1.Digital radiography Presenter Pratik 1Digital Radiography

2. GOOD MORNING.. Digital Radiography 2 3. Digital radiography Presenter Pratik 3Digital Radiography 4. Content 4 Introduction & History Terminologies Equipment Digital Image acquisition Types of receptor CCD CMOS Flat panel detectors PSP Digital Radiography 5. Content 5 Digital Image Processing Digital Radiographic Image Storage Digital Image Communication Digital Presentation and Display Advantage and Disadvantages Overall Conclusion Digital Radiography 6. Introduction Digital Radiography 6 7. Digital Radiography 7 Radiography Analog Digital Scanner (X-ray digitizer) Computed Radiography (CR) Direct Digital Radiography (DR or DDR) 8. A conventional system uses x-ray film to create a latent image with or without screens. The film is then processed, creating a manifest image that can be interpreted by a physician. It is later stored in the file room (physical storage for archival) Digital Radiography 8 9. Method is film-based. Method may uses intensifying screens. Film is placed between two screens. Screens emit light when x-rays strike them. Film is processed chemically. Processed film is viewed on view-box (lightbox). Digital Radiography 9 10. Digital Radiography 10 Chemical Processing in film radiography 11. Problems with Film ? 10% of films are not available when we want them! 15% of films are hard to locate or find! 25% of films are misplaced or not retrievable (misfiled). 10% of films are lost (referrals, residents, etc.) Recent study physicians spend two weeks/year (100 hours/year) trying to locate or find the films they need. Digital Radiography 11 12. Digital Radiography 12 Radiography Analog Digital Scanner (X-ray digitizer) Computed Radiography (CR) Direct Digital Radiography (DR or DDR) 13. Digital imaging or Digitization ? Digital Imaging is any modality / method of imaging that creates an image that can be viewed or stored on a computer. Digital Radiography 13 14. Introduction 14Digital Radiography 15. Introduction Since the discovery of X-rays in 1895, film has been the primary medium for capturing, displaying, and storing radiographic images. It is a technology that dental practitioners are the most familiar and comfortable with in terms of technique and interpretation. Digital radiography is the latest advancement in dental imaging and is slowly being adopted by the dental profession. 15Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 16. Introduction Digital imaging incorporates computer technology in the capture, display, enhancement, and storage of direct radiographic images. Digital imaging offers some distinct advantages over film, but like any emerging technology, it presents new and different challenges for the practitioner to overcome. 16Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 17. History Digital Radiography 17 18. Year Development 1500 BC The phenomenon of luminescence observed - China 1895 X-rays discovered 1895 Dr Walkoff first took dental radiograph 1919 Kodak produced first dental film 1955 Kodak D speed film 1963 CMOS invented 1969 CCD technology for video applications History 18Digital Radiography Pasler,Pocket Atlas of Dental Radiology, Thieme 2007 19. History 19Digital Radiography Pasler,Pocket Atlas of Dental Radiology, Thieme 2007 Year Development 1970 Alternate receptor system Xeroradiography 1975 Method of converting the information pattern into a digital form 1980 Computed radiography - storage phosphors 1981 Computed Radiography PSP method Kodak Ekta speed 1984 First Direct Digital Imaging System - RadioVisioGraphy 1987 Amorphous seleniumbased image plates 20. 20 Year Development 1990 Charge-coupled device (CCD) slot-scan direct radiography 1994 Storage phosphor system, DIGORA for intraoral use. 1995 CCD (Visualix 2/VIXA 2), which had a larger active area Computed Dental Radiography (CDR) system by Schick. Amorphous siliconcesium iodide (scintillator) flat- panel detector Selenium-based flat-panel detector Digital Radiography Pasler,Pocket Atlas of Dental Radiology, Thieme 2007 21. 21 Year Development 1997 Gadolinium-based (scintillator) flat-panel detector 2001 Gadolinium-based (scintillator) portable flat-panel detector Dynamic flat-panel detector fluoroscopy 2009 Wireless DR (flat-panel detector) Digital Radiography Lanca L, Silva A, Digital Imaging Systems for Plain Radiography, Springer 2013 22. Terminology Digital Radiography 22 23. Density - The overall degree of darkening of an exposed film Brightness - Digital equivalent to density or overall degree of image darkening. 23Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 24. Latitude - Measure of the range of exposures that will produce usefully distinguishable densities on a film. Dynamic Range - The numerical range of each pixel; in visual terms it refers to the number of shades of gray that can be represented. 24Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 25. Digital Radiography 25 Pasler,Pocket Atlas of Dental Radiology, Thieme 2007 26. Film Speed -Amount of radiation needed to produce a standard density; refers to the sensitivity of the film to radiation. The faster the film, the less radiation required. Linearity - Linear or direct relationship between exposure and image density. OR 26Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 27. Detector Sensitivity: Sensitivity of a detector is its ability to respond to small amounts of radiation. Intraoral film sensitivity is classified according to speed group using criteria developed by the International Organization for Standardization. Currently there are no classification standards for dental digital X-ray receptors. 27Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 28. Contrast Contrast - The difference in densities between various areas on a radiograph; high contrast images have few shades of gray between black and white while low contrast will demonstrate more shades of gray. Contrast Resolution - The ability to differentiate small differences in density as displayed on an image. 28Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 29. Contrast This is a function of the interaction of the attenuation characteristics of the tissues that are being imaged the capacity of the image receptor to distinguish differences in numbers of X-ray photons coming from different areas of the subject the ability of the computer display the ability of the observer to recognize those differences. 29Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 30. Resolution - Ability to distinguish between small objects that are close together; measured in line pairs per millimeter. Spatial Frequency - Measure of resolution expressed in line pairs per millimeter. Modulation Transfer Function - Measure of image fidelity as a function of spatial frequency; how close the image is to the actual object. 30Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 31. The theoretical limit of resolution is a function of picture element (pixel) size for digital imaging systems. Currently the highest resolution CCD detectors for dentistry have pixel sizes of approximately 20 microns. Digital Radiography 31 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 32. Resolution is often measured and reported in units of linepairs per millimetre. A line and its associated space are called a line pair (lp). At least two pixels are required to resolve a line pair, one for the dark line and one for the light space Digital Radiography 32 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 33. 500px 200px 50px 10px 5px 1px Digital Radiography 33 34. Typical observers are able to distinguish about 6 lp/mm without benefit of magnification. Intraoral film is capable of providing more than 20 lp/mm of resolution With 20- m pixels, a theoretical resolution of 25 lp/mm can be obtained. Current digital systems are capable of providing more than 7 lp/mm of resolution. Digital Radiography 34 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 35. Radiographic Motile (Noise) - Appearance of uneven density of an exposed film or graininess Background Electronic Noise Small electrical current that conveys no information but serves to obscure the electronic signal 35Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 36. Digital Radiography 36 37. Sharpness - Ability of a radiograph to define an edge or display density boundaries. Signal to Noise Ratio - Ratio between the fraction of the output signal (voltage or current or charge) that is directly related to the diagnostic information (signal) and the fraction of output that does not contain diagnostic information (noise) . 37Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 38. Scintillator A scintillator is a material that exhibits scintillation the property of luminescence when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate, (i.e., re-emit the absorbed energy in the form of light) 38Digital Radiography [Internet] [cited 2014 Apr 10]. Available from http://en.wikipedia.org/wiki/Scintillator 39. 39Digital Radiography Lanca L, Silva A, Digital Imaging Systems for Plain Radiography, Springer 2013 40. Pixel In digital imaging, a pixel [picture element] is the smallest controllable element of a picture represented on the screen Digital Radiography 40 [Internet] [cited 2014 Apr 10]. Available from http://en.wikipedia.org/wiki/Pixel 41. Pixel Digital Radiography 41 [Internet] [cited 2014 Apr 10]. Available from http://en.wikipedia.org/wiki/Pixel 42. Pixel Digital Radiography 42 [Internet] [cited 2014 Apr 10]. Available from http://en.wikipedia.org/wiki/Pixel 43. Analogue to Digital Conversion The term digital in digital imaging refers to the numeric format of the image content and its discreteness. Conventional film images can be considered an analog medium in which differences in the size and distribution of black metallic silver result in a continuous density spectrum. Digital Radiography 43 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 44. Analogue to Digital Conversion Digital images are numeric and discrete in two ways: (1) in terms of the spatial distribution of the picture elements (pixels) and (2) in terms of the different shades of gray of each of the pixels. Digital Radiography 44 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 45. Analogue to Digital Conversion A digital image consists of a large collection of individual pixels organized in a matrix of rows and columns. Production of a digital image requires a process called analog to digital conversion (ADC) Digital Radiography 45 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 46. ADC consists of 2 steps Quantization Sampling Digital Radiography 46 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 47. Sampling Sampling means that a small range of voltage values are grouped together as a single value Digital Radiography 47 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 48. Sampling Narrow sampling better mimics the original signal but leads to larger memory requirements for the resulting digital image Digital Radiography 48 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 49. Once sampled, every sampled signal is assigned a value. For the clinician to see the image, the computer organizes the pixels in their proper locations and displays a shade of gray that corresponds to the number that was assigned during the quantization step. Quantization Digital Radiography 49 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 50. Quantization Digital Radiography 50 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 51. Taxonomy Digital Radiography 52 52. Digital Radiography 54 Lanca L, Silva A, Digital Imaging Systems for Plain Radiography, Springer 2013 53. Digital Radiography Direct Indirect 55Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 54. Direct digital imaging 56 Sensor placed in pts mouth Exposed to radiation Sensor captures radiograp hic image Transmit image to a computer monitor Image appears on screen within seconds Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 55. Indirect digital imaging 57 Exisiting Xray film digitized using CCD camera Scans the image Digitizes displays on computer monitor Digital Radiography The Journal of Contemporary Dental Practice 2002 3(4):1-13 56. Types of digital image receptor 58Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 1. Solid state technology: Charge coupled device Complementory metal oxide semiconductors Flat panel detectors 2. Photostimulable phosphor plate 57. Digital image receptors Digital Radiography 59 Solid State Technology Uses semi-conductor based detectors 1. CCD 2. CMOS 3. Flat Panel Lanca L, Silva A, Digital Imaging Systems for Plain Radiography, Springer 2013 58. Charge coupled device Digital Radiography 60 59. Charge coupled device Introduced in 1987 1st intraoral digital receptor Consist of thin wafer of silicon with electronic circuit Consist of matrix, amplifier in plastic houisng 61Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 60. A number of manufacturers produce detectors with varying active sensor areas roughly corresponding to the different sizes of intraoral film Digital Radiography 62 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 61. Digital Radiography 63 Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 62. Structure 64Digital Radiography 63. Structure 65Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 64. 66 Exposure to radiation Break the covalent bond in silicon atoms Produce electron hole pair Electron attracted towards most positive potential in device create charge packet Charge pattern formed from individual pixels forms latent image Digital Radiography 65. 