Image quality evaluation of YVO4:Eu phosphor screens for use in x-ray medical imaging detectors

Kandarakis, I.; Cavouras, D.; Κανελλόπουλος, Ε.; Nomicos, C.; Panayiotakis, G.

doi:10.1016/s1350-4487(98)00058-4

Cited by 19 publications

(12 citation statements)

References 17 publications

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“…The consistency of our back-screen model with expected trends at normal incidence helps to suggest its validity. For example, in accord with experimental data in turbid phosphors, 20 we demonstrate that the backscreen has higher MTF than the front-screen. Because optical photons are predominately generated near the x-ray entrance surface of the phosphor, visible light exhibits less lateral spread before reaching the photocathode if the backscreen configuration is used.…”

Section: Comparison With Results In the Literaturesupporting

confidence: 88%

“…7 One shortcoming of DBT, however, is that it is more directly impacted by the resolution loss due to oblique incidence than DM. The maximum projection angle in DBT can be as large as 20 or 30 , and the angle of incidence at the edges of the detector is even higher if one takes into account the divergent x-ray beam geometry. While some DBT systems incorporate a rotating detector to counteract changes in obliquity, many systems employ a stationary detector.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of phosphor‐based detector design for oblique x‐ray incidence in digital breast tomosynthesis

Acciavatti

Maidment

2011

Medical Physics

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Purpose: In digital breast tomosynthesis (DBT), a volumetric reconstruction of the breast is generated from a limited range of x-ray projections. One trade-off of DBT is resolution loss in the projections due to non-normal (i.e., oblique) x-ray incidence. Although degradation in image quality due to oblique incidence has been studied using empirical data and Monte Carlo simulations, a theoretical treatment has been lacking. The purpose of this work is to extend Swank's calculations of the transfer functions of turbid granular phosphors to oblique incidence. The model is ultimately used as a tool for optimizing the design of DBT detectors. Methods: A quantum-limited system and 20 keV x-rays are considered. Under these assumptions, the modulation transfer function (MTF) and noise power spectra (NPS) are derived using the diffusion approximation to the Boltzmann equation to model optical scatter within the phosphor. This approach is applicable to a nonstructured scintillator such as gadolinium oxysulfide doped with terbium (Gd 2 O 2 S:Tb), which is commonly used in breast imaging and which can reasonably approximate other detector materials. The detective quantum efficiency (DQE) is then determined from the Nishikawa formulation, where it is written as the product of the x-ray quantum detection efficiency, the Swank factor, and the Lubberts fraction. Transfer functions are calculated for both front-and back-screen configurations, which differ by positioning the photocathode at the exit or entrance point of the x-ray beam, respectively. Results: In the front-screen configuration, MTF and DQE are found to have considerable angular dependence, while NPS is shown to vary minimally with projection angle. As expected, the high frequency MTF and DQE are degraded substantially at large angles. By contrast, all transfer functions for the back-screen configuration have the advantage of significantly less angular dependence. Using these models, we investigated the possibility for optimizing the design of DBT detectors. As an example optimization strategy, the phosphor thickness which maximizes the DQE at a fixed frequency is analyzed. This work demonstrates that the optimal phosphor thickness for the frontscreen is angularly dependent, shifting to lower thickness at higher angles. Conversely, the backscreen is not optimized by a single thickness but instead attains reasonably high DQE values over a large range of thicknesses. Although the back-screen configuration is not suited for current detectors using a glass substrate, it may prove to be preferred in future detectors using newly proposed plastic thin-film transistor (TFT) substrates. Conclusions: Using the diffusion approximation to the Boltzmann equation to model the spread of light in a scintillator, this paper develops an analytical model of MTF, NPS, and DQE for a phosphor irradiated obliquely. The model is set apart from other studies on oblique incidence in being derived from first principles. This work has applications in the optimization of DBT detector design.

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Section: Comparison With Results In the Literaturesupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Optimization of phosphor‐based detector design for oblique x‐ray incidence in digital breast tomosynthesis

Acciavatti

Maidment

2011

Medical Physics

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“…The energy transfers from 5 D 4 level of Tb 3+ to 5 D 1 level of Eu 3+ , then it will relax to the 5 D 0 level, and go to the ground state 7 F 2 by emitting a photon. When it reaches the stationary equilibrium state, there should be dn e dt Eu = −cn e + XIn g − XIn e + Kn e (8) where n e and n g are populations of excited and ground states of Eu 3+ ions, respectively. When this system reaches the stationary equilibrium state, (dn e /dt) Eu = 0.…”

Section: Luminescence Of Eu 3+ and Tb 3+ Co-activated Camoomentioning

confidence: 99%

“…It has good thermal stability and chemical stability, and it is also good host for luminescent materials under UV and X-ray excitation due to its luminescent center-MoO 4 tetrahedron unit. The Eu 3+ and Tb 3+ ions have been widely used in producing red and green color light-emitting phosphors, such as Y 2 O 2 S:Eu 3+ [7], YVO 4 :Eu 3+ [8], Y 2 SiO 5 :Tb 3+ [9], and Gd 2 O 2 S:Tb 3+ [10], etc. When Eu 3+ and Tb 3+ ions are codoped, they can modify the visible spectrum and there is obvious energy transfer from Tb 3+ to Eu 3+ in different matrices, such as porous silicon [11], or calcium tungstate [12], etc.…”

Section: Introductionmentioning

confidence: 99%

Preparation and luminescent properties of Eu3+ and Tb3+ ions in the host of CaMoO4

Zhang

Chen

Yang

et al. 2007

Materials Science and Engineering: B

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“…DQE, which is one of the parameters describing the signal-to-noise transfer properties of image detector, is used to evaluate the performance of imaging system [6]. Assuming that N x and Y follow the Poisson statistics, and Z x and C L have binomial probability distributions, DQE of the detector at zero frequency [7] becomes…”

Section: Calculation Of Photocurrent and Dqementioning

confidence: 99%

Comparative study of CWO and ZnSe(Te) scintillation detector on the performance of X-ray imaging system

Kwak

Cho

Kim

et al. 2005

Nuclear Instruments and Methods in Physics Research Section A:

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Image quality evaluation of YVO4:Eu phosphor screens for use in x-ray medical imaging detectors

Cited by 19 publications

References 17 publications

Optimization of phosphor‐based detector design for oblique x‐ray incidence in digital breast tomosynthesis

Optimization of phosphor‐based detector design for oblique x‐ray incidence in digital breast tomosynthesis

Preparation and luminescent properties of Eu3+ and Tb3+ ions in the host of CaMoO4

Comparative study of CWO and ZnSe(Te) scintillation detector on the performance of X-ray imaging system

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