What is a Doppler study? Indications of Doppler ultrasound during pregnancy. Dopplerography of cerebral vessels

Doppler study is an ultrasound technique that allows you to measure the speed and determine the direction of blood flow in the cavities of the heart and blood vessels. The method is based on the effect described by K. Doppler in 1842. Its essence is as follows: when an ultrasonic beam of a known frequency (fo) is sent to the heart, it is reflected from the blood cells. The frequency of the reflected ultrasonic beam (fr) is equal to the frequency of the sent beam (fo), if the reflection occurs from a stationary object.

This is only done when the child is suspected of being anemic, in cases where your child is suffering from Rh antibodies, or if your child is suffering from slap in the face. This test gives an idea of whether the baby's blood has sufficient oxygen carrying capacity or not and whether the baby requires any intervention such as blood transfusion.

What is cardiotocography or not a stress test?

Diagnosis of ductus venosus This is rarely done. In the first trimester, along with other tests, it gives an indication of chromosomal abnormality The child has. In the third trimester, it helps determine whether the baby is receiving adequate nutrition and oxygen. You can ask your doctor to listen to your baby's heartbeat on early stage, but it may make you anxious. This is because your baby's heartbeat may be difficult to find before 13 weeks.

Reflected ultrasonic beam frequency(fr) increases if blood cells move towards the ultrasound source and decreases when they move away from the ultrasound source. The difference in the frequencies of the sent and reflected beams (Af) is called the frequency shift of the ultrasonic signal or Doppler shift: Af=fr-fo.

Af depends on the frequency of the sent beam (fo), the speed of movement of the particles from which it is reflected (blood flow speed - V), the angle between the direction of the ultrasound beam and the direction of blood flow, the speed of propagation of ultrasound in the blood (1540 m/s), which is expressed by the Doppler equation: Af = 2fo x V x cos 9/c.

Dopplerography of cerebral vessels

If you can feel your baby moving regularly throughout the day, he will probably be fine. However, if your baby's movements slow down, it is very important to contact your doctor immediately. This is because doctors have other, less invasive monitoring options, which should be enough to care for you and your baby.

The reading can then be used as a baseline if hospital staff require it later in your labor. One of the main goals of routine prenatal care is to identify babies who are not thriving in the womb. It's possible that medical interventions may improve outcomes for these children if they can be identified. Doppler ultrasound uses sound waves to detect blood movement in vessels. It is used during pregnancy to study the circulation of the baby, uterus and placenta.

Thus, knowing Af, you can calculate the speed of blood cell movement: V = Af x c/2fo x cos 9.

If ultrasonic beam is parallel to the direction of blood flow, then angle 0 = 0, its cosine = 1. The cosine value of angle 0 less than 20° is also close to 1 (cosine of 20° = 0.94), so it can be neglected. If the direction of motion of an object is perpendicular to the direction of the emitted ultrasonic beam, then since the cosine of an angle of 90° is 0, such an equation cannot be calculated and the speed of the object cannot be determined. Therefore, for correct definition blood flow speed, the direction of the long axis of the sensor should be close to the direction of its flow (angle 9 should be< 20°).

Using it during pregnancy with high risk, when there are concerns about the child's condition, shows benefits. However, its value as a screening tool in all pregnancies must be assessed because of the potential for unnecessary interventions and adverse effects. there were no improvements identified for either the child or the mother, although more data will be needed to prove whether or not it is effective in improving outcomes.

Existing evidence does not provide convincing evidence that the use of routine Doppler ultrasound or a combination of Doppler ultrasound with a small or unselected population of the umbilical and uterine arteries benefits the mother or child. Future studies should be designed to address small changes in perinatal outcome and should focus on potentially preventable deaths.

IN echocardiography The following Doppler study options are most often used:
1) pulsed wave (PW);
2) continuous wave (CW);
3) color (color Doppler);
4) tissue (tissue velocity imaging - TVI, tissue myocardial imaging, Doppler tissue imaging).

