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Research Activities

  

TECHNOLOGICAL EDUCATIONAL INSTITUTION (TEI) OF ATHENS

DEPARTMENT OF BIOMEDICAL ENGINEERING

LABORATORY OF RADIATION PHYSICS, MATERIALS TECHNOLOGY AND BIOMEDICAL IMAGING*

(Imaging Systems: Medical Instrumentation, Medical Physics)
Agiou Spyridonos, 12210-Aigaleo, Athens, Greece
Tel. +30210 5385387, +30210 5385303

*(Coordinator: Prof. Dr. Ioannis Kandarakis)
e-mail:mailto:kandarakis@teiath.gr

  

RESEARCH ACTIVITIES
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I. Evaluation of powder phosphors and single crystal scintillators for application in medical imaging detector

Powder phosphors and single crystal scintillators are experimentally and theoretically evaluated under x-ray and gamma-ray exposure conditions. The aim of this research is to estimate the suitability of new scintillator and phosphor materials for use in radiation detectors of medical imaging systems in various fields, e.g. in Digital Mammography and Digital Radiography (DR), in Conventional Radiography, in x-ray Computed Tomography (CT), in Single Photon Emission Computed Tomography (SPECT), in Positron Emission Tomography (PET), in Portal Imaging (Imaging in Radiation Therapy). Parameters related to light emission efficiency; optical properties and imaging performance (MTF, NPS, DQE) are evaluated by the following methods and techniques:   
  1. Powder phosphor screen preparation: phosphor screens of various thicknesses and from various phosphor materials are prepared by sedimentation techniques. Screen coating thickness range from approximately 10 up to 200. Various materials (Terbium activated rare earth materials, Europium activated phosphors, and Cerium activated scintillators and phosphors as well as Cesium iodide crystals) have been tested.

  2. Absolute luminescence efficiency measurements and calculations: The absolute luminescence efficiency (AE), (emitted light energy flux over incident exposure rate), is experimentally evaluated for powder phosphors and single crystal scintillators. Experiments are performed under Diagnostic Radiology and Nuclear Medicine conditions. Theoretical models, based on the Boltzmann diffusion equation, have been developed to describe radiation and light transport through phosphor/scintillator materials. The models are employed to perform AE calculations and to fit theoretical curves to experimental data. Fitting allows the determination of intrinsic physical parameters (intrinsic x-ray to light conversion efficiency, reciprocal light diffusion length etc)

  3. Light emission spectrum measurements: The spectrum of light emitted by x-ray and gamma-ray excited phosphors and scintillators is experimentally evaluated. Spectral compatibility to optical sensors, currently employed in medical imaging detectors, is estimated.

  4. Angular distribution of light emission: The angular distribution of light emitted by excited phosphors and scintillators is experimentally determined and used to assess the corresponding geometric light collection efficiency in various detector configurations

  5. Image quality measurements and calculations: The imaging performance of powder phosphor screens is evaluated by Modulation Transfer Function (MTF) and Noise Power Spectrum (NPS) measurements and theoretical calculations. Using experimental AE, MTF and NPS data, the Signal to Noise Ratio (SNR) and the Detective Quantum Efficiency (DQE) (signal to noise ratio transfer efficiency) of the screens are determined. In addition theoretical models have been developed to fit image quality experimental curves.

 

II. Monte Carlo Simulations

Monte Carlo techniques are applied to study x-ray and gamma-ray radiation as well as optical photon transport through scintillator materials employed in radiation detectors of medical imaging systems. Special laboratory-developed Monte Carlo codes are used to simulate the radiation-matter interactions, the optical photon interactions (light absorption and light scattering effects) under various imaging conditions (Mammography, general purpose Diagnostic Radiology, and Nuclear Medicine-single photon and positron emission). Light transport through phosphor (granular scintillator) mass is simulated by a Monte Carlo code based on Mie light scattering theory.

 

Monte Carlo simulation has allowed the determination of detector parameters (quantum detection efficiency, energy absorption efficiency, light transmission efficiency and overall luminescence efficiency) as functions of incident photon energy. In addition imaging characteristics such as MTF, Swank Factor and DQE are estimated. Up to now, various materials have been studied such as: Gd2O2S:Tb (GOS, GaDOX), YAlO3:Ce (YAP), Y3Al5O12:Ce (YAG), LuAlO3:Ce (LuAP), Gd2SiO5:Ce (GSO), Lu2SiO5:Ce (LSO) and (Lu,Y)2SiO5:Ce (LYSO:Ce).

GATE (Geant4 Application for Tomographic Emission) Monte Carlo code is also used to simulate clinical Positron Emission Tomography (PET) and Single Photon Emission Tomography (SPECT) systems. MCNP, GEANT4, EGS4 and DETEC2000 codes are also being under development for correlation purposes.

 

III. Simulation of a Computed Tomography Breast Imaging (CTBI) system

The aim of this project is to use analytical simulation methods to investigate the performance of a Computed Tomography Breast Imaging system. The effects of x-ray spectrum, detector material and reconstruction algorithm on image quality and on carcinoma and calcification detectability are investigated.

