Intracranial mass lesions: Sequential thallium and gallium scintigraphy inpatients with AIDS

PURPOSE: TO determine the efficacy of sequential thallium and gallium scint igraphy to differentiate intracranial neoplasms (lymphoma and glioma) from other nonmalignant intracranial mass lesions among patients;; with acquired immunodeficiency syndrome (AIDS). MATERIALS AND METHODS: The authors reviewed the cases of 40 patients with h uman immunodeficiency virus (HIV) who underwent thallium and gallium scanni ng to evaluate intracranial mass lesions from October 1991 through November 1997. There was a definitive final diagnosis of the nature of the mass les ions in 21 of these cases. In these 21 cases, the scintigraphic patterns we re reviewed and were compared with the final diagnosis. RESULTS: On the basis of results at thallium and gallium scanning, the pati ents were divided into three groups. Group A included 13 patients (11 with brain tumors [lymphomas and gliomas] and two with progressive multifocal le ukoencephalopathy [PML]) with thallium-positive, gallium-positive scans. Gr oup B included five patients with intracranial infections (tuberculosis, Cr yptococcus, bacteria) with thallium-negative, gallium-positive scans. Group C included three patients (one with PML and two with infarcts) with thalli um-negative, gallium-negative scans. All patients with lymphomas were in gr oup A. The sensitivity and specificity of the thallium-positive, gallium-po sitive pattern for intracranial malignancy were 100% and 80%, respectively. CONCLUSION: Sequential thallium and gallium scanning helped differentiate t umors from nonmalignant intracranial mass lesions and may help differentiat e infections from PML or infarcts.