Environment Influence On Pspl-based Digital Dental Radiology Systems

Photo-stimulable phosphor luminescence technology (PSPL) has been used in Digora (Soredex, Finland) and Denoptix (CEDH Gendex, Italy) digital dental radiology imaging systems. PSPL plates store X-ray energy during exposition, being later processed by a laser reader and digitizer. Afterward they are erased and re-used. The large band of energy absorption provides PSPL systems with an extensive dynamic scale but at the same time a high sensibility to the incoming noise of environmental radiations. We have measured environment influences (electromagnetic radiation) for Digora and Denoptix plates after X-ray exposure and before digital processing. We have first compared the processing of PSPL plates "in dark" against "in light" environments. In another experiment, the exposed plates were also processed after being positioned 10 cm away from a 17 inches video monitor screen and to its laterals for 5, 10, 15, 20, 25 and 30 minutes (plates protected against light). The acquired images were used to calculate the noise power spectra (NPS) in each case. We have noticed that there was an increase in the noise spectra energy of "in light" processing compared to "in dark" processing. There was also an increment in the NPS energy when the images were processed after the exposition of the plates to the radiation emanated from video monitor.4320219226Huda, W., Comparison of a photostimulable phosphor system with film for dental radiology (1997) Oral Surgery Oral Medicine Oral Pathology, 84, pp. 725-731Brettle, D.S., The imaging performance of a storage phosphor system for dental radiography (1996) The British Journal of Radiology, 69, pp. 256-261Xinhua, A novel algorithm for measuring the MTF of a digital radiographic system with a CCD array detector (2000) SPIE, 3977, pp. 580-587Knüpfer, W., Novel X-ray detectors for medical imaging (1999) Nuclear Physics, 78, pp. 610-615Hildebold, C.F., Dental photostimulable phosphor radiology (2000) Dental Clinics of North America, 44 (2), pp. 273-297Stamatakis, Dose response of a storage phosphor system for intraoral radiography (1999) Dentomaxillofacial Radiology, 28, pp. 272-276Yoshiura, K., Physical evaluation of a system for direct digital intra-oral radiography based on a charged-coupled device (1999) Dentomaxillofacial Radiology, 28, pp. 277-283Workman, A., Brettle, D.S., Physical performance measures of radiographic imaging systems (1997) Dentomaxillofacial Radiology, 26, pp. 139-146Granfors, P.R., Performance characteristics of an amorphous silicon flat panel X-ray imaging detector (1999) SPIE, 3659, pp. 480-490Yoshiura, K., Physical evaluation of a system for direct digital intra-oral radiography based on a charged-coupled device (1999) Dentomaxillofacial Radiology, 28, pp. 277-283Kengyelics, S.M., Image quality evaluation of a direct digital radiology detector operating in a UK radiology department (1999) SPIE, 3659, pp. 24-35Granfords, P.R., Aufrichtig, P.R.R., DQE(f) of an amorphous silicon flat panel X-ray detector: Detector parameter influences and measurement methodology (2000) SPIE, 3977, pp. 2-13Dobbins III, J.T., DQE(f) of four generations of computed radiography devices (1995) Medical Physics, 22, pp. 1581-1593Cowen, A.R., Workman, A., A physical image quality evaluation of a digital spot flurography system (1992) Phys. Med. Biol., 37, pp. 325-342Daint, J.C., Shaw, R., (1976) Image Science - Principles, Analyses and Evaluation of Photographic-Type Imaging Process, , Academic Press, London, UKBethea, R.M., Duran, B.S., Benllion, T.L., (1995) Statistical Methods for Engineers and Scientists, , Mc Hill Reckker, New York, NYZanella, G., Zannoni, R., DQE of imaging detectors in terms of spatial frequency (1999) Nuclear Instruments and Methods Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 437, pp. 163-167Zanella, G., Zannoni, R., The role of the quantum efficiency on the DQE of an imaging detector (1996) Nuclear Instruments and Methods in Physics Research A, 381, pp. 157-160Costa, S., DQE measurement in a scintillating glass optical fiber detector for X-ray imaging (1996) Nuclear Instruments and Methods in Physics Research A, 380, pp. 568-571Meyer, R.R., Experimental characterization of CCD cameras for HREM at 300kV (2000) Ultramicroscopy, 85, pp. 9-13Onttonello, P., MTF and DQE measurement in imaging detectors by their single-event response (1998) Nuclear Instruments and Methods in Physics Research Section A, 419, pp. 731-735Kandarakis, I., An experimental method for the determination of spatial-frequency-dependent detective quantum efficiency (DQE) of scintillators used in X-ray imaging detectors (1997) Nuclear Instruments and Methods in Physics Research Section A, 399, pp. 335-34

