Usefulness of Post-enhanced Delayed FLAIR Imaging for Making the Diagnosis of Leptomeningitis

PURPOSE: To evaluate the usefulness of post-enhanced delayed FLAIR (fluid-attenuated inversion-recovery) images in the diagnosis of leptomeningitis. MATERIALS AND METHODS: We obtained the pre- and post-enhanced FLAIR images of 7 rabbits every hour after infusing triple doses of contrast, and we measured the signal intensities of the CSF (cerebrospinal fluid) and the brain parenchyma. Five leptomeningitis patients and 5 volunteers were enrolled to obtain the pre-enhanced FLAIR images, the early post-enhanced FLAIR images and the delayed post-enhanced FLAIR images, with using a standard dose of contrast, and to measure the signal intensities of the CSF and brain parenchyma. The statistical significances were determined by a mixed procedure and the Wilcoxon rank-sum test (p<0.05). RESULTS: In the rabbits, the signal intensities of the CSF began to increase after an hour of contrast infusion, but those of the parenchyma did not increase. The time of maximum CSF enhancement was 2 hours after contrast infusion (p<0.001; standard estimate=750.43) and we obtained the post-enhanced delayed FLAIR images for clinical studies according to this result. The signal intensities of the CSF in the subarachnoid space were higher in the patient group compared with those of the normal control group on both the early post-enhanced FLAIR images and the delayed post-enhanced FLAIR images (p=0.0096) (p=0.0391). In the patient group, changes of signal intensities of the CSF in the subarachnoid space were more conspicuous on the delayed post-enhanced FLAIR images than on the early post-enhanced FLAIR images (p=0.0042). However, those of the parenchyma were not different in either group. CONCLUSION: The post-enhanced delayed FLAIR images obtained at 2 hours after contrast infusion are more useful for making the the diagnosis of leptomeningitis than are the post-enhanced early FLAIR images.

CSF Flow Quantification of the Cerebral Aqueduct in Normal Volunteers Using Phase Contrast Cine MR Imaging

OBJECTIVE: To evaluate whether the results of cerebrospinal fluid (CSF) flow quantification differ according to the anatomical location of the cerebral aqueduct that is used and the background baseline region that is selected. MATERIALS AND METHODS: The CSF hydrodynamics of eleven healthy volunteers (mean age = 29.6 years) were investigated on a 1.5T MRI system. Velocity maps were acquired perpendicular to the cerebral aqueduct at three different anatomical levels: the inlet, ampulla and pars posterior. The pulse sequence was a prospectively triggered cardiac-gated flow compensated gradient-echo technique. Region-of-interest (ROI) analysis was performed for the CSF hydrodynamics, including the peak systolic velocity and mean flow on the phase images. The selection of the background baseline regions was done based on measurements made in two different areas, namely the anterior midbrain and temporal lobe, for 10 subjects. RESULTS: The mean peak systolic velocities showed a tendency to increase from the superior to the inferior aqueduct, irrespective of the background baseline region, with the range being from 3.30 cm/sec to 4.08 cm/sec. However, these differences were not statistically significant. In the case of the mean flow, the highest mean value was observed at the mid-portion of the ampulla (0.03 cm3/sec) in conjunction with the baseline ROI at the anterior midbrain. However, no other differences were observed among the mean flows according to the location of the cerebral aqueduct or the baseline ROI. CONCLUSION: We obtained a set of reference data of the CSF peak velocity and mean flow through the cerebral aqueduct in young healthy volunteers. Although the peak systolic velocity and mean flow of the CSF differed somewhat according to the level of the cerebral aqueduct at which the measurement was made, this difference was not statistically significant.