67 Bucket brigade form of charge transfer Finally transferred to amplifier Transmitted as voltage Analog to digital converter Image display Digital Radiography 66. Valence Band Mechanism 69Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 +e- e- Photoelectric absorption in Silicon Conduction Band e- + 67. Digital Radiography 70 [Internet] [cited 2014 Apr 10]. Available from http://www.vikdhillon.staff.shef.ac.uk/teaching/phy217/detectors 68. Digital Radiography 71 [Internet] [cited 2014 Apr 10]. Available from http://www.vikdhillon.staff.shef.ac.uk/teaching/phy217/detectors 69. Digital Radiography 72 [Internet] [cited 2014 Apr 10]. Available from http://www.vikdhillon.staff.shef.ac.uk/teaching/phy217/detectors 70. Digital Radiography 73 71. Digital Radiography 74 72. Digital Radiography 75 73. 76 Bucket brigade form of charge transfer Finally transferred to amplifier Transmitted as voltage Analog to digital converter Image display Digital Radiography 74. Digital Radiography 77 75. CCD Detectors without flaws are relatively expensive to produce, and expense of the detector increases with increasing matrix size (total number of pixels). Pixel size varies from 20 microns to 70 microns. Smaller pixel size increases the cost of the receptor. CCDs have also been made in linear arrays of a few pixels wide and many pixels long for panoramic and cephalometric imaging. Digital Radiography 78 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 76. Digital Radiography 79 CCD Linear array made up of few px wide and many px long Area array White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 77. Linear array Digital Radiography 80 Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 78. Area array Digital Radiography 81 Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 79. Advantages 82Digital Radiography Intact images or real time image production and display. Consistent quality X ray sensitivity is 80% greater than conventional film. Elimination of hazardous chemicals used in film processing and lead foil. Computer aided diagnosis 80. Disadvantages 83 High initial cost of system Unknown life expectancy of CCD sensor Rigidity and thickness of the sensor Decreased resolution CCDS cannot be sterilized Hard copy images fade with time Digital Radiography 81. Disadvantages 84 Image manipulation can be time consuming. The sensor may not be well tolerated by patients -more time-consuming The cable attached to the sensor is easily damaged and may interfere with sensor Actual area available for image capture may be as little as 60% of the sensor area Digital Radiography 82. Product Name Company CDR Schick CygnusRay MPS Cygnus Technologies Dexis ProVision Dental Systems Dixi2 Planmeca Group SIDEXIS Sirona SIGMA PaloDex Group SuniRayTM Suni Medical Imaging RVG Trophy VistaRay Drr Dental VisualiX . Gendex Intraoral CCD based systems 85Digital Radiography 83. Panoramic CCD based systems 86Digital Radiography Product Name Company CDRPan Schick Digipan Trophy Dimax3, ProlineXC, Promax Planmeca Group DXIS Signet Orthopantomograph OP100D PaloDex Group Orthoceph OC100D PaloDex Group ORTHOPHOS DS Sirona 84. 87Digital Radiography Product Name Company Cranex Base X D PaloDex Group Cranex Excel D PaloDex Group Scanora D PaloDex Group Orthoralix 9200 (DDE, DPI) Gendex - Dentsply Versaview (5D, SDCP) Morita 85. Complementary metal oxide semiconductors 88Digital Radiography 86. Complementary metal oxide semiconductors 89 Each pixel is isolated from its neighboring pixels and connected to transistor Electron hole pair generated within pixel Charge tranfer to transistor in form of voltage Each transistor voltage is read out separately by frame grabber Stored and displayed as digital gray value Digital Radiography Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 87. 90Digital Radiography ADC 88. 91Digital Radiography 89. These sensors do not require charge transfer, resulting in increased sensor reliability and lifespan. Require less system power to operate and are less expensive to manufacture Low cost Fixed pattern of noise Smaller active area 92Digital Radiography 90. CCD CMOS POWER COSUMPTION. 400mw 40mw SENSITIVITY TO LIGHT Excellent Excellent SENSITIVITY TO X RAYS High Unknown PIXEL SIZE. 40 micron 25 micron COST. High Medium MANUFACTURE. Expensive Cheap BREAKAGE RESISTANCE Low Medium DYNAMIC RANGE Excellent Excellent NOISE. Low High READOUT. Complex Simple EFFICACY. Excellent Fair Digital Radiography 93 91. Flat panel detector Digital Radiography 94 92. Flat panel detector Used for medical imaging, extraoral imaging device Provide large matrix area with pixel of less than 100 m Allows imaging of larger areas including head 2 types: direct indirect 95Digital Radiography Lanca L, Silva A, Digital Imaging Systems for Plain Radiography, Springer 2013 93. Flat panel detector 96Digital Radiography Indirect flat panel detector: sensitive to visible light use intensifying screen to convert X-ray to light Photoconductor material - aSi Lanca L, Silva A, Digital Imaging Systems for Plain Radiography, Springer 2013 94. Flat panel detector 97Digital Radiography Direct flat panel detector use selenium for efficient X- rays absorption Lanca L, Silva A, Digital Imaging Systems for Plain Radiography, Springer 2013 95. Flat panel detector It is a sandwich constructions consisting of a scintillator layer, an amorphous silicon photodiode circuitry layer, and a TFT array. 98Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 96. Thin Film Transistor (TFT) It is a special kind of field-effect transistor made by depositing thin films of an active semiconductor layer A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. Digital Radiography 99 [Internet] [cited 2014 Apr 10]. Available from http://en.wikipedia.org/wiki/Thin-film_transistor 97. Flat panel detector When x-ray photons reach the scintillator, visible light proportional to the incident energy is emitted and then recorded by an array of photodiodes and converted to electrical charges. These charges are then read out by a TFT array similar to that of direct conversion DR systems. 100Digital Radiography Lanca L, Silva A, Digital Imaging Systems for Plain Radiography, Springer 2013 98. Flat Panel Structure 101Digital Radiography Lanca L, Silva A, Digital Imaging Systems for Plain Radiography, Springer 2013 99. Advantages Real-time process With a time lapse between exposure and image display of less than 10 seconds. 102Digital Radiography 100. Disadvantages Large in size so cannot be used intraorally Expensive 103Digital Radiography 101. Thank you Digital Radiography 104 102. Digital radiography Presenter Pratik 105Digital Radiography 103. Digital Radiography 106 104. Content 108 Introduction & History Terminologies Equipment Digital Image acquisition Types of receptor CCD CMOS Flat panel detectors PSP Digital Radiography 105. Content 109 Digital Image Processing Digital Radiographic Image Storage Digital Image Communication Digital Presentation and Display Advantage and Disadvantages Overall Conclusion Digital Radiography 106. Product Name Company CDR, Schick CygnusRay, MPS Cygnus Technologies Dexis, ProVision Dental Systems Dixi2, Planmeca Group SIDEXIS Sirona SIGMA + PaloDex Group SuniRay, Suni Medical Imaging VistaRay, Drr Dental VisualiX . Gendex Intraoral CCD based systems 110Digital Radiography 107. Product Name Company RVG 6500, 6100, 5100 Carestream Intraoral CMOS based systems 111Digital Radiography 108. Photostimulable phosphor plates Digital Radiography 112 109. Photostimulable phosphor plates Also known as storage phosphor plates (spp),image plates or computed radiography Flexible, wireless indirect receptors Available in the same sizes as intraoral films. 