Chapter 19 Flashcards
what are the capabilities of carotid duplex study?
localize lesion in extracranial carotid arteries differentiate occlusion from stenosis document progression of disease identify surface characteristics evaluate pulsatile mass
what are limitations for carotid studies?
poor visualization secondary to: presence of dressings, skin staples, or sutures size or contour of neck depth of course of vessel acoustic shadowing from calcification
what are some ways you can over estimate the disease process in a carotid study?
accelerated flow mistakenly attributed to stenosis instead of : cardiac output tortuous vessel compensary flow inappropriate doppler angle
what are some ways you can under estimate the disease process in a carotid study?
accelerated flow not present and or not detected:
jet of accelerated flow missed
long, smooth plaque formation
stenosis of area of dilation i.e carotid bulb
inappropriate doppler angle
what is patient positioning for carotid?
supine with neck slightly hyperextended and head turned slightly
what are physical principles of spectral analysis?
info displayed electronically on a monitor
FFT method
displays true frq/velocities shifts
commonly used with imaging modalities
what is the FFT?
individual frq/ velocities displayed with time on horizontal axis and various freq and velocity on vertical axis
what are physical principles of CW?
two piezo-electric crystals- one constanly sending and one always recieving reflected waves
no range resolution
fixed sample size
what are physical principles of pulsed doppler?
one crystal sending and receiving
has range resolution
variable sample size
well-defined spectrum
what are physical principles of color doppler?
assigns color to display average freq (e.g due, brightness of color) and direction of moving blood
pulsed doppler beams evaluate multiple sample sites throughout specific area
scan rate are slower bc of multiple transmit/ received pulse cycles in each color line of site
several processing methods exist to produce color duplex
what scanning locations do you use with carotids?
clavicle to mandible using anterior, oblique, lateral and posterior oblique
what approach would you use to evaluate the vertebral artery?
posterior-lateral approach
identify artery by vertical shadows running through it
from tranverse process of the vertebrae
evaluate the direction of the verts
what should you document in a trans. cross sectional view of the carotids?
vessels followed from clavicle to mandible
plaque formation
percent stenosis may be calculated
what will a normal carotid have?
no wall irregularities or soft tissue abnormalities
what will hypoechoic and homogenous plaque look like?
low level echoes of similiar appearance ie. fatty streaks, found in persons of all age
what will homogenous plaque look like?
low to medium level echoes of similar appearance. i.e fibrous soft plaque
what will echoic and heter plaque look like?
all levels of echoes (soft and dense areas) ie. complex plaque of intraplaque hemorrhage (sonolucent area inside plaque)
what will hyperechoic plaque look like?
very bright/ highly reflective echoes. acoustic shadow from calcium deposit may result in erroneous calculation of % stenosis
what is thrombosis plaque?
same echogenicity of flowing blood on B mode
what are some surface characteristic of an abnormal vessel?
smooth, slightly irregular, grossly irregular surface
T/F stenosis should be visualized from 2 projections
true
what would an occluded artery look like?
varying degrees of echogenic material
vessel completely filled with echoes
vessel motion: horizontally or piston- like
what are normal ICA doppler signals?
more high-pitched and continours than ECA
waveform has rapid upstroke and down stroke with a high diastolic component
low resistance
what are normal ECA doppler signals?
signal more pulsatile-very similar to peripheral vessels
rapid upstroke and down stroke with low flow in diastole
dicrotic notch clearly seen. oscillations in waveform seen with tapping STA
