Duplex/color Flow Imaging (LE)

Question 1

With duplex/color flow imaging of the LE, a Doppler equation is used to find ______

Answer 1

Doppler shift frequency (DF)

DF = 2Fo V Cos0 / C

Fo (carrier frequency/transducer)
V (velocity of the moving reflectors)
Cos0 (angle)
C (speed of ultrasound through soft tissue)

Question 2

What is the speed of ultrasound through soft tissue (C)

Answer 2

1540m/sec

Question 3

In the Doppler equation, the number 2 represents TWO DOPPLER SHIFTS, what are they

Answer 3

• Red blood cell is first an observer of a stationary ultrasound field
• then acts as a wave source

Question 4

The equation:
C Df / 2 Fo Cos0 is used to calculate what

*Df = known value measured by Doppler and is proportional to velocity of the source
Cos0 = angle, determined from the image; cosine theta is calculated (e.g. Cos0 of 90 = 0)

Answer 4

This calculates VELOCITY (V)

• *calculated flow representing velocity of flow (moving reflectors)
• • must know the Df in order to calculate V

Question 5

Ideal Doppler angle for vascular exams is:
____ degrees
Obtained at ______
____ to walls

Answer 5

60 degrees
Obtained at CENTERSTREAM
PARALLEL to walls

• *tortuous vessels (or other conditions) will cause Doppler angles to be < 60, which is usable
• *> 60 degrees is NOT RELIABLE

Question 6

During an arterial Doppler exam, if a >50% diameter reduction is suspected, we need to obtain what 3 things

Answer 6

1. Pre-stenotic PSV
2. HIGHEST PSV in stenosis
3. Post-stenotic turbulence and decreased PSV

Question 7

Charectoristics of this type of bypass graft are:

• small end is now PROXIMAL
• Large end is now DISTAL
• vein valves stay open due to arterial flow pressure
• branches are ligated

Answer 7

Reversed saphenous vein graft (RSVG)

**size change of prox. And dist. Ends are often only evident in initial post-op study

Question 8

With vein bypass graft eval we check:
Inflow and outflow artery, proximal and distal anastomosis, entire length of vein bypass graft….. But we should also check for

Answer 8

Branches that could form AV fistulas, and valves

Question 9

What do we evaluate on a synthetic bypass graft (5)

Answer 9

-inflow artery
-proximal anastomosis
-mid graft
-distal anastomosis
Outflow artery

Question 10

Is biphasic arterial flow in LE arteries considered normal?

Answer 10

No, triphasic is normal. HOWEVER, it is possible to have biphasic flow without evidence of a disease

Question 11

With ABNORMAL findings of arterial studies, we compare stenotic PSV to pre-stenotic PSV to form a ratio….

• • 2:1 ratio = > or equal to 50% diameter reduction
• • 4:1 ratio = ?
• • > 400 cm/sec PSV =

Answer 11

2:1 ratio = > or equal to 50% diameter reduction
4:1 ratio = > or equal to 75% diameter reduction
>400 cm/sec PSV = > or equal to 75% diameter reduction

Question 12

When diagnosing a patient for stenosis, are we able to only use the value of “numbers” alone? If not, what else is used to help prove

Answer 12

No, we should include to presence of a post-stenotic turbulence

Question 13

In a NORMAL bypass graft, the flow should have ____ resistance, and some retrograde flow in the native artery at the ____ of the RSVG

Answer 13

LOWER resistant

Retrograde flow in native artery at DISTAL ANASTOMOSIS

Question 14

The normal presence of retrograde flow in a bypass graft at the native artery distal anastomosis is a result of ?

Answer 14

Pressure gradient

Question 15

When comparing current study with a prior study on the same patient, it would be abnormal to find a decrease of _____ cm/sec in any graft segment or a decrease in ABI of ____

Answer 15

Decrease of 30 cm/sec in graft

Decreased ABI of > 0.15

Question 16

Is a reduced PSV in smallest graft diameter when comparing it to prior study considered normal or abnormal

Answer 16

Abnormal

Question 17

In post endovascular intervention, normal stented arteries may have _____ peak systolic velocities

Answer 17

May have ELEVATED PSV

**however greatly elevated is abnormal and may suggest a hemodynamically significant diameter reduction

Question 18

This uses HIGHEST frequency transducers available to check patency of the anastomotic sites, as well as evaluate any suspicious stenotic/turbulent areas that can occur in a vein bypass graft (e.g. Valve cusp or suspected branch sites)

Answer 18

Intraoperative monitoring