113Digital Radiography 110. Structure The PSP material used for radiographic imaging is europium doped barium fluorohalide. Barium in combination with iodine, chlorine, or bromine forms a crystal lattice. The addition of europium (Eu + 2 ) creates imperfections in this lattice. Digital Radiography 114 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 111. Structure Digital Radiography 115 Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 112. Mechanism When exposed to a sufficiently energetic source of radiation, valence electrons in europium can absorb energy and move into the conduction band. These electrons migrate to nearby halogen vacancies (F-centers) in the fluorohalide lattice and may become trapped there in a metastable state. 116Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 113. Valence Band e- Plate prepared Plate exposed X ray photon F Center Eu+2 Eu+3Eu+2 F Center Conduction Band Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 114. Mechanism While in this state, the number of trapped electrons is proportional to x-ray exposure and represents a latent image. When stimulated by red light of around 600 nm, the barium fluorohalide releases trapped electrons to the conduction band. 119Digital Radiography Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 115. Mechanism When an electron returns to the Eu + 3 ion, energy is released in the green spectrum between 300 and 500 nm 121Digital Radiography Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 116. Valence Band e- Plate prepared Plate exposed Plate processed laser Photomultiplier tube X ray photon F Center Eu+2 Eu+3Eu+2 Eu+3Eu+2 F Center F Center Conduction Band Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 117. Mechanism Fiberoptics conduct light from the PSP plate to a photomultiplier tube. The photomultiplier tube converts light into electrical energy. A red filter at the photomultiplier tube selectively removes the stimulating laser light, and the remaining green light is detected and converted to a varying voltage. 124Digital Radiography Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 118. PROCEDURE 125Digital Radiography 119. PROCEDURE 126Digital Radiography 120. Stationary plate scans Method for "reading" the latent images on PSP plates. A rapidly rotating multifaceted mirror that reflects a beam of red laser light. As the mirror revolves, the laser light sweeps across the plate. The plate is advanced and the adjacent line of phosphor is scanned. 127Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 121. Digital Radiography 128 122. Rotating plate scans Rapidly rotating drum that holds the plate Consist of Rotation of drum and fixed laser 129Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 123. Advantages Storage phosphor plates can be reused indefinitely Receptor is cordless & flexible Linear or logarithmic response to radiation is available There is wide exposure range & fewer retakes Less radiation is required 130Digital Radiography 124. Advantages 131Digital Radiography No chemical processing required Image processing of acquired images is available Images can be transferred to easily Images can be easily & inexpensively stored & retrieved Computed aided diagnosis 125. Disadvantages Receptors must be erased before reuse High initial cost of the equipment The spatial resolution of film exceeds Some of the image processing routines are time intensive Phosphor plates must be packaged in sterile envelopes possibility of transfer of contaminated material to patient's mouth if integrity of plate's protective envelope is jeopardized 132Digital Radiography 126. Intraoral PSP systems 133Digital Radiography Panorama Xi Orex Combi-Xi Orex DenOptix Gendex - Dentsply Digora Optime PaloDex Group VistaScan Drr Dental VistaScan Intra Drr Dental 127. Panoramic PSP based systems 134Digital Radiography Product Name Company Panorama Xi Orex DenOptix Gendex - Dentsply Digora Optime PaloDex Group VistaScan Drr Dental VistaScan Intra Drr Dental 128. Computer Digital Radiography 135 [Internet] [cited 2014 Apr 10]. Available from http://www.dentistrytoday.com/radiography/1755 129. Computer Digital Radiography 136 [Internet] [cited 2014 Apr 10]. Available from http://www.dentistrytoday.com/radiography/1755 130. Imaging processing Any operation that acts to improve, restore, analyze or in some way change a digital image is a form of image processing. Some of these operations are integrated in the image acquisition and image management software and are hidden from the user. Others are controlled by the uses with the intention to improve the quality of the image or to analyze its contents. 137Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 131. Imaging processing 138Digital Radiography Image restoration Image enhancement Image analysis Image compression 132. Image restoration When the raw image data enter the computer, they are usually not yet ready for storage or display. Some of the pixels in CCD sensor are always defective. The image is restored by substituting the gray values of the defective pixels with some weighted average of gray values from the surrounding pixels. 139Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 133. Image restoration Depending on the quality of the sensor and the choices made by the manufacturer, a variety of other operations maybe applied to the image before it becomes visible on the display. They are executed very rapidly and are unnoticed by the user. 140Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 134. Image restoration Raw data enter computer Preprocessing -- Image corrected for known defects Adjustment of image intensities Substitution of defective pixels Preprocessing operations set by manufacturer 141Digital Radiography 135. Imaging processing 142Digital Radiography Image restoration Image enhancement Image analysis Image compression 136. Image enhancement The term image enhancement implies that the adjusted image is an improved version of the original one. Most image enhancement operations are applied to make the image visually more appealing (subjective enhancement). This can be accomplished by increasing contrast, optimizing brightness, and reducing unsharpness and noise. 143Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 137. Image enhancement Image enhancement operations are often task- specific; what benefits one diagnostic task may reduce the image quality for another task. For example, increasing contrast between enamel and dentin for caries detection may make it more difficult to identify the contour of the alveolar crest. Image enhancement operations are also dependent on viewer preference. 144Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 138. Image enhancement Change the visual appearance of the image Improved version of the original one Common enhancements tools include: Brightness and Contrast Adjustments Black/White Reversal Pseudocolor Application Sharpening and smoothing Zoom Digital Subtraction 145Digital Radiography 139. a) Brightness and Contrast: Digital radiographs do not always effectively utilize the full range of available gray values. They can be relatively dark or light, and they can show too much contrast in certain areas or not enough. The image histogram is a convenient tool to examine which of the available gray values the image is using. Digital Radiography 146 140. a) Brightness and Contrast: Digital Radiography 147 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 141. a) Brightness and Contrast: The maximum and minimum values and the shape of the histogram indicate the potential benefit of brightness and contrast enhancement operations. Digital imaging software commonly includes a histogram tool, as well as tools for the adjustment of brightness and contrast. Digital Radiography 148 Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 142. Brightness Digital Radiography 149 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 143. Brightness Digital Radiography 150 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 144. Contrast Digital Radiography 151 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 145. Increase in Decrease in Digital Radiography 152 146. ii. Negative Conversion Useful in visualizing the trabecular pattern of bone pulp canal and chamber anatomy 153Digital Radiography 147. b) Sharpening and Smoothing: The purpose of sharpening and smoothing filters is to improve image quality by removing blur or noise. Noise is often categorized as high frequency noise (speckling) or low frequency noise (gradual intensity changes). Filters that smooth an image are sometimes called despeckling filters because they remove high frequency noise. Digital Radiography 154 Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 148. b) Sharpening and Smoothing: Filters that sharpen an image either remove low frequency noise or enhance boundaries between regions with different intensities (edge enhancement). Sharpening and smoothing filters may make the dental radiographic images subjectively more appealing. Digital Radiography 155 Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 149. Digital Radiography 156 150. Digital Radiography 157 151. Digital Radiography 158 152. c) Colour: Most digital systems provide opportunities for color conversion of gray scale images also called pseudo-color. Transforming the gray values of a digital image into various colors could theoretically enhance the detection of objects with the image. When objects can be uniquely identified based on a set of image features, colour can be used to label or highlight these objects. 159Digital Radiography Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 153. c) Colour: 160Digital Radiography Whaites E, Essentials of Dental Radiography and Radiology, 4th edition, 2007 154. Imaging processing 161Digital Radiography Image restoration Image enhancement Image analysis Image compression 155. Image Analysis: Image analysis operations are designed to extract diagnostically relevant information from the image. This information can range from simple linear measurements to fully automated diagnosis. The use of image analysis tools brings with it the responsibility to understand their limitations. The accuracy and precision of a measurement are limited by the extent to which the image is a truthful and reproducible representation of the patient and by the operators ability to make an exact measurement. Digital Radiography 162 156. a) Measurement: Digital imaging software provides a number of tools for image analysis. Digital rulers, densitometers and a variety of other tools are readily available. The size and image intensity of any are within a digital radiograph can be measured. Tools are also being developed for measuring the complexity of the trabecular bone pattern. Digital Radiography 163 157. Digital Radiography 164 Measurement tool to determine the length of the crown and mesiobuccal root of the first molar. The measurement has been calibrated for a magnification factor of 1.05. White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 158. b) Diagnosis: Three basic steps of image analysis are : Segmentation - most critical step. Feature extraction Object classification. The goal of segmentation is to simplify the image and reduce it to its basic components. This involves subdividing the image, thus separating objects from the background. Digital Radiography 165 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 159. b) Diagnosis: Objects of interest are defined by the diagnostic task, for example, a tooth, a carious lesion, a bone level, or an implant. A unique set of values for a certain combination of features can lead to classification of the object. Automated cephalometric landmark identification is an example. Digital Radiography 166 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 160. DIGITAL SUBTRACTION RADIOGRAPHY 167Digital Radiography 161. Dental radiography by Ruttimann and colleagues in 1981 (Ruttimann et al, 1981) and was found to be a feasible method that increases the accuracy of detection of density changes between serial radiographs 168Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 162. When two images of the same object are registered and the image intensities of corresponding pixels are subtracted, a uniform difference image is produced. If there is a change in the radiographic attenuation between the baseline and follow-up examination, this change shows up as a brighter area when the change represents gain and as a darker area when the change represents loss Digital Radiography 169 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 163. The strength of digital subtraction radiography (DSR) is that it cancels out the complex anatomic background against which this change occurs. Subtraction radiography requires two images , which are exposed with the same geometry Digital Radiography 170 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 164. 171Digital Radiography 165. Digital Radiography 172 166. Digital Radiography 173 167. Two methods have been developed for the computerized alignment of the follow-up images: Reference point alignment method Real-time subtraction alignment method 174Digital Radiography 168. Subtraction radiography is a qualitative method that assists in visualization of small density changes. Additional methods have been developed for the quantification of these changes. 