American Journal of Neuroradiology, Vol 19, Issue 6 1105-1109, Copyright © 1998 by American Society of Neuroradiology
ARTICLES |
Thallium-201 brain SPECT of lymphoma in AIDS patients: pitfalls and technique optimization
LS Kessler, A Ruiz, MJ Donovan Post, WI Ganz, AH Brandon and JN Foss
Department of Radiology, University of Miami/Jackson Memorial Hospital, FL 33136, USA.
PURPOSE: Our aim was to examine the 201Tl-SPECT scans in AIDS patients with focal CNS lesions to identify those studies with a false-positive or false-negative result to determine any potential pitfalls in interpretation as well as to suggest methods for technique optimization. METHODS: We retrospectively reviewed the charts of 162 AIDS patients with cerebral mass lesions on 201Tl-SPECT studies. One hundred sixty-one patients had CT examinations, of which 50 also had MR studies. One patient had MR imaging without CT. Those patients in whom the diagnosis by 201Tl-SPECT did not correspond with the known pathologic or clinically proved diagnosis were then singled out and their CT, MR, and 201Tl-SPECT studies were reviewed, including blinded interpretation of the 201Tl-SPECT scans alone and alongside the corresponding CT and MR examinations. Studies were examined for lesion morphology, size, location, enhancement pattern, and presence of necrosis. The review of the 201Tl-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 201Tl-SPECT in depicting lymphoma were 100% and 93%, respectively, based on the initial qualitative analysis. Fifty-one patients had positive 201Tl- SPECT results, of whom 43 were determined to have lymphoma (four by biopsy/autopsy, 39 by clinical and radiologic findings). Upon reevaluation with both a quantitative and qualitative approach, those studies initially interpreted as positive in patients without lymphoma (false positives) were found to be negative. CONCLUSION: Brain 201Tl- 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.