Chapter 25: Digital Imaging
- 2. LEARNING OBJECTIVES LESSON 25.1: DIGITAL IMAGING 1. Define the key terms associated with digital imaging. 2. Describe the purpose and use of digital imaging. 3. Discuss the fundamentals of digital imaging. 4. Describe radiation exposure in digital imaging. 5. List and describe the equipment used in digital imaging. 6. List and describe the two types of digital imaging.
- 3. LEARNING OBJECTIVES LESSON 25.1: DIGITAL IMAGING (CONT.) 7. Describe the patient and equipment preparations required for digital imaging. 8. List and discuss the advantages and disadvantages of digital imaging.
- 4. INTRODUCTION • Advances in technology have produced a significant impact in the profession of dentistry as well as dental imagine • Digital imaging was introduced to dentistry in 1987 • Relatively new • Digital imaging is a dependable and versatile technique that provides clean, detailed images and enhance interpretation and diagnoses • An expensive investment for a dental office
- 5. BASIC CONCEPTS • Digital imaging is a technique used to record radiographic images • No film or processing chemistry is used • Uses an electronic sensor and computerized imaging system that produces x-ray images almost instantly on a computer monitor
- 6. TERMINOLOGY • Analog image: Radiographic image produced by conventional film. • Charge-coupled device (CCD): Solid-state silicon chip detector that converts light or x-ray photons into an electrical charge or signal. • Digital imaging: Filmless imaging system. • Digital image: An image composed of pixels that can be stored in a computer. • Digital subtraction: One feature of digital imaging; a method of reversing the gray scale as an image is viewed • Digitize: In digital imaging, to convert an image into a digital form that can be processed by a computer.
- 7. TERMINOLOGY (CONT.) • Direct digital imaging: Method of obtaining a digital image, in which an intraoral sensor is exposed to x-radiation to capture a dental image that can be viewed on a computer monitor. • Indirect digital imaging: Method of obtaining a digital image, in which a sensor is scanned following exposure to x-radiation and then converted into a digital form that can be viewed on a computer monitor. • Sensor: In digital imaging, a receptor that is used to capture an extraoral or intraoral image • Storage phosphor imaging: Method of obtaining a digital image in which the image is recorded on a phosphor-coated plate and then placed into an electronic processor.
- 8. PURPOSE AND USE • To generate images that can be used in the diagnosis and assessment of dental disease • To detect lesions, diseases, and conditions of the teeth and surrounding structures • To confirm or classify suspected disease • To localize lesions or foreign objects • To provide information during dental procedures • To evaluate growth and development • To illustrate changes secondary to caries, periodontal disease, or trauma • To document the condition of a patient at a specific point in time • To aid in the development of a clinical treatment plan
- 9. FUNDAMENTALS • Digital imaging • A method of capturing an image using a sensor, breaking it into electronic pieces, and presenting and storing the image using a computer • Film-based images are produced hen x-ray photons strike an intra oral film; knows as an analog image • Digital imaging receives the analog information and converts it a digital image • The digital image is an array of pixel elements • An electronic charge is produced on the surface of the sensor; this electronic signal is digitized; or converted into digital form • Software is used to store the image electronically and it is displayed within seconds to minutes • Can by manipulated to enhance its appearance for interpretation and diagnoses
- 11. RADIATION EXPOSURE • Digital imaging requires less x-radiation exposure than film- based imaging • The typical sensor is more sensitive to x-rays than conventional film. • Exposure times are 50% to 90% less than that required for conventional radiography • Supports the ALARA principle and therefore the use of digital imaging is recommended
- 12. EQUIPMENT • Digital imaging requires the use of specialized equipment • X-ray unit • Conventional intraoral dental x-ray unit may be used in both film-based and digital imaging; timer must be adapted • Units that are made for digital imaging are modern in appearance and feature adjustments for shorter exposure times
- 13. EQUIPMENT CONTINUED… • Sensor • A small detector that is placed in the mouth of the patient and used to capture the radiographic image • Most manufacturers produce sensors similar in dimension to size 0, 1, 2, and 4 intraoral films • Wired • The imaging sensor is linked by a fiber optic cable to a computer. • Wireless • The imaging sensor is not linked by a cable. • Most popular types of direct sensor technologies • Charge-coupled device • Complementary metal oxide semiconductor/active pixel sensor
- 14. CHARGE-COUPLED DEVICE (CCD) • The most common image receptor used in dental digital imaging • A solid-state detector that contains a silicon chip with an electronic circuit embedded in it • The silicon chip is what is sensitive to x-rays or light • Not new technology, developed in the 1960’s, CCD technology is also used in fax machines, home video cameras, microscopes, and telescopes. • The electrons that make up the silicon CCD can be visualized as being divided into an arrangement of blocks or picture elements known as pixels • Pixel • A small box or “well” into which the electrons produced by the x-ray exposure are deposited • A pixel is the digital equivalent of a silver crystal in conventional radiography • It is also more structured in an ordered arrangement, unlike the random arrangement of silver crystals
- 15. CHARGE-COUPLED DEVICE (CCD) (CONT.) • The x-ray photons that come into contact with the CCD cause electrons to be released from the silicon and produce a corresponding electronic charge. • Each pixel arrangement, contains an electronic charge proportional to the number of electrons that reacted within the well. • Each pixel arrangement corresponds to a specific area on the linked computer screen • Electronic latent image is produced
- 16. COMPLEMENTARY METAL OXIDE SEMICONDUCTOR/ ACTIVE PIXEL SENSOR (CMOS/APS) • One manufacturer uses a CMOS/APS sensor instead of a CCD. • The chip is less expensive to produce and offers greater durability than the CCD • Advantages are that the individual pixels can be made smaller, the power requirements are less, and the production cost of the chip is lower • CMOS sensors can be connected to a computer using a low-power external connection such as a USB.
