Chapter 21 - Vascular lab - arterial duplex

Question 1

Two parts of duplex

Answer 1

1) blood flow acquisition = pulsed doppler spectral analysis 2) anatomic = B-mode and color doppler imaging

Question 2

Duplex frequency for artery

Answer 2

5-12 MHz

Question 3

Duplex frequency for visceral or abdominal and transcranial doppler

Answer 3

2.5-3.5 MHz lower frequency = higher tissue attenuation

Question 4

Duplex image orientation

Answer 4

left towards head

Question 5

Two types of doppler ultrasound display

Answer 5

1) color flow doppler - flow velocity distribution over wide area 2) spectral doppler - time-varying flow velocity distribution at selected sample volume

Question 6

Optimal scan line angles for doppler

Answer 6

60 degrees or less relative to transducer insonation beam and arterial wall

Question 7

Doppler angle + or - 5 degrees away from recommended 60 results in this much measurement error

Answer 7

+5 = 15% -5 = 8%

Question 8

Pulse doppler sample volume criteria

Answer 8

1) size to < 1/3 of flow lumen 2) center stream of flow

Question 9

Color gain setting on duplex

Answer 9

1) increase gain until noise speckle appears within flow region 2) reduce slightly after that

Question 10

Excessive color gain problem

Answer 10

1) color-coded flow pixels bleed into or beyond artery wall 2) makes flow lumen appear larger than reality

Question 11

Blood flow velocity exceed mean peak velocity threshold of color bar

Answer 11

1) color aliasing

Question 12

Nyquist limit

Answer 12

When sampling rate defined by pulse reptition frequency no longer sufficient

Question 13

What does color aliasing look like

Answer 13

Wraparound color show in color bar showing flow in opposite direction

Question 14

How to fix color aliasing artifact

Answer 14

1) increase pulse reptetition frequency 2) increase doppler angle

Question 15

Color doppler appearance of stenotic lesion

Answer 15

Post-stenotic turbulence with flow jet mosaic color flow

Question 16

Tissue bruit

Answer 16

vibration of arterial wall appear as low velocity flow signal outside of artery lumen

Question 17

Power doppler

Answer 17

Display blood flow based on amplitude of backscattered signal increase sensitivity 3-5x “color angio”

Question 18

B flow imaging

Answer 18

1) shows blood flow in gray scale 2) demonstrate complex flow patterns at bypass graft anastomoses and AVF

Question 19

What does broadening or increased width of velocity spectra mean spectral broadening

Answer 19

1) sample volume of pulse doppler too large 2) too close to arterial wall

Question 20

Velocity spectra waveform parameters used to interpret duplex

Answer 20

TABLE 21.1

Question 21

Resistive index calculation

Answer 21

(PSV - EDV) / PSV

Question 22

Normal resistive index

Answer 22

< 0.7 Abnormal >0.85

Question 23

Pulsatility index calculation

Answer 23

peak-to-peak velocity spectral shift DIVIDED BY mean velocity

Question 24

Normal pulsatility index

Answer 24

> 4 (femoral > 6; popliteal > 8)

Question 25

Damping factor calculation

Answer 25

Division of distal artery pulsatility index by proximal artery pulsatility index

Question 26

Normal damping factor

Answer 26

> 0.9

Question 27

Systolic acceleration time during systole - normal value

Answer 27

< 133 ms

Question 28

Tardus-parvus

Answer 28

Slow systolic acceleration usually > 200 ms rounded upslope configuration on duplex

Question 29

Mirror image artifact what is it and cause

Answer 29

Tissue structure reproduced at an incorrect location When strongly reflecting surface is further reflected by other strongly reflecting surfaces

Question 30

Refraction what is it and cause

Answer 30

misregistration of image and doppler sample volume when ultrasound beam passes through mediums with different propagation speeds

Question 31

Crosstalk what is it and cause

Answer 31

mirror image when identical spectra appear above and below baseline when excessive receiver gain setting or incident angle near 90

Question 32

Ghosting what is it and cause

Answer 32

when low velocity motion from pulsating vessel walls produce small doppler shift that cause color flashing into surrounding anatomy fix with wall filters

Question 33

PSV ratio across stenosis correlation with diameter reduction

Answer 33

> 2 is > 50% stenosis > 4 is > 70% stenosis

Question 34

Signs of pressure-reducing arterial stenosis

Answer 34

1) PSV ratio > 3.5 2) PSV > 250 3) EDV > 40

Question 35

PSV measurement variation that’s normal

Answer 35

+/- 15%

Question 36

Artery diameter and PSV in healthy subjects in various segments

Answer 36

TABLE 21.2

Question 37

Duplex classification of PAD in terms of degree of stenosis

Answer 37

TABLE 21.3

Question 38

Using PSV ratio > 2.5 to define significant stenosis on duplex sen, spe and accuracy

Answer 38

Sen, spe, accuracy = 76, 93, 89%

Question 39

Duplex criteria for 50-75% stenosis

Answer 39

> 50% PSV > 200 PSV ratio > 2.5 > 75% PSV > 400 PSV ratio > 5 EDV > 40

Question 40

Velocity of CFA that signify proximal iliac lesion

Answer 40

< 45 cm/s with monophasic waveform

Question 41

Risk stratification for vein graft occlusion based on duplex

Answer 41

TABLE 21.4

Question 42

Time to repair based on risk stratification on duplex for vein grafts for each category

Answer 42

Category 1 = prompt repair Category 2 = elective repair 1-2 weeks Category 3 = serial scan 4-6 week interval Category 4 = 6 months rescan

Question 43

PSV predictive of prosthetic graft failure

Answer 43

> 300 cm/s < 60 cm/s

Question 44

duplex finding correlated with treatment failure after peripheral intervention

Answer 44

PSV > 300 PSV ratio > 2 ABI decrease > 0.15 abnormal CFA waveform analysis