Ioannis Kandarakis

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Absolute efficiency and modulation transfer function of laboratory prepared La2O2S:Tb phosphor screens of various coating thickness were studied. Detailed experimental data on the variation of absolute efficiency with x-ray tube voltage up to 200 kVp and screen coating thickness in transmission and reflection observation mode are given. Data were compared(More)
Differential diagnosis of liver parenchyma disease and grading of the hepatic disease on ultrasound is a common radiological problem that influences patient management. The aim of this study was to apply image analysis methods on ultrasound images for discriminating liver cirrhosis from fatty liver infiltration and for grading hepatic disease, which is(More)
Dual energy methods can suppress the contrast between adipose and glandular tissues in the breast and therefore enhance the visibility of calcifications. In this study, a dual energy method based on analytical modeling was developed for the detection of minimum microcalcification thickness. To this aim, a modified radiographic X-ray unit was considered, in(More)
The intrinsic phosphor properties are of significant importance for the performance of phosphor screens used in medical imaging systems. In previous analytical-theoretical and Monte Carlo studies on granular phosphor materials, values of optical properties, and light interaction cross sections were found by fitting to experimental data. These values were(More)
PURPOSE To evaluate modulation transfer function (MTF) in single photon emission computed tomography (SPECT) systems using the line spread function (LSF) method and a novel flood source which can be easily fabricated with materials accessible in hospital facilities. METHODS A Tc-99m-based flood source (E(γ) = 140 keV) consisting of a radiopharmaceutical(More)
A theoretical model has been developed for calculating the detective quantum efficiency (DQE) of scintillators, by taking into account the internal structure of granular scintillators often used in medical imaging detectors. Scintillators were considered to consist of N elementary thin layers containing spherical scintillating grains of equal size. Grains(More)
The suitability off a Y2O3:Eu3+ scintillator for use in radiation detectors and medical image receptors was studied. Y2O3:Eu3+ was used in the form of laboratory prepared screens of different coating thicknesses. The x-ray luminescence efficiency of the screens was measured for tube voltages between 50-200 kVp and in both transmission and reflection modes(More)
ZnSCdS:Ag was evaluated as a radiographic image receptor and was compared with Gd2O2S:Tb and Y2O2S:Tb phosphors often used in radiography. The evaluation of a radiographic receptor was modelled as a three-step process: (i) determination of light output intensity as related to the input radiation dose, (ii) determination of visible light characteristics with(More)
The scintillator effective luminescence efficiency, which may be defined in terms of the scintillator's X-ray luminescence efficiency and the scintillator-photodetector spectral matching and geometrical configuration, was studied for various X-ray imaging applications. Four scintillator materials Gd2O2S:Tb, Y2O2S:Tb, ZnSCdS:Ag and CsI:Na were used to(More)
Non-invasive dual energy methods have been used extensively on osteoporosis diagnosis estimating parameters, such as, Bone Mineral Density (BMD) and Bone Mineral Content (BMC). In this study, an X-ray dual energy method (XRDE) was developed for the estimation of the bone Calcium-to-Phosphorous (Ca/P) mass ratio, as a bone quality index. The optimized(More)