175Digital Radiography 169. Relative quantification One measurement method that describes density changes in mineralized oral tissues with ordinal scale data in some controlled situations, Computer Assisted Densitometric Image Analysis (CADIA). CADIA is a practical method of measurement of change in bone density occurring in the alveolar crest (Bragger et al, 1988). 176Digital Radiography 170. Relative quantification CADIA is based on the comparison of two serial images that are acquired with standardized projection geometry and equalized for the density differences in the images. The area of change is calculated, and the "depth" of the lesion in the bucco-lingual direction is measured as the density change between images. The final CADIA value is the product of the area of change and the average "depth" of the change, and thus represents a volumetric description of the density change. 177Digital Radiography 171. Absolute quantification A subtraction method that produces ordinal scale data can be transformed into a quantitative method that generates interval scale data by exposing one of the serial radiographs through a calibration wedge of known density and dimensions. 178Digital Radiography 172. Absolute quantification A subtraction method that produces ordinal scale data can be transformed into a quantitative method that generates interval scale data by exposing one of the serial radiographs through a calibration wedge of known density and dimensions. In the subsequent analysis process, the image of the wedge is used for the estimation of the density of the site. This radiographic photodensitometric method was first used in medical radiology for the estimation of skeletal bone mineral content Omnell (1957) was the first to apply radiographic densitometry, also called radiographic absorptiometry (Anderson et al, 1966; Yang et al, 1994), to the measurement of bone density changes in the alveolar bone. 179Digital Radiography 173. Imaging processing 180Digital Radiography Image restoration Image enhancement Image analysis Image compression 174. Image compression Process of file reduction. To reduce computer storage space and facilitate image retrieval and transmission. Compression becomes a more important issue as the number of patient records and image files to be stored increases over time Two types: lossless and lossy 181Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 175. 182Digital Radiography LOSSLESS LOSSY Donot discard any image data Discard image data Maximum compression rate < 3:1 Range from 12:1 to 28:1 More memory to manipulate Less memory Retrieval and transmission slow quick White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 176. Image compression methods Cartesian Perceptual Compression, also known as CPC Fractal compression JPEG JPEG 2000, JPEG XR, PGF, Progressive Graphics File Wavelet compression Digital Radiography 183 [Internet] [cited 2014 May 10]. Available from http://en.wikipedia.org/wiki/Image_compression 177. Joint Photographic Experts Group (JPEG) a common compression protocol that can support both lossless and lossy compression high compression ratios had a severe negative impact on the diagnostic quality of digital images in the detection of periapical lesions. compression ratios 25 :1 endodontics 12: 1 to 14:1 caries diagnosis 184Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 178. Joint Photographic Experts Group (JPEG) Compression rates of 12:1 and 14:1 were shown to have no appreciable effect on caries diagnosis. For determining endodontic file length, a rate of 254:1 was diagnostically equivalent to the uncompressed image. A compression rate of 28:1 was acceptable of the subjective evaluation of image quality and the detection of lesions in panoramic radiographs. 185Digital Radiography 179. Digital image display: 186Digital Radiography 180. Cathode Ray Tube (CRT): Conventional computer monitor use cathode ray tube (CRT) designs. A beam of electrons emanating from an electron 'gun' rapidly scans a phosphor-coated screen. The electron scan is horizontal and builds an image line by line. Digital Radiography 187 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 181. Cathode Ray Tube (CRT): The image is repeated or refreshed at a rate of 60 times a second (Hz) or more to avoid the appearance of flicker. Colour monitors utilize 3 electron guns one each for red, blue and green phosphors. The variable intensity of the electron beam is responsible for different shades of gray or colour line and intensity. High quality monitors are able to display 256 different gray values or a combination of grey and colour values. Digital Radiography 188 182. Cathode Ray Tube (CRT): CRT display involves conversion of digital information into analog voltages, which is supplied to the electron guns. Some loss of original image information is inherent in the digital-to-analog conversion process. A number of factors affect the subjective quality of a monitor. A dot pitch is a measure of the distance between groups of subpixels (red, green and blue phosphors) in the CRT. Digital Radiography 189 183. Cathode Ray Tube (CRT): Smaller dot pitches on the order of 0.28 mm or less provide more pixels per area and sharper looking images. The brightness of the monitor affects perceived contrast of the image. Brighter monitors are essential in working environments with greater amounts of ambient light. Digital Radiography 190 184. Cathode Ray Tube (CRT): Conventional computer monitor use cathode ray tube (CRT) designs. The image is repeated or refreshed at a rate of 60 times a second (Hz) or more to avoid the appearance of flicker. Colour monitors utilize 3 electron guns one each for red, blue and green phosphors. The variable intensity of the electron beam is responsible for different shades of gray or colour line and intensity. Digital Radiography 191 185. Parameter CRT LCD OLED Brightness. Poor Very poor Poor Contrast. Over 15,000:1 Over 1,000:1 Over 1,000,000:1 Color Excellent Good on most newer models Better Color depth Unlimited Better Excellent Black level. Excellent Poor Excellent Ghosting and smearing No ghosting or smearing artifacts Display motion blur on models with slow response time, and the elimination technique (strobing backlight) can cause eye-strain None even during fast motion Digital Radiography 192 [Internet] [cited 2014 Apr 10]. Available from http://en.wikipedia.org/wiki/Comparison_of_CRT,_LCD,_Plasma,_and_OLED 186. Parameter CRT LCD OLED Response time Sub-milisecond 18 ms typical (according to manufacturer data), older units could be as slow as 35 ms Sub-millisecond Eyestrain. Less if refresh rates below 85 Hz Depends; as of 2013, most LCDs use strobing to dim the backlight which can cause severe eyestrain Less Weight. Heavy, especially