Dopplerography of cerebral vessels

Ultrasound of the brain is considered one of the safest and at the same time effective methods. This procedure is carried out for both children and adults. With the help of ultrasonic diagnostics, it is possible to identify serious enough diseases at the initial stage of development and prescribe their treatment.

The main goal of the study of cerebral vessels with the use of color duplex sonography is to determine and quantify the degree of stenosis caused by atherosclerotic changes in patients with complaints and transient ischemic attack or stroke in the anamnesis. The study should establish the degree of stenosis and the extent of the affected segment of the vessel. For the purpose of preoperative or pre-interventional assessment of the risk of complications, the collateral system should be evaluated. The study requires knowledge of the anatomy of cerebral vessels and a normal ultrasound pattern, which will be discussed in this chapter prior to the exposition of the semiotics of cerebrovascular vascular disease in the basins of carotid and vertebral arteries.

[1], [2], [3], [4], [5], [6], [7], [8], [9]

Ultrasound carotid artery anatomy, research technique

Many doctors prefer to sit behind the head of a lying patient. Scanning can also be started from the front by placing the sensor next to the middle line and displaying a common carotid artery in the cross section. This vessel is located posteriorly and internally with respect to the internal jugular vein. The diameter of the jugular vein can be increased by the Valsalva test, usually this leads to an immediate visualization of the vessel in B-mode. The cross section is displayed, as shown below, with the reverse location of the right and left sides.

When you rotate the sensor 90 ° degrees along the longitudinal axis, the right side of the image is located at the bottom, and the left side - at the top, as well as with ultrasound of the abdominal cavity. Watch for the physiological separation of the crumb of the eye, occurring at the level of bifurcation of the common carotid artery and the transition to the carotid bulb of the internal carotid artery. This sharp expansion creates a rounded vortex that should not be mistaken for pathological poststenotic reverse blood flow, turbulence or blurring.

On the Doppler spectrum from the common carotid artery, a certain increase in peak systolic velocity is usually determined in comparison with the internal carotid artery due to the relatively low intracranial peripheral resistance. This pattern differs from the external carotid artery, in which a "wheezing" audio signal with relatively high systolic and low diastolic velocities . From the external carotid artery, a three-phase spectrum can be obtained that includes a component of the reverse blood flow. Here, in the color mode, the upper thyroid artery is visible.

Anatomical orientation

When visualizing along the longitudinal axis, the internal carotid artery is normally located posteriorly and outward from the sensor, while the external carotid artery remains close to it in a large extent. If there are doubts about the vessel, repeated compression of the superficial temporal artery leads to oscillations in the spectrum of the external carotid artery. The internal jugular vein can be easily distinguished from the internal carotid artery in the direction of the blood flow and the flat spectral trace.

[10], [11], [12]

Stenotic lesion of the internal carotid artery

Atherosclerotic deposits do not always contain calcifications with shading. "Soft plaques" look like hypoechoic cavities in the shape of a crescent or a circle in a colored lumen along the vascular wall. With the help of color duplex sonography, the craniocaudal extent of the plaque can be accurately determined. You can often see an eccentric increase in blood flow.

Vascular wall stratification

The exfoliating wall of the vessel with the presence of blood between the layers is a special condition that usually arises spontaneously, but can also be associated with neck trauma or physical overload at any age. It is characterized by the presence of a hypoechoic intramural hematoma, which causes significant disturbances of blood flow.

Aneurysm of the wall usually develops as a complication. The flap of the intima can cover the initial lumen of the vessel, which, with ultrasound, appears to end at an acute angle. After a few weeks, recanalization may occur, which can be accurately documented using color duplex sonography.

Ultrasound anatomy of the vertebral arteries system, research technique

The vertebral artery is scanned in longitudinal section from anterolateral access in the position of the patient on the back, starting from the site of its departure (V ₀ ), and the investigation continues to the point in the region of the vertebra C ₁ (including segment V ₂ ). It is best to use a linear sensor with a variable frequency (5.0-7.5 MHz). Intraforamennial segment V _{2 of} vertebral foramens is best available for duplex scanning. It can be clearly visualized along with the concomitant vein between the acoustic shadows of the cervical vertebral bodies.

