Flashcards in Duplex/color flow imaging UE and LE Deck (28):
Combination of real time B-mode imaging and Doppler spectral analysis
Doppler info is displayed on image after evaluated for phase and its frequency content.
Doppler color flow imaging
Sample size for acquiring pulsed doppler is usually?
Uncommon for arteries in the upper extremities to become stenotic. Main use is evaluation of?
Dialysis access grafts
Auscultate the access for bruit and/or palpate for a thrill (vibration). A patent ______, as well as a stenotic one can produce a thrill.
Evaluate dialysis access grafts as follows:
a) inflow artery
b) arterial anastomosis
c) continue through the body of the graft
d) observe for aneurysm, puncture sites, peri-graft fluid
e) observe color flow changes, turbulence
f) venous anastomosis
g) outflow vein
UE dialysis access Brescia-Cimino fistula assessment sites include?
Inflow artery, anastomosis, and outflow vein
Straight, looped, synthetic grafts
Normal peak systolic velocities vary widely with _____ changes. Doppler signal quality is usually triphasic.
If a > 50% diameter reduction is present, observe for characteristics of the?
post stenosis turbulence
What aneurysms can form in response to using the palm as a hammer?
What aneurysms are associated with embolization to the digits?
Peak systolic velocities and end diastolic velocities vary as to the type of access; normally both are elevated. Low PSV obtained in access graft could indicate arterial _____ problems.
Most common sites for stenosis in hemodialysis access?
venous anastomosis and outflow vein
Large blood volumes shunted from artery to lower resistant venous circulation, can increase venous return resulting in?
In what situation is the distal arterial blood flow reversed into the lower resistant venous circulation and can cause pain on exertion, pallor and coolness of the skin distal to the shunt?
Doppler equation for LE duplex/color flow imaging?
Df= 2 Fo V Cos theta/ c
Df- doppler shift freq
Fo- carrier freq
c- speed of US through soft tissue (1540 m/s)
V- velocity of moving reflectors
Cos theta- Angle
2 represents two doppler shifts
What do the two Doppler shifts represent in the LE doppler equation?
- RBC is first an observer of a stationary ultrasound field
- Then acts as a wave source when the waves scatter from its surface
Equation for velocity
V= c Df/ 2 Fo Cos theta
When solving for velocity, what increases its nonlinear influence as the angle becomes closer to 90 degrees?
Doppler angle theta
If there is a > 50 % diameter reduction is suspected what should be obtained?
PSV in stenosis
Post-stenotic turbulence signals
What is important to know about bypass grafts?
type, location, and age
Reversed saphenous vein graft (RSVG)
- Small end is now prox
- Large end is distal
- Vein valves stay open due to arterial flow pressure
- Branches are ligated
In-situ vein graft
- GVS stays in place
- Small end is distal
- Large end is prox
- Prior to surgery, valves broken up with special instrument, branches ligated
Vein bypass graft evaluation includes observation of gray scale, color flow, and PSV's of the following?
- Inflow artery
- Prox anastomosis
- Entire length of the vein bypass graft
- Distal anastomosis
- Outflow artery
- Also check for branches that could form AV fistulas, valves, and/or other abnormalities
Synthetic bypass graft evaluation include observation of gray scale, color image, PSV's of the following:
- inflow artery
- prox anastomosis
- mid graft
- distal anastomosis
- outflow artery
Compare stenotic PSV to pre-stenotic PSV:
2:1 ratio = > 50% diameter reduction
4:1 ratio = > 75% diameter reduction
>400 cm/s PSV = 75% diameter reduction
Never accept the value of numbers alone; post-stenotic turbulence should be present
Retrograde flow in the native artery may be evident at the distal anastomosis of a RSVG, which provides an additional source of collateral flow. Retrograde flow results from a?