IV. Evaluation of Electronic Portal Imaging Devices (EPID)*

Electronic portal imaging devices (EPID) are used in Radiation Therapy for treatment field verification. EPID systems are evaluated using the PIPS-PRO portal imaging processing system consisting of a rectangular QC-3 phantom and corresponding software for image manipulation, feature extraction and registration. Portal images acquired during x-ray beam irradiation are imported into the PIPS-PRO system for analysis. Various imaging parameters (MTF, NPS, contrast) are estimated and image processing techniques are applied to improve portal image quality.
_____________________
*In collaboration “Iaso” Hospital, Dept. of Radiotherapy


V. Environmental Radioactivity

Radon and radon daughter measurements are conducted on a research basis. Both passive and active techniques are employed. Passive techniques involve the use of CR-39 SSNTD’s both in cup and bare geometry. Active techniques are based on the use of Alpha GUARD (Genitron L.td.) and EQF3023 (SARAD G.bm.) portable monitors. Suitable probes for performing water and soil gas measurements are available. Water radon and soil gas measurements are being correlated to seismic activities. Specific activity is held in the field of thermal spas by employing all measurement technologies. In addition, analytical modelling of radon and daughter kinetics in indoor spa environment is being attempted. Modelling on Monte Carlo basis is also planned. Moreover, measurements of environmental gamma radiation can be performed. In all cases, dosimetry models are applied and risk analysis is being performed. There is also a tendency on measuring ELM fields.

VI. Image processing and analysis methods in Ultrasound images*

The aim of the project is the design and implementation of a computer aided system that integrates various image processing and analysis methods. Regarding image processing methods in ultrasound images, several wavelet based approaches will be implemented in order to reduce the presence of speckle in the US image and to segment the region of interest (ROI). Consequently, a range of textural and multi-scale features are going to be used as input into pattern recognition algorithms such as Support Vector Machines and Probabilistic Neural Networks in order to classify the ROI.
_____________________
*In collaboration with: 1.Medical Image and Signal Processing Laboratory, Dept. of Medical Instruments Technology, 2. Dept of Medical Physics, University of Patras, 3. Dept. of Medical Imaging, “Euromedica” Medical Center

VII. Scintimammography

The group is interested in using a dedicated gamma camera based on a PSPMTs for breast studies. Currently we asses the performance of a R3292 PSPMT camera using phantoms. In addition we simulate breast studies and optimize acquisition parameters.


VIII. Development of Dedicated Imaging Systems

The group works on the development of prototype systems for SPECT imaging in collaboration with international groups. We are specialized in detector components evaluation using phantoms. Recently we have extended our activities towards PET systems.

IX. Small Animal Imaging

A mouse sized camera has been built in collaboration with Jefferson Lab and it is now being used in radiopharmaceutical studies in small mice in collaboration with National Radiopharmacological laboratories. Our group provides technical assistance for animal imaging, data processing and analysis as well as detector optimization. Currently a rotating gantry is being purchased in order to upgrade this camera to SPECT mode. The future goal is the use of two opposite heads for developing a mini-PET system and finally work towards a(S)PECT/CT detector.


X. Evaluation of Electronic Portal Imaging Devices (EPID)*

Electronic portal imaging devices (EPID) are used in Radiation Therapy for treatment field verification. EPID systems are evaluated using the PIPS-PRO portal imaging processing system consisting of a rectangular QC-3 phantom and corresponding software for image manipulation, feature extraction and registration. Portal images acquired during x-ray beam irradiation are imported into the PIPS-PRO system for analysis. Various imaging parameters (MTF, NPS, contrast) are estimated and image processing techniques are applied to improve portal image quality.
_____________________
*In collaboration “Iaso” Hospital, Dept. of Radiotherapy


XI. Magnetic resonance spectroscopy (MRS) and magnetic resonance spectroscopic imaging (MRSI)*

Aim of the current project is the parameter analysis, protocol optimization and clinical application of MRS and MRSI procedures in prostate, brain and skeletal muscle tissue diagnosis. More specifically various acquisition parameters and their effect in spectrum quality are investigated. A series of experiments are conducted, using phantoms, to assess the quality of various spectroscopy and spectroscopic imaging techniques. The effectiveness of the available water and lipid suppression techniques and their compatibility with other parameters is also investigated.
_____________________
*Participation in the research program, entitled: “Combination of magnetic resonance spectroscopy and spectroscopic imaging in molecular imaging of prostate cancer” (scientific co-ordinator Assoc. Professor. Nikolaos Kelekis, 2nd Department of Radiology (Medical School, University of Athens, General University hospital Attikon (17/1/2005 – 30/1/2006).
-Collaboration with the 251 General Air Force Hospital (Athens).

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Members of the Research Group and Collaborators

1. I. Kandarakis, Professor. Department of Medical Instruments Technology, Laboratory of Radiation Physics, Materials Technology and Biomedical Imaging, TEI of Athens

2. D. Cavouras, Professor. Department of Medical Instruments Technology, Medical Image and Signal Processing Laboratory, TEI of Athens

3. G. Panayiotakis, Professor. Department of Medical Physics, University of Patras.

4. C. Nomicos, Professsor. Department of Electronics, TEI of Athens

5. D. Nikolopoulos, Laboratory collaborator. Department of Medical Instruments Technology, Ionizing Radiations Laboratory, TEI of Athens

6.G. Saatsakis,Laboratory collaborator. Department of Medical Instruments Technology, Ionizing Radiations Laboratory, TEI of Athens

7. N. Kalivas, Laboratory collaborator. Department of Medical Instruments Technology, Ionizing Radiations Laboratory, TEI of Athens.

