The AIUM Practice Parameter for the Performance of an Ultrasound Examination of the Extracranial Cerebrovascular System.

Abstract

Journal of Ultrasound in MedicineVolume 41, Issue 4 p. E21-E27 Practice ParameterFree Access The AIUM Practice Parameter for the Performance of an Ultrasound Examination of the Extracranial Cerebrovascular System First published: 18 November 2021 https://doi.org/10.1002/jum.15877AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Introduction The American Institute of Ultrasound in Medicine (AIUM) is a multidisciplinary association dedicated to advancing the safe and effective use of ultrasound in medicine through professional and public education, research, development of clinical practice parameters, and accreditation of practices performing ultrasound examinations. The AIUM Practice Parameter for the Performance of an Ultrasound Examination of the Extracranial Cerebrovascular System was revised by the AIUM in collaboration with other organizations whose members use ultrasound for performing this examination(s) (see “Acknowledgments”). Recommendations for personnel requirements, the request for the examination, documentation, quality assurance, and safety may vary among the organizations and may be addressed by each separately. This practice parameter is intended to provide the medical ultrasound community with recommendations for the performance and recording of high-quality ultrasound examinations. The parameters reflect what the AIUM considers the appropriate criteria for this type of ultrasound examination but is not intended to establish a legal standard of care. Examinations performed in this specialty area are expected to follow the Parameter with recognition that deviations may occur depending on the clinical situation. Indications Indications for an ultrasound examination of the extracranial carotid and vertebral arteries include, but are not limited to: Evaluation of patients with hemispheric neurologic symptoms, including stroke, transient ischemic attack, and amaurosis fugax1-3 Evaluation of patients with a cervical bruit Evaluation of pulsatile neck masses Preoperative evaluation of patients scheduled for major cardiovascular surgical procedures Evaluation of nonhemispheric or unexplained neurologic symptoms Follow-up evaluation of patients with known or documented carotid disease Postoperative or postintervention evaluation of patients following cerebrovascular revascularization, including carotid endarterectomy, stenting, or carotid to subclavian artery bypass graft Intraoperative monitoring of vascular surgery Evaluation for suspected subclavian steal syndrome4 Evaluation for suspected carotid artery dissection,5 arteriovenous fistula, or pseudoaneurysm Evaluation of patients with carotid reconstruction after extracorporeal membrane oxygenation bypass Evaluation of patients with syncope, seizures, or dizziness Screening high-risk patients, including atherosclerosis elsewhere, history of head and neck radiation, known fibromuscular dysplasia, Takayasu arteritis, or other vasculopathy in another circulation Neck trauma Hollenhorst plaque visualized on retinal examination Qualifications and Responsibilities of Personnel Physicians interpreting or performing this type of ultrasound examination should meet the specified AIUM Training Guidelines in accordance with AIUM accreditation policies. Sonographers performing the ultrasound examination should be appropriately credentialed in the specialty area in accordance with AIUM accreditation policies. Physicians not personally performing the examination must provide supervision, as defined by the Centers for Medicare and Medicaid Services Code of Federal Regulations 42 CFR §410.32. Request for the Examination The written or electronic request for an ultrasound examination must originate from a physician or other appropriately licensed health care provider or under the provider's direction. The clinical information provided should allow for the performance and interpretation of the appropriate ultrasound examination and should be consistent with relevant legal and local health care facility requirements. Specifications of the Examination Extracranial cerebrovascular ultrasound evaluation consists of assessment of the accessible portions of the common carotid, external and internal carotid, and the vertebral arteries. Scanning Technique All arteries are scanned using appropriate grayscale and Doppler techniques and proper patient positioning.2, 3, 6 The common carotid and internal carotid arteries are scanned in grayscale and with color Doppler, as completely as possible. Caudad angulation of the transducer in the supraclavicular area and cephalad angulation at the level of the mandible may aid visualization.3, 7 The vertebral arteries can be evaluated in the mid-neck between the vertebral transverse processes, proximally in the preforaminal (extraosseous) segment, or as they originate from the subclavian arteries. Grayscale imaging of the common carotid artery, its bifurcation, and both the internal and external carotid arteries is performed in longitudinal and transverse planes. Gain is optimized to detect the vessel wall, plaque, and other abnormalities. Color Doppler is used to detect areas of narrowing and abnormal flow to select areas for spectral analysis. Color Doppler is also helpful to detect external carotid branches to definitively identify the external carotid artery. Color Doppler is used to clarify the cause of image/pulsed Doppler mismatches and to detect narrow flow channels at sites of stenosis.8 Power Doppler evaluation may be complementary to color Doppler to search for narrow channels of residual