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).
- 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)