USE OF TL-201 BRAIN SPECT TO DIFFERENTIATE CEREBRAL LYMPHOMA FROM TOXOPLASMA ENCEPHALITIS IN AIDS PATIENTS

PURPOSE: To determine whether thallium-201 brain single-photon emissio n CT could be used to make the distinction between central nervous sys tem lymphoma and toxoplasma encephalitis, which may not be possible by routine MR and CT. METHODS: A total of 37 patients with acquired immu nodeficiency syndrome who had intracranial mass lesions found during a 9-month prospective study by either MR or CT underwent further evalua tion with Tl-201 brain single-photon emission CT. RESULTS: Twelve pati ents had increased intense focal Tl-201 uptake. Ail of these patients had either biopsy- or autopsy-proven lymphoma. Twenty-five of the pati ents studied had no Tl-201 brain uptake in the lesion(s); 24 of these patients had toxoplasma encephalitis on clinical follow-up. One patien t with no Tl-201 uptake was found by cerebrospinal fluid analysis to h ave mycobacterium tuberculosis abscess. CONCLUSION: Patients with acqu ired immunodeficiency syndrome who have intracranial mass lesions on M R or CT may benefit from Tl-201 brain single-photon emission CT becaus e it can help distinguish between lymphoma and infectious lesions such as toxoplasma encephalitis.