Purpose: The purpose of this study was to investigate CTDI100c (computed tomography dose indice at center) for various phantom shapes, sizes, and compositions by using GATE (geant4 application for tomographic emission) simulations. Method and Materials: GATE simulations were performed for various phantom shapes (cylinder, cylindroid, and hexagonal prism PMMA phantoms) and phantom compositions (water, PMMA, polyethylene, polyoxymethylene) with various diameters (1–50 cm) at various kVp (80, 100, 120, 140 kVp) and mAs (100, 200, 300, 400 mAs) levels. Results: The CTDI100c values of cylinder, cylindroid, and hexagonal prism phantom at 140 kVp, 200 mAs resulted in 20.1, 24.3, and 22.1 mGy, respectively. The cylindroid phantom may be needed to estimate CTdose, because it.s shape is closer to that of human body than cylinder and hexagonal prism PMMA phantom. The effect of phantom composition to CTDI100c was studied for water, PMMA, polyethylene, polyoxymethylene. For all phantom compositions, CTDI100c values were nonlinearly increased, linearly increased, and nonlinearly decreased as a function of kVp, mAs, and diameter, respectively. Among those compositions, CTDI100c values for water as a function of kVp, mAs, and diameter were changed most rapidly which indicating that CTDI100c values using PMMA could be underestimated and overestimated compared to those measured with water. Conclusion: In conclusion, the results of GATE simulations demonstrated that CTDI100c was able to be characterized for various phantom shapes, sizes, and compositions so that we may be able to investigate for estimating CTDIs in realistic applications.
Purpose: We have characterized a new flat‐panel digital x‐ray detector. Physical characteristics of new flat‐panel detector has been measured and evaluated by using previous flat‐panel detector as the reference method. Method and Materials: The new flat‐panel detector has a pixel size of 0.168mm and detecting area of 17″ × 17″. The previous flat‐panel detector has a pixel size of 0.139mm and detecting area of 14″ × 17″. The modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of the two systems were measured. For these two detectors use RQA5 radiographic condition. The MTF of the detectors were evaluated using slit method. The NPS were measured by two‐dimensional Fourier analysis of center portion of the averaged image. The DQE were assessed from the MTF, the NPS, given exposure and photons per mm2‐mR. Results: For the new flat‐panel detector, the MTF at 3cycles/mm which is Nyquist frequency of new detector was measured as 55%. The maximum DQE value at spatial frequencies between 0 and 1cycles/mm was 55% for the new flat‐panel detector. For the previous flat‐panel detector, the MTF at 3cycles/mm was measured as 59%. The maximum DQE value at spatial frequencies between 0 and 1cycles/mm was 50% for previous flat‐panel detector. The MTF of a new flat‐panel detector was slightly lower than that of a previous flat‐panel detector. The NPS curves of the two detectors were generally similar at the wide range of the spatial frequencies. For the DQE of the new flat‐panel detector was also similar with previous flat‐panel detector at frequency above 1cycles/mm. However, in the frequencies below 1cycles/mm, new flat‐panel detector was higher than previous flat‐panel detector. Conclusion: The new flat‐panel detector is able to provide good imaging performance in the detection of low contrast objects.
Purpose: This study aims to identify the feasibility of a novel cesium‐iodine (CsI)‐based flat‐panel detector (FPD) for removing scatter radiation in diagnostic radiology. Methods: The indirect FPD comprises three layers: a substrate, scintillation, and thin‐film‐transistor (TFT) layer. The TFT layer has a matrix structure with pixels. There are ineffective dimensions on the TFT layer, such as the voltage and data lines; therefore, we devised a new FPD system having net‐like lead in the substrate layer, matching the ineffective area, to block the scatter radiation so that only primary X‐rays could reach the effective dimension.To evaluate the performance of this new FPD system, we conducted a Monte Carlo simulation using MCNPX 2.6.0 software. Scatter fractions (SFs) were acquired using no grid, a parallel grid (8:1 grid ratio), and the new system, and the performances were compared.Two systems having different thicknesses of lead in the substrate layer—10 and 20μm—were simulated. Additionally, we examined the effects of different pixel sizes (153×153 and 163×163μm) on the image quality, while keeping the effective area of pixels constant (143×143μm). Results: In case of 10μm lead, the SFs of the new system (∼11%) were lower than those of the other system (∼27% with no grid, ∼16% with parallel grid) at 40kV. However, as the tube voltage increased, the SF of new system (∼19%) was higher than that of parallel grid (∼18%) at 120kV. In the case of 20μm lead, the SFs of the new system were lower than those of the other systems at all ranges of the tube voltage (40–120kV). Conclusion: The novel CsI‐based FPD system for removing scatter radiation is feasible for improving the image contrast but must be optimized with respect to the lead thickness, considering the system's purposes and the ranges of the tube voltage in diagnostic radiology. This study was supported by a grant(K1422651) from Institute of Health Science, Korea University.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.