Imaging Venous Transit Time and Blood–Brain Barrier Permeability of the Deep Brain

PURPOSE: Imaging of venous vessels with advanced pulse sequences allows the assessment of important hemodynamic parameters. Previous work has measured venous transit time (VTT) and blood-brain barrier (BBB) water permeability in cortical tissue. This study aimed to measure VTT and BBB permeability in the deep brain through imaging in the straight sinus (SS). METHODS: Two studies were conducted. Study I measured VTT of the deep brain using a Venous-transit-time-Imaging-by-Changes-in-T1-Relaxation (VICTR) MRI sequence. The obtained VTT was used in study II to optimize the imaging parameters of Water-Extraction-with-Phase-Contrast-Arterial-Spin-Tagging (WEPCAST) MRI pulse sequence, and the permeability-surface-area product (PS) was quantified in the deep brain. Test-retest reproducibility was assessed. RESULTS: SS VTT was found to be 2807.5 ± 349.5 ms, which was approximately half a second shorter than the SSS VTT (3365.0 ± 235.3 ms, p < 0.001). The SS VTT results were reproducible across repetitions, with a coefficient of variation of 2.8% ± 0.5%. The standard deviation of the VTT distribution in SS was 973.7 ± 48.1 ms, again shorter than the corresponding SSS values (1165.5 ± 37.2 ms, p < 0.001). The water extraction fraction, E, from the SS was 94.8% ± 1.9%, and the deep-brain PS was 141.3 ± 20.2 mL/100 g/min. The PS values were slightly lower than the cortical PS of 152.9 ± 20.9 mL/100 g/min (p = 0.039), and may reflect the lower vascularity in the deep-brain region. The intraclass correlation coefficient (ICC) of the deep-brain PS values from repeated runs was 0.863. CONCLUSION: This is the first study to measure two parameters associated with deep-brain physiology, specifically VTT and BBB water permeability, and provide their normative values.