Extracranial Examination

Extracranial examination uses continuous-wave (CW) Doppler to evaluate the direction and velocity of blood flow in the carotid and vertebral arteries. As a non-imaging, physiologic test it identifies hemodynamic signatures of significant disease — such as reversed flow in the periorbital or vertebral circulation — rather than grading or localizing a stenosis, which is the role of duplex ultrasound.

• Non-invasive and safe
• Assesses carotid and vertebral flow direction and velocity
• Highly specific findings (e.g., flow reversal) flag severe disease for confirmatory imaging

A 4 or 8 MHz CW Doppler probe insonates the extracranial arteries, capturing a velocity waveform and its direction (forward or reversed). Reversed flow in the supraorbital or periorbital arteries is a highly specific marker of critical internal-carotid disease, while reversed vertebral flow — together with an inter-arm systolic pressure difference (commonly ≥15–20 mmHg) — points to subclavian steal. Because CW Doppler is non-imaging and not range-gated, it confirms the presence and direction of flow rather than grading a stenosis; significant findings are referred for duplex.

• Real-time velocity waveform with directional (forward/reverse) display
• Audible Doppler with waveform indices (PI, RI, and S/D ratio)
• Findings suggestive of significant disease referred for confirmatory duplex

Extracranial CW Doppler is a useful physiologic adjunct for:

• Detecting the hemodynamic signature of critical carotid disease (reversed periorbital flow is highly specific)
• Screening for subclavian steal (reversed vertebral flow plus an inter-arm pressure difference)
• Documenting flow direction and velocity when imaging is pending or unavailable

Carotid duplex ultrasound — which this system does not perform — is the modality recommended by current guidelines for diagnosing, grading, and localizing carotid and vertebral stenosis. Extracranial CW Doppler complements that workup by flagging patients for definitive imaging; it is not a stand-alone stroke-screening test.

VasoGuard performs extracranial studies with its continuous-wave Doppler exam: 4 and 8 MHz probes, real-time velocity waveforms, and forward/reverse flow display. The common, internal, and external carotid and vertebral arteries are each selectable, with dedicated report fields and waveform indices captured for the record.

• 4 & 8 MHz CW Doppler probes with directional (forward/reverse) flow
• Carotid (common/internal/external) and vertebral vessels with per-vessel report fields
• Velocity-waveform indices: pulsatility index, resistance index, and S/D ratio
• Comprehensive data management and export