Phosphors tissue equivalence

LiF activated with magnesium, copper, and phosphorus (Mg, Cu, P) is a highly sensitive phosphor commonly used for radiation dosimetry nsing the TL technique. It is one of the most studied materials. LiF material has low effective atomic number (Z jf=8.2), which is sufficiently close to that of biological tissue (Z ff=7.4) so as to provide a response, which varies only slightly with photon energy. Thus, it can be considered as tissue equivalent. The preparation of LiF Mg,Cu,P,... 

Tissue equivalent phosphors - In most cases the TLDs have to provide warning from hazardous radiation. For this, their energy absorption has to fit that of the human body. In other words, they have to be tissue equivalent (Z=7.4). 

CaS04 Dy suffers from a high effective Z which differs considerably from tissue equivalence. This can be reduced by mixing with low-Z compounds. Li2S04 makes the phosphor almost tissue equivalent. 

Barium compound hosts. More has been published on R-activated Ba compounds compared to Sr compoimds. The two host compounds do not vary much in their properties as R-activated phosphors. In fact many papers deal with both Ba and Sr phosphors. The high effective Z of the Ba compoimds turns these phosphors further away fixim tissue equivalence compared to the Sr compounds. There are some variations in the energy dependence and in the TL intensities of the two phosphors. The R ions substitute for the alkaline earths in the lattice. The considerable difference between the ionic radius of Ba (0.153 nm) and that of Sr (0.112 nm) may explain the changes in the GCs of the two compounds. As before, the review will deal separately with the various host compounds. 

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