Chapter 25: Digital Imaging
Gray Scale
*Bite-depth image:* 2^8 the number of shades of gray visible in an image (0-255)
Sensor preparation
- Each sensor is sealed and waterproofed -The sensor must be covered with a disposable barrier because it cannot be sterilized
Characteristics of a Digital Image-->*Analog vs. Digital*
-*Analog image* = A continuous smooth blend from one color to another -*Digital image* = Like a mosaic made up of many small pieces but together make a whole. -Pixels are short for "picture elements" -Pixels are tiny dots that make up the digital image, the more pixels in an image the higher the resolution and the shaper the image. -*ppi* = Pixel per inch
Pixels
-*Bite-depth image* = digital has no physical form, it exists only as bits of information in a computer file. -*Pixels* = The pixels are arranged in structured order, the x-rays strike the sensor, the pixels cause a electronic charge. Electron Potential Well -*Grid of Pixels* = The sensors are made up of a grid of pixels that are sensitive to x-rays = small box or "well"
Characteristics of a Digital Image
-*Gray Value* = The amount of radiation received by a pixel -*Gray Scale* = refers to the *number of shades of gray visible* in an image - "quantify it by assigning a number" -Each pixel has 256 gray shades of levels: 0 being pure black and 255 pure white -The higher the gray scale, the more likely the image is to record subtle changes in the patients's conditions
Characteristics of a Digital Image
-*Spatial resolution* = is determined by number and size of pixels ~ The higher spatial resolution, the greater the capacity for distinguishing fine detail. -*Line pair/mm (lp/mm)* = Spatial resolution measurement: the greatest number of paired lines visible in 1mm of an image.
Intraoral Sensor-->*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 electrons that make up the silicon CCD can be visualized as being divided into an arrangement of blocks or picture elements known as pixels
Digital imaging
-A *Sensor*, or small detector, is placed inside the mouth of the pt. to capture the radiographic image.
Digital Imaging
-A method of capturing a radiographic image using a sensor, breaking it into electronic pieces, and presenting and storing the image using a computer -Image used to describe the pictures that are produced -A sensor placed inside the mouth -The electronic signal is digitized -We no longer need the photographic process. We no longer "take a radiograph" we "acquire an image"
Storage Phosphor Imaging
-A second type of indirect digital imaging which is a wireless digital imaging system. -Also referred to as photo-stimulable phosphor imaging (PSP) -In this system a reusable imaging plate coated with phosphors is used instead of a sensor with a fiberoptic cable. -The phosphor coated plate is flexible and is placed into the mouth in the same way as intraoral film, and resembles an intensifying screen that is used to expose an extraoral film in that it converts x-ray energy into light.
Pixel
-A small box, or "well" into which the electrons produced by the x-ray exposure are deposited. -This is a digital equivalent of a silver crystal used in conventional radiography. -As opposed to a film emulsion that contains a random arrangement of silver crystals, this is structured in an ordered arrangement. -The range of numbers for this varies from 0 t 255, which creates 256 shades of gray, referred to as a _________ gray-scale resolution. -The human eye can only perceive 32 shades of gray -The software allows for manipulation of these, enhancing contrast the density without additional x-ray exposure of the pt.
Intraoral Sensor
-A small detector that is placed in the mouth of the pt. and used to capture the radiographic image 1. *CCD*: Charge-coupled device = Wired - the imaging sensor is linked by a fiber optic cable to a computer 2. *CMOS or APS:* Complementary metal oxide semiconductor or active pixel sensor = Wireless - The imaging sensor is not linked by a cable
Intraoral Sensor-->*PSP Plate*
-About same size as regular film. PSP plates for panoramic don't require an intensifying screen **Do Not Bend the Plates*
Complementary Metal Oxide Semiconductor/Active Pixel Sensor (CMOS/APS)
-CMOS detector is silicon based and differs from the CCD detector in the way that the pixels are read. -One digital imaging manufacturer uses this sensor instead of a CCD and claims that it has a 25% greater resolution. -Additional advantages of this technology are the lower production cost of the chip and greater durability than the CCD.