- 17. CCD Sensor CMOS Sensor
- 18. COMPUTER • Used to store the incoming electronic signal • Converts the electronic signal from the sensor into a shade of gray that is viewed on the computer monitor • The computer digitizes, processes, and stores information received from the sensor • An image is recorded on a computer monitor in 0.5 to 120 seconds • Has split screen and magnification capability • Images may be stored permanently in the computer, printed on a hard copy for the patient record, or transmitted electronically to insurance companies or referring dental specialists.
- 22. TYPES OF DIGITAL IMAGING • The difference between the methods lies in how the image is obtained and in what size the receptor plates are available. • Direct digital imaging • Indirect digital imaging • Scanning traditional images • Storage phosphor imaging
- 23. DIRECT DIGITAL IMAGING • Components include an intraoral dental x-ray unit, a sensor, and a computer with imaging software. • A sensor is placed into the mouth of the patient and exposed. • The sensor captures the image and transmits it directly to the computer monitor. • Within seconds of exposing the sensor to radiation, an image appears on the computer screen. • Software is used to enhance and store the image.
- 24. INDIRECT DIGITAL IMAGING • Components include a scanner and a computer. • This concept is similar in theory to scanning an image, such as a photograph, to a computer screen • Extra step compared to direct digital imaging • An existing x-ray film is digitized using a PSP plate • The sensor is that put in the scanner • The image is displayed on a computer monitor.
- 25. STORAGE PHOSPHOR IMAGING • Also referred to as photo-stimulable phosphor imaging (PSP). • A wireless digital imaging system • A reusable imaging plate coated with phosphors is used instead of a sensor with a fiber optic cable. • The phosphor-coated plates are flexible and fit into the mouth. • A high-speed scanner is used to convert the information into electronic files. • This type of digital imaging is less rapid than direct digital imaging. • It is recommended that the dental radiographer review the mounted digital images and confirm the images with the clinical findings while the patient is present in the dental chair.
- 26. PSP PLATE • Following exposure, it converts x-ray energy into light • The image remains on the reusable plate until it is erased after the scanning process • In past years, images were erased or cleared from the PSP plates by exposure to viewbox light for several minutes • Currently, manufacturers use technology that scans and retrieves the digital image, followed by the clearing step for reuse of the PSP plate • Can be damaged by bending or scratching
- 28. INTRAORAL SENSOR PREPARATION • Each sensor is sealed and waterproofed. • The sensor must be covered with a disposable barrier because it cannot be sterilized. • Rigid digital sensors, wired or wireless, must be covered with a disposable barrier sleeve. • The number and size of the sensor vary with different manufacturers. • Digital sensors cannot withstand heat sterilization
- 31. INTRAORAL SENSOR PLACEMENT • The sensor is held in the mouth by bite-block attachments or devices that aim the beam and sensor accurately. • The paralleling technique is the preferred exposure method • As with conventional intraoral film, the sensor is centered over the area of interest.
- 34. ADVANTAGES OF DIGITAL IMAGING • Superior gray-scale resolution • Digital radiography uses up to 256 colors of gray compared with the 16 to 25 shades of gray differentiated on a conventional film. • The ability to manipulate the density and contrast of the image without additional exposure to the patient is also an advantage. • Reduced exposure to x-radiation • The exposure of digital radiography is 50% to 80% less than that required for conventional radiography. • Increased speed of image viewing • The images are able to be viewed instantaneously.
- 35. ADVANTAGES CONTINUED… • Lower equipment and film cost • No film cost or disposable necessary. • Increased efficiency • Requires less time • Enhancement of diagnostic image • Colorization, zoom, digital subtraction • Effective patient education tool • Eco-friendly tool • A “greener” alternative because it doesn’t use any chemical processing or generate any hazardous waste materials.
- 36. MAGNIFICATION
- 37. DIGITAL SUBTRACTION: THE GRAY-SCALE IS REVERSED TO THAT RADIOLUCENT IMAGES APPEAR WHITE AND RAIOPAQUE IMAGES APPEAR BLACK (ELIMINATES DISTRACTING BACKGROUND INFORMATION)
- 38. DISADVANTAGES OF DIGITAL IMAGING • Initial setup costs • Image quality • Up for debate • Sensor size and thickness • Some digital x-ray sensors are thicker and less flexible than intraoral film. • Infection control • digital sensors cannot withstand heat sterilization, therefore sensors require complete coverage with plastic sleeves that must be changed with each patient. • Wear and tear • Legal issues • Because the original digital image can be enhanced, it is questionable whether it can be used as evidence in court.