flow in arteries in which occlusion or near occlusion is suspected. Long-axis spectral Doppler velocity measurements with angle correction should be obtained at representative predetermined sites in all vessels. In addition, scanning in and through an area of stenosis or suspected stenosis must be adequate to determine the maximal peak systolic velocity and end-diastolic velocity associated with the stenosis and to document disturbances in the waveform distal to the stenosis. Consistent angle correction is essential for determining blood flow velocity.2 All angle-corrected spectral Doppler waveforms must be obtained from longitudinal images. All patients at a facility should be scanned with the same angle-correction technique (either parallel to the vessel wall or in line with the color flow lumen) to ensure consistency on serial examinations and among patients. The angle of insonation should be between 45 and 60° whenever possible. The potential velocity error related to incorrect angle assignment increases with increasing Doppler angle, especially at angles above 60°.3 Angles exceeding 60° should be avoided whenever possible. Techniques to obtain an appropriate angle (eg, heel and toe angulation of the transducer) may be necessary. Deviations from protocol may be unavoidable (eg, it may not be possible to obtain an appropriate angle with a very tortuous vessel) but should be minimized and documented on the technologist worksheet and final report. Spectral Doppler gain should be appropriate for the vessel scanned. Either excessive or inadequate gain may lead to errors. The Doppler scale should be set to maximize the size of the waveforms without aliasing to improve accuracy and reproducibility of measurement. Images must be obtained with appropriate color Doppler technique to demonstrate filling of the normal lumen and/or flow disturbances associated with stenosis. The color Doppler scale should be adjusted to avoid aliasing at typical carotid velocities, and the gain should be set to minimize artifacts. Recording Grayscale: for each normal side evaluated, representative grayscale images must be obtained at the following levels: long axis of common carotid artery; long axis at carotid artery bifurcation; long axis of internal carotid artery to include its origin; and short axis of proximal internal carotid artery. If abnormalities are found, additional images must be acquired: If atherosclerotic plaque is present, location, extent, and characteristics should be documented with grayscale imaging in both longitudinal and transverse planes. Other vascular or significant perivascular abnormalities should be documented. c. Color Doppler: for each normal side evaluated, color Doppler images (using color alone or as part of the spectral Doppler image) must be obtained at each of the following levels: long axis of distal common carotid artery; long axis of proximal and mid internal carotid artery; long axis of external carotid artery (with identification of a branch if possible); and long axis of vertebral artery. If abnormalities are found, additional images of the abnormality must be acquired. If atherosclerotic plaque is present, the extent and effect on the lumen should be determined and documented with a color flow Doppler image. In cases of occlusion, a color and/or power Doppler image of the occluded vessel must be acquired. Other vascular or significant perivascular abnormalities should be documented. d. Spectral Doppler: for each normal side evaluated, spectral Doppler waveforms and maximal peak systolic velocities and end-diastolic velocities must be recorded at each of the following levels: proximal common carotid artery; mid to distal common carotid artery (generally 2–3 cm proximal to the bifurcation where the walls are parallel to one another, namely, proximal to the bulb); proximal internal carotid artery; mid to distal cervical internal carotid artery; proximal external carotid artery; and vertebral artery (in the mid-neck or at/near the origin). If a significant stenosis is found or suspected, additional images must be recorded and the location of the stenosis determined: at the site of maximum velocity due to the stenosis and distal to the site of maximal velocity to document the presence or absence of poststenotic turbulent flow. Velocity ratios and diastolic velocities may also be calculated as warranted depending on the laboratory interpretation criteria. The peak systolic velocity, end-diastolic velocity, waveform shape, and flow direction in each of the vertebral arteries should be recorded. The duplex ultrasound examination after carotid angioplasty and/or stenting requires additional images. In these patients, grayscale, spectral, and color Doppler should be used to evaluate the lumen of the stented vessel, the stent deployment and apposition to the artery wall at the most proximal and distal extent of the stent/s, flow within the stents, and flow proximal and distal to the stent(s). The maximal in-stent peak systolic velocity and the waveforms distal to this site should be documented. Interpretation The interpretation of cerebrovascular ultrasound requires careful attention to protocol and interpretation criteria. Each laboratory must have interpretation criteria that are used by all members of the technical and physician staff. Diagnostic criteria must be derived from the literature or from internal validation based on correlation with other imaging modalities or correlation with surgery or pathology.2, 3, 5, 9-13 The report must indicate internal carotid artery stenosis categories that are clinically useful and nationally or internationally accepted and based primarily upon velocity