Carotid ultrasound

Overview of the Procedure

Carotid ultrasound is a non-invasive imaging technique primarily used to assess blood flow dynamics and structural abnormalities of the carotid arteries. This examination utilizes high-frequency sound waves to produce real-time images, allowing precise measurement of arterial stenosis, plaque size, and blood flow velocity. It is an essential tool for diagnosing atherosclerosis and preventing strokes. In Taiwan’s clinical practice, it is commonly used as a first-line screening method for cerebrovascular diseases.

Types of Treatments and Mechanisms

This examination is categorized into diagnostic and therapeutic adjunct types. Diagnostic ultrasound uses probes with a frequency of 8-12 MHz to clearly display vessel wall thickness and plaque composition; therapeutic adjuncts combine real-time imaging guidance for precise localization before endarterectomy. The core mechanism involves Doppler effect analysis of blood flow velocity changes; when blood flow is obstructed, changes in the reflected sound wave frequency enable accurate calculation of the degree of stenosis.

Indications

Main indications include:

Patients suspected of carotid stenosis or occlusion
Patients with recurrent transient ischemic attacks (TIA)
Cardiovascular risk assessment for patients with diabetes or hypertension

Additionally, it is used for follow-up in stroke survivors and for evaluating the efficacy of antiplatelet therapy.

Usage and Dosage

During the procedure, patients lie flat while the technician applies gel to the neck and moves the probe to scan. No anesthesia or radiation exposure is involved. The examination lasts approximately 20-30 minutes; in special cases (such as severe cervical spine deformity), it may need to be performed in multiple sessions. As a non-invasive procedure, there is no need for dose control, but patient positioning should be optimized to ensure clear imaging.

Benefits and Advantages

The main advantages include:

Non-invasive, suitable for health screening
Allows dynamic observation of blood flow changes
Cost 40-60% lower compared to angiography

Its imaging resolution can reach 0.1mm, capable of distinguishing calcified plaques from soft plaques, providing critical information for treatment decisions.

Risks and Side Effects

This examination has very low risks, but potential issues include:

Operator skill variability may lead to misdiagnosis (error rate approximately 3-5%)
Severe neck obesity may affect image quality
A very small number of patients may develop skin allergies from gel contact

It is important to note that this test cannot directly visualize cerebral vasculature.

Precautions and Contraindications

Contraindications include:

Post-neck surgery with excessive scar tissue
Severe coagulation disorders (which may affect interpretation)

Patients should remove necklaces or jewelry from the neck area before the exam. Hypertensive patients should have their blood pressure controlled prior to testing. If severe stenosis (>70%) is detected, further treatment evaluation should be conducted within 48 hours.

Interactions with Other Treatments

Often combined with the following treatments:

Follow-up after antiplatelet medication use
Comparison of stenosis before and after carotid stenting

Care should be taken to schedule with radiological examinations (such as CTA), usually performing ultrasound first to avoid repeated radiation exposure.

Treatment Efficacy and Evidence

According to a 2020 study in the journal Stroke, carotid ultrasound has a diagnostic accuracy of 92% for stenosis degree, with a correlation coefficient of 0.87 compared to angiography. Long-term follow-up studies show that regular examinations can reduce stroke risk by 35%. In Taiwan’s National Health Insurance coverage criteria, this test can predict stroke within 5 years in diabetic patients with an accuracy of 81%.

Alternatives

The main alternatives include:

Computed Tomography Angiography (CTA): higher spatial resolution but involves radiation exposure
Magnetic Resonance Angiography (MRA): suitable for patients with metal implants but takes longer

When economically feasible, three-dimensional ultrasound imaging can provide more detailed anatomical structures, though equipment availability is limited.

Frequently Asked Questions

Is there any special preparation needed before the exam? For example, fasting or stopping medication?

Generally, carotid ultrasound does not require fasting or discontinuation of medications. However, it is recommended to avoid wearing high-collared clothing to allow full exposure of the examination area. If you are taking anticoagulants or other chronic medications, inform the medical staff beforehand for assessment of any adjustments.

Will the procedure cause pain or discomfort?

The procedure is non-invasive and painless. It only involves applying gel to the neck and gently pressing and moving the probe. Some patients may feel slight pressure from the probe but are usually tolerable. The examination lasts about 15-30 minutes and is highly safe.

Is rest needed after the exam? Can I drive or engage in daily activities immediately?

Post-exam, you can resume normal activities immediately without special rest. Since the procedure is entirely non-invasive, it does not affect nerve or vascular functions. However, if severe stenosis is detected, your doctor may recommend follow-up observation or activity restrictions based on your condition.

What are the advantages and disadvantages of carotid ultrasound compared to CTA?

Carotid ultrasound has the advantages of no radiation, non-invasiveness, and lower cost, making it suitable for initial plaque screening or monitoring stenosis changes. However, for precise assessment of calcification or three-dimensional vascular structures, CTA or MRA may be necessary. The physician will choose the most appropriate examination based on individual case needs.

What should I pay attention to in daily life if the examination shows arterial stenosis?

If stenosis is found, control blood pressure, blood sugar, and blood lipids, avoid smoking and high-fat diets. Regular exercise and adherence to prescribed medications are recommended. If stenosis exceeds 70% or if there are stroke symptoms, surgical evaluation may be necessary. Be alert for symptoms such as dizziness or unilateral limb weakness and follow up regularly.