Indirect Digital Imaging
-Components include a CCD camera and computer -An existing x-ray film is digitized using a CCD camera. -The image is displayed on a computer monitor
Traditional Film-based radiography
-Consists of x-radiation interacting with the silver halide crystals of the emulsion, production of a latent image, and chemical processing to convert the latent image into a visible image
Digitizing
-Converting Film Base radiographs 1. Film radiographs can be *digitized by scanning* or by digitally photographing the existing radiograph 2. Use a *Transparency Adapter* to scan the film and send to the scanner, or photograph the film, that is placed on a view box, with a digital camera. 3. Both techniques make the new digital image, a copy, therefore the *quality is poor*
Analog Image
-Depicted by a continuous spectrum of gray shades between the extremes of white and black -Difficult to see where one shade ends and another begins -In digital imaging, the sensor receives this information and converts it to a digital image in the computer processing unit
D.I.C.O.M
-Digital Imaging and Communications In Medicine -Where digital imaging is widely utilized, the medical community has adopted these standards to allow different digital systems to interface with healthcare providers. *Standard of Care* - To improve patient Care
Radiation Exposure
-Digital imaging requires less x-radiation than does conventional radiography. -Less x-radiation is necessary to form a digital image on the sensor = typical sensor is more sensitive to x-radiation than conventional film. -Exposure times for digital imaging are 50% to 80% less than conventional -Exposure time required for digital imaging is 3 impulses (3/60 or 0.05 second)
Digital Imaging
-Digital imaging systems used in dentistry replace film -The main difference between film-based radiography and digital imaging is that the film is replaced with a digital image receptor ~Solid state image receptor = sensor --> direct ~ Photostimuable phosphor (PSP) plate = Polyester plate covered with phosphor crystals --> indirect
Radiation Exposure
-Digital x-rays decrease the amount of radiation exposure by up to 50% to 80% -Research indicates up to 80% reduction when compared to slower D-speed film -D-speed: smaller crystal & sharper image but require more x-ray exposure factor -F-Speed: Larger crystal & less sharper image but require less x-ray exposure factor
Direct Digital Imaging
-Electronically sent to the computer without processing or scanning the image -The sensor contains an electronic chip, the image is sent straight to the computer without need of a scanner *Image Receptor* -CCD = Charge - Coupled Device -CMOS = Complementary Metal Oxide Semiconductor
Radiation Exposure
-F-speed: 12 impulse (0.2 second) -Digital: 6 impulse (0.1 second) -Consideration: **Higher retake rate compared to film-based Radiographs**
Digital systems
-Feature split-screen technology, which allows the operator to view and compare multiple images on the same screen. -Allows specific images to be magnified up to 4 times the original size. -Include a measurement tool as part of the imaging software
Purposes of Digital Imaging
-Generate images that can be used in the diagnosis and assessment of dental disease. -Images produced are diagnostically equivalent to film-based imaging and enable radiographer to identify many conditions that may otherwise go undetected, as well as to see conditions that cannot be identified clinically -Allows radiographer to obtain a wealth of information about teeth and supporting structures
Characteristics of a Digital Image
-Gray scale is the most important characteristic of a radiographic image -Computer monitors can display 256 gray levels -Human eyes can distinguish about 32 shades of gray unaided -Quality of the radiographs - the combination of pixels, spatial resolution, and gray scale that determine the quality of the final image
Disadvantages of Digital Imaging
-Initial setup costs -Image quality = digital imaging performs at least as well as than traditional radiography -Sensor size and thickness -Infection control -Wear and tear -Legal issues
X-Radiation Source
-Most digital imaging systems use a conventional dental x-ray unit as the x-radiation source. -The x-ray unit timer must be adapted to allow exposures in a time frame of 1/100 of a second
Intraoral Sensor-->*Complementary Metal Oxide Semiconductor (CMOS)/Active Pixel Sensor (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 -Claims that 25% greater resolution than CCD
Charge-Coupled Device
-One of the most common image receptors used in dental digital imaging -Used in fax machines, home video cameras, microscopes, and telescopes. -A solid-state detector that contains a silicon chip with an electronic circuit embedded in it, and is sensitive to x-radiation or light -The electrons that compose the silicon CCD can be visualized as being divided into an arrangement of blocks or picture elements known as *pixels.*
Storage phosphor imaging
-Records diagnostic data on a plate after x-ray exposure and then uses a high-speed scanner to convert the information into electronic flies. -Plate is placed into an electronic processor, where a laser scans the plate and produces an image that is transferred to a computer screen. -Less rapid than direct digital imaging
Digital Imaging
-Refers to a method of capturing a radiographic image using a sensor, breaking the image into electronic pieces, and presenting and storing the image using a computer.