With hypoplasia of the invertebral artery, usually one of the arteries (usually the right one) has a diameter of less than 2.5 mm, while the opposite one is increased more than 4 mm in diameter (discrepancy is more than 1: 1,7). The normal diameter of the vertebral artery is approximately 3.8 ± 0.5 mm. In the hypoplastic vertebral artery, there is a decrease in the final diastolic component of the blood flow (Vdiast). Sometimes it is difficult to distinguish hypoplasia of the vertebral artery from distal stenosis or occlusion, since in all cases there is a decrease in Vdiast. The preferred locations of stenosis are the site of the vertebral artery from the subclavian, and the area at the level of the vertebra C1, which is scanned from the rear access behind the mastoid process. It is best to use a 5.0 MHz sensor, installing it immediately under the mastoid process and from behind, tilting it to the opposite eye socket with a slight turn of the head in the other direction.

Segment V4 is scanned by a sector sensor with a frequency of 2.5 or 2.0 MHz, which is located below the occiput and tilts to the orbit.

It should be noted that there are no significant criteria for determining the degree of stenosis of the vertebral artery, in contrast to the carotid artery.

With the normal patency of the vertebral artery, there is a two-phase spectrum with a clear spectral window, whereas stenosis is characterized by a significant increase in blood flow and filling of the spectral window.

Stratification of the vertebral artery after trauma can lead to embolic cerebral ischemia, resulting in a stroke. The results of color duplex sonography can be very diverse - from the presence of intramural hematoma to the occlusion of the affected segment of the artery. Sometimes you can see the exfoliated flap of the intima.

A thin scaly part of the temporal bone gives the best acoustic window for scanning the vilious circle with a 2.0 MHz sensor.

Horseshoe study of the main artery

A shotshee scan can be performed in the sitting position, with the patient's head tilted forward, or the patient lying on the back, and the head turned to the side. Thus, you can see both segments of V4 at the point of their merging into the main artery.

Anatomy of the cerebral vessels

The Vilisian circle is normally formed from carotid (anterior pool) and vertebral (posterior basin) arteries. At the point of separation of the common carotid artery from the arch of the aorta to the right and from the brachiocephalic trunk to the left, atherosclerotic plaques are rarely formed. Stenosis usually develops in the place of bifurcation of the common carotid artery to the internal carotid artery and external carotid artery. The first intracranial branch of the internal carotid artery is the orbital artery. Immediately after it, the internal carotid artery divides into the middle cerebral artery and the anterior cerebral artery.

Vertebral arteries in 4% of cases depart from the arch of the aorta, but usually their source is the subclavian artery. The left vertebral artery often begins proximal than the right artery. Each vertebral artery is divided into 5 segments. The proximal segment from the origin is called Vo. The Vi segment extends to the transverse process of the C6 vertebra, but sometimes the artery enters the hole at the Cs level. Segment V2 is the most accessible for examination in the middle of the neck. The loop of the vertebral artery at the level of the first cervical vertebra corresponds to segment V3. Segment V4 is located inside the skull, and from its distal segment begins the posterior lower cerebellar artery. In certain segments or throughout the course of the vertebral artery may be hypoplastic. The right and left vertebral arteries merge, forming the main artery, which is divided into the right and left posterior cerebral arteries.

