NMR imaging of experimental brain abscess: comparison with CT.

An experimental canine model of a brain abscess induced with alpha-streptococcus was imaged in the cerebritis and capsule stages by computed tomography (CT) with intravenous contrast enhancement and by nuclear magnetic resonance (NMR). An NMR imager equipped with a superconducting magnet operating at 3.5 kG was used for several imaging techniques. The NMR images were compared with the CT scans and with gross and microscopic neuropathologic findings. CT showed enhancement of the inflammatory focus at the site of capsule formation while the necrotic center retained its low-density appearance. Spin-echo NMR images demonstrated the presence and extent of abnormal infected brain tissue more accurately than contrast-enhanced CT. Spin-echo images showed the necrotic center, the surrounding inflammatory zone, and peripheral edema without discriminating distinctly between the latter two zones. Inversion-recovery NMR images depicted a lesion of lesser extent, showing the necrotic center circumscribed by the surrounding edematous brain tissue. The inversion-recovery technique was best for demonstrating gray- and white-matter contrast in normal brain and depicted edema as loss of contrast between the gray and white matter. NMR offers some advantages over CT in imaging brain abscess, and the variety of NMR imaging techniques is useful for characterizing the different pathologic areas.