Radiology PP-Y Dental x-ray image characteristics

  1. Diagnostic x-ray is one that exhibits proper ______, _______, _______ and is the same ______ as the object being radiographed
    • density, contrast, sharp outlines
    • shape and size
  2. What are some visual and geometric image characteristics
    • Visual
    • Density
    • Contrast
    • Geometric
    • Sharpness
    • Magnification
    • Distortion
  3. Image density is the overall ___________ of the radiograph. Proper density reveals ______
    • blackness (darkness)
    • white, black and gray areas
  4. What are the density influencing factors
    • Subject thickness/density
    • Three Exposure factors:
    • Milliamperage (mA)
    • Kilovoltage (kV)
    • Exposure time
  5. Increase in the thickness of the matter results in _________ radiograph
    low image density / lighter
  6. Increase in mA= __________ which results in a radiograph that is
    • more electrons produced and ultimately more x-rays to expose the receptor. 
    • darker  ↑ density
  7. Decrease in mA= ________ which results in a  ________ radiograph
    • less x-rays on receptor
    • lighter radiograph ↓ image density
  8. Ideal mA:
    7-15 mA required for a diagnostic dental radiograph (newer machines 6-8mA or 7mA fixed)
  9. mA and exposure time are ________ related. When the mA is increased the time is
    • inversely
    • decreased
  10. Increase in kVp = _______ density
  11. Decrease in kVp = ________ density
  13. The image contrast is the ________. High contrast results in _______ while low contrast results in _______
    • difference in the degrees of blackness between adjacent areas on a dental radiograph
    • Very light areas and very dark areas
    • Many shades of gray
  14. What are the influencing factors of contrast
    • 1. Inherent qualities of the receptor: determined by manufacturer
    • 2. Film processing (Conventional): Increase in development time or temperature =  increased contrast
    • 3. Subject: size and thickness of patient tissues, density, composition
  15. Subject contrast (densities of adjacent tissues)can be compensated for by increasing or decreasing
  16. High kV = ______ density with ___ contrast = ______
    • high image (darker image) 
    •  low
    • many shades of gray
  17. Low kV = _____ density and _____ contrast = ________
    • low image density (lighter image)
    • high
    • (black and white)
  18. _________ is the ONLY exposure factor that directly influences contrast
  19. What is a short scale of image contrast
    two densities (black & white)
  20. What is a long scale of image contrast
    many densities (many grays)
  21. What is considered a high and low kV
    • greater than 90
    • less than 70
  22. Penumbra
    • Unsharpness, or blurring of the edges
    • Fuzzy, unclear area that surrounds a radiographic image
    • Every dental image has some degree of penumbra
  23. Sharpness: Influencing Factors
    • Focal spot size
    • Film composition
    • Movement
  24. Focal spot is the _________. Smaller focal spots result in ________
    • (tungsten target at anode)
    •  sharper images and less heat
  25. Faster film contains _______ crystals that produce ______ image sharpness
    • larger
    • less
  26. What is magnification and what is the cause
    • image is larger than actual size
    • divergence of xray beam (xrays travel in diverging straight lines as they radiate from the focal spot)
    • all dental radiographs exhibit some degree of magnification (as with penumbra/unsharpness)
  27. Magnification: Influencing Factors
    • Target (Source) to Receptor Distance:
    • Determined by the PID lengthLonger PID=increased source to receptor=less magnification (also less divergent rays)
    • Object (tooth) to Receptor Distance:Closer the tooth is to the receptor, less magnification
  28. What is Dimensional Distortion and what are the influencing factors
    • deviates from true shape and size
    • Unequal magnification of different parts of the same object
    • Improper object to receptor alignment
    • Improper beam angulation
  29. X-ray beam must be directed ________ to the long axis of the tooth and receptor to minimize distortion
Card Set
Radiology PP-Y Dental x-ray image characteristics
Radiology PP-Y Dental x-ray image characteristics