Dose Calculations of the Ru/Rh-106 CCA and CCB Eyes Applicators

One of the tumors that radiotherapy can be implemented is the choroidal melanoma – eye cancer. Since it is possible to bring the radiation source into the tumor vicinity, the use of a sealed beta radiation source became an applicable treatment. A short range of radiation of few millimetres or less with a minimal radiation spread to the surrounding can be preferable. Since the eye is a very sensitive organ high dose radiation could seriously damage it and even to cause blindness. The sensitivity of the eye parts is – in a descending order - the lens, corona, conjunctiva, retina, optic nerve, therefore it is important to map the accurate absorbed dose to the eye during a treatment (Egbert et al., 1980). Medium and large sized tumors are vastly treated with 125I applicators, and - ray applicators such as 106Ru are in use for small- sized tumors in eyes. 106Ru ophthalmic applicators have been used for close to fifty years in the treatment of choroidal melanoma. Sixteen standard models of 106Ru applicators are currently manufactured by BEBIG GmbH, Germany (BEBIG, 2003). The form of these applicators is a spherically concave silver bowl with an inner radius of curvature between 12 and 14 mm, and a total shell thickness of 1 mm. Various shapes with diameters between 11.5 and 25.5 mm are available