Eye Tumor Identification Tests Using Semiconductor Detectors

The 32P eye tumor identification test is being reevaluated using semiconductor detectors. Diagnostic tests for both anterior and posterior lesions of the uveal tract are being performed on patients, and a comparison is being made between the conventional G. M. eye tumor counter and the silicon lithium drifted, Si(Li), silicon surface barrier and silicon avalanche beta detectors. Results from 31 tests performed to date indicate that among the detectors tested, the Si(Li) posterior detector gives the most consistent, sensitive and reliable results. For tumors of the uveal tract a beta energy threshold as determined by the detector window thickness and electronic noise can be as high as several hundred keV. Surface barrier detectors placed in suitable probes can therefore also be used for these lesions. For more deeply imbedded tissue tumors, such as lesions of the choroid, iris or retina, the silicon avalanche detector shows considerable promise because of its greater sensitivity for lower energy betas.