Digital x-ray procedure
-Sensor preparation -Sensor Placement
Indirect Digital Imaging
-Similar to the processing of film based conventional x-rays -*Photostimuable phosphor or PSP plate* - a polyester plate is covered with storage phosphor crystals -The image receptor is also called a storage phosphor which is a europium activated barium fluorohalide -*Analog data* = capture the image as analog data and "stores" x-ray energy
Characteristics of a Digital Image-->*Measuring spatial resolution*
-Since the spatial resolution refers to clarity, for different devices, different terms are used to measure it. *Dots per inch* = dpi is used in monitors *Lines per inch* = lpi is used in laser printers *Pixel per inch* = ppi is used to measure in different devices such as tablets, Mobile phones etc.
Disadvantages of Digital imaging
-Smaller overall sensor dimensions limits recording area -Initial investment cost -Learning curve -technology concern - system variation vs. up keeping the system -Restricted viewing digital images -Reliability
Advantages of Digital Imaging
-Superior gray-scale resolution -Reduced exposure to x-radiation -Increased speed of image viewing -Lower equipment and film cost (?) -Increased efficiency -Enhancement of diagnostic image -Effective pt. education tool -Environmental concerns.
Advantages of Digital Imaging
-Superior gray-scale resolution = digital imaging uses up to 256 shades of gray compared with the 16-25 shades of gray on conventional film. -Ability to manipulate the density and contrast of the digital image without additional exposure -Enables the dental professional to identify dental disease just as with traditional films -Ability to measure the diagnostic value through its ability capture detail or resolution -Reduced exposure to x-radiation -Increased speed of image viewing -Lower equipment and film cost -Increased efficiency -Enhancement of diagnostic image -Effective patient education tool
Indirect Digital Imaging-->*Laser scanning device*
-The PSP plate is placed into a processer, a *laser beam passes over the plate and energy is released in the form of light from the plate and transformed into a digital value.* -This digital value is reconstructed by the computer into an image -*Deactivation of the image plate* - The PSP plate analog data is erased by exposing the plate to bright light for 5 minutes.
X-radiation source
-The conventional x-radiation source is compatible with the digital imaging system. -The x-ray timer must be adapted to allow exposures in a time frame of 1/100 of a second. -A standard x-ray unit that is adapted for digital imaging can still be functional for conventional radiography
Disadvantages of Digital Imaging
-The ease of retakes may result in excess radiation exposure -Bulky, thicker sensor size -Greater discomfort to the pt. - wire, thicker plastic barriers, ridged sensors, etc. -Infection control requires careful adherence.
Indirect Digital Imaging
-The essential components of this system include a CCD camera and a computer. -In the scanning method, an existing radiograph is digitized using a CCD camera. -CCD camera scans the image on the film, digitizes or converts the image, and then displays it on the computer monitor. -This is inferior to direct digital imaging because the resultant image is similar to a "copy" of an image vs the "original" image.
Direct digital imaging
-The essential components of this system include an x-ray machine, an intraoral sensor, and a computer monitor. -Sensor with a fiberoptic cable linked to the computer is placed into the mouth of the pt. and exposed to x-radiation -The sensor captures the radiographic image and then transmits the image to a computer monitor. -Software is then used to enhance and store the image
Bit-depth image
-The number of possible gray-scale combinations per pixel is known as this. -This is determined by the computer software for the digital system. -An 8 bit-depth image has a gray-scale combination of 2^8, which equals 256 shades of gray.
