The global intracranial venous resistance is still unknown and hemodynamic abnormalities of the cerebral venous system are commonly recognized to be present in several cerebral diseases (1;2). The intracranial pressure is influenced by the blood outflow resistance. Cross-sectional anatomical information from MR angiography (MRA) techniques are currently used to examine cerebral venous insufficiency. However, such measurements of local vessels caliber does not enable the assessment of the total resistance to blood flow along branch of the cerebral venous tree. In this study we propose a new approach to estimate the vascular resistance (VR) of the cerebral venous tree using phase contrast (PC) MR angiography technique. In addition, we examined the correlations between the estimated resistances and the venous outflows measured by cine phase contrast (PC) MRI.Imaging: This study was IRB approved and informed consent was obtained from a cohort of 26 healthy subjects (age=27±6 years). Imaging was performed on a 32-channel, 3T system (Philips Healthcare, Best, The Netherlands). 3D PCA data were acquired with: FOV = 230x230 mm², resulting spatial resolution = 0.5x0.5x0.5 mm³, α= 12°, Venc = 30 cm/s, TR/TE = 6/3 ms, scan time= 5.9 mn. The scan parameters for the 2D PC-MRI sequence were: FOV = 120x120 mm², resulting spatial resolution = 0.5x0.5 mm², TR/TE = 14/8 ms, α= 30°, Venc = 80 cm/s, cardiac phases = 16, scan time = 2.6 mn. Post-processing: A semi-automatic software (www.tidam.fr) tool was applied to quantify the flows from the PC-MRI images. The 3D PC-MRA data were imported to Mimics (Materialise NV, MI, US A) for manual 3D segmentation of the cerebral venous tree (fig. 1) which was represented by the superior sagittal sinus (SSS), straight sinus (StS), left and right transverse sinuses (TS), sigmoid sinuses (SigS) and internal jugular veins (IJV). The length and mean hydraulic diameter were extracted from the segmented geometry. The VR of each branch was estimated using the laminar Poiseuille's law: $$$R_{branch}={\frac{8{\eta}L}{\pi{r_h^4}}}$$$, where $$$ {\eta} $$$ is the blood viscosity, $$${L}$$$ lenght of segment and $$${ r_{h}}$$$ hydraulic radius of segment. An equivalent resistance of the venous tree was calculated using an electric circuit analog to this venous system (fig. 2).Table1 presents estimated VR. The mean flows measured at the C2C3 cervical level were 353 ± 136 cm³/mn (left IJV) and 262 ± 110 cm³/mn (right IJV). The sum of resistances of the TS, SigS and IJV correlated with the blood flows measured at C2C3 level: R² = 0.39 for the left side and R² = 0.40 for the right side (p<0.05).By using PC-MRA this new approach allowed to evaluate the global resistance of the venous tree. The relative variability of VR across the subjects may reflect anatomical variations of the venous sinuses. The correlations between left and right C2C3 blood flow measurements and VR may indicate a high level of consistency between the two techniques and shows great promise to detect longitudinal pressure drop (ΔP) as the product between VR and cerebral venous flow measurements (3). The evaluation of ΔP in the venous system can be promising for understanding venous flow alterations in idiopathic intracranial hypertension (4) and hydrocephalus (1).