TOXOPLASMOSIS AND PRIMARY CENTRAL-NERVOUS-SYSTEM LYMPHOMA IN HIV-INFECTION - DIAGNOSIS WITH MR SPECTROSCOPY

PURPOSE: To differentiate intracranial lymphoma from Toxoplasma gondii lesions in patients infected with the human immunodeficiency virus, b y means of localized spin-echo proton magnetic resonance (MR) spectros copy. MATERIALS AND METHODS: Twenty-seven lesions were studied (18 T g ondii lesions, nine lymphoma lesions) at 1.5 T. Spectra were acquired at an echo time of 135 msec from voxels centered on the lesions. Both visual analysis and spectral fitting were used to obtain metabolite ra tios for choline (Cho), creatine (Cr), N-acetyl (NA), lactate, and lip ids. RESULTS: Three spectral categories were seen. One had large lipid peaks with suppression of other metabolites. Another had an elevated Cho/Cr ratio with relatively diminished NA. The third had features of the other two. Examples of each spectrum type were acquired from both T gondii and lymphoma lesions. Neither method of analysis allowed diff erentiation between lesion types. MR spectroscopy showed an overlap of spectra. CONCLUSION: The authors conclude that toxoplasmosis and lymp homa cannot be differentiated with spin-echo proton MR spectroscopy at 135 msec.