Velocity-coded colour magnetic resonance angiography and perfusion-weighted magnetic resonance imaging for the evaluation of extracranial-to-intracranial arterial bypass surgery

Background and purpose: Velocity-coded colour magnetic resonance angiography (VCCMRA) and perfusion magnetic resonance imaging (pMRI) were evaluated as methods for investigating the efficacy of extracranial-to-intracranial arterial bypass (EC-IC bypass) by comparing the findings of VCCMRA and those of cerebral angiography and by measuring the improvement ratio after EC-IC bypass by pMRI compared to that by single photon emission computed tomography (SPECT) using the autoradiographic technique. Methods: Thirteen patients who underwent VCCMRA, angiography, SPECT, and pMRI before and after surgery were analyzed. Findings of VCCMRA were compared to those of angiography. Improvement ratio was calculated compared to the cerebellum for cerebral blood volume, mean transit time (MTT), and regional cerebral blood flow (rCBF) as measured by pMRI and quantitative SPECT. Results: Findings of VCCMRA were in good agreement with those of angiography and clearly showed the direction of bypass flow. No statistically significant correlation was observed between the improvement ratios in CBF in the hemisphere and middle cerebral artery territory on the surgical and non-surgical sides and in rCBF in the same regions of interest (ROIs) (r=-0.574, 0.09). However, a statistically significant correlation was observed between the cerebrovascular reserve capacity (CVRC) in the hemisphere on the surgical side and in MTT in the same ROIs (r=0.955, P<0.001). Conclusion: VCCMRA may clearly show the direction of flow in the EC-IC bypass. MIT measured by pMRI may indicate the postoperative state of CVRC. These techniques could replace angiography and positron emission tomography or SPECT in patients undergoing EC-IC bypass.