The Construction and Measurement of Beta-ray Applicators for Use in Ophthalmology

Abstract

β-ray emitting ophthalmic applicators, using strontium 90 foil, have been developed following earlier work with phosphorus 32. Details are given of these strontium 90 applicators, which have the form of spherical caps. A number of physical investigations of these applicators are described. Dose-rate variations across the surface were studied using a scintillation probe; the same instrument was used to find the variation of dose-rate with depth in tissue equivalent material, and to compare the dose-rate from the applicators with that from a plane sheet of foil. The method used to determine in absolute units the surface dose-rate from this plane foil, and hence from the applicators, is also described. Surface dose-rates for applicators at present in use are of the order of 100 rad/min.