Diagnostic ultrasound ( PDFDrive )

966 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
Normal
Distal obstruction
Inflow obstruction
Arteriovenous fistula
Triphasic
Biphasic,
low velocity,
high resistance
Monophasic,
low velocity,
lower resistance
Monophasic,
high velocity,
lower resistance
iliac artery at the level of the inguinal ligament and extends
caudally a few centimeters until it divides into the supericial
femoral artery (SFA) and profunda femoris artery. he profunda
femoris artery supplies the femoral head and the deep muscles
of the thigh through perforators, as well as the medial circumlex
artery and the lateral circumlex artery. he SFA continues along
the medial thigh to the adductor canal in parallel with the femoral
vein (FV). Below the adductor canal, it becomes the popliteal
artery, coursing posterior to the knee and supplying branches
of the calf.
he popliteal artery branches into the anterior tibial artery
and the tibioperoneal trunk. he anterior tibial artery courses
laterally, perforating through the interosseous membrane between
the tibia and ibula into the anterior compartment of the lower
leg. he anterior tibial artery becomes the dorsalis pedis artery
in the dorsum of the ankle and along the irst intertarsal space
of the foot. he tibioperoneal trunk divides ater approximately
3 to 4 cm into the posterior tibial artery and the peroneal
artery. he posterior tibial artery courses posterior to the medial
malleolus of the ankle. he peroneal artery courses through the
interosseous membrane above the ankle, and then supplies
branches of the lateral ankle and foot.
Pseudoaneurysm
Biphasic,
reciprocating
FIG. 27.1 Diagrams of Doppler Flow Patterns in Normal and
Abnormal Scenarios. The normal Doppler spectrum of lowing blood
in the lower extremity arteries typically has a triphasic pattern: (1)
forward low during systole, (2) a short period of low reversal in early
diastole, and (3) low-velocity low during the remainder of diastole.
Arterial Doppler signals are altered depending on the pathologic change.
The four other patterns are examples of common arterial pathologies:
distal obstruction, inlow obstruction, arteriovenous istula, and
pseudoaneurysm.
within 4 cm upstream, and the draining artery within 4 cm
downstream. he inlow velocity is used as a reference to assess
for increased peak velocity at the stenosis, and the downstream
location is evaluated for peak velocity drop, decreased resistance,
and tardus parvus morphology. he same concepts apply to
bypass grats, when looking for stenosis and occlusion, with
additional evaluation at the anastomoses, which are common
sites of abnormality. Ultrasound is the primary screening for
bypass abnormalities but can be a time-consuming study if used
to cover all areas of concern in a patient with difuse atherosclerotic
disease. If difuse atherosclerotic disease is suspected, other
imaging techniques such as computed tomography (CT) or
magnetic resonance angiography may be able to survey large
areas more efectively.
Lower Extremity Arteries
Normal Anatomy
Each lower extremity arterial system is primarily supplied from
the common femoral artery, which originates from the external
Ultrasound Examination and Imaging Protocol
Lower extremity arterial inlow from the external iliac artery is
assessed by groin insonation in supine position, and then each
major vessel in the leg is directly evaluated throughout its entire
course. Normal arteries have thin smooth walls with anechoic
lumens and lack of atherosclerotic plaques or stenosis on grayscale
imaging (Fig. 27.2). Ater gray-scale evaluation, long arterial
segments can be screened rapidly with color Doppler to ind
areas of suspected stenosis. Color Doppler is set to barely ill
the lumen in a normal area of the artery. Color aliasing can alert
the sonographer to areas of luminal narrowing that need to be
evaluated further with spectral Doppler to determine signiicance.
For evaluation of focal abnormalities other than stenosis, the
examination may be limited to the general region of concern.
he ACR-AIUM-SRU practice parameter for the performance
of peripheral arterial ultrasound suggests that lower extremity
ultrasound should examine the common femoral artery; the
proximal, mid, and distal SFA; and the popliteal artery above
and below the knee. 2 Other arteries are examined as deemed
clinically appropriate. he practice parameter states that these
may include “iliac, deep femoral, tibioperoneal trunk, anterior
tibial, posterior tibial, peroneal, and dorsalis pedis arteries.” he
guideline further suggests that angle-corrected longitudinal
Doppler and/or gray-scale imaging should be documented in
each normal and at any abnormal segment. Angle-corrected
spectral Doppler is recommended proximal to, at, and beyond
any suspected stenosis. 2 Supine position of the patient is acceptable
for the thigh vessels, but a decubitus position may aid evaluation
of the popliteal artery. Depending on the symptoms and indings
of these arteries, imaging of the iliac arterial system may look
for inlow disease, or imaging of the calf arteries may be
indicated.
Normal outer diameters of the common femoral artery, SFA,
popliteal artery, posterior tibial artery, and anterior tibial artery