PROTON SPECTROSCOPY IN HIV-INFECTION - RELAXATION-TIMES OF CEREBRAL METABOLITES

In vivo proton spectroscopy has demonstrated abnormalities in the cere bral metabolite ratios from subjects with acquired immunodeficiency sy ndrome (AIDS). Some of the sequences employed are subject to T-1 or T- 2 weighting, which may affect spectroscopic interpretation. The relaxa tion times of choline (Cho), creatine (Cr), and N-acetyl (NA) resonanc es have been estimated at 1.5 T in 21 patients infected with the human immunodeficiency virus (HIV) and 8 controls using gradient localised, spin-echo spectroscopic sequences of varying echo and repetition time s. A statistically significant increase in the T-2 of NA was found in the HIV seropositive patients who had diffuse abnormalities on MR imag ing consistent with HIV encephalopathy (493 +/- 199 ms) when compared to controls (292 +/- 118 ms; p <.05). No other statistically significa nt differences were found in the relaxation times between patients and control subjects. These results demonstrate that signals from the NA resonance obtained using long echo time sequences in subjects who are HIV seropositive are not solely indicative of metabolite concentration .