Which conventional radiation units are commonly being used?

Until 1978 the “International Commission of Radiation Units and Measurements” (ICRU) used the conventional radiation units of roentgen (R), rad (rd), and curie (Ci). Since 1978 the ICRU has recommended the use of the international system units (SI) with special new units for radiation quantities; the Becquerel, Gray and Sievert. Table 1-3 shows the relationships of these new units to the older units.

In radiography and radiation safety, units are preceded by prefixes. Table 2-3 shows the ones mostly used.

What is half-value thickness (HVT)?