for larger units, a 20 inches (51 cm) screen weighs about 50 pounds (23 kg) Light Very light Digital Radiography 193 [Internet] [cited 2014 Apr 10]. Available from http://en.wikipedia.org/wiki/Comparison_of_CRT,_LCD,_Plasma,_and_OLED 187. Parameter CRT LCD OLED Size. Bulky depth, 7" smallest possible for color screen, over 40" is very heavy Compact, can be manufactured almost any size and shape, Compact, can be made in nearly any size or shape. Maintenance. Hazardous to repair or service due to high-voltage, requires skill. Difficult to replace backlight Electro-magnetic radiation emission. Emits strong electromagnetic radiation in the audio-frequency to low-frequency RF range Emits very little electromagnetic radiation Emits very little electromagnetic radiation Digital Radiography 194 [Internet] [cited 2014 Apr 10]. Available from http://en.wikipedia.org/wiki/Comparison_of_CRT,_LCD,_Plasma,_and_OLED 188. Electronic Display Considerations: The display of digital images on electronic devices is a fairly straightforward engineering issue. The quality, capabilities, and ease of use of display software vary from vendor to vendor, and these are numerous. Even with the same software the display of images can vary dramatically, depending on how the software handles resizing of windows or the size and resolutions of different displays. Digital Radiography 195 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 189. Electronic Display Considerations: Software may permit reduction in image size or scrolling around the window to compensate for smaller display areas. Bright background illumination from windows or other sources of ambient light reduce visual contrast sensitivity. Light reflecting off of a monitor surface may further reduce visibility of image contrast. Images are best viewed in an environment in which lighting is subdued and indirect. Digital Radiography 196 190. Hard Copies With the development of digital photography as a mainstream technology, digital image printing has become an economical solution for making digital radiographs transferable. Main types of printing technologies available for printing images include ; Laser Inkjet Dye-sublimation with the use of either film or paper. Digital Radiography 197 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 191. Laser Printer Laser printing is an electrostatic digital printing process that rapidly produces high quality text and graphics by passing a laser beam over a charged drum to define a differentially charged image. The drum then selectively collects charged toner and transfers the image to paper, which is then heated to permanently fix the image. Digital Radiography 198 192. Laser Printer Digital Radiography 199 193. Digital Radiography 200 194. Ink Jet Inkjet printing is a type of computer printing that creates a digital image by propelling droplets of ink onto paper, plastic, or other substrates. Inkjet printers are the most commonly used type of printer. Digital Radiography 201 195. Dye Sublimation It uses heat to transfer dye onto materials such as a plastic, card, paper, or fabric. The sublimation name was first applied because the dye was considered to transition between the solid and gas states without going through a liquid stage. This understanding of the process was later shown to be incorrect; since then the process is sometimes known as dye-diffusion. Digital Radiography 202 196. Dye Sublimation Digital Radiography 203 197. Image Storage: The use of digital imaging in dentistry requires an image archiving and management system that is very different from conventional radiography. Storage of diagnostic images on magnetic or optical media raises a number of new issues that must be considered. The file size of dental digital radiographs varies considerably, ranging from 200 KB for intra oral images to as much as 6 MB for extraoral images. 204Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 198. Image Storage: Once in a digital format, critical image data can be deleted or modified. The backup media suitable for external storage of digital radiographs include external hard drives, digital types, CDs and DVDs. 205Digital Radiography White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 199. COMMON PROBLEMS IN DIGITAL IMAGING 206Digital Radiography 200. 1. Noisy Images 2. Non uniform image density 3. Distorted Images 4. Double Images Digital Radiography 207 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 201. Noisy Images 208Digital Radiography 202. 2.Non uniform image density: 209Digital Radiography 203. 3. Distorted Images: 210Digital Radiography 204. 4. Double Images: 211Digital Radiography 205. Damaged Image receptors: 212Digital Radiography 206. Scratched phosphor surface mimicking root canal filling A and retake B. Digital Radiography 213 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 207. Image artifacts resulting from excessive bending of the PSP plate and excessive bending has resulted in permanent damage to the phosphor plate Digital Radiography 214 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 208. PSP circular artifact as a result of plate damage and localized swelling of the protective coating from disinfectant solution on work surface Digital Radiography 215 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 209. PSP image artifact resulting from plate surface contamination This artifact was caused by a glove powder smudge that prevented proper scanning of the affected area of the PSP plate. Digital Radiography 216 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 210. Malfunctioning CCD sensor resulting from rough handling (dropped sensor). The sensor produces geometric image artifacts Digital Radiography 217 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 211. Improper use of image processing tools, such as filters, may result in false-positive findings. An edge enhancement filter was applied to the panoramic image, which produced radiolucencies at restoration edges simulating recurrent caries These radiolucencies are not present in a follow- up intraoral image Digital Radiography 218 White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 212. Clinical comparison of Intraoral Imaging Alternatives 219Digital Radiography 213. 220Digital Radiography Imaging Step Film CCD/CMOS PSP Receptor preparation. None 1) Place protective plastic sleeve over receptor 2) Receptor must be connected to computer and patient identifying information entered for acquisition/archiving software 1) Erase plates 2) Package plates in protective plastic envelope Receptor placement. 1) Film holding devices 2) Film may be bent to accommodate anatomy 1) Specialised receptor holder 2) Inflexible and bulkiness 3) Receptor cable 4) Discomfort 1) Film holding devices 2) Bending of receptor may irreversibly damage it Exposure. Simple exposure Computer must be activated before exposure Simple exposure White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 214. 