[13], [14], [15],

Collateral pathways

1. Severe stenosis or occlusion of the internal carotid artery. At the main collateral path from the external carotid artery to the basin of the internal carotid artery, the blood enters the brain in a retrograde way along the supraclavicular and orbital arteries. Another way to compensate for the stenosis of the internal carotid artery is by a high degree of cross-flow through the anterior connective artery. To avoid risk during surgery, the surgeon should be aware of the possibility of hypoplasia or aplasia of the proximal segment A1 of the anterior cerebral artery. The vertebral artery system can receive collateral blood flow through the posterior connective artery if the posterior cerebral artery P1 segment from the corresponding side is not underdeveloped.
2. Severe stenosis or occlusion of the vertebral artery. Collaterals with proximal stenosis of the vertebral artery may be a deep artery of the neck, extending from the thyroid-cervical trunk or the branch of the occipital artery from the pool of the external carotid artery. In stenosis of the main artery, the only collateral pathways are the posterior connecting arteries or leptomeningeal anastomoses from the basin of the middle cerebral artery. In such cases, the positive side has a segment Paplasia, a posterior cerebral artery with a direct divergence of the posterior cerebral artery from the internal carotid artery.

[16], [17], [18]

Quantitative assessment of stenosis of the internal carotid artery

The local degree of stenosis can be counted on the cross-section by measuring the intra-stenotic color residual lumen (Ag) and its ratio to the original transverse diameter of the vessel in the affected area (AN) using the cross-section reduction formula / The more sensitive energy Doppler mode is used to accurately determine the cross section residual perfused lumen.

In both images, the hypoechoic plaque within the lumen is clearly differentiated from the hyperechoic calcifications.

The degree of stenosis can also be assessed by longitudinal scanning by measuring the peak velocities of the blood flow with their angular correction. With the help of digital subtraction angiography, for example, it is impossible to estimate the rate of blood flow. The method used in the largest multicentre study (North American Symptomatic Carotid Endarterectomy Trial: NASCET) was to measure stenosis of carotid arteries by determining the ratio of the diameter of the lumen in the narrowest part of the stenosis (ds) with the normal diameter of the carotid artery distal to the stenosis.

Considering the use of color duplex sonography for evaluation of stenosis, it was shown that using this technique, one can determine the degree of stenosis with high accuracy. To plan appropriate treatment, it is important to differentiate pre-occlusion "pseudocclusion" from the true one. The filiform residual lumen, invisible on native images, can sometimes be detected by intravenous administration of contrast medium. It must be remembered that sometimes after the introduction of a contrast drug, a higher peak flow velocity can be determined. Color duplex sonography also allows non-invasive control after carotid artery thrombédarietectomy or stent implantation in order to avoid stenosis recurrence. Several multicentre studies have shown that trombendarteriectomy reduces the individual risk of stroke in patients with clinical manifestations of high-grade internal carotid artery stenosis (more than 70%).

The thickness of intima-media in the system of the carotid artery

Long-term epidemiological studies have shown that the thickness of intima-media of the carotid artery is a predictor of stroke or myocardial infarction after evaluating all other risk factors (hypercholesterolemia, hypertension, smoking, etc.). How is it determined?

The study is carried out by a linear sensor with a frequency of more than 7.5 MHz, recording images with compression of 60 dB and measuring the vessels in systole. Do not use harmonic components and artifact contrast preparations. If we start the study from the lumen of the carotid artery, the first sonographically determined layer is the echogenic place of contact of the blood and intima, followed by a hypoechoic image of the intima-media, and finally - of the medulla and the adventitial layer. For physical reasons, the thickness of the intima-media can be more accurately measured at the far wall (4 =) than near, where the transition is less clearly defined. The thickness of the intima-media at the far wall is measured as the total thickness of the entire complex, since an exact separate measurement of both layers is impossible.

In scientific studies, usually 5-10 measurements are made in three segments of the carotid artery - the common carotid artery, the bifurcation area and the bulb of the internal carotid artery - and the average value is calculated for all three segments. In these studies, semiautomatic processing modules are often used, which sequentially register a variety of intima-media thickness values using a gray scale, which increases the reproducibility of the measurements.

For the practical application of this technique should be limited to the examination of the segment of the common carotid artery. One protocol consists in measuring a well-visualized segment of 10 mm in length, from 5 to 10 individual measurements and calculating the mean value. The resulting data are age-dependent and correlate with established risk factors. It was found that an effective effect on cardiovascular risk factors within 1-2 years reduces the thickness of the intima-media.

