Overview of Doppler Extra-Cranial Carotid Assessment, Protocols, and Interpretation
Over the past several years, a tool called a Doppler ultrasound has become one of the main ways doctors look at the carotid arteries in your neck without having to do surgery. This tool is widely used because it’s easy to access, doesn’t involve any invasive procedures, and it’s not too expensive. A Doppler ultrasound helps doctors screen for, diagnose, and monitor a condition called atherosclerosis, which is a hardening and narrowing of the arteries due to a buildup of plaque.
This is really important because atherosclerosis can increase your risk of having a stroke. The greater the narrowing of the arteries, the higher the risk, so it’s important for your doctor to keep a close eye on it. The Doppler ultrasound can measure the speed of blood flow (velocity) in your arteries, and combined with other imaging, can help your doctor assess the size and severity of the plaque and narrowing, or stenosis.
This evaluation is crucial for understanding a patient’s risk for stroke and can help doctors figure out if and when they need to perform surgery to treat the atherosclerosis and protect the patient from a potential stroke.
Anatomy and Physiology of Doppler Extra-Cranial Carotid Assessment, Protocols, and Interpretation
The vessels located outside the brain and skull are known as extracranial vessels. The most common structure of these vessels includes three main parts branching off from the aortic arch, the large vessel responsible for pumping the freshly oxygenated blood from the heart to the rest of the body. The first branch is the brachiocephalic artery, the main blood vessel supplying blood to the arms and the head. It further branches off into two arteries – the right common carotid artery, supplying blood to the right side of the neck, head, and brain, and the right subclavian artery, supplying blood to the right arm.
The second main branch is the left common carotid artery, supplying blood to the left side of the neck, head, and brain. The third branch is the left subclavian artery, supplying blood to the left arm.
Sometimes, the brachiocephalic artery and the left common carotid artery share a common origin point from the aortic arch. On reaching the upper border of the thyroid gland in the neck, both common carotid arteries further split into two – the external carotid artery and the internal carotid artery.
The point where this splitting or “bifurcation” happens is known as the carotid bulb. The internal carotid artery, generally located behind and to the side of the external carotid artery, usually has a larger size. The external carotid artery is responsible for supplying blood to the face and neck muscles and progressively becomes thinner as it moves towards the regions outside the skull.
Why do People Need Doppler Extra-Cranial Carotid Assessment, Protocols, and Interpretation
If you’ve been experiencing symptoms like sudden weakness or numbness on one side of the body, changes in vision, or difficulty with speech or understanding, your doctor might recommend a carotid Doppler ultrasound. This is a type of scan that helps doctors look at how blood flows through the carotid arteries (major arteries in your neck). They might also suggest this test if there’s a swishing noise (bruit) in your neck when they listen with a stethoscope, or if there’s a mass (lump) in your neck that can be felt pulsating.
This test may also be used before major heart surgery to assess the carotid arteries. If you already know that you have problems with your carotid arteries (carotid disease), you might need to have this test done on a regular basis as a check-up. There’s a condition known as ‘subclavian steal syndrome’ where blood flow is redirected as a result of a blockage in a major artery – this test may be used if that’s suspected too.
Equipment used for Doppler Extra-Cranial Carotid Assessment, Protocols, and Interpretation
The carotid arteries, which carry blood to your brain, are located fairly close to your skin’s surface. As such, our experts use a special medical tool called a high-frequency linear transducer that operates between 5.0 and 7.5 MHz. This is because the frequency of the ultrasound tool, or how fast the sound waves it emits are, is closer to the skin the higher it is.
This type of ultrasound, known as a Doppler ultrasound, is typically done together with something called grayscale imaging. Grayscale imaging is a method that uses different shades of grey to represent the structures within your body and provides us with a clear picture of the carotid arteries. For grayscale imaging, a transducer that operates between 5.0 and 12.0 MHz is used.
Preparing for Doppler Extra-Cranial Carotid Assessment, Protocols, and Interpretation
The patient should lie flat on their back with their head slightly tilted back and turned about halfway to the side that isn’t being examined. The radiologist who performs the ultrasound, or “sonographer”, will choose where to sit based on what feels most comfortable for them. Some prefer to sit behind the patient’s head, facing towards the feet, while others like to sit toward the side, facing upwards. The height of the patient’s bed will be adjusted to make sure the sonographer doesn’t have to bend over uncomfortably.
How is Doppler Extra-Cranial Carotid Assessment, Protocols, and Interpretation performed
The technique we’re discussing relies on something called the Doppler effect. This involves using sound waves to measure changes in the movement of red blood cells within the blood vessels. The calculations involve looking at the frequency shift, which is directly related to the speed and direction of the blood flow.
One of the first steps is ‘grayscale imaging’, also known as “B-mode”, this helps the doctor evaluate the state of your vessels. Specifically, they’re looking at things like the size of the vessel, thickness of the vessel wall, and any potential plaque build-up.
Plaque is a substance that can build up in your arteries and cause a blockage. The appearance of plaque can help the doctor determine how severe your disease may be. Some plaques have an increased risk of rupture, which can lead to a blood clot.
The scan is performed on the different carotid arteries in your neck, from the base of your neck to the point where your jawbone begins. Adjustments are sometimes necessary to get a clear image, especially when looking at vessels that may be curved or twisted.
To get the most accurate results, several factors need to be considered. The angle at which the sound waves are sent into your body should be less than 60 degrees, and as parallel as possible to the direction of blood flow. This increases the accuracy of the measurements taken. Another adjustment involves optimizing the gain settings so the visual representation of the blood flow is only present within the vessels.
The speed at which blood moves through your common carotid arteries (CCAs) is typically between 30 and 40 cm/sec, although this can vary if the vessels are diseased. Any abrupt changes require careful assessment and documentation.
The technology also evaluates the pattern of your blood flow. Certain changes can indicate specific diseases. For example, changes in the pattern of blood flow may indicate conditions such as metabolic disorders or blood vessel compression.
The evaluation will also examine your internal carotid artery (ICA), your external carotid artery (ECA), and your vertebral artery. Significant narrowing of these arteries could indicate a need for a surgical operation.
Finally, the technique also includes a check of your vertebral arteries to determine the direction of blood flow. Depending on the findings, this could indicate blockages in other nearby arteries.
In conclusion, Doppler ultrasonography is a powerful tool that provides doctors with important information about your blood vessels, the speed and direction of your blood flow, and any possible blockages or issues requiring further investigation or treatment.
What Else Should I Know About Doppler Extra-Cranial Carotid Assessment, Protocols, and Interpretation?
Stroke is the third biggest cause of death and severe disability in the United States. It’s most often caused by the hardening and narrowing of arteries both inside and outside the brain (a condition called atherosclerosis) which prevents blood flow, resulting in an ischemic stroke. It’s important to determine the amount and degree of these harden blood vessels as it can help predict the risk of a potential stroke.
A common method for examining this is using grayscale ultrasound imaging, bascially a type of scan. This, paired with color flow (Doppler) and wave analysis, allows medical professionals to examine the shape and features of hardened arteries, and detect any arteries that have narrowed significantly enough to impede blood flow.
In addition to screening for stroke risk, a Doppler scan can also help check for potential complications after a stroke or related procedures. These complications might include the formation of a false aneurysm (pseudoaneurysm), recurrence of narrowed arteries (restenosis), the creation of an abnormal connection between an artery and vein (fistula), and the deformation and breakage of a stent, which is a small mesh tube that’s used to treat narrow or weak arteries.
