The MDC can be calculated for an instrument by considering the background counts during a typical measurement, total detection efficiency, conversion factors, and the probe area.
Variability in the calculated MDC reflects natural variability in the detection efficiency and conversion factors. This variability may or may not be significant. For the MDC to be applicable, the sample or field measurement conditions must match the conditions under which the background was measured.
For more information on the MARSSIM process, visit Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM).