For day-in day-out work with soft gamma emitters such as 125I, 99mTc, and intermediate gammas having energies up to about 1 MeV, the Γ-RAM with its well- type Tl-activated NaI crystal and its heavy lead shield offers the best performance. Beta counters may be suitable for occasional measurement of 125I and 99mTc, though with lower counting efficiency. However, they are unsatisfactory for anything more energetic; counting efficiencies are low and sometimes unacceptable, and resolution is so poor as to preclude double-isotope analysis of two gamma emitters in the same sample.

On the other hand, a NaI crystal with its great stopping power for gammas gives high counting efficiencies, even for more energetic isotopes, as well as superior resolution which makes dual isotope counting practical.