8. I. Valais, Assistant Professor. Department of Medical Instruments Technology, TEI of Athens

9. A. Gaitanis, Institute of Biomedical Research of the Academy of Athens and Dept. of Medical Instruments Technology, TEI of Athens

10. S.Tsantis, Laboratory collaborator. Department of Medical Instruments Technology, Ionizing Radiations Laboratory, TEI of Athens.

11. I. Sianoudis, Professor. Department of Physics, Chemistry and Materials Technology, TEI of Athens

12. K. Kourkoutas, Professor, Department of Physics, Chemistry and Materials Technology, TEI of Athens

13. N. Dimitropoulos, Medical Doctor, Dept. of Medical Imaging, “Euromedica” Medical Center, Athens

14. Ι. Kalantzis, Laboratory collaborator. Medical Image and Signal Processing Laboratory, TEI of Athens

15. A. Louizi, Associate Professor. Dept. of Medical Physics, University of Athens

16. G. Loudos, Institute of Biomedical Research of the Academy of Athens

17. S. Nikoletopoulos, Department of Medical Physics, “Iaso” Hospital, Athens

18. F. Stromatia, Department of Medical Physics, “Iaso General” Hospital, Athens

19. P. Liaparinos, Doctorate student, (in collaboration with the University of Patras)

20. K. Koutsofios, Doctorate student, (in collaboration with the University of Patras)

21. S. David, Doctorate student, (in collaboration with the University of Patras)

22. C. Michail, Doctorate student, (in collaboration with the University of Patras

23. A. Konstantinidis, postgraduate student (in collaboration with the University of Patras)

24. V. Spyropoulou, postgraduate student (in collaboration with the University of Patras)

25. A. Karatopis, postgraduate student (in collaboration with the University of Patras)

26. N.Efthimiou, postgraduate student (in collaboration with the University of Patras)

27. A. Toutoutzis, postgraduate student (in collaboration with the University of Patras)

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Scientific Publications in International Journals

