Sodium iodide (NaI)-based detectors continue to be an excellent choice for field instruments, combining high efficiency and simplicity with good resolution at a reasonable cost. However, NaI basic response is a poor match to tissue response and its sensitivity varies dramatically with energy. Many NaI monitors merely use a discriminator above a particular gamma-ray energy threshold to yield the gamma dose, which gives such instruments poor energy-dependence relative to the calibration dose often based on 137Cs. In the MICROSPEC system, NaI response functions and efficiencies are stored in the on-board computer. The acquired spectrum is stripped and used to calculate dose equivalent using internationally accepted energy-dose conversion coefficients. The result is a NaI-based system that provides highly accurate, energy-independent, tissue equivalent dose.
Over the years, BTI has continually refined the advanced MICROSPEC spectroscopic survey systems and has developed a unique line of probes, all providing accurate dosimetric information as well as spectroscopic data.