Its main varieties:
tissue color (color tissue velocity imaging),
tissue nonlinear (C-mode),
pulsed wave tissue velocity imaging,
tissue trace (tissue tracking),
assessment of myocardial deformation and its speed (strain, strain rate),
vector analysis myocardial movements (vector velocity imaging - VVI).

Rationale for the Doppler method

One of the main goals of routine antenatal care is to identify fetuses at risk so that clinical interventions can be applied that can lead to a reduction in perinatal morbidity and mortality. Umbilical artery Doppler ultrasound is helpful in identifying compromised fetuses in high-risk pregnancies and therefore deserves evaluation as a screening test in low-risk pregnancies.

Assess the impact on obstetric practice and pregnancy outcomes of routine fetal and umbilical Doppler ultrasound in unselected and low-risk pregnancies. We searched the Cochrane Pregnancy and Childbirth Trials Register and reference lists of retrieved studies.

At pulsed Doppler study the same piezoelectric element of the sensor sends a series of pulses with a certain frequency and perceives signals reflected from moving blood cells. The advantage of the method is the possibility precise definition blood flow velocity in any selected area of the heart chamber or great vessel in which the control (test) volume is installed. At the same time, a graphical scan of the blood flow in the control volume area is recorded on the screen: time is plotted along the abscissa axis, and blood flow velocity is plotted along the ordinate axis.

Randomized and quasi-randomized controlled trials of Doppler ultrasound to investigate umbilical and fetal vascular signals in unselected pregnancies compared with Doppler ultrasound. Studies that assessed uterine vessels together with fetal and umbilical vessels were included.

Two review authors independently assessed studies for inclusion, assessed risk of bias, and performed data extraction. All trials had adequate retention of concealment, but none had sufficient blinding of participants, personnel, or outcome assessors. Overall, and apart from lack of blinding, the risk of bias for the included trials was considered low.

Streams that moving towards the sensor, are located above the isoline, the transmitter is located below it. Because the same piezoelectric element sends and receives ultrasound, the maximum frequency shift of the ultrasound signal that can be measured by pulse testing is half the frequency of the pulses sent, which is called the Nyquist limit. If the frequency shift of the ultrasound signal exceeds the Nyquist limit (at blood flow velocity > 2.5 m/s), distortion of the Doppler spectrum (aliasing) appears and part of it is recorded at the top or bottom of the opposite side of the isoline. That is, during a pulsed study, the Doppler shift is limited by the Nyquist limit and measurement of high blood flow velocities is impossible.

Overall, routine fetal and umbilical Doppler testing in low or unselected patients has not resulted in an increase in antenatal, obstetric, and neonatal interventions. There were no group differences noted for the primary outcome measures of perinatal and neonatal mortality. Only one of these included a study assessing serious neonatal morbidity and found no evidence of group differences.

For comparisons of Doppler assessment alone and Doppler assessment, evidence of group differences in perinatal mortality was found. However, these results are based on a single trial and we recommend caution when interpreting this finding.

At continuous wave Doppler study The sensor sends and receives reflected ultrasonic signals continuously using two separate piezoelectric elements. Therefore, the maximum recorded frequency shift of the ultrasonic signal is not limited by the frequency of the pulses sent, or the Nyquist limit. This allows high blood flow rates to be accurately measured. In contrast to the pulsed mode, with constant-wave Doppler examination, all frequency shifts of the ultrasonic signal (velocity) along the ultrasonic beam are measured. Therefore, the highest blood flow velocity along the ultrasound beam can be determined, but the location of the maximum measured velocity cannot be precisely determined.

There was no evidence of group differences in results caesarean section, techniques intensive care newborns or premature births less than 37 weeks. Evidence for stillbirth outcomes was rated according to patient subgroups—with a moderate quality rating for stillbirth and a low quality rating for stillbirth. The evidence for admission to the neonatal intensive care unit was rated as moderate quality, and data on outcomes of caesarean section and premature birth less than 37 weeks were assessed for quality.

