A NEW METHOD FOR CHARACTERIZING BETA-RAY OPHTHALMIC APPLICATOR SOURCES

A technique is described which enables one to obtain detailed dose characteristics of Sr-90 beta-ray ophthalmic applicators. A radiochromic radiation detector which is a solid-state solution of hexahydroxyethyl pararosaniline cyanide in a nylon polymer (i.e., thin foil), has been used to determine the surface dose rate and dose distribution of these sources. The detectors are rugged, easily handled, have an equivalent response (optical density per unit absorbed dose) to photons and electrons, and produce high-resolution images. They have been found useful for this application due to the high surface dose rates [0.10-1.0 Gy (H2O)/s] and their low sensitivity (approximately 10(4) Gy for an optical density of 1.0). The foils have been evaluated on a He-Ne scanning laser densitometer with a resolution of 0.3-mu-m. Comparison with NIST (formerly NBS) extrapolation ionization chamber measurements indicates surface dose-rate agreement within 6%. Spectral dosimetric characteristics are presented and discussed.