221Digital Radiography Imaging Step Film CCD/CMOS PSP Processing. 1) Dark room 2) Processing chemicals 3) Processing time 4) Hazardous wastes Image acquisation and display is almost immediate 1) Dim light envt 2) Processor must be programmed with patient and detector information so that images are identified, preprocessed and stored properly Display Preparation. Film mounts 1) Software digital mount 1) Individual mount 2) Digitally rotated Display 1) A room with subdued lighting and a masked viewbox 2) Any light source 1) subdued lighting 2) Acomputer and display with app. Software 3) Size of the display restrict the no. of images Image Duplication. Inferior to original and sometimes non- diagnostic 1. Electronic copies may be stored oon variety of media without loss of image quality 2. Output on Film or paper is inferior and non-diagnostic White SC, Pharoah MJ, Oral Radiology Principles and Interpretation, 6th Edition Mosby 2009 215. Advantages of digital imaging 222Digital Radiography 216. Dose reduction Dose reductions of up to 90 per cent compared to E speed film have been reported by some authors in the diagnosis of caries. Although some researchers do claim dose reductions compared with conventional extra- oral film, in practice the background noise rises to unacceptable levels. It is now accepted that there is no appreciable reduction compared with films used in conjunction with rare earth intensifying screens. 223Digital Radiography Dentomaxillofacial Radiology 1995; 24: 250 217. Image manipulation This is perhaps the greatest advantage of digital imaging over conventional film. It involves selecting the information of greatest diagnostic value and suppressing the rest. Manufacturers provide software programmes with many different processing tools, however some are more useful than others and these include: 224Digital Radiography Dentomaxillofacial Radiology 2012,41(3)203-210 218. 1. Contrast enhancement This can effectively compensate for over or under exposure of the digital image. It has been shown that contrast enhancement of CCD devices were more accurate than E-speed film for detecting simulated caries under orthodontic bands 225Digital Radiography The British Journal of Radiology 1991,64(763)591-595 219. 2. Measurements Digital callipers, rulers and protractors are some of the many tools available for image analysis. Many authors have reported on their application in cephalometric analysis. The images can also be superimposed onto each other and onto digital photographs. 226Digital Radiography Journal of Endodontics 2007, 33(1) 16 220. 3. 3-D reconstruction This application can be theoretically used to reconstruct intra- and extra-oral images. The uses range from profiling root canals to visualizing facial fractures in all three dimensions. 227Digital Radiography Brennan J. Journal of Orthodontics 2002 (29) 6669 221. 4. Filtration The addition of filters to the airspace around the face can clarify the soft tissue profile if the original soft tissue image was poor 228Digital Radiography Brennan J. Journal of Orthodontics 2002 (29) 6669 222. Time Much time is gained especially with the CCD system where the image is displayed at the chairside immediately post exposure. Although a lag time between scanning and the appearance of an image exists with the PSP method it is still substantially faster than conventional developing processes in general use. 229Digital Radiography Brennan J. Journal of Orthodontics 2002 (29) 6669 223. Storage Storage was initially a problem before the development of DVDs and CD ROMs as three peri-apical images would fill a floppy disc. However, now a CD ROM can hold over 30,000 images. This means that images can be stored cheaply and indefinitely. 230Digital Radiography Brennan J. Journal of Orthodontics 2002 (29) 6669 224. Teleradiology Teleradiology is the transmission of radiological patient images, such as x-rays, CTs, and MRIs, from one location to another for the purposes of sharing studies with other radiologists and physicians. This had the advantages of not losing radiographs in the post and saving time if an urgent appointment is required. 231Digital Radiography 225. Teleradiology Teleradiology is a growth technology given that imaging procedures are growing approximately 15% annually against an increase of only 2% in the Radiologist population. Teleradiology has the potential for off-site consultation, insurance submission and improved access to care for patients in remote locations 232Digital Radiography 226. Environmentally friendly No processing chemicals are used or disposed of. Both CCD sensors and the PSP plates are capable of being reused for many thousands of exposures. They can, however, become scratched and damaged if not handled carefully. 233Digital Radiography Brennan J. Journal of Orthodontics 2002 (29) 6669 227. Medico-legal Many insurance companies in the USA are accepting digital images as valid attachments when the claims are electronically claimed. Digital Radiography 234 Dentomaxillofacial Radiology 2000, 12(4)292-297 228. Disadvantages of digital imaging 235Digital Radiography 229. Cost Currently the cost of Intra oral sensor 1.2 2 lakh Extra oral machins 10 - 15 lakh 237Digital Radiography 230. Sensor dimensions These are still quite bulky for the CCD system and awkward to position due to trailing fibre optic wires. The original problem of small sensor active areas has been rectified and the same amount of information can be captured as conventional film. 238Digital Radiography Brennan J. Journal of Orthodontics 2002 (29) 6669 231. Cross-infection control Each intra-oral sensor and plate must be covered by a plastic bag, and this bag is changed between patients. However, if they become directly contaminated there is no way of sterilizing them and they should be discarded regardless of expense. 239Digital Radiography Brennan J. Journal of Orthodontics 2002 (29) 6669 232. Medico-legal Concerns have been raised in the past about the ability to manipulate the images for fraudulent purposes. Manufacturers of software programmes have installed audit trails, which can track down and recover the original image. 240Digital Radiography Dentomaxillofacial Radiology 2000, 12(4)292-297 233. Conclusion The technology is now available to run a practice almost paper free. It is theoretically possible to store clinical notes, photographs, radiographs, and study models on disc, and refer or consult online. Research is also continuing into the development of a credit card sized smart card, which could carry a patients medical and dental notes along with their radiographic images. It is important that advances in technology are accepted and the benefits that they produce utilized in order that clinical practice and patient care continue to improve. Digital Radiography 241 234. Thank You To be continue.. Digital Radiography 242