TL-201 BRAIN SPECT OF LYMPHOMA IN AIDS PATIENTS - PITFALLS AND TECHNIQUE OPTIMIZATION

PURPOSE: Our aim was to examine the Tl-201-SPECT scans in AIDS patient s with focal CNS lesions to identify those studies with a false-positi ve or false-negative result to determine any potential pitfalls in int erpretation as well as to suggest methods for technique optimization. METHODS: We retrospectively reviewed the charts of 162 AIDS patients w ith cerebral mass lesions on Tl-201-SPECT studies. One hundred sixty-o ne patients had CT examinations, of which 50 also had MR studies, One patient had MR imaging without CT. Those patients in whom the diagnosi s by Tl-201-SPECT did not correspond with the known pathologic or clin ically proved diagnosis were then singled out and their CT, MR, and Tl -201-SPECT studies were reviewed, including blinded interpretation of the Tl-201-SPECT scans alone and alongside the corresponding CT and MR examinations, Studies were examined for lesion morphology, size, loca tion, enhancement pattern, and presence of necrosis, The review of the Tl-201-SPECT studies included both a qualitative approach (subjective analysis of the scans for areas of abnormally increased uptake) and a quantitative approach (comparison of lesion activity versus activity within a reference standard, such as the scalp). RESULTS: Sensitivity and specificity of Tl-201-SPECT in depicting lymphoma were 100% and 93 %, respectively, based on the initial qualitative analysis. Fifty-one patients had positive 201TI-SPECT results, of whom 43 were determined to have lymphoma (four by biopsy/autopsy, 39 by clinical and radiologi c findings), Upon reevaluation with both a quantitative and qualitativ e approach, those studies initially interpreted as positive in patient s without lymphoma (false positives) were found to be negative. CONCLU SION: Brain Tl-201-SPECT is an effective study in the diagnosis of CNS lymphoma in AIDS patients. Specificity can be increased by routinely performing a quantitative analysis of all lesions.