2006 , 2005 , 2004 , 2003 , 2002 , before 2002

2006

  1. I. Kandarakis, Cavouras, D., Nikolopoulos D., Kalivas N., Episkopakis A., Liaparinos P.,Kagadis G.,Sianoudis I., Kourkoutas K., Nomicos C., Panayiotakis G. Theoretical model for evaluation of the angular distribution of the lumenescence emission in granular scintillating screens. AppliedRadiationandIsotopes (corrected proof), 2006
  2. Nikolopoulos D., Valais, I. Kandarakis I., Cavouras D., Linardatos D., Sianoudis I. Louizi A., Nomicos C. D. Vattis, Panayiotakis G. Evaluation of the GSO: Ce scintillator in the energy range from 40 to 140 kV for possible applications in medical imaging. Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment), Α 560, 577-583. 2006
  3. G. Patatoukas, A. Gaitanis, N. Kalivas, A. Konstandinidis, D. Nikolopoulos, I. Kandarakis, D. Cavouras, J. Sianoudis, N.Dimitropoulos, G. Panayiotakis. The effect of energy weighting on SNR under the influence of non-ideal detectors in mammographic applications.  Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment) (in print ), 2006
  4. N. Karakatsanis, N.Sakellios, X. Tsantilas, N. Dikaios, C. Tsoumpas, K. Nikita, D. Lazaro, G.Loudos, A. Louizi, I. Valais, D. Nikolopoulos, J. Malamitsi, I. Kandarakis. A Comparative Evaluation of two commercial Positron Emission Tomography (PET) Scanners using GATE. Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment) (accepted ), 2006
  5. Kalivas N., Valais I., Nikolopoulos D., Loudos G., Nikita K., Giokaris N., Cavouras D.,.. Panayiotakis G., I. Kandarakis. Imaging performance of cerium-doped yttrium aluminum perovskite (YAP: Ce) powder scintillating screens under x-ray excitation. Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment) (accepted ), 2006
  6. Liaparinos P., Kandarakis I., Cavouras D., Dellis H., Panayiotakis G. Investigating the effect of K-fluorescence characteristic radiation on the performance of nuclear medicine scintillators by Monte Carlo methods. Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment) (accepted ), 2006
  7. Nikolopoulos D., Kandarakis I., Tsantilas X., Valais I., Cavouras D., Louisi A. Comparative evaluation of the radiation detection efficiency of LSO, LuAP, GSO and GSO scintillators for application in positron emission (PET) imaging via Monte Carlo methods. Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment) (accepted-uncorrected proof ), 2006
  8. Liaparinos P., Kandarakis I., Cavouras D., Dellis H., Panayiotakis G. Evaluating the radiation detection of RbGd2Br7:Ce scintillator by Monte Carlo methods. Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment) (accepted revision), 2006
  9. Valais I., Kandarakis I., Nikolopoulos D……., N. Dimitropoulos, Cavouras D., Panayiotakis G. Evaluating the light emission efficiency of the LYSO: Ce scintillator under x-ray excitation for possible applications in medical imaging. Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment) (accepted under revision), 2006
  10. Nikolopoulos D., Kandarakis I., Cavouras D., et al. Investigation of the radiation absorption and x-ray fluorescence properties of medical imaging scintillators by Monte Carlo methods. Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment) (accepted corrected proof), 2006
  11. Gonias P., Bertsekas N., Saatsakis G., Nikolopoulos D.,….Kandarakis I.,  Panayiotakis G.: Validation of a GATE model for the simulation of the Siemens PET Biograph 6 scanner.  Nuclear Instruments and Methods in Physics Research A (Accelerators, Spectrometers, Detectors and associated Equipment) (accepted), 2006
  12. Valais I., Kandarakis I., Nikolopoulos D., Michail C., David S., Cavouras D., Panayiotakis G. Luminescence properties of (Lu, Y)2SiO5:Ce and Gd2SiO5:Ce single crystal scintilla;ators under x-ray excitation for use in medical imaging systems. IEEE Transactions on Nuclear Science (accepted for publication), 2006
  13. Efthimiou N., Kalivas N., Patatoukas G., Konstantinidis A., Valais I., Nikolopoulos D., Loudos G.,..Cavouras D. Panayiotakis G., Kandarakis I.: Investigation of the effect of the scintillator material on the overall x-ray detection system performance by application of analytical models. Nuclear Instruments and Methods in Physics Research A (accepted for publication). 2006
  14. Valais I., Nikolopoulos D.,  Kalivas N., Gaitanis A., Loudos G., Sianoudis i., Giokaris N., Cavouras D.,  Dimitropoulos N., Nomicos C., Kandarakis I., Panayiotakis G.: A systematic study of the performance of CsI:Tl single-crystal scintillator under x-ray excitation. Nuclear Instruments and Methods in Physics Research (accepted for publication). 2006
  15. Karatopis A., Benekos O., Efstathopoulos E., Valais I., Kandarakis I., Kelekis N.: Molecular imaging through 1H MRS and MRSI in every day routine: improvements in various clinical applications and parameter optimization of spectroscopic imaging sequences. Nuclear Instruments and Methods in Physics Research A (accepted for publication). 2006
  16. David S., Michail C., Valais I.,…. D. Cavouras D., Kandarakis I., Panagiotakis G. Efficiency of Lu2SiO5:Ce (LSO) powder phosphor under x-ray excitation for mammographic applications.Nuclear Instruments and Methods in Physics Research A (accepted for publication). 2006
  17. D. Nikolopoulos, I. Kandarakis, D. Cavouras, I.Valais, D. Linardatos, C. Michail, S. David, A. Gaitanis, C. Nomicos, A. Louizi, "Investigation of radiation absorption and X-ray fluorescence properties of medical imaging scintillators by Monte Carlo methods" Nucl. Instrum. Methods Phys. Res. A 565, 821-832, 2006
  18. C. Michail, S. David, P. Liaparinos, I. Valais, D. Nikolopoulos, N. Kalivas, A. Toutountzis, I. Sianoudis, D. Cavouras, N. Dimitropoulos, C. D. Nomicos, K. Kourkoutas, I. Kandarakis, G. S. Panayiotakis. “Evaluation of the imaging performance of LSO powder scintillator for use in x-ray mammography”, Nucl. Instrum. Meth. A, accepted.
  19. I. Valais, S. David, C. Michail, D. Nikolopoulos, P. Liaparinos, D. Cavouras, I. Kandarakis and G. S. Panayiotakis. “Comparative study of luminescence properties of LuYAP:Ce and LYSO:Ce single crystal scintillators for use in medical imaging”, Nucl. Instrum. Meth. A, accepted.
  20. D. Nikolopoulos, D. Linardatos, P. Gonias, N. Bertsekas, C. Michail , S. David, D. Cavouras and I. Kandarakis, "MONTE CARLO VALIDATION IN THE DIAGNOSTIC RADIOLOGY RANGE", Nucl. Instrum. Meth. A, accepted.
  21. N. Efthimiou, N. Kalivas, G. Patatoukas, I. Valais, D. Nikolopoulos, A. Gaitanis, A. Konstaninidis, S. David, C. Michail, G., G.Loudos, D. Cavouras, K. Kourkoutas, G.S. Panayiotakis and I. Kandarakis. " Investigation of the effect of the scintillator material on the overall X-ray detection system performance by application of analytical models", Nucl. Instrum. Meth. A, accepted.
  22. I. Kandarakis, D. Cavouras, D. Nikolopoulos, A. Episkopakis, N. Kalivas, P. Liaparinos, I. Valais, G. Kagadis, K. Kourkoutas, I. Sianoudis, N. Dimitropoulos, C. Nomicos, G. Panayiotakis. ‘A theroretical model evaluating the angular distribution of luminescence emission in X-ray scintillating screens’, Applied Radiation and Isotopes, 64, 508-519 (2006).
  23. G. Patatoukas, N. Kalivas, P. Liaparinos, A. Konstantinidis, I. Kandarakis, G. Panayiotakis. “The effect of non-ideal detectors on energy weighted spectra used in x-ray medical imaging”, Nucl. Instrum. Meth. A, 569, 260-263, (2006).
    P. Liaparinos, I. Kandarakis, D. Cavouras, N. Kalivas, H. Delis, G. Panayiotakis. “Evaluation of high packing density powder x-ray screens by Monte Carlo methods”, Nucl. Instrum. Meth. A , accepted.
  24. C. Michail, S. David, P. Liaparinos, I. Valais, D. Nikolopoulos, N. Kalivas, A. Toutountzis, I. Sianoudis, D. Cavouras, N. Dimitropoulos, C. D. Nomicos, K. Kourkoutas, I. Kandarakis, G. S. Panayiotakis. “Evaluation of the imaging performance of LSO powder scintillator for use in x-ray mammography”, Nucl. Instrum. Meth. A, accepted.
    I. Valais, S. David, C. Michail, D. Nikolopoulos, P. Liaparinos, D. Cavouras, I. Kandarakis and G. S. Panayiotakis. “Comparative study of luminescence properties of LuYAP:Ce and LYSO:Ce single crystal scintillators for use in medical imaging”, Nucl. Instrum. Meth. A, accepted.
  25. P. Gonias, N. Bertsekas, G. Saatsakis, D. Nikolopoulos, X. Tsantilas, G. Loudos, N. Sakellios, N. Karakatsanis, A. Gaitanis, L. Papaspyrou, A. Daskalakis, P. Liaparinos, D. Cavouras, I. Kandarakis and G.S. Panayiotakis. « VALIDATION OF A GATE MODEL FOR THE SIMULATION OF THE SIEMENS PET/CT BIOGRAPH™ 6 SCANNER » International Conference « Euromedim 2006, 1st European Conference on Molecular Imaging Technology, Marseille, France, 2006
  26. P. Gonias, N. Bertsekas, G. Saatsakis, D. Nikolopoulos, X. Tsantilas, G. Loudos, N. Sakellios, N. Karakatsanis, A. Gaitanis, L. Papaspyrou, A. Daskalakis, P. Liaparinos, D.Cavouras, I. Kandarakis and G.S. Panayiotakis. « VALIDATION OF A GATE MODEL FOR THE SIMULATION OF THE SIEMENS PET/CT BIOGRAPH™ 6 SCANNER » International Conference « Euromedim 2006, 1st European Conference on Molecular Imaging Technology, Marseille, France 2006
  27. P. Gonias, N. Bertsekas, N. Karakatsanis, G. Saatsakis, D. Nikolopoulos, G. Loudos, N. Sakellios, X. Tsantilas, A. Gaitanis, L. Papaspyrou, A. Daskalakis, P. Liaparinos, A. Louizi, D. Cavouras, G.S. Panayiotakis and I. Kandarakis. « VALIDATION OF A MONTE CARLO MODEL FOR THE SIMULATION OF THE SIEMENS PET/CT BIOGRAPH™ 6 SCANNER USING GATE.»International Conference « Eanm ’06 – Annual Congress Of The European Association of Nuclear Medicine, 2006

