Week 4 Part 2 Flashcards
Transcranial Doppler is used to
assess cerebral hemodynamics and evaluate intracranial cerebrovascular disease
What’s used in TCD
power Doppler, duplex sonography and contrast agents
Transcranial instruments have a ______ bandwidth
Lower
What is the transmitting power on TCD instruments
b/w 10 and 100mW/cm/sec
Focusing of beam is _______ to _______ from probe
40-60mm
What type of transducer is used with TCD?
2MHz pulsed range gated Doppler device
What are the indications for a TCD? Part 1
Detection of intracranial stenosis and occlusions in the major arteries
Evaluation of intracranial hemodynamics and collateral flow where there is extracranial disease
Monitoring of intracranial vessel recanalization in acute stroke
Monitoring intracranial hemodynamics after:
Hemorrhage
Endarterectomy/angioplasty
What are the indications for a TCD? Part 2
Detection of right to left shunts Detection of cerebral microemboli During functional tests: Stimulation with vasoconstrictive drugs External stimulation of visual cortex Before neurosurgery During open heart surgery
The ACA has __ segments.
2 – A1 and A2
Carotid Siphon (just proximal to ICA intracranial branches) has ____ segments.
3 – C1, C2, C3
Opthalamic artery branches at the junction of _____ and _____
C2 and C3
MCA has ___ segments.
M1 and M2
PCA has ___ segments.
P1 and P2
Segments that are labelled 1 are closest to ____ ________ __ ____ _________.
The midline of the brain
What are the windows for TCD?
temporal
orbital
submandibular
suboccipital
Submandibular approach:
probe is directed towards proximal intracranial ICA
window- below mandible at the angle using the carotid triangle
We use the submandibular approach to visualize the _______ ________ ____.
proximal intracranial ICA
Suboccipital approach:
probe is placed under base of skull and angled up into foramen
Patient is laying on their right or left side w/ their back towards you for a suboccipital approach.
Left
head tucked in towards chest
Transorbital approach:
carotid siphon and opthalamic artery
probe is directed toward the orb to locate the OA and then followed to the carotid siphon - distal to the intracranial ICA
Transtemporal approach:
cephalad to zygomatic arch
immediately anterior and slightly superior to tragus of ear
Patient is in a ________ position for a transtemporal approach
supine
When we’re in the anterior orientation of the transtemporal approach, what do we visualize?
M1 and M2
C1 of carotid siphon
A1 of ACA and AComm
When we’re in the posterior orientation of the transtemporal approach, what do we visualize?
P1 and P2 of PCa
top of basilar artery
Pcomm’s
Suboccipital-transforaminal is essential screening what?
distal vertebral arteries (V4) and the basilar artery through its entire length
Suboccipital-transforminal approach:
probe is placed between the posterior margin of the foramen magnum and the spinous process of C1 vertebra
laying on side with head tucked into chest
beam is aimed at bridge of nose
What types of people pose a difficulty for scanning using the suboccipital transforminal approach?
the elderly
What are some other approaches that can be used?
transorbital (can see OA and anterior circulation)
submandibular (extracranial studies, probe is placed in retromandibular area, useful for carotid dissections and chronic ICA occlusion w/ collaterals)
What are the typical insonation depths for the following vessels? (transtemporal approach–mm) MCA, ACA, carotid siphon, PCA and basilar
MCA- 50 ACA- 70 CS- 65 PCA- 65-70 B- 75
What are the typical velocities for the following vessels? (transtemporal approach–cm/s) MCA, ACA, carotid siphon, PCA and basilar
MCA- 55 ACA- 50 CS- 39 PCA- 40 B- 40
How do we identify cerebral arteries?
insonation depth direction of flow @ insonation depth flow velocity probe position (window) direction of US beam (ex. posterior, anterior) traceability of vessels
What flow is seen in the cerebral arteries?
Low resistance flow spectrum similar to ICA flow
How to start exam:
Start with the transtemporal approach
Identify the midline of the brain
If the midline is not visible,then the exam may be futile
Once it is identified,turn on the color
The MCA is identified on either side of the midline at a depth of 50-55 mm
Track the ipsilateral arterial network,by angling he probe anteriorly toward the ACA and then posteriorly toward the PCA
MCA and other arteries can be tracked from more shallow insonation depth ____mm to deeper sites _____mm
35-55
Changes in what can indicate disease?
flow profile and direction
When tracking the MCA medially (65-70mm depth),an abrupt change in flow direction-away from the probe-indicates insonation of A1 segment. Is this normal?
Yep
