Insonation angle impact on micro-Doppler evaluation in cerebrovascular surgery: technical note

Abstract

Introduction: The insonation angle consideration is important in the Doppler-sonographic evaluation of blood flow velocities and volume, however, the concept is rarely applied to the intraoperatively used micro-Doppler.This technical note aims to emphasize the possibility and necessity of insonation angle correction and preservation for the blood flow assessment in cerebrovascular surgery.Methods: Bi-directional surgical Doppler with a 20MHz flexible bayonet 1.2mm diameter probe was used for the intraoperative blood flow assessment, with the variable insonation angle on the straight parts of the arteries, and the results were recorded to demonstrate the importance.Results: The measurements performed confirmed that the blood flow features, including the direction, velocity, and especially the volume, are highly susceptible to the insonation angle variations. Although there were significant alterations, positioning the probe at an angle of ~60 degrees resulted in the variable but less altering measurements.Conclusion: Positioning the probe at ~60 degrees is desirable; however, it appears that it is even more important to maintain the same insonation angle and probe position when assessing the vessels repeatedly for blood flow alterations that might occur in the course of cerebrovascular surgery.