2005

  1. Kandarakis I., Cavouras D., Nikolopoulos D., Anastasiou A., Ventouras E., Kalatzis I., Dimitropoulos N., Kalivas N., Panayiotakis G.: “Evaluation of ZnS: Cu phosphor as x-ray to light converter under mammographic conditions”. Radiation Measurements, 39: 263-267, 2005
  2. D. Cavouras, I. Kandarakis, D. Nikolopoulos, I.Kalatzis, A. Episkopakis, G. Kagadis, N. Kalivas, D. Linardatos, M. Roussou, E. Nirgianaki, D. Margetis, I. Valais, I. Sianoudis, K. Kourkoutas, N. Dimitropoulos, A. Louizi, C. Nomicos, G. Panayiotakis.: Light emission efficiency and imaging performance of Y2Al5O12: Ce (YAG: Ce) powder screens under diagnostic radiology conditions. Applied Physics B (Lasers and Optics). 80: 923-933, 2005.

2003

  1. Kandarakis I., Cavouras D., Ventouras E., Nomicos CD. Theoretical evaluation of granular scintillators quantum gain incorporating the effect of K-fluorescence emission into the energy range from 25 to 100 keV. Radiation Physics and Chemistry , 66: 257-267, 2003

2002

  1. Cavouras D., Kandarakis I., Panayiotakis G., Nomicos C.D. Integrated model for estimating phosphor signal and noise transfer characteristics on medical images: application to CdPO3Cl:Mn phsphor screens. Medical and Biological Engineering and Computing. 40, 2002.
  2.  Kalivas N., Costaridou L., Kandarakis I., Cavouras D., Nomicos C.D., and Panayiotakis G.S., “Modelling quantum and structure noise of phosphors used in medical x-ray imaging detectors” Nuclear Instruments and Methods in Physics Research, A (Accelarators, Spectrometers, Detectors and Associated Equipment), 490: 614-629, 2002 

