Absolute efficiency of rare earth oxysulphide screens in reflection mode observation

Giakoumakis, G. E.; Nomicos, C. D.; Yiakoumakis, E N; Evangelou, E. K.

doi:10.1088/0031-9155/35/7/015

Cited by 24 publications

(18 citation statements)

References 11 publications

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“…The phosphors were used in the form of thin layers (test screens) to simulate the intensifying screens employed in X-ray mammography. For the purposes of the present study, a 25 mg/cm 2 Lu 2 SiO 5 :Ce and a 33 mg/cm 2 Gd 2 O 2 S:Eu thick scintillating screens were prepared by sedimentation of the powder phosphors on fused silica substrates (spectrosil B) [11], [12].…”

Section: Methodsmentioning

confidence: 99%

A comparative investigation of Lu<inf>2</inf>SiO<inf>5</inf>:Ce and Gd<inf>2</inf>O<inf>2</inf>S:Eu phosphor scintillators for use in a medical imaging detectors

Michail

Stoppa

Toutountzis

et al. 2008

2008 IEEE International Workshop on Imaging Systems and Techniques

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The dominant powder scintillator in most medical imaging modalities for decades is Gd 2 O 2 S:Tb due to the very good intrinsic properties and overall efficiency. Except Gd 2 O 2 S:Tb there are alternative powder phosphor scintillators like Lu 2 SiO 5 :Ce and Gd 2 O 2 S:Eu that has been suggested for use in various medical imaging modalities. Gd 2 O 2 S:Eu emits red light and can be combined mainly with digital detectors like CCDs and wavelength selective detectors. Lu 2 SiO 5 :Ce emits blue light and can be combined with blue sensitivity films, photocathodes and some photodiodes. For the purpose of this study two Lu 2 SiO 5 :Ce and Gd 2 O 2 S:Eu powder phosphor scintillators with screen coating thicknesses of 25 and 33 mg/cm 2 respectively, were prepared by the method of sedimentation in our laboratory. The output efficiency of the phosphor screens were evaluated with respect to incident exposure rate and the spatial frequency dependent Modulation Transfer Function (MTF). Furthermore the spectral compatibility of those materials with various detectors was evaluated. Results were compared to published data for the commercially employed 'Kodak Min-R film-screen system', based on a 31.7 mg/cm 2 thick Gd 2 O 2 S:Tb phosphor. For Gd 2 O 2 S:Eu, MTF data were found comparable to those of Gd 2 O 2 S:Tb, while the MTF of Lu 2 SiO 5 :Ce was even higher. The different spectral compatibility of these phosphors could be interesting for application based on red and blue sensitive optical sensors respectively.

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Section: Methodsmentioning

confidence: 99%

A comparative investigation of Lu<inf>2</inf>SiO<inf>5</inf>:Ce and Gd<inf>2</inf>O<inf>2</inf>S:Eu phosphor scintillators for use in a medical imaging detectors

Michail

Stoppa

Toutountzis

et al. 2008

2008 IEEE International Workshop on Imaging Systems and Techniques

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“…The fluorescent light flux emitted during irradiation was recorded by an EMI 9558 QB photomultiplier connected to a Cary 401 electrometer. The emitted light flux was measured at both sides of the screen, the irradiated front side and the non-irradiated rear side, in order to simulate light emission from both screens included in a radiographic cassette [2]. For determining the phosphor's light emission efficiency, X-ray exposure measurements were performed employing an appropriate for the X-ray energies used (40±120 kVp) PTW dosimeter (ionization chamber type no.…”

Section: Methodsmentioning

confidence: 99%

“…The X-ray exposure rate was converted to energy fluence rate using an appropriate conversion factor [5]. Details of the experimental setup are given elsewhere [2,4,6].…”

