Today our topic of discussion is Doppler Imaging.
Doppler Imaging
DOPPLER IMAGING
Ultrasound technology provides information about the flow velocity of blood through cerebral vessels using non- invasive technique. A Doppler is placed externally over the vessel, where ultrasonic waves are generated and blood flow velocities are calculated.
Definition
Doppler imaging is a noninvasive diagnostic method to study the flow velocity of blood through cerebral vessels, specifically the circle of Willis.
Indications
- This procedure is used in the intensive care unit to monitor clients who have experienced cerebrovascular disorders, such as stroke, head trauma or subarachnoid hemorrhage
- It can help detect intracranial stenosis, vasospasm and arteriovenous malformation as well as assess collateral pathways (Fig. 29.62).
Purposes
- To detect carotid artery disease such as atherosclerosis arterial occlusion
- To detect vertebral artery disease such as stenosis or reversal of flow
- To detect jugular vein disease such as thrombosis or recanalization.
Advantages
- It is a noninvasive procedure, which causes no pain It is a safe procedure
- It is relatively inexpensive It has high accuracy.
Types
- Extracranial Doppler studies: Extracranial Doppler studies are used as a routine screening. It is used monitor the intraluminal narrowing of the common and internal carotid arteries as a result of arteriosclerotic plaques or atheromata
- Transcranial Doppler studies: Transcranial Doppler studies monitor cerebral blood flow velocity through cranial windows or thinned areas of the skull.
- One such area, the most popular is the temporal bone.
Client Preparation
- Prepare the client physiologically and psychologically
- Explain the entire procedure in simple words
- Inform the client not to move during the procedure.
Equipment
- Transcranial
- Doppler unit
- Transducer with an attachment system
- Terry cloth headband.
- Ultrasonic coupling gel
- Tissues.
Special Consideration
- Velocity changes in the transcranial
- Doppler signal correlate with changes in cerebral blood flow.
- Parameter the most clearly reflects this changes in the mean velocity, Embolus appears as high-intensity transients that occur randomly during the cardiac cycle.
- Emboli make a distinctive clicking, chirping or plunking sound
- Various screens can be stored on the system’s hard drive and can recall or printed Before using the transcranial
- Doppler system, be sure to remove turban head dressing or thick dressings over the test site.
Procedure
- Place the client comfortably on the examination table
- A Doppler probe is placed externally over the vessel, where the ultrasonic waves are generated and blood flow velocities are calculated
- As the diameter of the vessel changes, the velocity of the flow of the blood through the vessel changes
- The Doppler probe represents the velocity of the blood flow
- These data are amplified, a graphic and sound recording of the blood flow are produced
- This procedure takes 15-45 minutes to complete.
After Care
- Check the vital signs
- Document the entire procedure in nurse’s record.
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