Intraoperative evaluation of cerebral hemodynamics using directional Doppler technique

Abstract

The use of a pulsed echo Doppler technique during surgery for cerebral arteriovenous malformation is described. The equipment and the methods employed are presented. The main advantages are easy determination of flow direction and pattern of the vasculature involved, allowing a precise discrimination between inflow and outflow channels. Deep-seated malformations, not visible at the brain surface, can be located with the Doppler technique. The ultrasound probe was placed on the brain surface with a slight pressure on the intact pia mater. The precise direction and depth of the malformation could be determined in relation to the recording site. This facilitated the planning of cortical incisions, identification of vessels involved, and the vascular procedure to be employed.

Intraoperative microvascular Doppler ultrasonography in cerebral aneurysm surgery

“…Technical progress made it possible to reduce the size of the ultrasound probe by increasing the ultrasound frequency. Further studies of Nornes et al 2 and Gilsbach3 4 led to the development of microprobes for direct investigation of small cerebral vessels.…”

Intraoperative Doppler to Measure Cerebrovascular Resistance as a Guide to Complete Resection of Arteriovenous Malformations

“…Resistance to inflow by the normal cerebral capillary bed results in relatively low diastolic flow in the supplying artery and results in a relatively higher value for the RI. A low resistance, as in an AVM with an absence of capillaries, results in higher diastolic flow and a low RI (8,19). The RI of the artery feeding the AVM is lower than the RI of the surrounding normal vessels because of the lack of this intervening capillary bed.…”

Monitoring Techniques for Prevention of Procedure-Related Ischemic Damage in Aneurysm Surgery

“…The Doppler technique, originally designed for extracranial vessels, was adapted in the 1980s for transcranial evaluation of cerebral vessels (1) and thereafter, with the development of small probes, also applied to small intracerebral arteries (44,45,94). The Doppler effect takes advantage of the ultrasound wave modified by the impact of fluid particles (e.g., red blood cells in the bloodstream) moving at a velocity within the vessel, together with the bloodstream that is related to the diameter.…”