Diffusion-weighted MR imaging of pyogenic intraventricular empyema

Introduction Pyogenic intraventricular empyema (PIE) is a potentially fatal CNS infection. However, it is sometimes difficult to diagnose PIE on the basis of clinical and conventional MRI findings. Diffusion-weighted imaging (DWI) has been accepted as a useful MR sequence for the diagnosis of various intracranial infections. The purpose of this study was to determine the DWI characteristics of PIE and the role of DWI in the diagnosis of PIE. Methods Eight patients with PIE underwent MRI including DWI. We assessed the presence and signal characteristics of PIE. In seven patients, the signal intensities of the PIE and cerebrospinal fluid (CSF) were measured and the contrast-to-noise ratio (CNR) percentage was calculated. ADC values of the PIE, CSF, and white matter were also determined. Results PIE was detected in all patients by DWI, in five (63%) by FLAIR imaging, and in two (25%) by T1- and T2-weighted imaging. The CNR percentages of the PIEs in relation to the CSF were highest for DWI, followed by FLAIR, T1-, and T2-weighted imaging. There were statistically significant differences between the images of each sequence. In all patients, PIE showed hyperintensities on DWI and hypointensities to the CSF and hypo- or isointensities to the white matter on ADC maps. The ADC values (mean±SD) of the PIE, CSF, and white matter were 0.60±0.27, 2.81±0.04, and 0.79±0.08 (×10⁻³ mm²/s). There was a statistically significant difference between PIE and the CSF. Conclusion PIE shows a bright intensity on DWI, and DWI is a sensitive MR sequence for the diagnosis of PIE.