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 because of the dimensional accuracy if images produced and the ease of standardizing such images
Gray value
-The value of each pixel -Descriptions of the intensity = composed exclusively of shades of gray -The gray value is increased (toward 255) or decreased (toward 0) in proportion to the number of x-rays that hit each pixel
Charge-Coupled Device (CCD)
-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, or electron potential well, contains an electronic charge proportional to the number of electrons that reacted within the well. -Each electronic well corresponds to a specific area on the linked computer screen. -When x-radiation activates electrons and produces such electronic charges, an electronic latent image is produced. -The latent image is then transmitted and stored in a computer and can be converted to a visible image on screen or printed on paper.
Intraoral Sensor-->*Charge-Coupled Device (CCD)*
-The x-ray photons that come into contact with the CCD cause electrons to be released from the silicon chip and produce a corresponding electronic charge -Each pixel arrangement, or electron potential well, contains an electronic charge proportional to the number of electrons that reacted within the well. -Each electronic well corresponds to a specific area on the linked computer screen
Indirect Digital Imaging-->*A wireless digital imaging system*
-This is a reusable imaging plate coated with phosphors, and 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
Digital image
-This is an array of picture elements called *pixels*, with discrete gray values for each pixel. -More of a mosaic pattern instead of the shades flowing together
Spatial resoltuion
-This is defined as the number of line pairs per millimeter.
Purpose and use
-To detect lesions, diseases and conditions of the teeth and surrounding structures -To confirm or classify suspected diseases -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
Uses of digital imaging
-To detect lesions, diseases, and conditions of teeth and surrounding structures -Confirm or classify suspected disease -Provide information during dental procedures (root canal therapy instrumentation and surgical placement of implants) -Evaluate growth and development -To illustrate changes secondary to caries, periodontal disease, or trauma -To document the condition of a pt at a specific point in time
Software
-Used to manipulate the images. 1. Side by side images - To compare 2. Magnification - make it larger 3. Density and Contrast - to adjust intensity 4. Measurement tools - for endodontic therapy 5. Charting - allows placing notes directly on the image, arrows or circles to mark on the areas of interest.
Computer
-Used to store the incoming electronic signal -Responsible for converting the electronic signal from the sensor into a shade of gray that is viewed on the monitor -Each pixel is represented in numerically in the computer by location and the color level of the gray -Digitizes, processes, and stores information received from the sensor.
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
Two methods of obtaining a digital image currently exist
1. Direct digital imaging 2. Indirect digital imaging
Direct Digital Imaging Receptors
1. Wired = connected to the computer by fiber optic cable called CCD or Charge-Coupled device 2. Wireless = needs a receiver to connect the image to the computer, called CMOS or complementary metal oxide semiconductor -Both convert x-rays into electronic signals that are sent to the computer
Software
6. Digital Subtraction - Comparing differences over time. Merged together electronically. Effective method of measuring periodontal changes, assessment of implants and healing of periapical pathosis 7. Artificial intelligence - computer makes decisions about interpretation of images 8. Reversing Gray Scale - Embossing and colorization - helpful in interpreting images
Pixel
A discrete unit of information. In digital electronic images, digital information; also termed picture element
Digital Subtraction
A process of digitally merging 2 images to show changes that occur over time or the result of treatment intervention
Fundamental Concepts
A. Digital imaging B. Pixels C. Gray Value
Methods of Acquiring a Digital Image
A. Direct digital imaging B. Indirect Digital Imaging C. Digitizing - Scanning traditional radiographs
Intraoral Sensor
A. Kodak #2 film B. Soredex Optime #2 PSP plate sittin in barrier envelope to demonstart packaged size C. Gendex #2 CCD Sensor D. Schick #2 CMOS wireless sensor
Digital X-ray Equipment
A. X-radiation source B. Intraoral sensor 1. Charge-coupled device 2. Complementary metal oxide semiconductor/active pixel sensor 3. PSP plate C. Computer D. Software
Digital image
An image composed of pixels
Complementary metal oxide semiconductor/active pixel sensor (CMOS/APS)
Another sensor technology that is used in digital imaging
CCD & CMOS
Charge-Coupled device & complementary metal oxide semiconductor
________ 10 In digital imaging, the term used to describe the picture that is produced is radiograph.
False
________ 11 Digital imaging requires more x-radiation than does conventional radiography.
False
Digital imaging
Filmless imaging system; a method of capturing a radiographic image using a sensor, breaking it into electronic pieces, and presenting and storing the image using a computer.
