Page 163 - Libro 2

9 — Duplex Ultrasound of Lower Extremity Arteries
143
A variety of transducers are used to obtain high- quality B-mode, color, and power Doppler images as well as reliable velocity spectra. Curvilinear 5-2 MHz and phased array 3-2 MHz probes are typically used for aortoiliac scanning, but these lower frequency probes may be needed to insonate deeper lower extremity vessels in heavier limbs. Linear 7-4 MHz transducers used for visualization of the femoral, popliteal, and tibial vessels. The high resolution of a compact linear 15-7 MHz transducer allows better visualization of superficial arteries on the ankle and foot.
The duplex ultrasound examination of the infrain- guinal vessels begins at the groin. At this position, the distal portion of the external iliac artery and the com- mon femoral artery (CFA) can be identified. The trans- ducer is moved slightly down the leg to next identify the bifurcation of the superficial femoral artery (SFA) and deep femoral or profunda femoris artery (PFA) (Fig. 9-3). Most laboratory protocols require only the first few centimeters of the PFA to be scanned. After a short distance, the PFA courses deeper in the thigh, giving rise to multiple branches. The SFA is then fol- lowed through its entire course using a medial ap- proach. In the lower thigh, the SFA passes through the adductor canal, also known as Hunter’s canal. Once through the canal, the SFA becomes the popli- teal artery, which is now along the posterior aspect of the leg. This can be viewed by moving the transducer posteriorly to the knee joint and following the vessels proximally onto the lower thigh. Combining both me- dial and posterior approaches, the full course of the SFA and popliteal artery can be appreciated.
The popliteal artery is examined as it courses through the popliteal fossa. There are multiple small branches, including the gastrocnemius arteries, which
Figure 9-3 The common femoral artery (CFA) bifurcating into the superficial femoral artery (SFA) and deep femoral or pro- funda femoris artery (PFA).
Figure 9-4 The popliteal artery, along with the gastrocnemius arteries.
can be observed (Fig. 9-4). In a complete examina- tion, all three tibial arteries are followed throughout the calf. The anterior tibial artery can be observed with a posterior approach branching off the popliteal artery (Fig. 9-5). As this vessel courses lower in the calf, it can be followed with an anterior–lateral ap- proach. The posterior tibial artery can be followed through the calf with a medial approach. Depend- ing on its depth, the peroneal artery can be followed with a medial approach or with a posterior–lateral approach (Fig. 9-6). Often, the lower extremity ex- amination includes the dorsalis pedis artery. Care should be taken when insonating the distal posterior tibial, distal anterior tibial, and dorsalis pedis arter- ies. These vessels are very superficial and can eas- ily be partially compressed with the transducer if too much pressure is applied.
Figure 9-5 The origin of the anterior tibial artery (ATA) off the popliteal artery (POP). The tibioperoneal trunk (TPT) is also shown.