criteria and waveform analysis.1-3, 14 Stenosis above 50% should be graded to within a range to provide adequate information for clinical decision-making. Numerous factors may falsely increase or decrease velocities (eg, systemic disease, cardiovascular disease, contralateral severe disease or occlusion, and near occlusive stenoses).6, 15-17 Simple velocity criteria may not be valid for children or younger adults, and other criteria, such as ratios, may be helpful in these circumstances. The report should describe abnormal waveforms, if present.4, 18, 19 The report must indicate vertebral artery flow direction. The report may characterize plaques, depending on the laboratory interpretation criteria.20-24 The report should describe significant nonvascular abnormalities. The criteria for common carotid and vertebral artery stenosis differ from internal carotid artery criteria.25, 26 A velocity threshold that indicates an external carotid stenosis is not established. A simple description indicating a stenosis, if present, may be reported. Identification of stenosis can be based on grayscale and/or color flow narrowing, elevated velocity through the stenosis, and typical poststenotic waveforms. The velocity criteria for stenosis after interventions may require different criteria than native vessels.27, 28 Stents require different velocity criteria than native vessels.29-32 Documentation Accurate and complete documentation is essential for high-quality patient care. Written reports and ultrasound images/video clips that contain diagnostic information should be obtained and archived, with recommendations for follow-up studies if clinically applicable, in accordance with the AIUM Practice Parameter for Documentation of an Ultrasound Examination. The initials of the operator should be accessible on the images or electronically in the electronic record (eg, PACS or radiology information system). Equipment Specification Equipment performance monitoring should be in accordance with the AIUM Routine Quality Assurance of Clinical Ultrasound Equipment, Version 2.0.33 The examination should be conducted with a real-time scanner with color, flow, and spectral Doppler capability, preferably using a linear transducer. The examination should use the highest clinically appropriate frequency, realizing that there is a trade-off between resolution and beam penetration. Imaging frequencies should be 5.0 MHz or greater. Doppler flow analysis should be conducted with a carrier frequency of 3.0 MHz or greater. Lower frequencies are occasionally appropriate in patients with a large body habitus or densely calcified vessels. Examination using lower-frequency transducers can also be useful when the vessels are not adequately imaged at higher frequencies. Color Doppler imaging can be used to localize blood flow abnormalities for range gate placement for the Doppler spectral analysis, thus facilitating the examination. Quality and Safety Policies and procedures related to quality assurance and improvement, safety, infection control, and equipment performance monitoring should be developed and implemented in accordance with the AIUM Standards and Guidelines for the Accreditation of Ultrasound Practices. ALARA (As Low as Reasonably Achievable) Principle The potential benefits and risks of each examination should be considered. The ALARA principle should be observed for factors that affect the acoustical output and by considering transducer dwell time and total scanning time. Further details on ALARA may be found in the current AIUM publication Medical Ultrasound Safety. Infection Control Transducer preparation, cleaning, and disinfection should follow manufacturer recommendations and be consistent with the AIUM Guidelines for Cleaning and Preparing External- and Internal-Use Ultrasound Transducers Between Patients, Safe Handling, and Use of Ultrasound Coupling Gel. Equipment Performance Monitoring Monitoring protocols for equipment performance should be developed and implemented in accordance with the AIUM Standards and Guidelines for the Accreditation of Ultrasound Practice. Acknowledgments This parameter was developed by the AIUM in collaboration with the American College of Radiology (ACR), the Society for Pediatric Radiology (SPR), and the Society of Radiologists in Ultrasound (SRU). We are indebted to the many volunteers who contributed their time, knowledge, and energy to developing this document. Collaborative Subcommittees AIUM Susan Back, MD George Berdejo, BA, RVT, FSVU Harris L. Cohen, MD, FACR, FAIUM, FSRU ACR Laurence Needleman, MD, FACR, FAIUM Chair Tara Catanzano, MD Safwan Halabi, MD Stephen I. Johnson, MD Kristin L. Rebik, DO SPR Rachel Crum, DO Andrew Phelps, MD Cicero Silva, MD SRU Edward I. Bluth, MD, FACR Comment Reconciliation Committee Eve Clark, MD, Chair Traci Pritchard, MD, FACR, Co-Chair Susan J. Back, MD Richard A. Barth, MD, FACR George Berdejo, BA, RVT, FSVU Edward I. Bluth, MD, FACR Tara Catanzano, MD Harris L. Cohen, MD, FACR, FAIUM, FSRU Rachel Crum, DO Richard Duszak Jr., MD, FACR Lauren P. Golding, MD Shiva Gupta, MD Safwan Halabi, MD Stephen I. Johnson, MD Amy Kotsenas, MD, FACR David B. Larson, MD, MBA Paul A. Larson, MD, FACR Terry L. Levin, MD, FACR Laurence Needleman, MD, FACR, FAIUM Mary S. Newell, MD, FACR Andrew Phelps, MD Kristin L. Rebik, DO Sheila Sheth, MD, FACR Cicero Silva, MD AIUM Clinical Standards Committee James M. 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AIUM routine quality assurance of clinical ultrasound equipment. http://aium.s3.amazonaws.com/resourceLibrary/rqa2.pdf. Accessed January 15, 2020. Volume41, Issue4April 2022Pages E21-E27 ReferencesRelatedInformation