Papastamati, F., Bakas, A., Michail, C., Koukou, V., Martini, N., Ninos, K., Lavdas, E., Valais, I., Fountos, G., Kandarakis, I., Kalyvas, N., 2020. Spatial frequency domain analysis of a commercially available digital dental detector. Measurement 151, 107171. https://doi.org/10.1016/j.measurement.2019.107171 Bertolini, M., Nitrosi, A., Rivetti, S., Lanconelli, N., Pattacini, P., Ginocchi, V., Iori, M., 2012. A comparison of digital radiography systems in terms of effective detective quantum efficiency: eDQE comparison of digital radiography systems. Med. Phys. 39, 2617 – 2627. https://doi.org/10.1118/1.4704500 Bohndiek, S.E., Cook, E.J., Arvanitis, C.D., Olivo, A., Royle, G.J., Clark, A.T., Prydderch, M.L., Turchetta, R., Speller, R.D., 2008. A CMOS active pixel sensor system for laboratory- based x-ray diffraction studies of biological tissue. Phys. Med. Biol. 53, 655 – 672. https://doi.org/10.1088/0031-9155/53/3/010 Bosmans, H., Carton, A.-K., Rogge, F., Zanca, F., Jacobs, J., Van Ongeval, C., Nijs, K., Van Steen, A., Marchal, G., 2005. Image quality measurements and metrics in full field digital mammography: an overview. Radiat. Prot. Dosimetry 117, 120 – 130. https://doi.org/10.1093/rpd/nci711 Cho, M.K., Kim, H.K., Graeve, T., Yun, S.M., Lim, C.H., Cho, H., Kim, J.-M., 2008. Measurements of X-ray Imaging Performance of Granular Phosphors With Direct-Coupled CMOS Sensors. IEEE Trans. Nucl. Sci. 55, 1338 – 1343. https://doi.org/10.1109/TNS.2007.913939 Dobbins III, J.T., 2000. Image Quality Metrics for Digital Systems (Part I, Chapter 3), in: Beutel, J., Kundel, H.L., Van Metter, R.L. (Eds.), Handbook of Medical Imaging. Volume 1: Physics and Psychophysics. SPIE Press, Bellingham, Washington, pp. 161 – 222. Dobbins III, J.T., 1995. Effects of undersampling on the proper interpretation of modulation transfer function, noise power spectra, and noise equivalent quanta of digital imaging systems. Med. Phys. 22, 171 – 181. https://doi.org/10.1118/1.597600 Dobbins III, J.T., Godfrey, D.J., 2003. Digital x-ray tomosynthesis: current state of the art and clinical potential. Phys. Med. Biol. 48, R65 – R106. https://doi.org/10.1088/0031-9155/48/19/R01 Endrizzi, M., Oliva, P., Golosio, B., Delogu, P., 2013. CMOS APS detector characterization for quantitative X-ray imaging. Nucl. Instrum. Methods Phys. Res. Sect. Accel. Spectrometers Detect. Assoc. Equip. 703, 26 – 32. https://doi.org/10.1016/j.nima.2012.11.080