Evaluation Of Pspl Plate Erasing Time Of A Digital Dental Radiology System

Denoptix (CEDH Gendex Dental System, Milan, Italy) dental imaging system uses photo-stimulable phosphor luminescence (PSPL) plates to store energy during X-ray exposure, being later processed by a laser reader and digitizer. Afterwards the plate is erased and re-used. The cleaning process described by the manufacturer consists of exposing the PSPL plates to negatoscope light for 5 minutes. Proper light intensity and exact erasing time must be considered in order to guarantee good quality procedures in its re-utilization. X-ray exposed plates were submitted to four negatoscopes with different measured light intensities for several periods of light exposure, until the Denoptix system was unable to process the latent image in the plates, and we considered then that the plates were cleaned. We have found the relationships between erasing time, exposed dose and negatoscope light intensity. We have also measured the relative plate image fading with negatoscope light exposure time. We have concluded that a Poisson process governs plate erasing. Considering clinical situations, we have shown that it was possible to largely reduce erasing time and increase plate re-utilization. The exponential decay of image data also suggested a still smaller erasing time, representative of a partial cleaning status assuming that residual noise presence in the erased plate is clinically acceptable.4320227235Janhom, A., Effect of noise on the compressibility and diagnostic accuracy for caries detection of digital bitewing radiographs (1999) Dentomaxillofacial Radiology, 28, pp. 6-12Huda, W., Comparison of a photo-stimulable phosphor system with film for dental radiology (1997) Oral Surgery Oral Medicine Oral Pathology, 84, pp. 725-731Brettle, D.S., The imaging performance of a storage phosphor system for dental radiography (1996) The British Journal of Radiology, 69, pp. 256-261Yoshiura, K., Physical evaluation of a system for direct digital intra-oral radiography based on a charged-coupled device (1999) Dentomaxillofacial Radiology, 28, pp. 277-283Xinhua, A novel algorithm for measuring the MTF of a digital radiographic system with a CCD array detector (2000) SPIE, 3977, pp. 580-587Hildebold, C.F., Dental photostimulable phosphor radiology (2000) Dental Clinics of North America, 44 (2), pp. 273-297(1998) Denoptix System User Manual, , CEDH Gendex Dental System, Milan, ItalyBethea, R.M., Duran, B.S., Benllion, T.L., (1995) Statistical Methods for Engineers and Scientists, , Mc Hill Reckker, New York, NYWebb, S., (1995) The Physics of Medical Imaging, , Institute of Physis Publishing, Bristol, UK(1996) Mathematics and Physics of Emerging Biomedical Imaging, , National Research Council, Institute of Medicine, National Academy Press, Washington D.CBarret, H., Harrison, H., Swindell, W., (1981) Radiological Imaging: The Theory of Image Formation, Detection and Processing, 1-2. , Academic Press, London, UKDaint, J.C., Shaw, R., (1976) Image Science - Principles, Analyses and Evaluation of Photographic-Type Imaging Process, , Academic Press, London, U

Practical Method For Photon Fluency Evaluation Of Digital X-ray Image System

Quantum Detective Efficiency (DQE) is referred in literature as the most robust object-independent parameter for characterization of radiation detectors efficiency. DQE evaluation is particularly important in digital X-ray detectors, where the efficiency loss implies in image quality degradation and increase of patient exposed radiation dose. However, DQE cannot be evaluated directly. Its evaluation is derived of four other measurements: the Modulation Transfer Function (MTF), the Noise Power Spectrum (NPS), the Gamma factor (γ) and the Photon fluency (φ). The Photon fluency has a not easy experimental evaluation, being calculated by the integral of the X-ray radiation emission spectrum, using spectrophotometers or X-ray tube mathematical modeling. These approaches may lead to errors. In this study, Photon fluency was extrapolated from the measurements of absorbed dose and of half value layer, using monochromatic radiation. Assuming this restriction, the Photon fluency can be evaluated using only a conventional dosimeter. Therefore, this technique is compatible with the investments allocated for regular services of preventive maintenance and image quality control. As an evaluation of the viability in using this methodology in clinical environment, a DQE evaluation routine was implemented for the Digora (Soredex, Helsink, Finland) dental digital X-ray system with very good results that agreed with those obtained with conventional techniques.430563059Workman, A., Brettle, D.S., Physical performance measures of radiographic imaging systems (1997) Dentomaxillofacial Radiology, 26, pp. 139-146Barret, H.H., Swindell, W., (1981) Radiological Imaging: The Theory of Image Formation, Detection and Processing, 1-2. , Academic Press, London, UKDaint, J.C., Shaw, R., (1976) Image Science - Principles, Analyses and Evaluation of Photographic-type Imaging Process, , Academic Press, London, UKAlbuquerque, J.A.G., (2001) Avaliação Automática de Parâmetros Fisicos de Qualidade de Imagem em Sistemas de Radiologia Digital Odontológica, , http://www.rau-tu.unicamp.br/nou-rau/sbu/, M.Sc. dissertation, Biomed. Eng. Program, Unicamp, Campinas, Brazil, in PortugueseAlbuquerque, J.A.G., Costa, E.T., Haiter Neto, F., Paganinni, G.A., Bóscolo, F.N., Oliveira, A.E.F., Evaluation of PSPL plate erasing time of a digital dental radiology system Proc. SPIE Medical Imaging 2001, 4320, pp. 227-239. , San Diego, CACosta, E.T., Albuquerque, J.A.G., Haiter Neto, F., Paganinni, G.A., Bóscolo, F.N., Oliveira, A.E.F., Environment influence on PSPL-based digital dental radiology systems Proc. SPIE Medical Imaging 2001, 4320, pp. 219-226. , San Diego, CAHanam, J., (1992) Quality Control of Gamma Cameras and Associated Computer Systems, , Institute of Physical Sciences in Medicine, Bradford, UKAttix, F.H., (1986) Introduction to Radiological Physics and Radiation Dosimetry, , Wiley-Interscience, New York, NYSeelentag, W.W., Panzer, W., Equivalent photon energy including Rayleigh (coherent) scattering (1979) Gesellschaft für StrahlenBrettle, D.S., Wokman, A., Ellwood, R., Launders, J.H., Horner, K., Davies, R.M., The imaging performance of a storage phosphor system for dental radiography (1996) The British Journal of Radiology, 69, pp. 256-261Granfords, P.R., Aufrichtig, R., DQE(f) of an amorphous silicon flat panel X-ray detector: Detector parameter influences and measurement methodology Proc. SPIE Medical Imaging 2000, 3977, pp. 2-1