RPVI-Cerebrovascular Flashcards
what is the accuracy of carotid US?
> 95%
what linear transducer should be used for carotid?
5-12MHz
what are indications for carotid sonography?
TIA resolving ischemic neuro deficit CVA bruits F/U post-op suspected dissection signif RF
what are signs of anterior circulation accidents?
paresis, parathesia, paralysis unilateral aphasia dysphasia dysphagia amaurosis fugax
what are signs of posterior circulation accidents?
vertbral or posterior cerebral bilateral vision problems diploplia drop attack (fall with no LOC) vertigo ataxia
what are non-localizing symptoms?
dizzy lightheadedness
syncopy
H/A
confusion
what are some anatomic variation of carotid anatomy?
L CCA can come of innominant 10% common origin innominate and LCCA 12% l vert of arch 3% r CCA off arch rare R sub off arch distal to L sub rare
at which level does vert enter brain?
C6
how many branches of ECA?
8 we can see the following* sup thyroid* asc pharyngeal lingual facial* occipital * post auricular temporal* maxillary
what are collateral pathways?
circle of willis-anterior communicating
opthalmic-facial
how do we tell arteries from veins?
artery wall usually thicker
shape-vein elongate usually because of scanning pressure
flow direction
compressibility
position-vein ant above umbilicus usually
what does red signify?
red away transducer
where is the bifurcation usually?
65% at c4
above c4 17%
below c4 18%
what is the position go ICA to ECA
usually posterolateral 50%
too may exceptions though
how to distinguish ICA fro ECA
int jug vein usually follows ICA ICA>ECA ICA usually posterolateral ICA no branches in neck ECA does temporal tap ICA is low resistance, ECA high resistance ECA is usually medial and anterior
what anatomy should be imaged in 2d or colour
CCA, bulb, bifurcation, ECA, ICA, SCA
when should you freeze the colour image?
systole
how should the sample angle be positioned?
parallel to arterial wall
if 60 not possible what angle should you use?
lower angle
higher has more error
what are normal hemodynamics in CCA
laminar flow shape peak brisk acceleration open spectral window forward flow
what is normal flow in the bulb?
flow separation
low resistance
loss of spectral window-turbulence
bidirectional flow
normal flow in ICA
laminar flow
low resistance
forward flow
normal flow in ECA?
laminar flow high resistance minimal diastolic flow pulsatile dicrotic notch
normal vertebral flow
laminar
low resistance
forward flow
looks like CCA
when should you look at subclavian
> 20 mmhg BP difference
abnormal flow in vert
What do you do if no colour?
inrease gain, lower PRF, change filter, check angle, check with pulse doppler
what do you do if lots of colour noise?
decrease gain, increase PRF, use higher filter, check baseline
where do you sample the ICA?
where do you sample CCA?
3 cm from bifurcation
1-2 sample from bifurcation
what is normal intimal thickness?
1.2mm
what features do we describe plaque by?
location extent severity
appearance
what does high echogenicity of plaque signify?
higher content of calcification hypo likely fat content low echo--fatty medium high--calcified
how do we classify plaque PS?
Plaque
P1 homogeneous
P2 hetero
remember specular reflector will have brighter surface
surface
S1 smooth
S2 irregular 2mm
what is the SRU criteria for a normal ICA?
PSV <125
Esv <40
Ratio <2
no plaque
what is the SRU criteria for <50%
same as normal but <50% diameter reduction of plaque
what is the SRU criteria for 50-69%
PSV 125-230
ratio 2-4
ICA EDV 40-100
>50% diameter reduction
what is the SRU criteria >70-99%
PSV >230 cm/s low if near occlusion
ICA/CCA PSV ratio >4
ICA EDV >100 cm/s
what is the SRU criteria occlusion
PSV, Ratio, EDV not useful
where do you place the doppler gate in a high grade stenosis?
area of highest aliasing
can open gate
what can indicate downstream stenosis?
decrease diastolic flow
what does the image at a stenosis look like?
elevated v
spectral bradening
audible high pitch
what about image distal to stenosis
slow systolic–dampened
rounded systolic peak
increased diastolic flow
turbulent flow
what happens to flow velocity as stenosis goes up?
it increases until about 95% then it rapidly decrease and is at zero at 100%
what are primary effects of stenosis?
increased PSV and EDV
what are secondary effects of stenosis?
downstream turbulence
parvus tardus
higher pulsatily index upstream
lower pulsatility downstream
What are tertiary effects of stenosis?
compensatory flow
collateral flow
reversed vertebral flow due to subclavian stenosis
what are exceptions to grading criteria?
long stenosis
tandem stenosis
what sources of error can cause misinterpretation?
CHF
arrhtymias
irregular HB
evident bilateral
HTN-effect pulsatility
diminished arterial compliance
resp motion-changes doppler angle
AS
compensatory flow on contra side
What happens with compensatory flow?
side contra to stenosis has compensatory flow through collateral systems and therefor velocities may meet criteria when there is not plaque present
what effects outflow of the ICA
distal ica occlusion
mca occlusion
distal disection aneurysm, avm
distal near occlusion of ICA or MCA–increased PI at prix sites
distal avm result in lower PI at prix sites
how do we tell if era is imp collateral?
reversed flow in ECA to ipsi ICA
contr/ipsi ECA to circle through opthalmic
subclavian to infer thyroidal to sup thyroidal
what are common errors in imaging
careless angle correct adjustment–can lead to great error 5 degrees = 15%error
inappropriate steering of the colour box
color or pulsed doppler gain too high or too low
bad adjustment of colour scale (PRF too high or low)
bad adjustment of pulsed doppler scale–innacuracy in measuring velocities
inappropriate update timing
d
if colour scale is too high there will be no aliasing. the flow will be laminar. if the colour scale is too low it will all be aliasing. need to find the middle ground
w
if colour scale is too high you might miss trickle flow. need to turn it down
w
increasing sweep speed will allow you to examine the spectral better i.e. if patient has tacky.
what is update timing?
change from one image modality to another. colour to pulsed
power doppler
can confirm the absence of hypo echoic plaque
what angle is 2d best at and for doppler?
90
60
