Protocol for Duplex Scanning of the BCA: Location Points, Modes, Norms, and Report Structure
Importance of Protocol Standardization
Duplex scanning of the cervical segments of the carotid and vertebral arteries is the most common vascular study, and systematic approach is crucial: a missed segment or incorrectly identified artery can change the approach up to surgical indications. A unified reproducible protocol serves as a framework for all clinical tasks.
Patient Positioning and Access
No special preparation is required; the examination is conducted in a state of relaxed wakefulness. By agreement, the transducer indicator in the transverse plane is always directed to the patient's right side.
Location Points and Scope of Examination
Duplex assessment of the carotid arteries generally includes bilateral examination:
| Segment | Comment |
|---|---|
| Common carotid artery (CCA) | Bilaterally |
| Internal carotid artery (ICA) | Bilaterally |
| External carotid artery (ECA) | Bilaterally |
| Vertebral artery | At the mid-neck level |
| Proximal segment of the subclavian artery | Mandatory |
| Middle and distal segments of the subclavian artery | If proximal abnormalities are detected |
| Brachiocephalic trunk (innominate artery) | If indicated |
In special circumstances, unilateral or limited examination may be performed.
Scanning Modes
Gray-scale B-mode (for wall morphology and plaques), color Doppler mapping (CDM), and spectral Doppler are used. During operation, depth is optimized, spontaneous aliasing is eliminated, and the velocity scale is correctly set. The shape of the spectrogram, the rate of rise of the systolic peak, and the nature of the systolic decline are assessed.
Blood Flow Norms in the Subclavian Arteries and Brachiocephalic Trunk
The brachiocephalic trunk is short and wide, located on the right. Normally, blood flow in the brachiocephalic artery and subclavian arteries is triphasic, with a spectral window. The appearance of biphasic or monophasic flow indicates stenotic-occlusive lesions distal to the location. Reversed or pendulum-like flow in the ipsilateral vertebral artery indicates proximal stenosis/occlusion of the subclavian artery (subclavian steal syndrome).
Assessment of Atherosclerotic Plaque
According to the American Society of Echocardiography (ASE, 2020) recommendations, plaque measurement begins in the same plane as the measurement of the intima-media thickness (IMT) for consistency in determining plaque exceeding the threshold IMT >1.5 mm. Measurement can be performed from any segment in the long and short axes of the carotid artery (bulb, ICA, CCA) with indication of the segment and projection. Plaque area is the most advanced method of two-dimensional quantitative analysis; it begins with manual scanning, usually in cross-section.
Structure of the Report
[clarify] — in the provided fragments, the formalized structure of the report (list of mandatory protocol form items) is not presented. Based on the content of the fragments, the report should reflect: identification and patency of each examined segment (CCA, ICA, ECA, VA, subclavian, if indicated — brachiocephalic trunk), plaque characteristics with indication of the segment and projection and comparison with the IMT threshold >1.5 mm, as well as the nature of the spectrum (tri-, bi-, or monophasic) and presence/absence of signs of steal syndrome.
Frequently asked questions
Which segments are mandatory in the standard BCA duplex protocol?
Bilaterally the CCA, ICA, ECA, vertebral artery at the mid-neck level, and proximal segment of the subclavian artery. Middle and distal segments of the subclavian artery if proximal abnormalities are detected, brachiocephalic trunk if indicated.
What blood flow is considered normal in the subclavian arteries and brachiocephalic trunk?
Triphasic, with a spectral window. The appearance of biphasic or monophasic flow indicates stenotic-occlusive lesions distal to the location.
How to suspect subclavian steal syndrome on ultrasound?
By reversed or pendulum-like flow in the ipsilateral vertebral artery, indicating proximal stenosis or occlusion of the subclavian artery.
From what IMT threshold is a structure considered a plaque according to ASE 2020?
A structure is considered a plaque if it exceeds the threshold IMT >1.5 mm; measurement begins in the same plane as the IMT measurement, with indication of the segment and projection.
Is patient preparation required for BCA examination?
No special preparation is required; the examination is conducted in a state of relaxed wakefulness. The transducer indicator in the transverse plane is directed to the patient's right side.