G-M meters, also known as Geiger counters, are commonly used for portable instrumentation due to their sensitivity, simple counting circuit, and ability to detect low-level radiation. They are generally more sensitive to low-energy, low-intensity radiation than proportional or ion chamber detectors. Geiger counters measure the rate of exposure or the intensity of radiation at a location at some point in time. This is done by using a Geiger tube instead of an ion chamber.
Geiger counters are particularly useful for measuring low levels of radiation, such as searching for surface contamination. In nuclear medicine departments, routine radiation screening is an important part of overall radiation safety for working personnel, radiology workers, patients and visitors. Radiation monitoring is usually done with topographical meters based on the Geiger Muller counter or the ionization chamber. The type of instrument used depends on the nature and level of radiation expected in the environment.
To compare the sensitivity of topographical meters based on the Geiger Muller counter and the ionization chamber, a study was conducted. The results showed a positive correlation between the reading of Geiger Muller meters and topographical meters based on ionization chambers.