1. 1 DIGITAL RADIOGRAPHY

2. 2 Digital Radiography A “filmless” imaging system introduced in 1987 Digital radiography uses an electronic sensor, instead of “film” Requires a computerized imaging system to produce an image. No film is used, and no processing chemicals are required. A “filmless” imaging system introduced in 1987 Digital radiography uses an electronic sensor, instead of “film” Requires a computerized imaging system to produce an image. No film is used, and no processing chemicals are required.

3. 3 Analog vs. Digital “film based” Produces a “radiograph” Produced when x-ray photons strike the film Shows on film as a continuous spectrum of gray shades between the extremes of white and black The shades “flow into” one another like a painting “film based” Produces a “radiograph” Produced when x-ray photons strike the film Shows on film as a continuous spectrum of gray shades between the extremes of white and black The shades “flow into” one another like a painting “sensor” is recording medium Produces a computerized “image” Uses an array of “pixel” elements with exact gray and discrete gray values for each pixel. More like a mosaic pattern instead of the shades “flowing together”

4. 4 Digital vs. Analog X-ray photons Strike sensor creating a surface electrical charge Which is converted to digital form (digitized) Sensor transmits digitized image to computer Image is produced almost instantly! Computer stores the information X-ray photons Strike sensor creating a surface electrical charge Which is converted to digital form (digitized) Sensor transmits digitized image to computer Image is produced almost instantly! Computer stores the information X-ray photons Interact with silver halide crystals Produces a latent image Chemical processing takes time Visible image Stored on mounts within the patient’s paper record

5. 5 Analog to Digital Converter The data acquired by the sensor is communicated to the computer in analog form, then converted by the use of the analog –to-digital-converter (ADC) The image is displayed within seconds and may be readily manipulated to enhance diagnosis. The data acquired by the sensor is communicated to the computer in analog form, then converted by the use of the analog –to-digital-converter (ADC) The image is displayed within seconds and may be readily manipulated to enhance diagnosis.

6. 6 Types of Digital Sensors Charge-Coupled Device (CCD) Complimentary Metal Oxide Semiconductor/Active Pixel Sensor (CMOS/APS) Charge-Coupled Device (CCD) Complimentary Metal Oxide Semiconductor/Active Pixel Sensor (CMOS/APS)

7. 7 CCD One of the most common digital sensors used in dental digital imaging The CCD is a sensor that contains a silicon chip with an electric circuit built into it. The silicon chip is sensitive to x-radiation The electrons that compose the silicon CCD are arranged in “blocks” or picture elements known as pixels. A pixel is the digital equivalent of the silver halide crystal on conventional film. One of the most common digital sensors used in dental digital imaging The CCD is a sensor that contains a silicon chip with an electric circuit built into it. The silicon chip is sensitive to x-radiation The electrons that compose the silicon CCD are arranged in “blocks” or picture elements known as pixels. A pixel is the digital equivalent of the silver halide crystal on conventional film.

8. 8 CCD Unlike the silver halide crystals contained in the film emulsion, which is randomly distributed, the pixel arrangement is ordered. The sensor will contain 307, 200 pixels! Each pixel is linked to a specific area on the computer screen. As the x-ray photons come in to contact with the sensor, this produces an electronic charge that is connected to a specific area on the computer screen Unlike the silver halide crystals contained in the film emulsion, which is randomly distributed, the pixel arrangement is ordered. The sensor will contain 307, 200 pixels! Each pixel is linked to a specific area on the computer screen. As the x-ray photons come in to contact with the sensor, this produces an electronic charge that is connected to a specific area on the computer screen

9. 9 CMOS Sensor The CMOS differs from the CCD in the way that the pixels are read by the computer. They claim a 25% greater resolution than CCD technology. The CMOS sensor is also less costly to produce and the sensor has greater durability The CMOS differs from the CCD in the way that the pixels are read by the computer. They claim a 25% greater resolution than CCD technology. The CMOS sensor is also less costly to produce and the sensor has greater durability

10. 10 So what does the computer do in digital radiography??

11. 11 The Computer It stores the incoming electronic signal. It also converts the the signal into a shade of grey that is viewed on the computer monitor. Each pixel is represented in the computer by location and color level of the gray. The pixel can create 256 shades of gray, but the human eye can only perceive 32 shades of gray! It stores the incoming electronic signal. It also converts the the signal into a shade of grey that is viewed on the computer monitor. Each pixel is represented in the computer by location and color level of the gray. The pixel can create 256 shades of gray, but the human eye can only perceive 32 shades of gray!

12. 12 Types of Digital Imaging Direct Indirect Direct Indirect

13. 13 Two Ways to Obtain a Digital Image Direct Sensor placed in mouth and exposed to x-rays. Sensor captures image and transmits to computer monitor Image appears within seconds Indirect Scanning in traditional radiographs This method is inferior because the resulting image is a “copy” vs. the original

14. 14 Analog vs. Digital

15. 15 Analog vs. Digital Analog Silver halide crystals Random arrangement on the film Digital Pixel – the digital equivalent of a silver halide crystal, but in an ordered arrangement 307,200 pixels on a sensor! Produce a sort of “electronic” latent image.

16. 16 Digital Imaging Advantages Superior gray scale resolution Decreased patient exposure to radiation Increased speed of image viewing Some cost reductions (no film, processing or darkroom needed) Increased efficiency Enhanced diagnostic image known as digital subtraction Effective patient education tool Disadvantages Initial set-up costs Image quality (on-going debate) Sensor size – thicker and less flexible for patient Legal Issues – because the image can be enhanced

17. 17 Other Features of Digital Imaging “Subtraction” Magnification Measurement “Subtraction” Magnification Measurement

18. 18 Digital Subtraction With digital subtraction, the gray scale is reversed so that radiolucent images (normally black), appear white and radiopaque images (normally white), appear black. Digital subtraction helps to eliminate distracting background information. This feature permits the operator to remove all anatomic structures that have not changed between radiographic examinations to facilitate identification of changes in diagnostic information. With digital subtraction, the gray scale is reversed so that radiolucent images (normally black), appear white and radiopaque images (normally white), appear black. Digital subtraction helps to eliminate distracting background information. This feature permits the operator to remove all anatomic structures that have not changed between radiographic examinations to facilitate identification of changes in diagnostic information.

19. 19 Digital Subtraction

20. 20 Measurement

21. 21 Magnification