Sensor
In digital imaging, a small detector that is placed intraorally to capture a radiographic image
Digitize
In digital imaging, to convert an image into a digital form that, in turn, can be processed by a computer
Line pairs/millimeter (1p/mm)
Measurement used to evaluate the ability of the computer to capture the resolution (or detail) of a radiographic image
Storage Phosphor imaging
Method of obtaining a digital image in which the image is recorded on phosphor-coated plates and then placed into an electronic processor, where a laser scans the plate and produces an image on a computer screen.
Indirect digital imaging
Method of obtaining a digital image, in which an existing radiograph is scanned and converted into a digital form by using a CCD camera
Direct digital imaging
Method of obtaining a digital image, in which an intraoral sensor is exposed to x-radiation to capture a radiographic image that can be viewed on a computer monitor
Bit-depth image
Number of possible gray-scale combinations for each pixel (8 bit-depth image has gray-scale combination of 2^8, which equals 256 shades of gray)
Digital subtraction
One feature of digital imaging; a method of reversing the gray scale as an image is viewed; radiolucent images (normally black) appear white, and radiopaque images (normally white), appear black.
PSP (Photo-Stimuable Phosphor)
Photostimuable phosphor Plate - coated plate. Storage phosphor imaging
Pixel
Picture element. Discrete units of information that together constitue an image
Analog image
Radiographic image produced by conventional film -Film based images are produced when x-ray photons strike an intraoral film; the information recorded on the film is known as this -Depicted by a continuous spectrum of gray shades between extremes of white and black.
________ 1, A small detector that is placed intraorally to capture the radiographic image.
Sensor
Charge-coupled device (CCD)
Solid-state detector used in many devices (fax machine, home video camera) in digital imaging, CCD is an image receptor found in the intraoral sensor
Gray Value (Hue)
The amount of radiation received by a pixel
Spatial Resolution
The discernible separation of closely adjacent image details
Intraoral Sensor
The most popular types of sensor technology include the *charge-coupled device* and the *complementary metal oxide semiconductor*
X and Y coordiates
Values assigned to dimensions of a pixel that tell the computer where the pixel is located
Image
With digital imaging this term (not radiograph or x-ray film) is used to describe the pictures that are produced -Not limited to intraoral images; panoramic, cephalometric, and other extraoral images may also be obtained.
________ 2, An image receptor found in the intraoral sensor.
charge-coupled device
Analog
data is represented by continuously variable physical quantities - Conventional film
________ 9. A filmless imaging system; a method of capturing a radiographic image using a sensor, breaking the image into electronic pieces, and presenting and storing the image using a computer.
digital radiography
________ 8. A method of reversing the gray scale as a digital image is viewed.
digital subtraction
________ 4. To convert an image into digital form that, in turn, can be processed by a computer.
digitize
________ 5. A method of obtaining a digital image in which an intraoral sensor is exposed to x-rays to capture a radiographic image that can be viewed on a computer monitor.
direct digital imaging
________ 7. A method of obtaining a digital image, in which an existing radiograph is scanned and converted into a digital form using a CCD camera.
indirect digital imaging
Ip/mm
line pairs per millimeter - sharpness or resolution of a radiographic image
________ 6. A discrete unit of information; a picture element.
pixel
________ 3, A form of indirect digital imaging in which the image is recorded on phosphor-coated plates and then placed into an electronic processor, where a laser scans the plate and produces an image on a computer screen.
storage phosphor imaging
