Shared 1979 Nobel Prize for Physiology or Medicine with Allan MacLeod Cormack

• HU  Hounsfield Units
  • relative quantitative measurement of radio density
    • measured by  linear attenuation coefficient for each material at the selected effective energy
    • physical density of tissue is proportional to the absorption/attenuation of the X-ray beam.
    • Assigned numbers
    • 4096 values levels of gray (12 bit) and
      • ranges from
        • -1024 HU to 3071 HU
          • -1024 HU is black as in air
          • 0 HU represents water (
          • 3071 HU is white
            • represents the densest tissue in a human body,
            • tooth enamel.
      • All other tissues are somewhere within this scale; fat is around -100 HU, muscle around 100 HU and bone spans from 200 HU (trabecular/spongeous bone) to about 2000 HU (cortical bone).
    • Hounsfield scale is  displayed as
      • gray tones
        • dense tissue, with greater X-ray beam absorption,
          • has positive values
          • appears bright;
        • less dense tissue, with less X-ray beam absorption,
          • has negative values and
          • appears dark.
    • distilled water (at standard temperature and pressure) is arbitrarily defined to be zero HU
    • air defined as -1000 HU.
    • bones – 1000 for bones,
    • dense bones like the cochlea 2000,
    • metals like steel or silver more than 3000
  • Densities
    • For practical purposes in the body ie approximate
      • density of calcium +50 to +500
      • density of soft tissue  +50
      • density of lung-  -700 to -800
      • density of fluid  +5to +15
      • fat  -5 to -100
      • iodinated contrast  + 100 to +500

 

Links and References

DenOtter  TD et al  Hounsfield Unit