The technique of ultrasound dopplerography of vessels

No special preparation for ultrasound dopplerography is required. It is necessary that 2 h before the study the patient does not receive treatment that affects the condition of the vessels and physiotherapy.

The study of ultrasonic dopplerography of the vessels is carried out in the position of the patient on the back, better without a pillow. The doctor sits down next and first carefully examines the area of the face and neck. Particular attention is paid to identifying the presence, location and severity of increased pulsation in the projection of carotid arteries and jugular veins. Then the doctor carefully palpates all available segments of the carotid arteries: general carotid, bifurcations, branches of the external carotid arteries - facial in the angle of the lower jaw, superficial temporal - at the level of the ears of the ears. Preliminary auscultation of the projection of the common carotid artery, bifurcations, subclavian arteries and orbital arteries with omitted eyelids is prerequisite. It is more convenient to use the cone-shaped socket of the stethoscope. The presence of systolic murmur over the projection of the carotid and / or subclavian artery, as a rule, is characteristic of stenotic constriction. Whistling noise in orbit can sometimes be heard with a pronounced narrowing of the inner carotid artery siphon. After tentative palpation and auscultation, the sensor is lubricated with a contact gel, then the location of the extracranial segments of the carotid arteries, indicated by palpation, begins. The most important condition for the adequacy of diagnostic manipulation is an alternate study of symmetrical sites of extracranial vessels on the right and on the left. At first, there are difficulties in determining the force of pressing the sensor to the skin. It is important that the researcher's hand holding the probe does not hang without support - this position is inconvenient and interferes with obtaining a steady signal of blood flow, since there is no uniform and constant contact of the sensor with the skin. The forearm of the doctor should be free to lie on the patient's chest. This greatly simplifies the movement of the brush when the vessels are located and is especially important when the compression sample is adequately applied. Having accumulated a certain experience, the doctor catches the optimal position and pressing of the sensor to the skin, which allows to obtain the maximum sounding and pure arterial or venous signal by means of small changes in the angle of inclination of the sensor (the optimal angle is 45 °).

The study of the carotid system begins with the location of the common carotid artery at the inner edge of the sternocleidomastoid muscle in its lower third.

The 4 MHz sensor is positioned at an angle of 45 ° to the blood flow line in the vessel in the cranial direction. They trace the spectrum of the common carotid artery throughout its entire extent up to bifurcation. It should be noted that before bifurcation - just below the upper edge of the thyroid cartilage - usually a slight decrease in the linear velocity of the blood flow with a moderate spreading of the spectrum is associated with a small increase in the diameter of the carotid artery - the so-called bulb of the common carotid artery. In part of the observations, approximately in the same zone, but slightly medially, an arterial signal of medium amplitude having an opposite direction can be identified. This is recorded by the blood flow along the upper thyroid artery - the branch of the homolateral external carotid artery.

Above the bifurcation of the common carotid artery, the origins of the inner and outer carotid arteries are ground. It is important to emphasize that the place of the beginning of the carotid artery should be called precisely the "source", but not the "mouth" (the settled, but incorrect term). Since this is a flow of fluid (in this case blood), in these terms, of course, means an analogy with the river. But in this case, the initial or proximal segment of the internal carotid artery can in no way be called the mouth - this is the source, and the mouth should be called the distal carotid artery, at the point of its branching to the middle and anterior cerebral arteries.

When locating the post-bifurcation region, it should be borne in mind that the source of the internal carotid artery is often located posteriorly and lateral to the external carotid artery. Depending on the level of bifurcation, it is sometimes possible to further localize the internal carotid artery up to the angle of the lower jaw.

The internal carotid artery is characterized by a much higher rate of diastolic flow due to low circulatory resistance of intracranial vessels and normally has a characteristic "melodious" sound.

In contrast, the external carotid artery as a peripheral vessel with high circulatory resistance has a systolic peak that is clearly superior to diastole and a characteristic jerky and higher tone. Depending on the angle of divergence in the branches of the common carotid artery, signals from the inner and outer carotid arteries can be isolated both in isolation and overlapping one on another.

The location of blood flow along the branches of the orbital arteries (supratrochlear and supraorbital) is the most important part of ultrasonic dopplerography. According to a number of researchers, it is this component of the Doppler location that carries the basic information in the recognition of hemodynamically significant carotid stenoses. The sensor with the contact gel is carefully placed in the inner corner of the eye socket. Experience shows that with periorbital dubbing it is more convenient and safer for the patient to keep not the sensor housing, but the wires at its base. This allows you to more accurately dose the degree of pressing the head of the sensor to the orbit and minimize possible (especially for a beginner physician) pressure on the eyelid when compressing the common carotid artery. Slightly changing the degree of compression and tilt, they achieve obtaining the maximum amplitude of the pulsating arterial signal - this is a reflection of the blood flow along the supra-block artery. After spectroscopic evaluation, the direction of the flow is fixed: from the cavity of the skull - antegrade (orthograde, physiological); inside the orbit - retrograde; or bidirectional.

After symmetrical scoring of the opposite supratrochlear branch, the probe is placed slightly higher and lateral to register the flow on the supraorbital artery.

The locating of the vertebral artery is carried out at a point located just below and medial to the mastoid process. However, obtaining a pulsating arterial signal in this area does not yet guarantee the presence of the vertebral artery, since in the same zone the occipital artery (branch of the external carotid artery) is localized. Differentiation of said vessels is carried out on two grounds.

• Normally, the dopplerogram of the vertebral artery has a more pronounced diastolic component. The values of its systolo-diastolic components are approximately 2 times lower than that of the internal carotid artery, and the pattern of the pulsating curve more closely resembles trapezoidal complexes due to lower peripheral resistance. The nature of the spectrogram of the occipital artery is typical for the peripheral vessel - a high pointed systole and a low diastole.
• To distinguish the vertebral artery from the occipital helps a compression test with a 3-second pressure of the homolateral common carotid artery. If the registration of the signal from the sensor located in the projection of the proposed vertebral artery is stopped, then the vertebral column rather than the occipital artery is not losated. In this case, a small displacement of the sensor is necessary, and upon receipt of a new signal, repeat pressing of the common carotid artery. If the flow is still registered from the artery, then the operator has found the desired vertebral vessel.

To locate the subclavian artery, the sensor is positioned 0.5 cm below the clavicle. Varying the angle of inclination and the degree of compression, as a rule, a pulsating arterial complex with a characteristic for the peripheral vessel pattern - pronounced systole, low diastole and an element of "reverse" flow below the isoline.

After the initial examination of the main arteries of the head, a series of refining compression probes are performed, which indirectly determine the functioning of the collateral brain system, which are of crucial importance both in pathogenesis and in the sanagenesis of stenotic and occlusive lesions. There are several types of collaterals:

• extra-intracranial overflows:
  • anastomosis between the occipital artery (branch of the external carotid artery) and the cervical arteries (muscular branches of the vertebral artery);
  • connection between the upper thyroid artery (branch of the external carotid artery) and the lower thyroid artery (branch of the subclavian-vertebral artery);
• extra-intracerebral overflows - anastomosis between the supra-lateral artery (branch of the temporal artery that extends from the external carotid artery) and the orbital (branch of the internal carotid artery);
• intra-intracerebral overflows - along the connecting arteries of the Willis circle.

With stenosing and occlusive lesions of the internal carotid artery, more than 70% of the main collaterals are most often the following:

• homolateral external carotid artery (external carotid artery → temporal artery → superficial artery → orbital artery);
• contralateral internal carotid artery → flow through the anterior connective artery to the ischemic hemisphere
• flow on the posterior connective artery from the vertebral artery system.