# DIGITAL RADIOGRAPHY College of Dentistry 516 MDS Asma ’ a Al-Ekrish A REVIEW.

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DIGITAL RADIOGRAPHY College of Dentistry 516 MDS Asma ’ a Al-Ekrish A REVIEW

HISTORY Image Plate Systems 1947- Berg and Kaiser 1975- optical scanner and digitizer 1981- publicly presented in 1994- the first dental PSP (Digora-Sordex) Solid State Systems 1960's- development of CCD and CMOS 1970’s- CCD (Bell Laboratories) 1988- CMOS (Scotland) 1980’s- first intraoral digital system - Francis Mouyen (Radiovisiography system RVG, Trophy, France

TYPES OF DENTAL IMAGES Analogue: Gray shades are continuous and show a gradual changeGray shades are continuous and show a gradual change Digital: Gray shades have discrete values and are assigned to individual picture elements. Smooth transitions changed into a checker pattern, by the pixels

IMAGE RECEPTORS Sensors When X-rays hit sensor, an electronic charge is produced on the surface of the sensor. Electronic signal is sent to the computer (either directly or indirectly) as an analogue signal and there is digitized ( by a frame-grabber or A-D converter) Measurements of the photon intensity are transmitted to the computer where they are recorded numerically

THE DIGITAL IMAGE C) Numerical representation of pixel values. A) X-ray shadow. B) Image as detected by the digital sensor; each square is a pixel. D) Digital image on the computer screen. (van der Stelt 2000; van der Stelt 2005)

THE DIGITAL IMAGE C) Numerical representation of pixel values. A) X-ray shadow. B) Image as detected by the digital sensor; each square is a pixel. D) Digital image on the computer screen.

THE DIGITAL IMAGE

binary numerals binary numerals 0 (zero) 1(one) 01101001  2 8 = 256 possible combinations 0011100011010101  2 16 = 64,000 possible combinations

DIRECT AND INDIRECT DIGITAL IMAGING A.Direct Digital Radiography: Real Time Systems (CCD or CMOS) B.Semi-direct Digital Radiography SPS Image Plates C.Indirect Digital Radiography Converting a pre-existing analogue image to a digital one

REQUIREMENTS OF DIGITAL SYSTEM 1.X-ray generator 2.Sensor 3.Computer 4.Software 5.Monitor 6.Printer

REQUIREMENTS OF DIGITAL SYSTEM COMPONENTS OF THE SYSTEM MUST BE DICOM COMPATIBLE ( Digital Imaging Communication in Medicine )

REAL TIME SYSTEMS A- Charged Couple Device (CCD) Sensors B- Complementary Metal Oxide Semiconductors (CMOS) sensors

REAL TIME SYSTEMS CCD CCD fibreoptics Intensifying screen SILICON CHIP WITH ELECTRONIC CIRCUIT EMBEDDED INTO IT.

REAL TIME SYSTEMS CCD Production of the image X-rays electronic signal To A-D converter light from scintillating layer

REAL TIME SYSTEMS CCD Production of the image A-D Converter 1- Sampling 2- Quantization White and Pharoah (2004)

REAL TIME SYSTEMS CMOS RAM Micro- controller unit

REAL TIME SYSTEMS CCD vs. CMOS CCDCMOS When invented1967 Power consumption400mW40mW Sensitivity to lightExcellent Sensitivity to x-raysHighUnknown CostHighLow ManufacturingExpensive Fixed pattern noiseLowHigh Quantum efficiencyExcellentFair Adapted from Langlais, R.P., and Miles D.A. Digital radiographic imaging: Technology for the next millennium. www. Learndigital.net

REAL TIME SYSTEMS ADVANTAGES 1.Image immediately displayed 2.Higher spatial resolution than semi-direct systems (PSP)

REAL TIME SYSTEMS DISADVANTAGES 1.Cost 2.Bulky 3.Electrical 4.cords 5.Rigid 6.Active- area limitations

Photostimulable Phosphor Plates (PSP) IMAGE PLATE SYSTEMS backing barium flourohalide Protective coating

IMAGE PLATE SYSTEMS Production of the Image Decay of the Image

IMAGE PLATE SYSTEMS ADVANTAGES 1.Thin 2.Flexible 3.Cordless 4.Size comparable to standard size films 5.Reusable 6.Broad exposure latitudes 7.May be used with existing x-ray generators

IMAGE PLATE SYSTEMS DISADVANTAGES 1. Extra step- scanning procedure 2. Dose reduction not as much as with solid- state detectors

EXTRA-ORAL RADIOGRAPHY CCD or PSP may be used CCD or PSP may be used Tomography only with PSP Tomography only with PSP

QUALITY FACTORS Resolution: how well closely spaced objects can be distinguished Resolution: how well closely spaced objects can be distinguished Sharpness: distinctiveness of feature boundaries Sharpness: distinctiveness of feature boundaries Contrast: distinctiveness of light and dark areas. Contrast: distinctiveness of light and dark areas. Distortion: the difference between the apparent and true locations of points on an image. Distortion: the difference between the apparent and true locations of points on an image.

