Tumor localization using fundus view photography for episcleral plaque therapy.

The accurate localization of ophthalmic tumors on the scleral surface is important when calculating radiation dose to the tumor and adjacent structures from episcleral I-125 plaques. This is particularly true for tumors close to the fovea or optic nerve. A fundus view diagram of the eye is often used by ophthalmologists to describe the size and shape of the tumor perimeter as well as its geographical location on the retinal surface. There is, however, an inherent inaccuracy associated with the use of a hand drawn diagram to obtain physical measurements. A computer planning program has been developed which uses CT and a digitized photographic montage of the posterior hemisphere to estimate the size and location of posteriorly located tumors. A simple phantom was constructed to test the software and a direct comparison made between planned versus measured tumor size and location in an excised eye.