Introduction to digital radiography and pacs


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Introduction to digital radiography and pacs

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