Before 2002

  1. Kandarakis Ι., Cavouras D., Panayiotakis G.S., Agelis T., Nomicos C.D., and  Giakoumakis G. "X-ray induced luminescence and spatial resolution of La2O2S:Tb phosphor screens". Physics in Medicine and Biology.41: 297-307, 1996.
  2. Panayiotakis G.S., Cavouras D., Kandarakis I., Nomicos C.D. “A study of X-ray luminescence and spectral compatibility of europium-activated yttrium-vanadate (YVO4:Eu) screens for medical imaging applications.” Applied Physics. A (Materials Science and Processing) 62, 483-486, 1996.
  3. Cavouras D., Kandarakis I., Panayiotakis G.S., Evangelou E., and Nomicos C.D. “An evaluation of theY2O3: Eu3+ scintillator for application in medical X-ray detectors and image receptors”. Medical Physics 23 (12), 1965-1975,1996.
  4. Kandarakis I., Cavouras D., Panayiotakis G,S., and Nomicos C.D. “Evaluating x-ray detectors for radiographic applications: Comparison of ZnSCdS:Ag with Gd2O2S:Tb and Y2O2S:Tb screens”. Physics in Medicine and Biology, 42, 1351-1373, 1997.
  5. Kandarakis I., Cavouras D., Panayiotakis G.S., Triantis D., and Nomicos C.D. “An experimental method for the determination of spatial frequency dependent detective quantum efficiency (DQE) of scintillators used in x-ray imaging detectors”. Nuclear Instruments and Methods in Physics Research A., (Accelerators, Spectrometers, Detectors and Associated Equipment) 399, 335-342,1997.
  6. Kandarakis I., Cavouras D., Panayiotakis G.S., Triantis D., and Nomicos C.D. “Europium activated phosphors for use in x-ray detectors of medical imaging systems”. European Radiology , 8, 313-318, 1997.
  7. Cavouras D., Kandarakis I., Panayiotakis G.S., Kanellopoulos E., Triantis D., and Nomicos C.D. “An investigation of the imaging characteristics of the Y2O2S:Eu phosphor for application in x-ray detectors of digital mammography”. Applied Radiation and Isotopes, 49, 931-937, 1998.
  8. Cavouras D., Kandarakis I., Panayiotakis G.S., Bakas A., Triantis D., and Nomicos C.D. “An experimental method to determine the effective efficiency of scintillator-photodetector combinations used in x-ray medical imaging systems”. British Journal of Radiology, 71, 766-772, 1998.
  9. Kandarakis I., Cavouras D., Kanellopoulos E., Nomicos C.D., and Panayiotakis G.S..    “Image quality evaluation of YVO4: Eu phosphor screens for use in x-ray medical imaging detectors”. Radiation Measurements, 29:481-486, 1998.
  10. Kandarakis I., Cavouras D., Kanellopoulos E., Panayiotakis G.S., and Nomicos C.D. “Experimental determination of detector gain, zero frequency detective quantum efficiency, and spectral compatibility of phosphor screens: comparison of CsI: Na and Gd2O2S:Tb for medical imaging applications”. Nuclear Instruments and Methods in Physics Research, A, (Accelerators, Spectrometers, Detectors and Associated Equipment) 417: 86-94, 1998.
  11. Cavouras D., Kandarakis I., Prassopoulos P., Kanellopoulos E., Nomicos C.D., and   Panayiotakis G.S. “Experimental evaluation of noise equivalent passband, information capacity, and informational efficiency of yttrium based europium activated phosphors for use in x-ray imaging detectors”. Physica Medica 14:119-126, 1998.
  12. Kandarakis I., Cavouras D., Prassopoulos P., Kanellopoulos E., Nomicos C.D., and   Panayiotakis G.S. “Evaluating Zn2SiO4:Mn phosphor for use in medical imaging radiation detectors”. Applied Physics, A (Materials Science and Processing), 67:521-525, 1998.
  13. Kandarakis I., Cavouras D., Kanellopoulos E., Nomicos C.D., and Panayiotakis G.S. “A method for information capacity determination of x-ray scintillators used in medical imaging detectors”. Medical and Biological Engineering and Computing, 37:25-30, 1999.
  14. Cavouras D., Kandarakis I., Prassopoulos P., Kanellopoulos E., Nomicos C.D., and   Panayiotakis G.S. “A method to evaluate the performance of x-ray imaging scintillators by means of the brightness-sharpness index (BSI).” Acta Radiologica, 40: 211-216, 1999.
  15. Cavouras D., Kandarakis I., Prassopoulos P., Kanellopoulos E., Nomicos C.D., and   Panayiotakis G.S.“Evaluating phosphors for use in x-ray image detectors by the effective performance index (EPI) method: application to Eu3+ activated yttrium based materials.” Technology and Health Care, 7: 53-61, 1999.
  16. Kandarakis I., Cavouras D., Prassopoulos P., Kanellopoulos E., Nomicos C.D., and   Panayiotakis G.S. “Evaluating scintillators used in radiation detectors of medical imaging systems by the effective fidelity index (EFI) method.” European Journal of Radiology. 30:  61-66, 1999.
  17. Cavouras D., Kandarakis I., Kanellopoulos E., Nomicos C.D., and  Panayiotakis G.S. “Signal to Noise Ratio (SNR) of x-ray imaging scintillators determined by luminescence measurements.” Applied Radiation and Isotopes, 51: 59-68, 1999.
  18. Kandarakis I., Cavouras D., Nomicos C.D., and Panayiotakis G.S.“Phosphor material evaluation for use in medical imaging radiation detectors by the Noise Equivalent Quanta (NEQ) method”. Applied Physics B (Lasers and Optics), 68: 1121-1124, 1999.
  19. Kalivas N., Kandarakis I., Cavouras D., Costaridou L., Nomicos C.D., and Panayiotakis G.S., “Modeling quantum noise transfer function (QNTF) of phosphors used in medical x-ray imaging detectors” Nuclear Instruments and Methods in Physics Research, A (Accelarators, Spectrometers, Detectors and Associated Equipment), 430: 559-569, 1999.
  20. Kandarakis I., Cavouras D., Kalivas N., Nomicos C.D., and Panayiotakis G.S. “Estimation of the information content of medical images produced by scintillators interacting with diagnostic x-ray beams”. Nuclear Instruments and Methods in Physics Research, B. (Beam Interactions with Materials and Atoms), 155:199-205, 1999.
  21. Kalivas N., Costaridou L., Kandarakis I., Cavouras D., Nomicos C.D., Panayiotakis G.S. “ Effect of intrinsic-gain fluctuations on quantum noise of phosphor materials used in medical X-ray imaging” Applied Physics A (Materials Science and Processing), 69: 337-341, 1999.
  22. Cavouras D., Kandarakis I., Nomicos C.D., Panayiotakis G.S., and Fezoulidis I. “ Assessing the information content of phosphor produced medical images: application to Zn2SiO4:Mn phosphor”. Applied Radiation and Isotopes, 52: 119-126, 2000.
  23. Cavouras D., Kandarakis I., Nomicos C.D., Bakas A., and Panayiotakis G.S. “Performance evaluation of (Gd,La)2O2:Tb phosphor for medical imaging applications under x-ray excitation’’. Radiation Measurements, 32: 5-13, 2000.
  24. Cavouras D., Kandarakis I., Maris T., Panayiotakis G.S., and Nomicos C.D. “Assessment of the gain transfer function (GTF) of phosphors for application in medical imaging radiation detectors.” European Journal of Radiology 35:70-77, 2000.
  25. Cavouras D., Kandarakis I., Maris T., Panayiotakis G.S., and Nomicos C.D. “Entropy as a measure of the performance of phosphors used in medical imaging radiation detectors”  Applied Physics A.(Materials Science and Processing), 72: 67-72, 2000
  26. Kandarakis I. and Cavouras D.: ‘’Experimental and theoretical assessment of the performance of Gd2O2S: Tb and La2O2S: Τb phosphors and Gd2O2S:Τb–La2O2S:Τb mixtures for X-ray imaging. European Radiology. 11: 1083-1091, 2001.
  27. Kandarakis I. and Cavouras D.: “ Modeling the effect of light generation and light attenuation on the performance of phosphors used in medical imaging radiation detectors”. Nuclear Instruments and Methods in Physics Research, A. (Accelerators, Spectrometers, Detectors and Associated Equipment), 460: 412-423, 2001.
  28. Kandarakis I. and Cavouras D.: “Role of the activator on the performance of scintillators used in x-ray imaging. Applied Radiation and Isotopes, 54: 821-831, 2001.
  29. Kandarakis I., Cavouras D., Nomicos C.D., and Panayiotakis G.S.  Measurement of the X-ray luminescence and spectral compatibility of the CdPO3Cl: Mn phosphor. Radiation Measurements, 33: 217-225, 2001
  30. Kandarakis I., Cavouras D., Panayiotakis G.S, Nomicos C.D.Experimental investigation of the optical signal, gain, signal to noise ratio and information content of x-ray phosphor screens. Applied Physics B (Lasers and Optics),  72: 887-883, 2001
  31. Kandarakis I., Cavouras D., Nomicos CD.,and Panayiotakis G.S. X-ray luminescence of ZnSCdS: Au,Cu scintillator. Nuclear Instruments and Methods in Physics Research,B (Beam Interactions with Materials and Atoms), 179, 215-224. 2001.
  32. Cavouras D., Kandarakis I., Tsoukos S., Kateris A., Nomicos C.D., Panayiotakis G.S. Theoretical model for calculation of the detective quantum efficiency of granular scintillators. Applied Radiation and Isotopes. 55, 831-842, 2001

