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Chapter 1 Introduction to Digital Radiography and PACS

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  • 1. Chapter 1 Introduction to Digital Radiography and PACS
  • 2. Objectives
    • Define the term digital imaging .
    • Explain latent image formation for conventional radiography.
    • Describe the latent image formation process for computed radiography.
  • 3.
    • Compare and contrast the latent image formation process for indirect capture digital radiography and direct capture digital radiography.
    • Explain what a PACS (picture archiving and communication system) is and how it is used.
    • Define digital imaging and communications in medicine.
    Objectives
  • 4. Key Terms
    • Computed radiography
    • DICOM (digital imaging and communications in medicine)
    • Digital imaging
    • Digital radiography
    • Direct capture DR
    • Indirect capture DR
    • PACS
    • Teleradiology
  • 5. Conventional Radiography
    • Method is film-based.
    • Method 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 lightbox.
  • 6. Digital Imaging
    • Digital imaging is a broad term.
    • Term was first used medically in 1970s in computed tomography (CT).
    • Digital imaging is defined as any image acquisition process that produces an electronic image that can be viewed and manipulated on a computer.
    • In radiology, images can be sent via computer networks to a variety of locations.
  • 7. Historical Development of Digital Imaging
    • CT coupled imaging devices and the computer.
    • Early CT scanners required hours to produce a single slice.
    • Reconstruction images took several days to produce.
    • First CT scanners imaged the head only.
    • First scanner was developed by Siemens.
  • 8.
    • Magnetic resonance imaging (MRI) became available in the early 1980s.
    • Lauterbur paper in 1973 sparked companies to research MRI.
    • Many scientists and researchers were involved.
    • Advancements in fluoroscopy occurred in the 1970s as well.
    • Analog-to-digital converters allowed real-time images to be viewed on TV monitors.
    Historical Development of Digital Imaging
  • 9.
    • Fluoroscopic images could also be stored on a computer.
    • Ultrasound and nuclear medicine used screen capture to grab the image and convert it digitally.
    • Eventually, mammography converted to digital format.
    Historical Development of Digital Imaging
  • 10. Digital Radiography Development
    • Concept began with Albert Jutras in Canada in the 1950s.
    • Early PACS systems were developed by the military to send images between Veterans Administration hospitals in the 1980s.
    • Development was encouraged and supported by the U.S. government.
  • 11. Digital Radiography Development
    • Early process involved scanning radiographs into the computer and sending them from computer to computer.
    • Images were then stored in PACS.
    • Computed and digital radiography followed.
  • 12. Computed Radiography
    • Uses storage phosphor plates
    • Uses existing equipment
    • Requires special cassettes
    • Requires a special cassette reader
    • Uses a computer workstation and viewing station and a printer
  • 13. Computed Radiography
    • Storage phosphor plates are similar to intensifying screens.
    • Imaging plate stores x-ray energy for an extended time.
    • Process was first introduced in the United States by Fuji Medical Systems of Japan in 1983.
    • First system used a phosphor storage plate, a reader, and a laser printer.
  • 14. Computed Radiography
    • Method was slow to be accepted by radiologists.
    • Installation increased in the early 1990s.
    • More and more hospitals are replacing film/screen technology with digital systems.
  • 15. Digital Radiography
    • Cassetteless system
    • Uses a flat panel detector or charge-coupled device (CCD) hard-wired to computer
    • Requires new installation of room or retrofit
  • 16.
    • Two types of digital radiography
    • Indirect capture DR
      • Machine absorbs x-rays and converts them to light.
      • CCD or thin-film transistor (TFT) converts light to electric signals.
      • Computer processes electric signals.
      • Images are viewed on computer monitor.
    Digital Radiography
  • 17.
    • Direct capture DR
      • Photoconductor absorbs x-rays.
      • TFT collects signal.
      • Electrical signal is sent to computer for processing.
      • Image is viewed on computer screen.
    Digital Radiography
  • 18.
    • First clinical application was in 1970s in digital subtraction.
    • University of Arizona scientists applied the technique.
    • Several companies began developing large field detectors.
    Digital Radiography
  • 19.
    • DR used CCD technology developed by the military and then used TFT arrays shortly after.
    • CCD and TFT technology developed and continues to develop in parallel.
    • No one technology has proved to be better than the other.
    Digital Radiography
  • 20. Comparison of Film to CR and DR
    • For conventional x-ray film and computed radiography (CR), a traditional x-ray room with a table and wall Bucky is required.
    • For DR, a detector replaces the Bucky apparatus in the table and wall stand.
    • Conventional and CR efficiency ratings are about the same.
    • DR is much more efficient, and image is available immediately.
  • 21.
    • Latent image formation is different in CR and DR.
    • Conventional film/screen
      • Film is placed inside of a cassette that contains an intensifying screen.
      • X-rays strike the intensifying screen, and light is produced.
