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Introduction: Pencil Beam type presaturation (BeamSAT) pulse on a major cervical vessel enables selective suppression of blood flow signal of the applied vessel in MR angiography (MRA). By subtracting the BeamSAT pulse-added MRA of an internal carotid artery (ICA) from conventional MRA, only the contralateral ICA image (SubBeamSAT image) can be obtained (Figure A, B). In this way, an ICA-selective MRA with more physiologial flow pattern can be obtained, because it requires no powerful injection of contrast medium.Purpose: The aim of this study was to investigate whether preoperative assessment of the flow of Acom/A1 by SubBeamSAT image and posterior communicating artery (Pcom) by conventional MRA could identify patients at risk for intolerance to intraoperative temporary ICA occlusion.Method: 29 patients who underwent carotid endarterectomy (CEA) (n = 17) or carotid artery stenting (CAS) (n = 12) were enrolled in the current study. All patients underwent the SubBeamSAT images and conventional MRA pre- and post-operatively. Response to ICA temporally occlusion was recorded during the revascularization procedure.Results: Among twenty-nine patients, 4 patients who demonstrate neither the Acom/A1 flow on SubBeamSAT image (Figure. B) nor Pcom flow on MRA showed intolerance. In contrast, the remaining 25 patients who demonstrated Acom/A1 (Figure. A) and/or Pcom flow showed tolerance. Intolerance to ICA occlusion was excellently predicted by visualization of collateral flow via Acom and Pcom (specificity: 100%, sensitivity: 100%, p=0.00004).Conclusions: SubBeamSAT image is useful for evaluating the flow of Acom from A1 portion of the healthy side to A2 portion of the contralateral side, which is often difficult to evaluate with conventional MRA. With the SubBeamSAT image, it is feasible to evaluate the Acom/A1 flow accurately. In conclusion, SubBeamSAT image enables excellent prediction for the intolerance to temporary ICA occlusion.