Chapter 18: Carotid Duplex

Question 1

over estimating of the disease process (thinking theres a stenosis) can be from

Answer 1

cardiac output (faster flow on young people)
tortuous vessel
compensatory flow
inappropriate doppler angle

Question 2

under estimation of the disease process

Answer 2

jet of accelerated flow missed
long smooth plaque formation
stenosis are area of dilation (carotid bulb)
inappropriate doppler angle

Question 3

patient positioning

Answer 3

supine
neck slightly hyperextended
head turned slightly

Question 4

what is used to Carotid imaging

Answer 4

spectral analysis
continous wave doppler
pulsed doppler

Question 5

continous wave doppler

Answer 5

two piezo-electric crystals (one constantly sending and one receiving)
no range resolution
fixed sample size

Question 6

pulsed doppler

Answer 6

crystals send then receive
high range resolution
variable sample size
well defined spectrum

Question 7

color doppler

Answer 7

color displays average frequencies and direction
pulsed doppler eval multiple sample sites
slower scan rates

Question 8

hypoechoic and homogeneous level echoes

Answer 8

low level echoes of similar appearance
fatty streaks
found in person of all ages

Question 9

homogenous echoes

Answer 9

low to medium level echoes of similar appearance

fibrous plaque

Question 10

echoic and heterogenous echoes

Answer 10

all levels of echoes

complex plaque of intraplaque hemorrhage

Question 11

hyperechoic echoes

Answer 11

bright reflective echoes

shadowing from calcium deposits

Question 12

suface characteristics

Answer 12

smooth
slightly irregular
grossly irregular

Question 13

a stenosis should be visible from

Answer 13

at least two projections

Question 14

occluded artery

Answer 14

varying echogenicity but vessel completely filled

vessel motion: horizontally or piston like

Question 15

ICA doppler signals

Answer 15

high pitched and continous compared to ECA

waveform has rapid upstroke and down stroke with high diastolic component

Question 16

ECA doppler signals

Answer 16

pulsatile, similar to peripheral vessels

rapid upstroke and down stroke with low flow in disatole

Question 17

temporal tap technique

Answer 17

tapping STA you will see vibration in ECA waveforms

Question 18

CCA doppler signals

Answer 18

similar to both ICA and ECA

Question 19

Stenosis doppler signal

Answer 19

high pitched sound and waveform with higher velocity
spectral broadening (representing turbulence)
loss of spectral window (represents loss of laminar flow)

Question 20

distal to stenosis doppler

Answer 20

distrubed flow patterns

turbulent, bidirectional, dampened and monophasic

Question 21

when high resistant flow patterns in ICA, consider

Answer 21

disease at carotid siphon ( S shaped part of ICA)

Question 22

diminished CCA velocities bilaterally may indicate

Answer 22

poor cardiac output or stroke volume

Question 23

diminished velocities unilaterally suggest

Answer 23

proximal disease of innominate or CCA

Question 24

Normal PSV

Answer 24

<125 cm/sec

Question 25

Less than 50% stenosis

Answer 25

PSV <125cm/sec

Question 26

50-79% stenosis

Answer 26

PSV >125cm/sec | EDV <140 cm/sec

Question 27

80-99% stenosis

Answer 27

PSV >125cm/sec | EDV >140cm/sec

Question 28

NASCET criteria > / = 70% stenosis

Answer 28

ICA/CCA ratio >/= 4.0 | highest ICA divided by Mid CCA

Question 29

Occlusion signals

Answer 29

CCA may have low or absent diastolic component collaterals (ECA high diastolic flow) Absent ICA signal or pre-occlusive thump

Question 30

absent signal may indicate occlusion but what can never be ruled out

Answer 30

a very significant stenosis

Question 31

alaising is

Answer 31

misrepresenttation of high doppler signal due to limitations of equipment being used PRF is too low

Question 32

maximum frequency is

Answer 32

1/2 PRF

Question 33

nyquist limit

Answer 33

flow greater than 1/2 PRF cannot be displayed | waveform has a flat crew cut appearance

Question 34

methods of increasing the PRF/Nyquist limit

Answer 34

``` decrease baseline increase doppler scale change transducer frequency change angle of insonation decrease depth use CW doppler ```

Question 35

mirror imaging (crosstalk)

Answer 35

doppler shifts above and below baseline display duplicate spectrum artifact from strong reflectors or too much gain

Question 36

Helical flow occurs when

Answer 36

``` flow moves into a wider portion of the vessel (bulb) doppler shifts above and below baseline spectral waveforms different doppler angle constantly changing flow is not laminar spectral broadening is present ```

Question 37

Intraoperative monitoring is used to

Answer 37

identify defects secondary to surgery and/or areas of platelet aggregation eval wall irregulatirty

Question 38

intraoperative monitoring technique

Answer 38

``` 12MHz sterile sleeve containing gel wound filled with sterile saline areas of flow disturbance identified gray scale imaging for wall defects ```