QUALITY FACTORS Modulation Transfer Function (MTF): Describes the ability of a system to record the spatial frequencies that are available to be recorded Modulation Transfer Function (MTF): Describes the ability of a system to record the spatial frequencies that are available to be recorded Noise: unwanted fluctuations in image density Noise: unwanted fluctuations in image density Detector Quantum Efficiency (DQE): combined effect of noise and contrast performance of an imaging system, expressed as a function of object detail. Detector Quantum Efficiency (DQE): combined effect of noise and contrast performance of an imaging system, expressed as a function of object detail.

QUALITY FACTORS CONTRAST RESOLUTION

QUALITY FACTORS SPATIAL RESOLUTION

QUALITY FACTORS SPATIAL RESOLUTION

QUALITY FACTORS SPATIAL RESOLUTION

QUALITY FACTORS SIGNAL TO NOISE RATIO (SNR): Reproduced from Oakley (2003 )

QUALITY FACTORS ARTIFACTS Distortions are any unwanted elements in the image Produced by either: the image sensor (CCD/CMOS), optical system, internal image processing algorithms, or compression algorithm.

IMAGE DISPLAY- MONITORS Cathode Ray Tubes (CRT) Flat panel- Liquid Crystal Displays (LCD) Reproduced from Oakley (2003 )

IMAGE DISPLAY- MONITORS QUALITY FACTORS OF MONITORS 1. dot pitch 2. resolution 3. luminance 4. brightness and contrast settings

IMAGE DISPLAY- MONITORS QUALITY FACTORS OF MONITORS 5. refresh rate 6. color depth 7. footprint and weight 8. contrast layer

FACILITIES OFFERED BY DIGITAL RADIOGRAPHY Dose reduction ( van der Stelt 2000; van der Stelt 2005 )

FACILITIES OFFERED BY DIGITAL RADIOGRAPHY Dose reduction

Image processing Image Enhancement Contrast enhancement Filtering Subtraction Color Image Restoration System defects Geometric Transformation Image Analysis Measurement Segmentation Feature extraction Object classification CADIA Image Compression Lossless Lossy Image Synthesis Tomosynthesis TACT Localized CT FACILITIES OFFERED BY DIGITAL RADIOGRAPHY Miles, D. (2000). "The future of digital imaging in dentistry." Dental Clinics of North America 44: 427-438

Storage, archiving, retrieval FACILITIES OFFERED BY DIGITAL RADIOGRAPHY

Electronic transmission FACILITIES OFFERED BY DIGITAL RADIOGRAPHY

1.Dose reduction 2.Time- faster to acquire 3.No chemical processing- eliminating processing errors, saving space and money on the long term. Environmentally friendly 4.Long term savings on film processing 5.Better gray scale resolution 6.Image processing 7.Teleradiology 8.Less storage space GENERAL ADVANTAGES

1.Initial setup cost 2.Less spatial resolution 3.Sensor size 4.Requires more space in the operatory- but no dark room. 5.more time to process information GENERAL DISADVANTAGES

Quality diagnostic images Quality diagnostic images Radiation dose less than film Radiation dose less than film Lossless archiving is allowed in an image file format DICOM compatible Lossless archiving is allowed in an image file format DICOM compatible ESSENTAIALS OF ANY SYSTEM

The paperless office The paperless office Computer aided diagnosis and detection of defects Computer aided diagnosis and detection of defects 3-D visualization of dental structures based on radiographic data at the level of single teeth 3-D visualization of dental structures based on radiographic data at the level of single teeth Wireless technology Wireless technology FUTURE of DIGITAL RADIOGRAPHY

Continued reduction is storage media and size Continued reduction is storage media and size Testing, maintenance, and upgrade of equipment and software online Testing, maintenance, and upgrade of equipment and software online Research towards a "smart card"- which could carry a patient's medical and dental notes along with their radiographic images Research towards a "smart card"- which could carry a patient's medical and dental notes along with their radiographic images Global education and distanc learning Global education and distanc learning FUTURE of DIGITAL RADIOGRAPHY

Analoui, M. and K. Buckwalter (2000). "Digital radiographic image archival, retreival, and management." Dental Clinics of North America 44(2): 339-358 Farman, A. and T. Farman (2005). "A comparison of 18 different x-ray detectors currently used in dentistry." Oral Surg Oral Med Oral Pathol Oral Radiol Endod 99: 485-9. Miles, D. (2000). "The future of digital imaging in dentistry." Dental Clinics of North America 44: 427-438. Oakley, J. (2003). Digital imaging. A primer for radiographers radiologists and health care professionals. London, Greenwich Medical Media Limited. van der Stelt, P. F. (2000). "Principles of digital imaging." Dental Clinics of North America 44(2): 237-247. van der Stelt, P. F. (2005). "Filmless imaging. The uses of digital radiography in dental practice." JADA 136: 1379-1387. White, S. C. and M. J. Pharoah (2004). Oral radiology.Principles and interpretation. St. Louis, Mosby. References:

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