In this regard, in the presence of laminar low-velocity intracardiac flows(normally) it is advisable to use a pulsed Doppler study; for turbulent high-speed flows (with stenosis, valve insufficiency, intracardiac blood discharge) - a constant-wave study.

Colored Doppler study is a variety pulse, when not one control volume is used, but many (250-500), forming a so-called raster, shaped like a truncated cone. In this case, in each control volume, the frequency shift of the ultrasonic signal is measured, which is converted into digital format, automatically compared to a given color scheme and displayed on the screen against the background of a two-dimensional image. If the blood flow velocity does not exceed the Nyquist limit, then the flow towards the sensor is usually coded in red, and away from the sensor - in blue and their shades.

There are no data available to assess the impact on long-term long-term outcomes such as child neurodevelopment, and no data are available to assess maternal outcomes, especially maternal satisfaction. Using a special ultrasonic method, called Doppler sonography, we measure and determine the speed and direction of blood flowing in arteries and veins. This gives us the opportunity to control the blood supply to certain organs and tissues important for the development of the unborn child. The flow of blood between the uterus and placenta, as well as between the fetus, is the human embryo after the formation of internal organs.

When the blood flow speed above this limit (with turbulence), the flow is coded in shades of green and yellow flowers. The advantages of the method are the ability to quickly assess blood flow in the chambers of the heart and main vessels, identification and semi-quantitative assessment of the degree of valve regurgitation, identification of intracardiac blood discharges.

The fetus and placenta can be assessed and assessed in this way. Like conventional ultrasound, Doppler sonography uses ultrasound as an imaging technique to study organic tissue. Doppler sonography is harmless to you and your baby.

In principle, we distinguish two coverage areas. The first area of care is the blood vessels that supply the uterus and placenta. The most important vessel is the umbilical artery, which indirectly shows how the baby is delivered through the placenta. With color Doppler sonography, vessels and vascular areas can be further stained. This is necessary, in particular, for the diagnosis of cardiac activity for an accurate statement. The exam is possible throughout pregnancy. . Doppler sonography uses ultrasound as an imaging technique to study organic tissue.

Tissue Doppler study- a type of Doppler study in which the movement of the myocardium, valves, valve rings or other tissues is recorded. When Doppler study of blood flow, the speed of movement of red blood cells is measured (more than 20 cm/s, reaching 800 cm/s in case of valvular pathology). The speed of myocardial movement is less (usually 5-20 cm/s), but its amplitude is greater than that of erythrocytes.

Doppler sonography is based on. Hypertension, preeclampsia - a disorder of high blood pressure during pregnancy, also known as pregnancy hypertension. The initial main symptom is the release of sugar in the urine. . Doppler ultrasound as a method of prenatal diagnosis.

Doppler ultrasound can monitor blood flow in the blood vessels of the unborn baby, uterus and placenta. As a result of Doppler ultrasound, conclusions can be drawn about the care of the child, as well as the functioning of internal organs. B. hearts are drawn.

At Doppler blood flow study the high-amplitude and low-speed (low-frequency) signal from the myocardium is considered noise and is removed by filters that pass only high-frequency signals (usually more than 400-500 Hz). In tissue Doppler examination, on the contrary, high blood flow velocities are cut off using filters and low myocardial velocities are recorded (frequencies 0-50 Hz).

Doppler ultrasound, also called Doppler sonography or duplex ultrasound, is a special form of ultrasound that can be used particularly in the second half of pregnancy. Doppler ultrasound scans specific blood vessels for the baby and mother, as well as the blood flow between the baby and the placenta, and gives the doctor answers to questions about whether the baby is adequately supplied nutrients and oxygen and such internal organs Like a child, the heart develops according to plan.

Tissue examination can be represented in color mode. In this case, as in the color study of blood flow, the average speed of movement is reflected. Red color indicates movement towards the sensor, blue - away from the sensor. Brighter shades correspond to more high speeds motion up to the Nyquist limit. The color tissue Doppler image is superimposed on the B- or M-mode image of the myocardium.

