What does TCD stand for?
What is TCD?
It is a non-invasive assessment of the cerebral blood flow in the basal cerebral arteries.
*Most of them will relate to the circle. of wilis*
What is TCD usually used for?
- Stroke patients
- Cerebral deficiency
What type of frequency does a TCD use?
- Low frequency lets you penetrate deeper.
- Skull bone attenuates 90% of your ultrasound beam.
What is the standard probe used for TCD?
2 MHZ probe
Ultrasound passes through many_______
What type of information does TCD provide?
It provides information regarding velocity (mean velocity) and direction of cerebral blood flow.
Who introduced the first ultrasound transtemporal approach?
Dr. Rune Aaslid in 1982
Who first published the transorbital approach?
Dr. Merrill Spencer in 1984
Who first published the suboccipital approach?
Dr. M. Von Reutern in 1986
When was the first commerical TCD unit invented?
What is the circle of wilis?
- It is a network of vessels at the base of the brain that distributes flow to all regions of the RT & LT hemispheres of the brain.
- Primarly from the anterior circulation: ICA supply
- Primarily from the posterior circulation: Vertebral supply
- Most important source of cerebral blood supply and collateral circulation.
Where is the circle of wilis located?
It is located at the base of the brain.
What percentage of people have a complete circle of wilis?
What is the criteria for vessel identifcation?
- Depth of sample volume
- Direction of flow
- Traceability of the vessel
- Transducer angulation
- Spatial relationship of waveform spectra
What direction can the probe only go towards?
Towards the probe.
Usually 50 cm/s
Every waveform has its own special type of spectral waveform.
What is the landmark for vessels?
What are some TCD characterisitics?
- Povides instanteous and continuous cerebral blood flow info.
- Can be used in any hospital enviroment
What are the main accepted clinical application uses for TCD’s?
- Detect/monitor intracranial vasospasm
- main use
- Detect/monitor intracranial stenoses
- Confirm the diagnosis of brain death
- Assist in the detection and mangement of ASD
Other used for TCD include:
- Assess of collateral pathways
- Assess autoregulation and vasomotor reactivity
- ICU monitoring (effects of ICP)
- Surgical montitoring (CEA, CABG)
- Detecting of emboli (HITS)
What are some TCD intraoperative monitoring applications?
- Carotid endarectomy
- Carotid stenting
- Coronary artery bypass surgery
- Cardiac valve surgery
- Abdominall aortic aneurysm
- Liver transplants
What are some pitfalls and trouble spots of using TCD?
- Variations and incomplete circle of willis
- e.g. Missing ACA and PCA stemming directly from ICA
- Absent or small windows
- Approx. 90-95% of the population have a temporal window.
- Not identifying/finding best temporal window
- Improper doppler settings
- e.g. too low/too high gain, too large sample volume, low power
A TCD exam is extremely user dependent.
How should you set up the equipment pior to beginning a TCD exam?
- Wipe down transducer and cable
- Label vessel, adjust depth, power and direction of flow before applying transducer on the patient.
How should you position the patient pior to beginning a TCD exam?
- Exam can be preformed in a supine or sitting position
- DO NOT reposition a patient with a EVD, without nursing assistance
- Know the status of the extracranial vessels.
What window is the MCA in?
What is the depth, velocity, and direction associated with the MCA?
Depth: 30-60 mm
Velocity: 50 +/- 12
Direction: Towards the probe
What window is the MCA/ACA bifurcation?
What is the depth, velocity, and direction associated with the MCA/ACA bifurcation?
Depth: 55-65 mm
What window is the ACA located in?
What is the depth, velocity, and direction associated ACA?
Depth: 60-80 mm
Velocity: 50 +/- 11
What window is PCA-P1 located in?
What is the depth, velocity, and direction associated with PCA-P1?
Depth: 60-70 mm
Velocity: 39 +/- 10
In what window is PCA-P2 seen in?
What is the depth, velocity, and direction associated with PCA-P2?
Depth: 60-70 mm
Velocity: 40 +/- 10
In what window is the OA located in?
What is the depth, velocity, and direction associated with the OA?
Depth: 40-60 mm
Velocity: 21 +/- 5
In what window is the carotid siphon seen in?
What is the depth and velocity associated with the carotid siphon?
Depth: 60-80 mm
Velocity: 43 +/- 11
In what window is the VA seen in?
What is the depth, velocity, and direction associated with the VA?
Depth: 60-90 mm
Velocity: 38 +/- 10
In what window is the BA seen in?
What is the depth, velocity, and direction associated with the BA?
Depth: 80-1208 mm
Velocity: 41 +/- 10
What are the 3 areas of the transtemporal window?
- Anterior →ACA
LABEL THESE WINDOWS:
The MCA is bigger than the basilar artery.
The basilar artery is twice the size of the MCA
Where is the MCA window?
What is the angle used to find the MCA?
Anteriorly and posteriorly.
What is the depth range of the M1 segment?
What is the depth range for the M2 segment?
What is the flow direction found in the MCA?
Towards the transducer
How should you sample the MCA?
Sample at 2mm increments
Can the MCA change directiosn?
No, it will never change direction
Where is the MCA/ACA birfucation?
What is the angle used to find the MCA/ACA bifur.?
Anteriorly and superiorly
What is the segment depth range for the MCA/ACA bifurc.?
What is the flow direction for the MCA/ACA bifurc.?
ACA flow direction is….
Away from the transducer
What is the segment depth range for the ACA?
What is normal flow direction in the ACA?
Away from the transducer.
It CAN chnage direction in the presence of disease.
What window is used for the PCA?
What angle is used to find the PCA?
Posteriorly and inferiorly
What is the segment depth range of the PCA?
What is the flow direction in the PCA?
It can change direction with presence of disease
Normal velocity relationships
MCA>ACA>PCA~VA & BA
The more shallow you are….
The more distal and superfical you are.
What is hyperostosis?
Hyperostosis is an excessive growth of bone