Overview of Sonography Vascular Peripheral Arterial Assessment, Protocols, and Interpretation
The most common health issue that impacts the arteries that circulate blood to the outer parts of the body, often referred to as the peripheral arterial system, is a condition called atherosclerosis. This condition is a type of peripheral arterial disease (PAD), which narrows or blocks the arteries and can sometimes cause them to unusually widen, known as aneurysm. In the USA, it affects over 8.5 million people. It can result in symptoms ranging from intermittent claudication, which is pain during exercise that relieves with rest, to pain even when at rest. If not addressed, the disease can lead to worse scenarios like skin ulcers, gangrene, and even loss of limbs. PAD usually impacts the legs more than it does the arms, but a similar examination can be applied to both.
The first steps to diagnose this condition often involve noninvasive tests. This can include physical exercises, ankle-brachial index (a test that compares blood pressure in your ankle and arm), or checking blood pressure in different sections of your limbs. Duplex ultrasonography, a type of scan using sound waves, can support these tests to confirm the diagnosis, monitor the disease’s development, and unveil any complications.
Conducting and understanding a scan of the peripheral arteries calls for sufficient knowledge of the standard structure and size of these blood vessels, the disease’s nature, and how normal and abnormal blood flows work. It also requires a basic understanding of the different types of ultrasonography and the suitable settings and techniques for this test. The person operating the scan and the doctor interpreting the results should know what a comprehensive study looks like.
The ultrasound has advantages; it is quite accessible, does not expose the patient to any harmful radiation, generally costs less, and does not take up a large space compared to other imaging methods. On the other hand, it has limitations. It is not very effective through air and bone and the sound waves it uses can weaken as they go through soft tissues, especially in patients who are on the larger side. This is particularly pronounced for the large vessels in the chest and abdomen. Also, checking the peripheral arteries presents its unique challenges, particularly in patients with significant swelling, wounds, or scarring.
Anatomy and Physiology of Sonography Vascular Peripheral Arterial Assessment, Protocols, and Interpretation
The abdominal aorta, a major blood vessel in your abdomen, splits into two common iliac arteries around the lower back area. These arteries are about 8-10 millimeters in diameter and they are positioned in front of the iliac veins. The common iliac arteries then continue to form the external iliac artery, after branching off another artery, known as the internal iliac artery.
The external iliac artery travels downward before dividing to form the common femoral artery, which is between 5 to 9 millimeters in diameter. The common femoral artery and vein are encased within the femoral sheath, a protective covering, located in your thigh, with the femoral nerve positioned on the side. The common femoral artery then splits into two smaller arteries called the superficial femoral artery and the profunda femoris artery. The superficial femoral artery supplies blood to the thigh and eventually changes to be called the popliteal artery when it reaches the space behind the knee (the popliteal fossa).
In the upper part of the calf, the popliteal artery further branches into the anterior tibial artery, which supplies blood to the front of the lower leg and turns into the dorsalis pedis artery, and the tibioperoneal trunk, a smaller blood vessel, which then splits off into the posterior tibial artery and the peroneal artery. Both of these arteries supply the different muscles in your calf.
Normally, the amount of blood flowing through a healthy artery remains the same at any two points along that artery. If there’s a narrowing (stenosis) in the artery due to any reason, the blood must speed up to maintain the same flow, causing turbulent, irregular blood flow at that point. This principle is used to identify problems in your arteries by using an ultrasound. When the blood flow is normal and smooth, the ultrasound ‘picture’ of the blood flow appears clear and distinct. When the blood flow is turbulent, the ultrasound ‘picture’ appears blurred because the flow speeds and directions are not uniform.
Ultrasound is a tool that uses high-frequency sound waves to view the inside of your body. There are several modes of ultrasound used for evaluating your arteries: B-mode, Doppler, color, and power Doppler.
B-mode ultrasound creates a grayscale image which can measure the size of blood vessels or identify any changes in the walls of the arteries, such as build-ups of plaque (a fatty material) or blood clots. When an ultrasound beam is directed perpendicular (at a right angle) to the blood vessels, the best quality images are obtained.
Doppler ultrasound uses the Doppler effect, which is a change in frequency or wavelength of a wave in relation to an observer, to estimate the speed of blood flow in your arteries. The ultrasound shows this information as a graph of velocity against time.
Color Doppler maps use different colors to show blood flow in a certain region. It helps in quickly identifying and locating vascular structures. It gives an overview of the vessel parameters and draws attention to areas where the blood flow becomes turbulent.
Power Doppler shows the quantity of moving red blood cells, regardless of their direction or speed. This method is more sensitive to slower blood flow.
Normal arterial blood flow is triphasic, i.e., it consists of a sharp increase in blood flow (systolic upstroke), early flow reversal after the systolic upstroke (diastolic flow reversal), and late return to forward blood flow. However, a monophasic waveform is considered abnormal and is usually seen after narrowing, blockages or in blood vessels formed around the area of blockage.
In conditions of complete blockages, the blood flow stops and the subsequent ultrasound images will show no color flow at the site of occlusion and the resumption of blood flow past the occlusion with low-speed, monophasic waveforms.
When the narrowing or stenosis in the artery goes beyond 50%, symptoms like pain upon exertion may arise. If the narrowing reaches approximately 90%, symptoms might appear even at rest.
