DIAGNOSIS OF INTRACRANIAL LYMPHOMA IN PATIENTS WITH AIDS - VALUE OF (TI)-T-201 SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY

OBJECTIVE. Although the prevalence of intracranial lymphoma is high am ong patients with AIDS, current imaging techniques are not reliable fo r differentiating this tumor from other common nonneoplastic lesions, such as those seen in toxoplasmosis. The purpose of this study was to prospectively investigate the use of Tl-201 singlephoton emission comp uted tomography (SPECT) in identifying intracranial lymphoma in patien ts with AIDS. SUBJECTS AND METHODS. Thirteen patients with AIDS and in tracranial masses underwent 201Tl imaging with a three-headed SPECT ca mera. Six of the 13 were subsequently proved to have lymphoma. Studies were interpreted prospectively as showing tumor if uptake of Tl-201 w as increased in the region where the lesion was seen on MR images. A l esion-to-nonlesion uptake ratio (counts/pixel) was calculated retrospe ctively. RESULTS. The SPECT images of six patients were interpreted pr ospectively as showing no lymphoma. Uptake ratios in these six patient s were 0.77-1.95 (mean, 1.45). In each, tumor was excluded as a final diagnosis (four had toxoplasmosis, one had progressive multifocal leuk oencephalopathy, and one had venous angioma). Among the seven patients with SPECT images interpreted as showing lymphoma, six were later pro ved to have lymphoma (uptake ratio: mean, 3.65; range, 2.95-4.30; p < .005), The SPECT findings in the seventh patient were classified as fa lse-positive for tumor on the basis of the prospective interpretation of the images; three concurrent infections were found at autopsy. The uptake ratio in this patient was low (1.81), suggesting that quantific ation might have diagnostic usefulness for improving accuracy. CONCLUS ION. This preliminary study indicates that Tl-201 SPECT might be a use ful, noninvasive method for differentiating intracranial lymphoma from nonneoplastic lesions in patients with AIDS.