Chemical quantitation of the tapetum lucidum with application to 226Ra dosimetry of the canine eye

A chemical technique to quantify the mass of canine tapetum lucidum and underlying choroid is described. The technique, when applied to zinc analysis, indicates the tapetum lucidum contains approximately 17 percent zinc. Preliminary 226Ra studies show that this radionuclide is uniquely concentrated by tapetal cells and that 226Ra distribution is similar to that of zinc. Initial dose calculations indicate a dose rate to tapetal cells ten-fold that to the skeleton and suggest that the 226Ra sensitivity of the tapetum lucidum can be attributed to the high dose rate resulting from the unique ability of this tissue to concentrate radium