Aneurysms, or abnormal widening of a portion of an artery due to the weakening of the artery’s wall, are a common issue associated with atherosclerotic disease. Atherosclerotic disease is a condition where plaque builds up inside your arteries, making them narrow and less flexible.
Why do People Need Sonography Vascular Peripheral Arterial Assessment, Protocols, and Interpretation
Peripheral arterial disease is a condition where the arteries, which supply blood to your limbs, are blocked. It often leads to symptoms such as leg pain while walking (claudication), pain at rest, and changes in skin appearance. Other tests may suggest that arterial disease is present, and then these specific symptoms further confirm it.
Did you know your doctor can track how your disease is moving along or monitor the success of any procedures you’ve had? If you’ve had surgery like bypass surgery or stent placement to help blood flow better, your doctor will keep a close eye on these sites to ensure they are functioning properly. Procedures like inserting a small mesh tube (known as stents) into arteries or rerouting blood flow (which is what happens in bypass surgery) are done to treat blocked arteries, and it’s crucial to ensure they’re doing their job.
Sometimes, before any surgical procedure is done, the doctors need to understand the layout of your arteries. This is known as surgical mapping and it helps them know what they’re working with. It’s kind of like looking at a roadmap before heading out on a journey.
Peripheral arterial disease can also occur as a result of injury or trauma. In such cases, doctors will look out for similar signs and symptoms to make sure your blood flow is not compromised in these situations too.
Equipment used for Sonography Vascular Peripheral Arterial Assessment, Protocols, and Interpretation
When performing an ultrasound scan of the main artery and its branches near the waist area, a tool that transmits a low-frequency sound wave of 3.5-5 megahertz (MHZ) is typically used. For the smaller arteries further away from the heart, a tool that emits a higher frequency sound wave of 5.0-7.5 MHZ (or more) is often preferred.
In patients with a larger body size, a tool that uses lower frequency sound waves may be needed. These sound waves can penetrate deeper into the body, making them ideal for such cases.
Who is needed to perform Sonography Vascular Peripheral Arterial Assessment, Protocols, and Interpretation?
Ultrasound technicians, who are trained medical professionals, usually do the majority of ultrasound scans that focus on the parts of your body referred to as ‘the periphery’ – basically, this means places that are not the chest or abdomen. Doctors who have received specific training can also perform these ultrasounds. Furthermore, ultrasounds that are done right at the patient’s bedside or in the examination room by well-trained providers are really helpful. These types of ultrasounds help the doctors figure out what type of care or treatment you might need next.
How is Sonography Vascular Peripheral Arterial Assessment, Protocols, and Interpretation performed
Grayscale ultrasound is a method used to get a picture of the condition of your arteries and identify any build-up of plaque (fatty deposits). Sometimes, the plaque may not be very visible and may blend in with the artery. In such cases, a technique called color Doppler is used to clearly display the artery. Color Doppler is also used to tell apart arteries and veins based on the direction in which the blood is flowing. It’s particularly helpful in quickly showing areas with uneven blood flow and narrowing of the arteries.
The comprehensive peripheral arterial ultrasound test starts at the main artery in your stomach area (the abdominal aorta) and follows the path of the arteries down to the ankle. It examines the arteries both lengthwise and crosswise using different ultrasound techniques.
During the test, you will be asked to lie flat on your back. A device that emits low-frequency sound waves, called a transducer, is used to look at the aorta from just below the breastbone and from slightly to the left of the belly button. Certain arteries in the belly area help to guide the procedure. The transducer is then placed at the top of the pelvic bone to examine the arteries around this area.
The deeper part of your body requires a low-frequency transducer, while the shallower areas like near the skin can be examined using a high-frequency transducer. The arteries in your thighs and legs are carefully examined, tracing down to your ankles. Some adjustments may be needed, like turning you on your stomach to better access certain arteries in your leg.
Certain parts of the arteries are more likely to develop atherosclerotic disease, a condition where plaque builds up in your arteries and restricts blood flow. These include the artery that delivers blood to the pelvic region, the main leg artery at the point of the thigh bone, the artery in the knee and the branch off from that to the foot. Any suspect areas are thoroughly examined and the extent of any narrowness is judged by comparing the sections of the artery before and after the narrow part. Usually, it takes a reduction of half the width of the artery (which is a 75% decrease in area) to impact blood flow.
Depending on the percentage of narrowing in the arteries, different patterns are seen in the behavior of the blood flow. These patterns are observed by comparing the section where the blood flow enters, passes through, and exits the narrowed area. In serious cases of narrowing (76% to 99%), significant changes to blood flow patterns are observed, indicating restricted blood flow.
What Else Should I Know About Sonography Vascular Peripheral Arterial Assessment, Protocols, and Interpretation?
Peripheral arterial disease is a common health condition that can have serious effects beyond just losing a limb. It also increases the chance of heart problems and can lower your quality of life, including causing you to feel depressed. Duplex ultrasonography is a simple and easily accessible test used to diagnose this condition. This special type of ultrasound is advantageous because it doesn’t expose you to any harmful radiation, and is typically less expensive than other image-taking techniques. Along with other simple, non-invasive tests, ultrasound can accurately spot and assess the disease stage. This will help your doctor make a treatment plan and keep an eye on how the disease is progressing or how well the treatment is working.