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Direct Conversion Semiconductor Detectors for Radiation Imaging
Published in Salim Reza, Krzysztof Iniewski, Semiconductor Radiation Detectors, 2017
Shiva Abbaszadeh, Craig S. Levin
For x-ray imaging, the MTF can be used for characterizing the spatial resolution of the system and the DQE can be used to quantify the signal quality in terms of SNR. The numerous sources that affect the spatial resolution include K-fluorescence reabsorption, Compton scattering, and primary photoelectron range, while noise sources such as electronic noise affect the DQE. a-Se is a common direct conversion detector material for mammography and low x-ray energy applications. Benefits of a-Se include good charge transport properties, low dark current, and high spatial resolution. In addition, avalanche multiplication has been observed in a-Se, which could potentially be leveraged for x-ray imaging. The blocking layer also plays an important role, as this layer is essential to maintain low dark current and prevent charge injection at high electric fields.
Emerging Digital Data Capabilities in Electron Microscopy
Published in Jeffrey P. Simmons, Lawrence F. Drummy, Charles A. Bouman, Marc De Graef, Statistical Methods for Materials Science, 2019
The quality improvement across successive generations of imaging technology can be seen by plotting the detective quantum efficiency (DQE) for different detector technologies. DQE indicates the capacity of an imaging device to generate signal (contrast) above the noise inherent in the imaging system, and it is recognized as the objective measure for both the ultimate resolution and sensitivity of an imaging device [703, 702, 573]. Figure 2.2 shows the DQE measured with a 300 keV electron beam for SO-163 Film, the Gatan Ultrascan US4000 CCD camera with an ultrahigh-sensitivity scintillator, and the Gatan K2 direct detection camera operating in both intensity integration (Base / In Situ) and super-resolution (Summit) modes.
Physical Basis of X-ray Breast Imaging
Published in Paolo Russo, Handbook of X-ray Imaging, 2017
Chai Hong Yeong, Kwan Hoong Ng, Noriah Jamal
Therefore, for an ideal imaging system, the DQE is equal to one. If there are other sources of noise, SNRout will decrease below the value predicted by the number of interacting quanta and the DQE will be less than one. A high DQE improves the visibility of small, low contrast objects, which is a very important parameter in mammography. The DQE is often related to radiation dose whereby the detectors with higher DQE use the photons more efficiently, hence require less radiation exposure to achieve an adequate SNR.
Comparison of the conventional reusable cotton and disposable nonwoven fabric patient gowns in digital chest radiography
Published in Radiation Effects and Defects in Solids, 2021
Myeong Seong Kim, Dae Cheol Kweon
In current DR systems, incident X-ray photons are converted into electrical signals by photoconductor materials (9–12). The advantages of X-ray imaging with DR include a low pixel size and improved spatial resolution as compared to other systems (e.g. the film-screen system or indirect computed radiography). Additionally, it has a wider dynamic range (the signal response to the X-ray dose is a narrow S-shape in film systems so that displayed in low image quality due to a limited tolerance for X-ray dose but is a wider and linear proportional shape in the DR system), ultimately achieving high detective quantum efficiency (9–12). DR systems can obtain high-quality images that can represent low-density structures that would not be visible when using older, conventional systems. Therefore more care should be taken due to artifacts caused by gown or foreign materials especially in low X-ray dose. To improve X-ray image quality, patient gowns made of conventional cotton material must be replaced according to the changing environment in departments of radiology.
X-ray-acquired imaging and detection radiography system using digital radiography with a DSLR digital camera: preliminary results of a pilot study
Published in Radiation Effects and Defects in Solids, 2023
Jae Yul Lee, Kyum Cha Lee, Dae Cheol Kweon
As a limitation of the research on X-ray systems using DSLR cameras in this study, a quantitative analysis of modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) according to X-ray exposure is required. Second, the image should be evaluated by measuring the radiation dose according to the X-ray exposure (23). Third, additional experiments are needed to evaluate the image by removing noise and blurring from the DR image acquired using a DSLR camera and scintillator (14,24). Finally, a quantitative comparison between images acquired using a DSLR camera and CR and DR is required.