Abstract
Comparison is done between single-hole collimated detector and coincidence detection of imbedded radioactivity in tissue-equivalent phantom. Planar isocount distribution is plotted using a computer program for different gamma-radiation energies up to 0.662 MeV. The improvement in spatial resolution and efficiency is studied for a single source and for multiple sources in air and in phantom. Results show that coincidence detection is much more sensitive than single detector to depth variations and to the separation distance between different radioactive sources.