Signal Intensity Changes for the Middle Cerebral Artery on 3-Dimensional Time-of-flight Magnetic Resonance Angiography Indicate Acute Hemodynamic Changes after Carotid Endarterectomy

BackgroundFor 3-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA), the signal intensity (SI) loss depends on the flow velocity. In this study, we aimed to evaluate whether 3D-TOF-MRA could be used as an alternative to single-photon emission computed tomography (SPECT) for assessing the increase in the regional cerebral blood flow (rCBF) after carotid endarterectomy (CEA). To do this, we compared the SI of the middle cerebral artery (MCA) on magnetic resonance angiography (MRA) and the rCBF on SPECT.MethodsWe enrolled 30 patients with internal carotid artery stenosis. SPECT and MRA were performed before and 3-4 days after CEA. rCBF was assessed using SPECT, and the SI of the MCA was assessed using single-slab 3D-TOF-MRA. Regions of interest were placed in the bilateral middle M1 portions of the MCA on MRA, and their mean SI was measured. The increase ratio of the rCBF on SPECT and the increase ratio of the SI of the MCA on MRA were calculated using the formula: (post-CEA ipsilateral/post-CEA contralateral)/(pre-CEA ipsilateral/pre-CEA contralateral).ResultsA significant correlation was observed between the increase ratio of the rCBF on SPECT and the increase ratio of the SI of the MCA on MRA (r = .894, y = .4863 + .5184x, P < .001). All values obtained by MRA were greater than or equal to the SPECT values, indicating that MRA tends to overestimate the post-CEA rCBF increase.ConclusionBecause MRA identified increased rCBF after CEA, we recommend that patients first be screened using MRA.