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RVT Review > Chapter 19 > Flashcards

Chapter 19 Flashcards

1
Q

what are the capabilities of carotid duplex study?

A 
localize lesion in extracranial carotid arteries
differentiate occlusion from stenosis
document progression of disease
identify surface characteristics 
evaluate pulsatile mass
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2
Q

what are limitations for carotid studies?

A 
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
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3
Q

what are some ways you can over estimate the disease process in a carotid study?

A 
accelerated flow mistakenly attributed to stenosis instead of :
cardiac output
tortuous vessel 
compensary flow 
inappropriate doppler angle
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4
Q

what are some ways you can under estimate the disease process in a carotid study?

A

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

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5
Q

what is patient positioning for carotid?

A

supine with neck slightly hyperextended and head turned slightly

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6
Q

what are physical principles of spectral analysis?

A

info displayed electronically on a monitor
FFT method
displays true frq/velocities shifts
commonly used with imaging modalities

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7
Q

what is the FFT?

A

individual frq/ velocities displayed with time on horizontal axis and various freq and velocity on vertical axis

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8
Q

what are physical principles of CW?

A

two piezo-electric crystals- one constanly sending and one always recieving reflected waves
no range resolution
fixed sample size

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9
Q

what are physical principles of pulsed doppler?

A

one crystal sending and receiving
has range resolution
variable sample size
well-defined spectrum

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10
Q

what are physical principles of color doppler?

A

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

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11
Q

what scanning locations do you use with carotids?

A

clavicle to mandible using anterior, oblique, lateral and posterior oblique

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12
Q

what approach would you use to evaluate the vertebral artery?

A

posterior-lateral approach
identify artery by vertical shadows running through it
from tranverse process of the vertebrae
evaluate the direction of the verts

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13
Q

what should you document in a trans. cross sectional view of the carotids?

A

vessels followed from clavicle to mandible
plaque formation
percent stenosis may be calculated

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14
Q

what will a normal carotid have?

A

no wall irregularities or soft tissue abnormalities

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15
Q

what will hypoechoic and homogenous plaque look like?

A

low level echoes of similiar appearance ie. fatty streaks, found in persons of all age

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16
Q

what will homogenous plaque look like?

A

low to medium level echoes of similar appearance. i.e fibrous soft plaque

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17
Q

what will echoic and heter plaque look like?

A

all levels of echoes (soft and dense areas) ie. complex plaque of intraplaque hemorrhage (sonolucent area inside plaque)

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18
Q

what will hyperechoic plaque look like?

A

very bright/ highly reflective echoes. acoustic shadow from calcium deposit may result in erroneous calculation of % stenosis

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19
Q

what is thrombosis plaque?

A

same echogenicity of flowing blood on B mode

20
Q

what are some surface characteristic of an abnormal vessel?

A

smooth, slightly irregular, grossly irregular surface

21
Q

T/F stenosis should be visualized from 2 projections

A

true

22
Q

what would an occluded artery look like?

A

varying degrees of echogenic material
vessel completely filled with echoes
vessel motion: horizontally or piston- like

23
Q

what are normal ICA doppler signals?

A

more high-pitched and continours than ECA
waveform has rapid upstroke and down stroke with a high diastolic component
low resistance

24
Q

what are normal ECA doppler signals?

A

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

25
Q

T/f CCA has both ICA and ECA chara?

A

true

26
Q

what will a waveform at stenosis be?

A

higher pitched sound and waveform with higher amplitude ( from elevated freqs)
spectral broadening evident (representing turbulance)
loss of spectral window also represents loss of laminar flow

27
Q

what will the waveform by like distal to a stenosis?

A

disturbed flow patterns e.g turbulent, bi- dire then can become dampened and monophasic. continous what

28
Q

where will disease be located when there is a high resistant flow pattierns in the ICA

A

carotid siphon

29
Q

what will diminshed CCA velocities bilaterally indicate?

A

poor cardiac output or stoke volume

30
Q

what does diminisehd velocities unilatteraly suggest?

A

proximal disease

i.e innominate or CCA

31
Q

T/F is it not important to compare flow chara bilaterally, and prox to distal segements of the same vessel

A

false

32
Q

what is the normal PSF, EDF, PSV, and EDV of a vessel with no stenosis?

A

<4KHz
NA
<125cm/s
NA

33
Q

what is the normal PSF, EDF, PSV, and EDV of a vessel with 1-15% stenosis, and 16-49%?

A

<4 KHz
NA
<125cm/s
NA

34
Q

what is the normal PSF, EDF, PSV, and EDV of a vessel with 50-79% stenosis?

A

> 4KHz
<4KHz
125 cm/s
<140cm/s

35
Q

what is the normal PSF, EDF, PSV, and EDV of a vessel with 80-99%stenosis?

A

> 4KHz
4KHz
125 cm/s
140cm/s

36
Q

what is the normal PSF, EDF, PSV, and EDV of a vessel with occlusion?

A

absent all throughout

37
Q

what is the criteria critical in determining an occlusion?

A

CCA may have a very low or absent diastolic component
evidence of collateralization e.g ECA may exhibit high flow in end diastole
absent ICA Doppler signal or pre occlusive thump

38
Q

T/F an absent signal may indicate occlusion, an tight stenosis also called a string sign cannot be ruled out

A

true

39
Q

what is aliasing?

A

misrepresentation of Doppler signal due to limitation of equipment being used
waveform has flat, crew out appearance

40
Q

what is the nyquist limit?

A

1/2 PRF

41
Q

methods of increasing PRF to prevent aliasing?

A 
decrease the baseline
increase doppler scale 
change transducer freq (low)
alter angle of insonation
decrease depth
use CW doppler
42
Q

what is mirror image artifact?

A

doppler shifts above and below baseline
display duplicated spectrum or color-flow doppler
artifact from strong reflectors or too much gain

43
Q

what is helical flow?

A

occurs when flow moves into a wider portion of the vessel (bulb)

44
Q

what will the waveform look like with helical flow?

A

doppler shifts above and below the baseline
spectral waveforms are diff
doppler angle constantly changing
flow is not laminar, spectral broadening present

45
Q

what are the capa for intraoperative monitioring for carotids?

A

id of defects secondary to surgery and or area of platelet aggregation
evaluates hemodyn signficance of wall irregularity

46
Q

what is the technique for intraoperative monitioring?

A

sterile sleeve/ plastic bag containing acoustic gel
wound filled with sterile saline
area of flow distrubance id with color flow doppler
gray scale imaging critical in detecting subtle wall defects

RVT Review (30 decks)

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