Doppler ultrasound uses the Doppler effect. The devices that are used for Doppler ultrasound use the so-called Doppler effect, expectant mothers may still be familiar with it from physics lessons. It is an acoustic phenomenon first described in this century by the Austrian Christian Johann Doppler. If the transmitter and receiver of an acoustic signal move away from or towards each other, the Doppler effect causes a widening or is recognized by the receiver due to a significant shift in the frequency of the signal.

Indications for Doppler ultrasound during pregnancy

An example from Everyday life for this is ambulance with a siren whose frequency audibly changes as soon as the car has passed and the noise goes away again. This effect is also used in Doppler ultrasound by radiation ultrasonic waves on solid components of blood using a transducer and makes the movement of blood visible based on reflections. Thus, both blood flow direction and velocity can be detected using Doppler ultrasound. They, in turn, provide information about the progress blood vessels, their diameter, as well as the condition of the inside of the vessel.

The advantages of the method are opportunity rapid assessment of myocardial movement, including in the subepicardial and subendocardial layers, as well as the possibility of simultaneous recording of the speed of movement of various myocardial segments and delayed assessment of the movement of individual segments. This method allows you to detect areas of local contractility disturbance and clarify the endocardial border if it is poorly visualized in B-mode. The main limitation of this method is the possibility of overestimating or underestimating velocities due to intraventricular block causing paradoxical motion of the heart walls, due to the Nyquist limit, and also due to complex mechanism heart contractions.

Doppler ultrasound is mainly used in the second half of pregnancy. In principle, examination with Doppler ultrasound is possible throughout pregnancy. However, this is mainly done in the second half of pregnancy, because at this time the development of the child can already be assessed well. Because Doppler ultrasound is not a standard precaution during pregnancy, it is initiated by the treating physician. This is especially true in cases where anomalies were detected during regular ultrasound, or a pregnancy condition makes it more likely organic disease or fetal malnutrition - for example, if there is multiple pregnancy, the mother smokes during pregnancy or alone A high blood pressure disorder or blood type intolerance between mother and child has been detected.

Tissue nonlinear(C-mode) - color graphic image of movement interventricular septum, apex and lateral wall of the left ventricle in time. The advantage is the possibility of detailed assessment of the direction of movement of the heart walls in different zones and identification of local contractility disorders. A limitation is intraventricular block, which causes paradoxical movement of the heart walls and complicates diagnosis.

Tissue pulsed Doppler examination(pulsed wave tissue velocity imaging) - a graphical representation of the movement of heart structures in the control volume area: time is plotted along the abscissa axis, and the speed of movement of heart structures is plotted along the ordinate axis. In this case, systolic (Sm), early (Em) and late diastolic (Am - corresponds to atrial systole) components of movement are distinguished. The diastolic movement of the myocardium is shaped like an inverted image of transmitral blood flow, so the peaks are named similarly, but using the subscript m (Em, Am), apostrophe (EA) or lowercase letters(e, a).

Between end of systolic movement and the beginning of the movement corresponding to early (fast) relaxation of the myocardium, the time of isovolumic relaxation of the left ventricle (IVRT) is recorded; between the end of the late diastolic component and the beginning of the systolic component, the time of isovolumic contraction of the myocardium (IVCT) is recorded. The nature of the movement of the fibrous ring mitral valve used to identify and determine the type of left ventricular diastolic dysfunction.

Doppler measures how sound waves bounce off moving objects. The computer processes the information and creates a two-dimensional color image that shows whether there is any obstruction in the blood flow, such as due to cholesterol deposits – atherosclerotic plaques.
Modern devices with continuous wave, pulsed wave and color Doppler combine the information obtained from all these types of studies. In B-mode it is possible to see the structure vascular wall. Doppler shows how blood flows through the vessels and measures the speed of blood flow. Doppler ultrasound can also be helpful in determining the diameter of the vessel, as well as the amount of stenosis (blockage) in the blood vessel.

