Overview of Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation
Today, various types of medical imaging are used to examine a wide variety of harmless and serious medical conditions. Their use has greatly increased over recent decades. Despite the advancement in imaging techniques, hand-held ultrasound machines are still heavily used in radiology and vascular surgery departments across the country.
This type of ultrasound plays a key role in diagnosing and monitoring conditions such as blood clots in both shallow and deep veins (venous thrombosis) and abnormal blood vessels (vascular malformations). It is also used for ongoing care of certain devices implanted within blood vessels. This article focuses on how veins look in ultrasound images, the pros and cons of this type of imaging, the basic science behind ultrasound imaging, and uses Doppler ultrasound technique which measures the flow of blood in our body. It will also provide an overview of standard procedures related to ultrasound scanning of peripheral veins, the veins that are not in the heart or brain.
Anatomy and Physiology of Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation
The veins distributing blood throughout our bodies generally fall into three categories: deep veins, superficial veins, and perforating veins. Deep veins lie within the muscles, superficial veins are underneath the skin and handle blood flow close to the surface, and perforating veins connect the two types. This structure is like a three-way highway system with separate lanes for deep, superficial, and connecting blood flow.
Veins, seen from outside to inside, are composed of an outer layer made of collagen, a layer of smooth muscle, and an innermost layer lining the vein. When you do an ultrasound, healthy veins and arteries differ by the pulsing of blood in arteries, not easily seen in veins, and the way veins easily compress when pushed.
The veins in your arms and legs work against gravity to take blood back to the heart. They do this with the help of ‘pumps’ (heartbeats and movements of your muscles), a pressure gradient, and one-way valves. This process allows blood to move smoothly and uniformly, much like cars on a highway in a synchronized flow. However, unhealthy veins or certain disorders can cause turbulent blood flow, like traffic chaos on the road, which can be identified by a change in color patterns in Doppler ultrasound.
There might be some challenges with imaging studies due to variant anatomy because veins in our bodies can greatly differ in their layout. For instance, the way veins are positioned in your arms and legs can vary. Also, sometimes these variant layouts can lead to health problems, like a persistent sciatic vein that is linked to certain disorders of the leg and chronic venous insufficiency.
A few common disorders detected by Venous Duplex Ultrasound might include venous malformations, venous insufficiency and deep venous thromboses. Venous malformations are abnormal growths in veins that can cause blood clots, leading to pain and swelling. Venous insufficiency is when veins in the legs can’t effectively pump blood back to the heart, appearing as enlarged veins, usually in the lower legs. Deep venous thrombosis is a condition in which blood clots form in deep veins, which might cause pain and swelling, or no symptoms at all. If a clot breaks off and moves to the lungs, it can cause a pulmonary embolism, which is a serious condition.
Pseudoaneurysm is another condition that could happen after a procedure involving your veins. This is when blood leaks and forms a new path that is still connected to the main vessel. The Doppler ultrasound can show a swirling flow pattern that looks like a whirlpool. Doctors can treat a pseudoaneurysm by applying compression to stop the abnormal blood flow and convert it to a simple clot or hematoma, potentially avoiding the need for any intervention or surgery.
Why do People Need Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation
A peripheral venous Doppler ultrasound scan is a test that can be carried out for several reasons. This test is often used to check for possible blood clots in the veins, also known as venous thrombotic disease, or blockages in your veins. A doctor might order this test if they think you have a blood clot or if they need to check how a blood clot you had before is doing. The results of this test can help guide the treatment plan.
This test can also be used for several other purposes. These include checking for vein problems such as weak or leaky veins (venous insufficiency), backward blood flow (reflux), or enlarged, twisted veins (varicosities). This test can also be used to map out your veins before procedures like preparing for blood dialysis access using a graft or a fistula, which links an artery and a vein in your arm. It can also be used to check for any unusual blood vessel structures, evaluate the peripheral vessels after interventions, or check the peripheral veins before inserting a tube for delivering drugs or nutrition into your body.
The good thing about a peripheral venous Doppler ultrasound is that it doesn’t expose you to harmful radiation, it’s non-invasive (meaning it doesn’t require any cuts or insertions into your body), it can be carried out anywhere, and patients generally tolerate it well.
When a Person Should Avoid Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation
There aren’t any hard and fast rules against using a type of ultrasound called Doppler peripheral venous duplex US. However, some situations might make it difficult to use properly. For example, if a person is overweight or has bandages or a cast on the body parts that need to be examined, it might be difficult for the ultrasound waves to get through. Similarly, if a person has a recent injury, burns, or surgery, then their open or new wounds may cause too much pain to use the ultrasound effectively.
Equipment used for Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation
An evaluation of your body’s peripheral veins using a Doppler ultrasound needs a special machine. This machine has three main capabilities: It can display images in gray-scale B-mode, show the flow of your blood in color (color-flow Doppler), and record video clips for future analysis. Through this process, the ultrasound machine can document how compressible your blood vessels are, the pattern of blood flow (smooth or chaotic), and any diseases or abnormalities in the peripheral vessels (the veins farthest from your heart).
Most of the time, the doctors use a device called a ‘transducer’ that emits sound waves at a frequency of 5 megahertz (MHz). This transducer can either be straight (linear) or curved. Sometimes, a different transducer that emits sound waves at a frequency of 2.5 MHz is used because it is better at examining deeply located blood vessels. Therefore, depending on where your veins are located and how deep within the body they are, different transducers may be used.
