Indicators Used In Radiation Sterilization

Physical Indicator: In radiation sterilization, a plastic or perspex dosimeter which gradually darkens in proportion to the radiation it absorbs gives an accurate measure of the radiation dose.

Chemical Indicator: A chemical dosimeter acidified with ceric ammonium sulfate or ceric sulfate solution is used as a chemical indicator. These respond to irradiation by dose change in the applied density.

Biological Indicator: It consists of a standardized bacterial spore preparation, which is usually suspended in water or culture medium or dried on paper or plastic carriers and placed in a sterilizer (Table).

Table: Indicators used in radiation sterilization

Indicator	Sterilization Method	Principle	Device	Parameter monitored
Physical	Radiation	Recording charts	Recording charts	Radiation Dose
Chemical	Radiation	Radio chromic chemicals	Plastic devices impregnated with radio-sensitive chemicals undergo color changes at relatively low radiation doses.	Only indicates radiation exposure.
		Dosimeter device	Acidified ferric ammonium sulfate solutions respond to irradiation by dose-related changes in their optical density.	Accurately measures radiation doses.
Biological	Radiation	Radiation sensitive microbes	Bacillus pumilus	D-value