Articles in journal supplements and in international publications, book series

  1. Kandarakis I., Cavouras D., Panayiotakis G.S., and Nomicos C.D. “Comparative Evaluation of Signal and Noise Transfer Characteristics (MTF, DQE) of Y2O2S:Tb and Y2O2S:Eu Medical Image Receptors.” Medical & Biological Engineering and Computing, 34 (Suppl. 1), 225-226, 1996.
  2. Cavouras D., Kandarakis I., Panayiotakis G.S., and Nomicos C.D. “X-ray detection and Optical Signal Properties of Gd2O2S:Tb, La2O2S:Tb, and ZnSCdS:Ag Phosphors for Use in Digital Mammography.” Medical & Biological Engineering and Computing, 34 (Suppl. 1), 223-224, 1996.
  3. Cavouras D., Kandarakis I., Panayiotakis G.S.,. "Enhancement of static and motion blurred images by an inverse digital filtering method." Computers in Cardiology.  IEEE-Computer Society.  14, 287-290,1987.
  4. Kandarakis I, Cavouras D, Koutsourakis K, Triantis D, Bakas A, Panayiotakis G.S, Nomicos C.D. “ A model for image formation and image quality prediction in Diagnostic Radiology”. Studies in Health Technology and Informatics, (Medical Informatics Europe-MIE), 43, Pt B;  517-521, 1997.
  5. Cavouras D., Kandarakis I., Theotokas I., Kanellopoulos E., Triantis D., Behrakis I.,  Manesis E.K., Vafiadi-Zoumpouli I., Zoumpoulis P. “Computer image analysis of ultrasound images for discriminating and grading parenchymal liver disease employing a hierarchical decision tree scheme and the multilayer perceptron neural network classifier”. Studies in Health Technology and Informatics (Medical Informatics Europe-MIE), 43, Pt B; 522-526, 1997.
  6. Kandarakis I. Nikolopolos D., Cavouras D., Liaparinos P.,Episkopakis,…, Panayiotakis G . Angular Distribution of light emitted by fluorescent screens excited by x-rays. Α. Mendez-Vilas (Editor): Recentadvancesinmultidisciplinaryappliedphysics. Elsevier, 2005. pages 600. ISBN: 0-08-044648-5

Recent publications in scintimammography, small animal imaging, dedicated imaging systems and GATE by G. Loudos et al

