Carotid Duplex Ultrasound

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Vertebral and Carotid Ultrasound

Indications:

Cerbral Vascular Accident
Transient Ischemic Attacks
Cervical Bruit detected on physical exam
Subclavian Steal Syndrome
Preoperative screening for patients with cervical bruit
Post Carotid Stenting
Post Carotid endarterectomy
Pulsatile neck mass
Serial evaluation of known carotid disease

Technique:

Generally a complete extra cranial carotid and vertebral study if technically feasible will include scanning of the great vessels through the extra cranial carotids. On the right side this would include the Right Innominant artery --> Right Subclavial/Common Carotid bifurcation --> Right Common Carotid --> Right Vertebral --> Right External Carotid --> Right Internal carotid. On the left this would include Left subclavian --> Left vertebral. Then Left Common Carotid --> Left External Carotid --> Left Internal Carotid.

Careful attention needs to be paid to method with with each study is performed and obtained. This ensures the reproducibility and validity of the study which is often interpreted after the acquisition of imaging by the technologist.

A constant angle of measurement between the vessel and the ultrasound beam should be maintained and documented for each image acquisition. Classification of disease states is determined for an angle of inclination of 60 degrees. Any variance of this angle should be noted by the technologist.

Sample volumes should be kept as small as possible and placed in the middle of the vessel lumen for acquisition.

Scan planes should be taken in both vessel longitudinal and cross sections. Spectral waveforms should be obtained in the longitudinal vessel for reasons documented above.

Specific Vessel Notes:

Common Carotid Artery: The normal spectral waveform of the common carotid artery is that of a LOW RESISTANCE VESSSEL. Waveforms should be obtained proximal, mid and distal in the vessel. Changes in waveforms can be indicative of disease states.

   1) High Grade Internal Carotid Stenosis:  Runoff of the common carotid is shunted through the external carotid and the vessel will take on the wave form of this vessel. ie…high     
      resistance with low end-diastolic flow.  
   2) Common Carotid Stenosis:  Comparison with the contralateral common carotid flow will demonstrate dampened velocities and a slow upstoke to systolic peak velocity in the  
      affected carotid.  Post stenotic dilatation may be present.

External Carotid Artery: The external carotid artery is a HIGH RESISTANCE VESSEL. Branches may be present. Superficial temporal oscillations (Temporal Tap) should be performed at image acquisition to demonstrate the vessel.

Carotid Bulb: Usually located in the proximal internal carotid artery. Identified by flow separation and reversal.

Proximal And Mid Internal Carotid Artery: LOW RESISTANCE VESSEL. The flow disturbances of the carotid bulb may extend into these vessel segments.

Distal Internal Carotid Artery: Low resistance vessel. Begins at least 3 cm above the carotid bifurcation. Usually atherosclerosis is found in the 1st 2 cm of the vessel, more rarely in the distal vessel. Tortuosity may make image acquisition difficult.

   1) FMD can cause distal vessel stenosis and high velocities.    
   2) A HIGH resistance profile can be important clues to resistance in the distal bed such as with siphon disease, intracranial disease or distal dissection.  
   3) Increased end-diastolic velocities compared to the contralateral spectral profile could be seen with changes in distal resistance ie…AVM.

Vertebral Artery: Origins difficult to visualize. Drop out of vessel flow common due to bony vertebral bodies. The most important thing to visualize is the direction of flow. Ie..reversed with subclavian steal syndrome.

Subclavian/Innominant arteries: Triphasic typical peripheral waveform.

Diagnostic Criteria:

Internal Carotid Stenosis (Note: these may vary from institution to institution)

Diameter Reduction	   Peak Sysole	      Peak Diastole	                     Flow Character
      0-19%	           <105 cm/sec	          n/a	                  Mild Spectral Broadening during systolic deceleration
      20-39%	           <105 cm/sec	          n/a	                  Spectral Broadening present
      40-59%	           105-150 cm/sec         n/a	                  Increased Spectral Broadening
      60-79%	           151-240 cm/sec	  n/a	                  Marked Spectral Broadening
      80-99%	           >240 cm/sec	         >135 cm/sec	          Marked Spectral Broadening
      100%/Occluded	       n/a	          n/a	                  No flow. Common carotid with low or reversed diastolic flow.