Figure 13.

Acute and chronic infections. MR spectra of acute abscesses can be strikingly unusual. In the above example (A), common brain metabolites are absent, whereas prominent signals form succinate (Suc) and acetate (Act) as well the cytosolic amino acids leucine (Leu), isoleucine (ILeu), and valine (Val) are observed. lactate (Lac), alanine (Ala), and moderate amounts of lipids are also detectable. On the other hand, only lipids and lactate are observed in a shrinking abscess after 20 days of antibiotics treatment (B). A spectrum of acute cerebellitis shows elevated lipids and lactate as well as reduced N-acetylaspartate (NAA). Glutamine (Gln) is elevated, whereas myo-inositol (mI) is low (C). In a spectrum acquired from a 2 ½-year-old child with a history of meningoencephalitis, lipids are unremarkable, lactate is close to normal, and both myo-inositol and glutamine are unremarkable. NAA is reduced, indicating some permanent neuronal/axonal injury (D). Spectra were acquired on 3T (A,C,D) and 1.5T (B) scanners with SV-PRESS, TE = 35 ms, and TR = 2 s (3T) or TR = 1.5 s (1.5T).