1. Diagnostic Medical Sonography Program
Lecture 12: Duplex Scanning and Color Flow Imaging of the Lower Extremities
Holdorf

2. Duplex / Color Flow Imaging of the Lower Extremities
Capabilities:
Determines presence or absence of > 50% diameter reduction of occlusion
Determines presence or absence of aneurysms
Follow-up of bypass grafts
To localize the stenotic lesion prior to balloon angioplasty

3. Limitations Presence of dressings, skin staples, sutures, open wounds
Incisional tenderness, hematomas
Obesity- may be difficult to image vessels
Calcific shadowing from diabetes and or atherosclerosis

4. Patient Positioning Patient supine with head on pillow
Extremity positioned close to the examiner
Patient’s hip minimally rotated externally, with knee flexed
Prone or lateral decubitus position may be required for assessment of popliteal artery

5. Physical Principles: the Doppler equation may be written as:

6. Df. =. Doppler shift frequency Fo. =. Carrier frequency c. =
Df = Doppler shift frequency Fo = Carrier frequency c = Speed of ultrasound through soft tissue (1540m/sec) V = Velocity of the moving reflectors Cos 0 (theta) = Angle

7. Ideal Doppler angle for vascular exams is 60 degrees, obtained center-stream, parallel to walls.
Vessel tortuosity and other conditions will cause the Doppler angle to be < 60 degrees, which IS usable.
Not reliable: Doppler angle > than 60 degrees.

8. Technique: Native Arteries
Scan with a 5 or 7 MHz linear array transducer for the following:
Distal external iliac artery
Common femoral artery (CFA)
CFA bifurcation
Superficial femoral artery (SFA)
Profunda Femoris
Superficial artery (proximal to distal)
Popliteal artery (proximal to distal)
Trifurcation
Anterior tibial artery (ATA)
Posterior tibial artery (PTA)
Peroneal artery

9. Observe gray scale for plaque or other abnormalities
Observe color flow patterns
Obtain peak systolic velocities (PSV) from each major vessel (proximal, mid and distal if vessel is long) and more if disease suspected
Characterize the Doppler signals: triphasic (normal). Biphasic, or monophasic (abnormal)
Observe wave form for any spectral broadening

10. If a > 50% diameter reduction is suspected, obtain:
If a > 50% diameter reduction is suspected, obtain: Pre-stenotic PSV (approaching the stenosis) PSV (highest) in stenosis

12. Post –Stenotic turbulence signals
Document as previously described for UE

13. Technique: Bypass Grafts
A. Know type, Location , and age:
Synthetic (e.g. Gortex)

14. REVERSED SAPHANEOUS VEIN GRAFT (RSVG)
Small end is now proximal *
Large end is distal *
Vein valves stay open due to arterial flow Pressure
Branches are ligated
* Size change often evident in the initial post-op study

15. Saphenous vein

16. In-Site Vein Graft
GSV stays in place
Small end is distal *
Large end is proximal *
Prior to surgery, valves broken up with special instrument; Branches ligated
* Size change often evident in the initial post-op study

17. Technique Continued…
B. Protocol usually combined with ABIs. C. Vein bypass graft evaluation includes: Observation of gray scale, color flow, and PSVs of the following: Inflow artery Proximal 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

18. Technique continued…
D. Synthetic bypass graft evaluation include observations of gray scale, color image, PSVs of the following: Inflow artery Proximal anastomosis Mid Graft Distal anastomosis Outflow artery

19. Interpretation: Native Arteries
A. Normal
Doppler signals are triphasic; a change to biphasic can be significant: however, some patients normally have biphasic flow without evidence of disease

20. B. Abnormal findings Compare stenotic PSV to Pre-Stenotic PSV
2:1 ratio = > 50% diameter reduction
4:1 ratio = > 75% diameter reduction
>400 cm/sec PSV = > 75% diameter reduction
Never accept the value of numbers alone; post-stenotic turbulence should be present
Observe for occlusions and aneurysms

21. Pre-stenotic Doppler spectra demonstrates a waveform that is
Monophasic
Dampened
Doppler spectra obtained AT the stenosis
Documents the highest PSVs
Post-Stenotic Doppler spectra demonstrates a waveform that shows turbulence (Usually distal to a > 50% stenosis

22. Interpretation: Bypass Grafts
A. Normal:
Lower resistance flow patterns may normally be expected.
Some retrograde flow in the native artery may be evident at the distal anastomosis of a Reversed Saphenous Vein Graft (RSVG), which provides an additional source of collateral flow. (Retrograde flow results from a pressure gradient)

23. B. Abnormal Findings
Compare results with previous studies and observe for changes such as:
Decrease of 30 cm/sec in any graft segment
Reduced PSVs in smallest graft diameter that were greater previously
Change from Triphasic to biphasic signals
Decrease in ABI of > .15
Observe for post-complications such as: AV fistula (can siphon off graft flow); valve cusp
Can also apply previous data used for native artery stenosis

24. C. Synthetic Grafts Can loosely apply the previous data to determine whether a > 50% diameter reduction exists. Anastomotic sites should be evaluated well for aneurysm and or stenosis Observe for graft occlusion

25. Synthetic LE Bypass grafts

26. Post Endovascular Intervention
In general, normal stented arteries may have elevated peak systolic velocities
Greatly elevated peak systolic velocities are abnormal and suggest a hemodynamically significant diameter reduction

27. Intraoperative monitoring
Used for checking patency of anastomotic sites
Evaluate any suspicious stenotic or turbulent areas that can occur in vein bypass grafts (e.g., valve cusp sites or suspected branch sites)
Use highest frequency imaging transducer available

28. Additional Notes Lecture 12 Duplex / Color flow imaging (LE)
Calculating for velocity is the only thing that we do not know.
Calculation is based on your angle.
Doppler angle of greater than 60 degrees is not good

29. Bypass grafts
For In-situ Vein Graft, will use as an artery
All braches must be ligated.
Now arterial.
For synthetic bypass graft
Looking at prox and distal ends.

30. Pay close attention to the ratios
2:1
4:1 difference is bad.
Telling the story
Systole: Proximal issues
Diastole: distal issues.
Blood flows because of a pressure gradient. High to low pressure.

31. Interpretation of bypass grafts
Normal splash of blue color in systole (reversal) is normal due to mixed pressure gradient.
If Velocity 1 (study one) showed a peak systolic Velocity PSV of .89 and the second study shows a PSV of 5.56, then this is a greater than 4:1 ratio, which is bad.
AV fistula: two things are connected that normally would not be.

32. Homework
Chapter 13:
Pages
SDMS assignments