      • The light and x-ray photons interact with the silver halide grains in the film emulsion.
    Comparison of Film to CR and DR
  • 22. Comparison of Film to CR and DR
      • An electron is ejected from the halide.
      • Ejected electron is attracted to the sensitivity speck.
      • Speck now has a negative charge, and silver ions will be attracted to equal out the charge.
      • Process happens many times within the emulsion to form the latent image.
      • After chemical processing, the sensitivity specks will be processed into black metallic silver and the manifest image is formed.
  • 23. Comparison of Film to CR and DR
    • CR
      • A storage phosphor plate is placed inside of CR cassette.
      • Most storage phosphor plates are made of a barium fluorohalide.
      • When x-rays strike the photosensitive phosphor, some light is given off.
      • Some of the photon energy is deposited within the phosphor particles to create the latent image.
      • The phosphor plate is then fed through the CR reader.
  • 24. Comparison of Film to CR and DR
    • CR, continued
      • Focused laser light is scanned over the plate, causing the electrons to return to their original state, emitting light in the process.
      • This light is picked up by a photomultiplier tube and converted into an electrical signal.
      • The electrical signal is then sent through an analog-to-digital converter to produce a digital image that can then be sent to the technologist review station.
  • 25. Comparison of Film to CR and DR
    • DR
      • No cassettes are required.
      • The image acquisition device is built into the table and/or wall stand or is enclosed in a portable device.
      • Two distinct image acquisition methods are indirect capture and direct capture.
  • 26. Comparison of Film to CR and DR
    • DR, continued
      • Indirect capture is similar to CR in that the x-ray energy stimulates a scintillator, which gives off light that is detected and turned into an electrical signal.
      • With direct capture, the x-ray energy is detected by a photoconductor that converts it directly to a digital electrical signal.
  • 27. Image Processing
    • Conventional radiography
      • Image is determined by the film itself and the chemicals.
    • CR and DR
      • Image processing takes place in a computer.
      • For CR, the computer is located near the readers.
      • For DR, the computer is located next to x-ray console, or it may be integrated within the console, and the image is processed before moving on to the next exposure.
  • 28. Exposure Latitude or Dynamic Range
    • Conventional radiography
      • Based on the characteristic response of the film, which is nonlinear.
      • Radiographic contrast is primarily controlled by kilovoltage peak.
      • Optical density on film is primarily controlled by milliampere-second setting.
  • 29. Exposure Latitude or Dynamic Range
    • CR and DR
      • Contain a detector that can respond in a linear manner.
      • Exposure latitude is wide, allowing the single detector to be sensitive to a wide range of exposures.
      • Kilovoltage peak still influences subject contrast, but radiographic contrast is primarily controlled by an image processing look-up table.
      • Milliampere-second setting has more control over image noise, whereas density is controlled by image-processing algorithms.
  • 30. Scatter Sensitivity
    • It is important to minimize scattered radiation with all three acquisition systems.
    • CR and DR can be more sensitive to scatter than screen/film.
    • Materials used in the many CR and DR image acquisition devices are more sensitive to low-energy photons.
  • 31. Picture Archival and Communication Systems
    • Networked group of computers, servers, and archives to store digital images
    • Can accept any image that is in DICOM format
    • Serves as the file room, reading room, duplicator, and courier
    • Provides image access to multiple users at the same time, on-demand images, electronic annotations of images, and specialty image processing
  • 32.
    • Custom designed for each facility
    • Components/features can vary based on the following:
      • Volume of patients
      • Number of interpretation areas
      • Viewing locations
      • Funding
    Picture Archival and Communication Systems
  • 33.
    • Early systems did not have standardized image formats.
    • Matching up systems was difficult.
    • Vendors kept systems proprietary and did not share information.
    • DICOM standards helped change this by allowing communication between vendors’ products.
    Picture Archival and Communication Systems
  • 34.
    • First full-scale PACS
      • Veterans Administration Medical Center in Baltimore used PACS in 1993.
      • PACS covered all modalities except mammography.
      • Shortly after, PACS was interfaced with radiology information systems, hospital information systems, and electronic medical records.
    Picture Archival and Communication Systems
  • 35. PACS Uses
    • Made up of different components
      • Reading stations
      • Physician review stations
      • Web access
      • Technologist quality control stations
      • Administrative stations
      • Archive systems
      • Multiple interfaces to other hospital and radiology systems
  • 36.
    • Early PACS seen only in radiology and some cardiology departments.
    • PACS now can be used in multiple departments.
    • Archive space can be shared among departments.
    • PACS reading stations may also have image processing capabilities.
    • PACS allows radiologists to reconstruct and stitch images in their offices.
    PACS Uses
  • 37.
    • Orthopedic workstations are available for the following:
      • Surgeons can plan joint replacement surgery.
      • Specialized software allows matching of best replacement for patient with patient anatomy.
      • System saves time and provides better fit.
    PACS Uses