The ultrasound machine’s display screen is handy as it shows both the direction of your blood flows and how fast it’s moving (amplitude).
Who is needed to perform Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation?
Ultrasound scans (US) require a high level of skill to operate. So, it’s important that these scans are carried out by trained professionals, like sonographers (people specialized in performing ultrasound scans), vascular technologists (experts in scanning blood vessels), or doctors. These professionals need to have the right qualifications and recognition from established medical organizations. Whether they specialize in radiology (looking inside your body using different technologies) or vascular surgery (surgery related to blood vessels), they must follow strict guidelines set out by these organizations.
Furthermore, whoever performs and interprets your ultrasound must understand: the science of how imaging works, any issues that can arise during the scan (artifacts), the limitations of ultrasound scans, what to expect from a healthy body, and also, the common signs of diseases affecting the peripheral venous system (that’s the network of veins that carries blood towards your heart). The latter is especially important because their expertise can help identify any possible health issues you may have.
Preparing for Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation
Getting ready for a Doppler peripheral venous duplex ultrasound (US) is simple. This is a type of scan that helps doctors examine the veins in your body. The patient may be asked to lie down in a position like Trendelenburg (where your body is laid flat on the back with the feet higher than the head by 15-30 degrees), prone (lying flat with the front facing down), or lateral decubitus (lying on your side), depending on what’s most comfortable and gives the best view of the area being checked. You may need to remove your clothes or any medical support devices, but your privacy will be respected at all times. The ultrasound machine is set up at a comfortable distance from you, and can be adjusted by the ultrasound technician as necessary.
How is Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation performed
The information in this section mainly discusses the use of hand-held ultrasound machines that use a feature called pulse wave Doppler mode. To understand how to do an ultrasound, we need to discuss some specific wording and the foundational ideas that help form the images and allow us to study them. The most common mode used in making ultrasound images is called Brightness mode (B-mode). Ultrasound machines create images by sending and receiving a variety of ultrasound frequencies in a particular path. The image is then displayed in terms of brightness, with items that are closer and/or reflecting stronger signals appearing brighter.
The Doppler effect refers to the changes in sound frequency resulting from a moving object and a stationary receiver – essentially how the sound changes as the object moves towards or away from the receiver. Interesting to note, how strong the Doppler shift is, is directly related to the speed the moving object is going. Within the human body, this Doppler technique does not return just one frequency shift, but a whole range of frequencies. This range of frequencies is influenced by both body structures and changes such as the strength of heartbeats. This technology is often referred to as Spectral Doppler imaging (SDI) and is usually observed on graphs displaying frequency versus time or velocity versus time, creating what is often referred to as a waveform. This study is further enhanced using color flow imaging/color Doppler imaging also known as CFI or CDI, these modes use the Doppler effect to create a two-dimensional color image overlaid onto a B-mode image. Commonly, ultrasound machines use filters to improve the Doppler signals from the patient.
Pulsed wave Doppler, also known as duplex Doppler, is commonly used for examining blood vessels. This method uses B-mode to create the basic grayscale images, with Doppler frequency analysis performed at specific depths and for set periods. This method provides information about both the physical appearance and the flow dynamics of the examined blood vessel.
Doing the ultrasound correctly is very important and even more so when looking at blood vessels. The focal point of the ultrasound machine should be within 1-2 cm of the area of interest. When studying this using the Doppler effect, it is necessary to maintain an angle less than 60 degrees, due to the principles of the Doppler effect. The angle of the Doppler, however, is less important when we’re looking at veins in our arms and legs and is only really important if we think there may be problems with blood flow in veins or certain types of implants.
When examining the arms, the arm being studied is usually placed over the patient’s head while they lie on their back. Any part of the veins near the shoulder and neck that is accessible or visible should be examined with grayscale, color, and spectral ultrasound. Additionally, the veins in the arm should also undergo compression evaluation with grayscale. If venous pathology is suspected in the legs, the veins should be examined from the groin to the ankle, although not all medical facilities follow this recommendation. Regardless of the institution, examination with grayscale, CDI, SDI, and compression at the femoral and popliteal veins should be performed.
In preparation for surgical procedures, examining the veins is generally performed, and discussion with the medical provider, vascular surgery, and/or interventional radiology may also be necessary. According to published standards from the AIUM, essential details such as patient identification and labeling of the site should be clearly displayed on the image. If the site is outside the standard protocol, a targeted ultrasound evaluation should be performed. Additionally, if unusual conditions such as blood clots, malformations, non-vascular causes, or unusual anatomy are present, further examination to document the size and extent of the region involved is warranted.
Possible Complications of Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation
Getting an ultrasound of your blood vessels, also known as a peripheral vascular ultrasound, doesn’t have any immediate or long-term risks or side effects.
What Else Should I Know About Doppler Peripheral Venous Duplex Assessment, Protocols, and Interpretation?
The results of a medical examination can greatly affect your health based on what the doctor finds (pathology). For example, if the doctor finds a condition called deep venous thrombosis, which is a blood clot in a deep vein, usually in your leg, long-term medical treatment with the possibility of some surgical procedures may be necessary.
Additionally, if the doctor identifies an unusual structure or feature in your blood vessels (vascular anomaly), how it’s treated depends on its size and specific characteristics. Sometimes, these anomalies may require complicated medical procedures or surgery.