US-semiotics of intracranial vascular lesion

In patients with stenosis of the internal carotid artery of high degree or one-sided occlusion, it is important to determine the presence of retrograde collateral blood flow in the ophthalmic artery from the basin of the external carotid artery opposite to zero or normal. The picture of intracranial collateralization can be estimated by comparing the Doppler spectra from the arteries.

In bilateral occlusion of the internal carotid arteries, collateral blood flow proceeds from the vertebral artery system through an intact wilysian circle or through the orbital collaterals. In order to avoid erroneous interpretation, it is always necessary to examine all the main arteries of the vilizian circle that are available for dopplerography.

Increased blood flow can occur for other reasons than stenosis. For example, with anemia, there may be a functional increase in blood flow in the internal carotid artery, as shown in this patient with a hemoglobin level of only 6.2 g / l. Also, increased blood flow can occur with aneurysms, which can be detected using color duplex sonography at a size of more than 5-10 mm and location in accessible scanning locations.

Critical Assessment

Sleepy arteries, due to their superficial location and scanning capabilities with good resolution at high frequencies, are ideal for examining them with non-invasive color duplex sonography. To a certain extent, this also applies to the vertebral arteries. It is quite difficult to visualize using the color duplex sonography, the site of the left vertebral artery, often located at a sufficiently low level. A similar problem also exists in 4% of vertebral artery divergence from the aortic arch. An alternative non-invasive technique for studying excision of vertebral or carotid artery separation is MR angiography (MRA), which can be performed during the time-of-flight mode or with the administration of a contrast agent.

Another, more invasive, method is digital subtraction angiography. Its main advantages are the ability to determine slow blood flow in stenoses with a very narrow lumen and reveal lumens of small intracranial vessels. In this case, a small aneurysm is revealed. Digital subtraction angiography can also determine collaterals and venous drainage with the exclusion of venous sinus thrombosis.

In 15% of cases, the penetration of ultrasound in Doppler examination is so difficult (for example, with thick bones of the arch) that contrast preparations should be used.

[19], [20], [21], [22]

Where to make ultrasound of the brain?

Where to make ultrasound of the brain, an urgent issue for patients suffering from severe headaches, frequent dizziness and other pathological symptoms.

The main indications for ultrasound of the brain are: stroke, headaches of unknown origin, impaired coordination of movements, hypertension, obesity, diabetes mellitus, trauma and damage to the skull. The study does not need special training, but still it is worth noting the use of alcohol, strong tea or coffee, as this can lead to changes in tone.

Kiev:

• The network of medical clinics "Viva" - ul. Lavrukhina, 6, tel. [phone].
• Clinic "Olgerd" - boulevard of Academician Vernadsky, 36, tel. [phone].
• Clinic of efferent therapy of Dr. Chornomysa - ul. Popudrenko, 32, tel. [phone].
• Medical Center "Health Capital" - st. Mazepy, 6V, tel. [phone].
• Medical Center "Euroclinic" - st. Melnikova, 16, tel. [phone].

Moscow:

• National Medical and Diagnostic Center - ul. Skotoprogonnaya, 31, tel. [phone].
• Medical Center "Medisan" - st. Maroseika, 10/1.
• Clinic "Fizio-Med" - st. Bibirevskaya, 17B.
• An open clinic under the scientific supervision of V.I. Dikul - st. 1905, 7, tel. [phone].
• Medical Center "World of Health" - ul. Krasnodonskaya, 2A, tel. [phone].

St. Petersburg:

• ЦМРТ «Petrogradskiy» - ул. X-ray, 5, tel. [phone].
• AndroMed Clinic - ul. Ordinary, 21, tel. [phone].
• Ultrasound "21st century +" - Stachek Avenue, 37/211, tel. [phone].
• Medical Center "Longevity" - lane Krestyansky, 4, tel. [phone].
• Medical center "Rami" - st. Kirochnaya, 13, tel. [phone].