This work aims to explore the permeability of cortical cerebral vessels in the cortical areas by using the combination of DCE-MRI and 3D-pCASL in MMD. This work aims to explore the permeability of cortical cerebral vessels in the cortical areas by using the combination of DCE-MRI and 3D-pCASL in MMD. Patients From June 2014 to July 2015, 26 patients (17 males and 9 females, mean age was 40±11.6 years old) were included in this study with the combined scan of 3D-pCASL and DCE-MRI. Detailed information with angiography for patients was shown as Table 1. MRI scan 3D-pCASL was performed with TR = 4590 ms, TE = 10.5ms, labeling time = 1500ms, post-labeling delay (PLD) = 1525 ms, slice thickness = 4 mm (gapless), matrix = 512×8, flip angle=111°, NEX =3, scanning time = 4 min 29 s; DCE-MRI was performed using 3 dimensional LAVA sequence with the same scanning range and slice thickness with 3D-pCASL: TR=3.4ms, TE=1.6ms, flip angle=15°, matrix= 256×160, NEX=1. Before contrast-medium injection, T1 mapping scan with flip angles of 5°, 8°, 12° and 15° were performed, respectively. A power injector was employed for a bolus injection of gadolinium-based agent.Sixty dynamic phases were obtained with the administration of contrast medium at the fifth phase.Total scan time was 4 min 24 s. Data analyses According to the feeding distribution of the anterior、middle and posterior cerebral artery, 10 regions of interest were drawn manually on cortical areas of each section through the basal ganglia; the bright signals of arterial transit artifact (ATA) were scored as 0, 1 or 2 points for each region in the cortical areas, otherwise, the normal regions were scored as 3 points as control according to the results of angiography. The method of scoring scale was shown as Fig.1a-c. All the 260 regions were divided into 0, 1, 2 and 3 groups according to the scoring results.The CBF was calculated automatically via the in-built software in the workstation. And K^trans was calculated via Patlak model.Then the corresponding values of CBF and K^trans were calculated, respectively. The statistical tests of ANOVA and Kruskal-Wallis H were performed to compare the measurements of CBF and K^trans among 0-3 groups, respectively.One example with the proximal tenosis of left MCA was shown as Fig1.d-h, including MRA (d), ASL(e), cortical divided regions (f) and Ktrans map (f), and the results of measurement (h).The CBF values were significantly different in the cortical areas with different scoring points among 4 groups（F=38.57, P < 0.01)(Fig.2a). No significant differences were observed for Ktrans values on among 4 groups (c2=3.092, P = 0.378) (Fig.2b).DSA is gold standard to visualize the vasculature in cerebral vascular disease. However, it cannot provide information about the permeability of vascularization. Based on prior studies of MMD，the fragile collateral pial vessels with increasing vascular permeability after revascularization surgery could lead to post-operative high perfusion syndrome, rehemorrhage and other complications(1, 2). Early detecting the permeability of collateral vesseles could potentially help predict post-operative high peffusion status, and even prevent the rehemarrhage after surgical revascularization.With the signal of ATA, 3D-pCASL may identify the presence of collateral neovascularization, which has been described with a high consistency between the techniques of DSA and ASL (3).DCE-MRI can quantitatively calculate the permeability of neovascularization, which has been extensively used in cerebral tumor and ischemic stroke. To the best of our knowledge, almost no prior studies were focused on evaluating the characteristic of collateral vascular permeability in MMD. Quantitative assessment of collateral vascular permeability in the cortical areas using the combination of 3D-pCASL and DCE-MRI suggest no significant abnormality of permeability in cortical regions with collateral neovascularization.