Showing papers by "George Fountos published in 2023"
TL;DR: In this paper , the energy absorption efficiency (EAE) of the PbF2 scintillator was evaluated under X-ray and gamma-ray excitation under the conditions of 50 to 130 kVp and I-131 365 keV.
Abstract: Background: In this research, the response of a 10 × 10 × 10 mm3 commercially available PbF2 crystal was experimentally assessed under X-ray and gamma ray radiation to verify the possible application of this material in X-ray medical imaging. Methods: The measurements were performed under X-ray from 50 to 130 kVp and gamma ray excitation (Tc-99m 140 keV and I-131 365 keV). The PbF2 response was experimentally assessed by the determination of the absolute luminescence efficiency (AE), X-ray luminescence efficiency (XLE), and the stopping power of this scintillating crystal in terms of the energy absorption efficiency (EAE). The results were compared with bismuth germanate (BGO) crystal, which is commonly used in medical imaging modalities. Results: The AE of PbF2 gradually decreased from 50 kVp up to 130 kVp. The maximum value was 0.61 efficiency units (EU) at 140 keV, and the minimum value was 0.03 EU at 71 keV (130 kVp). Similarly, low values appeared for the XLE, where the maximum value was 16.9 × 10−5 at 140 keV. Conclusions: These findings show that the PbF2 scintillator has unacceptably low luminescence efficiency. Although PbF₂ can effectively absorb radiation, the scintillation light, at room temperatures, is negligible, and, thus, it could not be used in medical imaging applications in the examined energy range.
TL;DR: In this paper , a methodological approach is introduced and described for creating digital phantom images based on the measured image quality properties of the sensor, such as the response curve that yields high contrast and image latitude, frequency response given by the Modulation Transfer Function (MTF), which enables small detail imaging and the Normalize Noise Power Spectrum (NNPS) that shows the extent of the noise effect on image clarity.
Abstract: Background: Mammographic digital imaging is based on X-ray sensors with solid image quality characteristics. These primarily include (a) a response curve that yields high contrast and image latitude, (b) a frequency response given by the Modulation Transfer Function (MTF), which enables small detail imaging and (c) the Normalize Noise Power Spectrum (NNPS) that shows the extent of the noise effect on image clarity. Methods: In this work, a methodological approach is introduced and described for creating digital phantom images based on the measured image quality properties of the sensor. For this purpose, a mathematical phantom, simulating breast tissue and lesions of blood, adipose, muscle, Ca and Ca(50%)-P(50%) was created by considering the corresponding X-ray attenuation coefficients. The simulated irradiation conditions of the phantom used four mammographic spectra assuming exponential attenuation. Published data regarding noise and blur of a commercial RadEye HR CMOS imaging sensor were used as input data for the resulting images. Results: It was found that the Ca and Ca(50%)-P(50%) lesions were visible in all exposure conditions. In addition, the W/Rh spectrum at 28 kVp provided more detailed images than the corresponding Mo/Mo spectrum. Conclusions: The presented methodology can act complementarily to image quality measurements, leading to initial optimization of the X-ray exposure parameters per clinical condition.