Radioactive Phosphorus for the Detection of Ocular Melanomas

Abstract

The concentration of radioactive phosphorus (³²P) in several malignant melanomas of the choroid, as well as in adjacent normal ocular tissues in the same eyes, was determined. A polymerized methyl methacrylate phantom was designed so as to determine the minimum tumor size that could be detected with an ocular probe. Finally, the importance of tissue penetration was defined. The concentration of radioactive phosphorus in choroidal melanoma averaged 0.020 microcurie/gm. With the detecting probe 2 mm away from the tumor, the minimum detectable tumor size had a 10 mm diameter and a 5 mm thickness. This was at the concentration actually found in choroidal melanomas. The use of radioactive phosphorus in ophthalmology has been very limited and used only if the detecting device can be placed within 2 mm of the suspected tumor.