Detector Efficiency Is Defined as
A)the Ratio of the Number $\mu$

Detector efficiency is defined as

A) the ratio of the number of detected events to the number of source emissions.
B) the geometric efficiency and is defined as the fraction of emitted photons (gamma or x-rays) that hit the detector; it depends on the detector configuration and its distance from the source.
C) the fraction of gamma rays that are detected when they hit the detector; it depends on the thickness (t) and attenuation coefficient ( $\mu$ ) of the detecting material.
D) the amount of blurring that is produced by an imaging system, characterized by point spread function and line spread function.