PURPOSE: To demonstrate the presence of a multilayer appearance of the capsule on contrast-enhanced (CE) susceptibility-weighted imaging (SWI) in patients with pyogenic brain abscesses. Possible origins for the appearance and effects of postprocessing settings are discussed. MATERIALS AND METHODS: Fourteen patients with pyogenic brain abscesses underwent post gadolinium-enhanced SWI at 1.5 T. All SWI images were postprocessed with various filter and mask settings to compare the image appearance. Computer simulations using a paramagnetic spherical shell model were performed to verify the clinical findings. RESULTS: Pyogenic brain abscesses demonstrated a multilayer appearance with a darkened ring within the enhanced capsule on CE-SWI in all patients. The multilayer appearance was slice-orientation-dependent, decreased with larger widths of the high-pass filter, and increased with larger numbers of phase mask multiplication operations, consistently on both simulation results and the clinical images. CONCLUSION: CE-SWI shows the multilayer appearance of the capsule in pyogenic brain abscesses, which may arise from postprocessing procedures originally designed to enhance susceptibility contrast. Although SWI may provide additional information valuable in the diagnosis of pyogenic brain abscesses, image interpretation should be exercised with caution, particularly for CE-SWI.
Journal of Magnetic Resonance Imaging 36(6),1353-1361