RADR 1201 Chapters 7-9

• 1. rays were discovered


  1895
• Image Production Process


  1. X-rays produced using high-voltage electricity

  2. X-rays pass through matter and strike an image receptor

  3. Image receptor converts the energy of x-rays into an image
• Classes of Diagnostic Radiographic Imaging

  • Film/Screen Radiography
  • Fluoroscopic Imaging
  • Digital or Computerized Radiography
• 1. ray Production


  • Requires a vacuum
  • Requires a source of free electrons
  • Requires a means of rapid acceleration
  • Requires a means of rapid deceleration
• Categorizing X-radiation


  • Primary Radiation
  • Remnant Radiation
  • Absorbed Radiation
  • Scatter Radiation
• Attenuation of Radiation


  • Loss of radiation energy as a result of passing through an absorbing material
  • High attenuation - radiopaque matter
  • Low attenuation - radiolucent matter
• Imaging Chain


  1. Primary radiation from the x-ray tube travels through matter, and its energy is finally detected by an image receptor

  2. Remnant radiation creates physical changes within the receptor that are invisible (latent image)

  3. Latent image must be processed to convert it to a visible image (radiograph)
• Technical Exposure Factors


  • Milliamperage (mA) and time (seconds)
  • Kilovoltage peak (kVp)
  • Source-to-image distance (SID)
• The Scope of Practice of the American Registry of Radiologic Technologist states "under no circumstances (shall a radiographer) give out oral or written diagnosis."
• Diagnosis and Treatment of Image Quality

  • The diagnosis of technical problems in the imaging process required the same skills that a physician uses in a medical diagnosis
  • Even radiologists are not trained in the finer points of creating & analyzing images
  • In this area, the radiographer is the true professional expert
• Evaluating the Radiograph


  • OPTIMAL
  • DIAGNOSTIC
  • UNACCEPTABLE
• Radiographic Quality


  • Requires a proper balance between photographic and geometric qualities
• Photographic Qualities


  • If the visibility of recorded detail is acceptable, the image is of diagnostic quality
  • If the recorded detail is not adequately visualized, the image is unacceptable and must be repeated
• Radiographic Density


  • The amount of overall blackness produced on the image after processing
  • Excessive Density
  • Insufficient Density
  • Optimal
• Image Receptor Exposure


  • Directly related to x-ray exposure hitting the receptor
  • Greatly affected by milliamperage (mA), exposure time (S), source-to-image distance (SID)
• mAs


  • A change in mAs has a direct effect on exposure
  • mA controls the current flowing through the filament, the filament temperature, the amount of electrons liberated by thermionic emission, and the QUANTITY of radiation
  • TIME (EXPOSURE TIME) (s) controls the length of time voltage is applied across the tube and the length of time radiation is being emitted from the tube
  • mA x s = mAs, which is the TOTAL QUANTITY OF RADIATION PRODUCED
• Regardless of the mA and time combinations, the same mAs value will yield the same exposure (mAs reciprocity law)
• Adjusting Millamperage, Exposure Time, or Both to control IR exposure

  • If an image has insufficient exposure, mAs can be doubled by doubling the mA or doubling the exposure time
  • Doubling mAs doubles exposure
• mA - TIME Relationship

  An inverse relationship - as one factor increases, the other factor must decrease to maintain the same mAs
• A traumatized patient is semi-conscious, unable to cooperate fully, unable to control respiration, and has possible muscle spasms, so you need to control the patient's motion
• Patient Factors


  • Differential attenuation (body habitus, tissue density, pathologic conditions)
  • Kilovoltage Peak (kVp) controls x-ray beam penetration and is directly related to a polyenergetic or heterogeneous x-ray beam
• 15% Rule


  Changing the kilovoltage peak by 15% will have the same effect on IR exposure as doubling the mAs, or reducing the mAs by 50%
• Using the 15% Rule

  1. To increase IR exposure: Multiply the kVp by 1.15 (original kVp + 15%)

  2. To decrease IR exposure: Multiply the kVp by 0.85 (original kVp - 15%)

  3. To Maintain IR Exposure: When increasing kVp by 15% (kVp + 15%) divide the original mAs by 2, when decreasing kVp by 15% (kVp - 15%) multiply mAs by 2
• Distance


  • The distance affects the amount of exposure to an image receptor, displayed as source-to-image distance (SID)
  • X-ray production is similar to a point light source and behaves according to the laws of light and intensity as a function of distance
• SID and IR Exposure

  • As SID increases, IR exposure decreases as a result of the square of the distance
  • As SID decreases, IR exposure increases as a result of the square of the distance
• Beam Modification


  • Changes the nature of the radiation beam to improve image quality & reduce dose
  • Can be done before (primary) or after (remnant) the beam enters the patient
• Primary Beam Modification


  • Filtration
  • Beam limitation (collimation)
• Scatter Control


  • Scatter radiation provides little diagnostic information and detracts from image quality
  • Common methods are grid usage and technical selection
• Grids


  • Reduce the amount of scatter radiation reaching the image receptor
  • Intercept a portion of the remnant radiation
  • Improve image quality
  • Described according to grid ratio & frequency
• Grids and Density


  • When a grid is added, removed, or changed, an adjustment in mAs is required to maintain IR exposure
  • Adding a grid decreases IR exposure
  • As grid ratio increases, IR exposure decreases
• Image Receptor (IR) Types

  • Film-Screen Receptors
  • Digital Receptor (DR) Systems
• Film-Screen Systems


  • Film is placed between two intensifying screens in a light-tight cassette
  • Light from screens causes chemical changes in the film & creates the latent image
  • Film is removed from cassette in a darkroom environment and placed in an automatic film processor
  • Intensifying screens allow for lower x-ray dosages to patients
• Digital Receptor (DR) Systems

  • Use photostimulable storage phosphor (PSP) technology, also known as computed radiography (CR)
  • Exposed imaging plate in cassette is placed in a reader for electronic processing of the latent image into a manifest image displayed on a monitor
  • Eliminates need for darkroom and creates a digital image through computer software
• Computed Radiography and Exposure

  • Exposure to plate is stored in barium fluorohalide crystals that create electron "traps"
  • Requires the optimum combination of mAs, kVp, and SID for optimum image quality
• Film processing


  1. Film removed from cassette in darkroom

  2. Film placed in automatic film processor
• Manifest image


  Processed film image
• Film-Screen Systems


  • Requires rigorous quality control measures
• Intensifying screens


  Allow for lower x-ray dosages to patients
• Digital Receptor (DR) Systems

  • Photostimulable storage phosphor (PSP) technology
  • Also known as computed radiography (CR)
• Computed Radiography (CR)


  1. Cassette with imaging plate (IP)

  2. IP is reusable for thousands of exposures

  3. Exposed IP in cassette is placed in a reader for electronic processing

  4. Eliminates need for darkroom

  5. Ultimately creates a digital image through computer software