Traditional ultrasound uses painless sound waves that are inaudible human ear, which are reflected from the vessels. Duplex ultrasound can use images that are color coded to show the doctor where blood flow is severely blocked, as well as the speed and direction of blood flow. Your doctor may recommend Doppler to help diagnose or investigate conditions that affect the blood vessels. These conditions include:

Atherosclerosis of the carotid arteries
Vein thrombosis of the lower and upper extremities
Diseases of the arteries of the legs
Diseases of the arteries of the hands
Aortoiliac occlusive diseases
Varicose veins
Aneurysms of large vessels of the abdominal cavity or extremities

Doppler duration (USD)

Doppler ultrasound usually lasts 20-60 minutes. Duplex ultrasound does not require the administration of special drugs and is usually associated with minimal discomfort.

How to prepare for Doppler?

For most types of Doppler ultrasound not related to abdominal cavity, no special training required. Your doctor ordering the test may give special instructions for a specific type of Doppler. For example, you will not have to eat the night before the test. Ultrasound cannot pass through gas in the intestines or air in the lungs.

What happens during Doppler?

Before the examination, the doctor will ask you to lie on the table with your head slightly elevated. The gel is then applied over the area to be examined. The gel improves the transmission of ultrasonic waves.
The doctor presses the sensor to the skin and begins to move it. The pressure from the ultrasound transducer may cause some discomfort, but most people do not find the procedure painful. The ultrasound sensor sends signals to the computer, which the computer converts into images that are displayed on a monitor similar to a television. You may hear a whistling sound, which is the sound the ultrasound machine uses to map the movement of blood in your body.

What to expect after Doppler ultrasound (Duplex ultrasound)?

Dopplerography of cerebral vessels

Transcranial Doppler (another name Doppler ultrasound cerebral vessels) began to be used in medicine in 1983. Doppler of cerebral vessels is used to assess blood flow (blood circulation in the vessels of the brain), - this is a complex study, the effectiveness of which depends not only on the experience and knowledge of the doctor performing Doppler ultrasound, but also on the acoustic window (thickness and structure temporal bone, through which the research is conducted). Cerebral vascular Doppler is used to evaluate:

Risk of violations cerebral circulation– stroke
Vascular spasm of the brain
After operation coronary artery bypass surgery(to assess the risk of embolism in cerebral vessels)
In neurosurgical patients
Anomalies of cerebral vascular development

In some cases, neurologists prescribe transcranial Doppler for:

Migraine
Vegetative-vascular dystonia
Dizziness
Headaches of unknown origin

Dopplerography of neck vessels

Doppler of neck vessels allows identifying diseases of the carotid and vertebral arteries. Doppler sonography is usually prescribed by a neurologist. Doppler (Doppler or Duplex ultrasound) is indicated for the following symptoms:

A picture of transient ischemic attacks with temporary paralysis of half the body or arm (hemiparesis), speech impairment, etc.);
Temporary blindness in one eye;
Noise in the head;
Dizziness;
Flashing before the eyes;
Headaches without clear localization;
Short-term loss of consciousness;
Falls without loss of consciousness;
Temporary imbalances;
Migraine or migraine-like headaches
Detection of atherosclerotic plaques in other vessels

Dopplerography of blood vessels lower limbs

Doppler ( Duplex scanning) vessels of the lower extremities allows you to identify diseases of the arteries and veins of the lower extremities. Lower extremity Doppler is prescribed vascular surgeon. Doppler is performed for the following symptoms and diseases:

Diseases of the arteries of the lower extremities
Intermittent claudication (pain in calf muscles which appear when walking and disappear after a short rest)
Chilliness, increased sensitivity feet to the cold
Feeling of numbness in the feet
Diseases of the veins of the lower extremities
Heavy legs
Swelling of the legs
Skin pigmentation on the legs

The attending doctor determines which vessels the patient needs to examine.