=====Pulsatility index===== A measure of the variability of blood velocity in a vessel, equal to the difference between the peak systolic and minimum diastolic velocities divided by the mean velocity during the cardiac cycle. Larger [[intracranial aneurysm]] size correlates with higher ipsilateral MCA PI, demonstrating that aneurysms affect distal intracranial hemodynamics ((Hussein AE, Brunozzi D, Shakur SF, Ismail R, Charbel FT, Alaraj A. Cerebral Aneurysm Size and Distal Intracranial Hemodynamics: An Assessment of Flow and Pulsatility Index Using Quantitative Magnetic Resonance Angiography. Neurosurgery. 2017 Aug 17. doi: 10.1093/neuros/nyx441. [Epub ahead of print] PubMed PMID: 28945889. )). ---- [[Pulmonary artery pulsatility index]]