January 22, 2009

Biological Effects of Radiation Used in Imaging (2): Stochastic Effect

Stochastic Effect of Radiation
  • Effect of radiation that occurs by chance.
  • Late effect such as cancer and genetic defects
  • Probability (not severity) depends on dose. "As doses increase, the chance of cancer or genetic defect increases."
  • No threshold dose
  • Effects can occur even in human never been exposed to radiation above background level (remember normal background radiation from standing on Earth).
Effective Dose
  • This term is used to determine probability of health effect from radiation (i.e. stochastic effects)
  • Unit = Sv (sievert)
  • Derived from calculation of i.e. entrance skin dose (based on dose indicator used in radiography), dose-area product (based on dose indicator in fluoroscopy), and CT dose index (based on dose indicator in CT)
  • Good for dose optimization of procedures and balance radiation risks and information obtained from imaging
  • Example: posteroanterior chest radiograph - <0.1>
Verdun FR, et al. Radiation risk: what you should know to tell your patients. Radiographics 2008 (September)

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