Cerebral Hemodynamics and Microemboli During Placement of Relay®Branch Thoracic Stent-Graft System

"Transcranial Doppler (TCD) is a non-invasive ultrasound-based technique that facilitates insonation of the cerebral arteries. TCD probe design enables continuous monitoring of cerebral blood flow velocity (CBFv). TCD has a variety of clinical applications, including intraoperative monitoring for detection of microemboli. The TCD probe can be comfortably secured to the patient's head by a headframe in order to maintain continuous vessel insonation. Microembolic signals (MES) can be reliably detected based on standard criteria:~1. Brief in duration (\<300msec)~2. High intensity (amplitude \>3 dB above background)~3. Unidirectional~4. Audible chirp or snap~Further, CBFv monitoring during may inform flow perturbations that occur during cardiac or vascular manipulations."