  1. G.K. Loudos, K.S. Nikita, N.K. Uzunoglu, N.D. Giokaris, C.N.Papanicolas, S.C. Archimandritis, A.D. Varvarigou, D. Maintas, “Improving Spatial Resolution in SPECT with the Combination of PSPMT Based Detector and Iterative Reconstruction Algorithms” Computerized Medical Imaging and Graphics, Volume 27, Issue 4, July-August 2003, Pages 307-313.
  2. D Lazaro, I Buvat, G Loudos, D Strul, G Santin, N Giokaris, D Donnarieix, L Maigne, V Spanoudaki, S Styliaris, S Staelens and V Breton “Validation of the GATE Monte Carlo simulation platform for modelling a CsI(Tl) scintillation camera dedicated to small-animal imaging”.Phys. Med. Biol. 49 2004, 271-285.
  3. N. Giokaris, G. Loudos, D. Maintas, A. Karabarbounis, M. Lembesi, V. Spanoudaki, E. Stiliaris, S. Boukis, A.Gektin, A. Boyarintsev, V. Pedash, V. Gayshan, "Partially slotted crystals for a high-resolution γ-camera based on a position sensitive photomultiplier", submitted for publication in Nuclear Instruments and Methods in Physics Research Section A, (2005).
  4. G. K.Loudos, K.S. Nikita, N.D. Giokaris, E. Styliaris, S.C. Archimandritis, A. D. Varvarigou, C.N.Papanicolas, S. Majewski, D. Weisenberger, R. Pani, F. Scopinaro, N.K. Uzunoglu, D. Maintas, K. Stefanis, “A 3D High Resolution gamma-camera for Radiopharmaceutical Studies with Small Animals”Applied Radiation and Isotopes, Volume 58, Issue 4, April 2003, Pages 501-508.
  5. N. D. Giokaris, G. K. Loudos, D. Maintas, D. Papapanagiotou, K. S. Nikita, N.K. Uzunoglu, A. Karabarbounis, C.N. Papanicolas, E. Stiliaris, S. C. Archimandritis, A. D. Varvarigou, C.N. Stefanis, S. Majewski, R. Pani, F. Scopinaro, “Imaging Of Breast Phantoms Using A High Resolution Position Sensitive Photomultiplier Tube”Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 497, Issue 1, pp. 141-149, 21 January 2003.

Recent publications in Ultrasonic Imaging by S. Tsantis et al

  1. Development of a support vector machine-based image analysis system for assessing the thyroid nodule malignancy risk on ultrasound. S. Tsantis, D. Cavouras, I. Kalatzis, N. Piliouras, N. Dimitropoulos, and G. Nikiforidis. Ultrasound in Medicine and Biology, Vol. 31, No. 11, pp. 1451–1459, 2005.
  2. Inter-Scale Wavelet Analysis for Speckle Reduction in Thyroid Ultrasound Images. S. Tsantis, N. Dimitropoulos, M. Ioannidou, D. Cavouras and G. Nikiforidis. Accepted for publication in computerized medical imaging and graphics
  3. A Hybrid Multi-Scale Model for Thyroid Nodule boundary detection on Ultrasound Images. S. Tsantis, N. Dimitropoulos, D. Cavouras and G. Nikiforidis. Computers Methods and Programs in Biomedicine, Vol 84, pp. 86-98, 2006.

 

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  FINANCIALLY SUPPORTED RESEARCH PROJECTS

  1. Evaluation of phosphor and scintillators for use in radiation detectors of medical imaging systems. Medical imaging using ionizing radiations / category: Exact sciences  (Scientific coordinator  É. Kandarakis ) Program EPEAEK / EEOT "Archimidis"

  2. Development of thin films (phosphors) for use in high resolution optical imaging in near infrared / Medical imaging with non-ionizing radiations / /category: Exact sciences ( Scientific coordinator Å. Koudoumas ). Program EPEAEK / EEOT "Archimidis"

  3. Software development  for the introduction of  DRG system/ category: Computer science (Scientific coordinator B. Spyropoulos ) Program EPEAEK / EEOT "Archimidis"

  4. Computer aided system for automatic diagnosis of the thyroid cancer / category: Technology  ( Scientific coordinator  D.Cavouras) Program EPEAEK / EEOT "Archimidis"

  5. Software development for pattern recognition of evoked potentials and endocranial currents with SVMs  / category: Technology ( Scientific coordinator E.Ventouras ) Program EPEAEK / EEOT "Archimidis"

  6. Research and analysis   of factors that affect  the production of hygienic and safe victuals using advanced technological methods ( irradiating the victuals with  Co -60 or X-rays) / category: Health sciences ( Scientific coordinator K. Spholmos ) Program EPEAEK / EEOT "Archimidis"

  7. Development simulation and experimental evaluation of scintillation crystals for the optimization of a high resolution ã-ray imaging system for the localization of cancerous tumors (GSRT) – Greece-Ukraine 2004-2006

  8. Lesion detectability optimisation in mammography by Monte-Carlo methods. (Scientific coordinator E. Costaridou) Program EPEAEK / EEOP "Pythagoras II".

  9. Experimental investigation and Monte-Carlo simulation of Radiation Detection Materials used in Diagnostic Radiology and Nuclear Medicine. (Scientific coordinator K. Kourkoutas). Program EPEAEK / EEOT "Archimidis II".

 



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Stratos Charokopos
Lampis Kyriazopoulos
Êostas Papagiannopoulos


   
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