Section: Methodsmentioning

confidence: 99%

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Europium-activated phosphors for use in X-ray detectors of medical imaging systems

et al. 1998

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Three europium-activated phosphors Y2O2S:Eu, Y2O3:Eu, and YVO4:Eu emitting red light were studied to investigate their suitability for radiographic cassettes or digital imaging systems. Screens were prepared from phosphor powders with various coating thicknesses by sedimentation. To assess phosphor light producing efficiency in relation to patient dose, each screen was X-rayed using 40-120 kVp and the number of light photons emitted per X-ray incident was experimentally and theoretically evaluated. Additionally, the capability of the emitted light to sensitize films or to generate electrons in silicon photodiodes used in digital imaging systems was examined. Y2O2S:Eu screens were most efficient in light emission, and when combined with either red sensitive films or Si photodiodes, they were found superior to Y2O3:Eu or YVO4:Eu screens in film grain or electron signal generation. In many cases they were also found superior to terbium-activated phosphors. Provided that several problems related to industrial production (special dyes, reflective backing, crossover effects) are dealt with, those europium-activated screens could be employed in low-tube-voltage radiographic applications.

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“…Down conversion is a process in which absorption of a high energy X-ray photon yields the emission of numerous lower energy photons within the visible range [20][21][22][23][24]. The X-ray induced visible light emission spectral characteristics depend on the doping element in the lattice.…”

Section: Introductionmentioning

confidence: 99%

Novel applications of diagnostic X-rays in activating a clinical photodynamic drug: Photofrin II through X-ray induced visible luminescence from "rare-earth" formulated particles

Abliz

Collins

Bell

et al. 2011

Journal of X-Ray Science and Technology

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Introduction: In this communication we report on a novel non-invasive methodology in utilizing "soft" energy diagnostic X-rays to indirectly activate a photo-agent utilized in photodynamic therapy (PDT): Photofrin II (Photo II) through X-ray induced luminescence from Gadolinium Oxysulfide (20 micron dimension) particles doped with Terbium: Gd2O2S:Tb. Photodynamic agents such as Photo II utilized in PDT possess a remarkable property to become preferentially retained within the tumor's micro-environment. Upon the photo-agent's activation through (visible light) photon absorption, the agents exert their cellular cytotoxicity through type I and type II pathways through extensive generation of reactive oxygen species (ROS); namely, singlet oxygen 1 O2, superoxide anion O − 2 , and hydrogen peroxide H2O2, within the intra-tumoral environment. Unfortunately, due to shallow visible light penetration depth (∼ 2 mm to 5 mm) in tissues, the current PDT strategy has largely been restricted to the treatment of surface tumors, such as the melanomas. Additional invasive strategies through optical fibers are currently utilized in getting the visible light into the intended deep seated targets within the body for PDT.Methods: X-ray induced visible luminescence from Gd2O2S:Tb particles were spectroscopically characterized, and the potential in-vitro cellular cytotoxicity of Gd2O2S:Tb particles on human glioblastoma cells (due to 48 Hrs Gd2O2S:Tb particle exposure) was screened through the MTS cellular metabolic assay. In-vitro human glioblastoma cellular exposures in presence of Photo II with Gd2O2S:Tb particles were performed in the dark in sterile 96 well tissue culture plates, and the corresponding changes in the metabolic activities of the glioblastoma due to 15 minutes of (diagnostic energy) X-ray exposure was determined 48 Hrs after treatment through the MTS assay.Results: Severe suppression (> 90% relative to controls) in the cellular metabolic activity of human glioblastoma was measured due to the treatment of clinically relevant concentrations of 20 µg/ml Photo II, with Gd2O2S:Tb particles, and (120 kVp) diagnostic X-rays. Taken together, the in-vitro findings herein provide the basis for future studies in determining the safety and efficacy of this non-invasive X-ray induced luminescence strategy in activating photo-agent in deep seated tumors.

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Absolute efficiency of rare earth oxysulphide screens in reflection mode observation

Cited by 24 publications

References 11 publications

A comparative investigation of Lu<inf>2</inf>SiO<inf>5</inf>:Ce and Gd<inf>2</inf>O<inf>2</inf>S:Eu phosphor scintillators for use in a medical imaging detectors

A comparative investigation of Lu<inf>2</inf>SiO<inf>5</inf>:Ce and Gd<inf>2</inf>O<inf>2</inf>S:Eu phosphor scintillators for use in a medical imaging detectors

Europium-activated phosphors for use in X-ray detectors of medical imaging systems

Novel applications of diagnostic X-rays in activating a clinical photodynamic drug: Photofrin II through X-ray induced visible luminescence from "rare-earth" formulated particles

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