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E2169. Pitfalls and Artifacts in Carotid Ultrasound
Authors
  1. Amit Desai; Mayo Clinic
  2. Alok Bhatt; Mayo Clinic
  3. Shweta Bhatt; Mayo Clinic
Background
Doppler ultrasound is an important noninvasive imaging modality for assessment of the extracranial cerebrovasculature. Most commonly, it is used in the setting of a transient ischemic attack/stroke, syncope, or cervical bruit to assess the severity of carotid atherosclerotic disease including plaque morphology and severity of stenosis. Other indications for carotid ultrasound include preoperative screening for carotid stenosis, assessment of carotid stent patency, and evaluation of suspected subclavian steal, dissection, pseudoaneurysm, fibromuscular dysplasia, or pulsatile neck mass. Doppler artifacts are an integral part of vascular ultrasound. Nonrecognition or false interpretation of Doppler artifacts can steer the radiologist astray, leading to erroneous diagnoses. Therefore, it is critical for radiologists to be aware of Doppler artifacts that are commonly encountered with carotid ultrasound. Some of the Doppler artifacts may also be useful to the radiologist, helping in making the correct diagnosis. This presentation demonstrates normal carotid anatomy and hemodynamics as well as standard scanning protocols and Doppler settings to produce consistent and accurate images. Common pitfalls and artifacts in carotid Doppler are then reviewed. Techniques to avoid or correct these pitfalls and artifacts are demonstrated. Advantages of the Doppler artifacts in diagnosis of carotid artery pathologies will also be highlighted.

Educational Goals / Teaching Points
1. Highlight common errors in the interpretation of carotid ultrasounds and how to avoid them. 2. Demonstrate common and uncommon grayscale and color Doppler artifacts in carotid ultrasound. 3. Review how to correct artifacts. Discuss which artifacts cannot be corrected, and which can be useful in making the diagnosis.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Review of normal carotid anatomy and hemodynamics. Review of pitfalls and how to avoid them. Cases include but are not limited to: a. Tortuous artery mimicking stenosis b. Aortic stenosis leading to decreased carotid velocities c. Hyperdynamic circulation causing elevated carotid velocities d. Elevated velocities in stented carotid artery mimicking stenosis e. Anatomic variations f. Altered waveforms due to cardiovascular devices (LVAD, Aortic balloon etc.) g. Technical errors affecting grayscale, color images, as well as waveforms due to inappropriate selection of: transducer frequency, Doppler gain, wall filters, velocity scale, etc. Review of artifacts. What causes them and how to correct it. Cases include but are not limited to: a. Aliasing b. Twinkling c. Mirror image d. Directional Ambiguity e. Pseudoflow f. Reverberation g. Acoustic Shadowing h. Ghosting

Conclusion
Doppler ultrasound is an important noninvasive tool for assessment of the extracranial cerebrovasculature. A standardized reproducible scanning protocol is imperative to produce consistent, accurate, high-quality images. Understanding of the normal carotid anatomy and physiology as well as common Doppler pitfalls and artifacts is critical for accurate interpretation.