Fig. 1.

Shown are averaged spectra computed from all grade II astrocytoma and of all grade III astrocytoma. Overall, the patterns were comparable (A). When grade II astrocytomas were subdivided into 2 groups according to clinical outcome, citrate (Cit) at ∼2.6 ppm was significantly more prominent in aggressive astrocytoma (B). Other chemicals that can be quantified with in vivo MR spectroscopy include N-acetyl-aspartate (NAA), creatine (Cr), lactate (Lac), choline (Cho), and myo-inositol (mI). Note that NAA levels in aggressive astrocytoma were significantly lower than in stable astrocytoma but to a much lesser extent than citrate. Despite the more prominent appearance of lactate in grade II astrocytomas with malignant progression, significance was not reached due to considerable scatter of measured concentrations. All spectra are scaled to the measured concentrations to allow direct comparison.