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Editor's Notes
- #5: This process is relatively new technology. Does your particular dental office use digital imaging? (Answers will vary.) This technology is currently an expensive investment for a dental office.
- #6: What kind of film is used in digital imaging? (No film is used.) Are radiographic solutions used in digital radiography? (No) How are images “processed”? (An electronic sensor sends images to a computer.) What is a sensor? (A small wired or wireless electronic square or rectangle) How long does it take for the sensor to transmit the information on the computer to display the image? (Seconds)
- #7: Analog image: Radiographic image produced by conventional film. Bit-depth image: Number of possible gray-scale combinations for each pixel. Charge-coupled device (CCD): Solid-state silicon chip detector that converts light or x-ray photons into an electrical charge or signal. Digital imaging: Filmless imaging system. Digital image: An image composed of pixels that can be stored in a computer. Digital subtraction: One feature of digital imaging; a method of reversing the gray scale as an image is viewed. Digitize: In digital imaging, to convert an image into a digital form that can be processed by a computer.
- #8: Direct digital imaging: Method of obtaining a digital image, in which an intraoral sensor is exposed to x-radiation to capture a dental image that can be viewed on a computer monitor. Indirect digital imaging: Method of obtaining a digital image, in which a sensor is scanned following exposure to x-radiation and then converted into a digital form that can be viewed on a computer monitor. Line pairs/millimeter (lp/mm): Measurement used to evaluate the ability of the computer to capture the resolution of an image. Pixel: A discrete unit of information. Sensor: In digital imaging, a receptor that is used to capture an extraoral or intraoral image. Storage phosphor imaging: Method of obtaining a digital image in which the image is recorded on a phosphor-coated plate and then placed into an electronic processor.
- #9: The images produced are diagnostically equivalent to or better than film-based images, thus enabling the dental radiographer to see conditions that cannot be identified clinically.
- #10: What type of technique is used with digital imaging? (The sensor picks up the x-rays and transmits an image to the computer, which digitizes the image and displays it in seconds.)
- #12: Since there is less x-radiation used with digital imaging, does the patient still need to wear a lead apron? (Yes.)
- #13: Conventional intraoral dental x-ray unit may be used in both film-based and digital imaging; timer must be adapted. Sensor can be wireless. CCD is a solid-state detector that contains a silicon chip with an electronic circuit embedded in it. Computer must be up-to-date.
- #14: Most manufacturers produce sensors similar in dimension to size 0, 1, 2, and 4 intraoral films.
- #15: CCD technology is also used in fax machines, home video cameras, microscopes, and telescopes. The silicon chip is what is sensitive to x-rays or light. A pixel is the digital equivalent of a silver crystal in conventional radiography. It is also more structured in an ordered arrangement, unlike the random arrangement of silver crystals.
- #16: The pixel size varies depending on the digital receptor.
- #17: CMOS sensors can be connected to a computer using a low-power external connection such as a USB.
- #19: The speed of image recording is extremely useful during certain dental procedures. Images may be stored permanently in the computer, printed on a hard copy for the patient record, or transmitted electronically to insurance companies or referring dental specialists.
- #23: The difference between the methods lies in how the image is obtained and in what size the receptor plates are available.
- #24: Within seconds of exposing the sensor to radiation, an image appears on the computer screen. Extraoral imaging machines can also use direct digital sensors with either CCD or CMOS detectors.
- #25: This concept is similar in theory to scanning an image, such as a photograph, to a computer screen. Image is similar to a copy of the image versus the original.
- #26: Also referred to as photo-stimulable phosphor imaging (PSP). It is recommended that the dental radiographer review the mounted digital images and confirm the images with the clinical findings while the patient is present in the dental chair.
- #29: The number and size of the sensor vary with different manufacturers. The intraoral sensor is placed inside of the patient's mouth similar to the technique used in conventional film placement.
- #32: Paralleling technique film holders must be used to stabilize the sensor in the mouth. As with conventional intraoral film, the sensor is centered over the area of interest.
- #35: Digital radiography uses up to 256 colors of gray compared with the 16 to 25 shades of gray differentiated on a conventional film. The ability to manipulate the density and contrast of the image without additional exposure to the patient is also an advantage. The exposure of digital radiography is 50% to 80% less than that required for conventional radiography. The images are able to be viewed instantaneously. No film cost or disposable necessary. A “greener” alternative because it doesn’t use any chemical processing or generate any hazardous waste materials.
- #39: Some digital x-ray sensors are thicker and less flexible than intraoral film. Some digital sensors cannot withstand heat sterilization, therefore sensors require complete coverage with plastic sleeves that must be changed with each patient. Because the original digital image can be enhanced, it is questionable whether it can be used as evidence in court.