Figure 4.

Examples for MR spectra of pediatric brain tumors outside the posterior fossa. Metabolic profiles of pilocytic astrocytomas elsewhere in the brain (A) are comparable with those in posterior fossa PAs, except that, often, higher myo-inositol (mI) is observed [42]. The MR spectra of germ cell tumors, including pure germinomas, (B) frequently show prominent lipids, and their quality is often limited (broad signals) possibly due to calcification and heterogeneity at microscopic levels. Among choroid plexus tumors (C), papillomas present regularly with prominent myo-inositol (mI), whereas choline (Cho) is prominent in carcinomas. Dysembryoplastic neuroepithelial tumors (DNETs, (D)) are low-grade glioneuronal tumors. Note that the signal at ≈2 ppm (with a corresponding broad signal at ≈3.8 ppm), is more similar (position on ppm axis and line width) to the N-acetyl (NA) signal observed in pilocytic astrocytoma than to N-acetylaspartate (NAA) in normal brain. A noncancerous hamartoma (E) shows a spectrum that is consistent with a mixture of tumor cells with normal tissue with only slightly reduced NAA and unremarkable lipids and lactate (Lac) as well as unremarkable other metabolic features. The presence of alanine (Ala) and high glutathione (GSH) [43,44] identifies meningiomas (F), a dural-based tumor. In addition, creatine (Cr) is depleted in meningiomas, and lactate and lipids are readily detectable. All spectra were acquired on 3T scanners with SV-PRESS, TE = 35 ms, and TR = 2 s.