RU2584135C1 - Method for determining homogeneity of atherosclerotic plaque structure - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to functional diagnosis in cardiology, and can be used to evaluate homogeneity of structure of atherosclerotic plaque in carotid arteries or other large and medium-presence in patients with atherosclerotic lesions of arteries. Series of sequenced ultrasonic image frames of an atherosclerotic plaque in a longitudinal section of an artery over one cardiac cycle is obtained. Performing contouring of base and surface of plaque on one of initial training and selection by contour lines of three segments - distal, proximal and central. Estimating motion parameters assigned plaque surface segments relative to base period of cardiac cycle by determining tangential velocity plaques segment motion and/or speed changes of shear deformation segment plaques followed by plotting measured speeds from time. When a segment of collinear curves of plaque is obtained, conclude a homogeneous structure of plaque.

EFFECT: method enhances diagnostic accuracy due to objectification of interpretation of information received on surface of plaque motion relative to its base.

6 cl, 14 dwg, 4 tbl, 1 ex

Description

The invention relates to medicine, namely, functional diagnostics in cardiology, and can be used to assess the uniformity of the structure of atherosclerotic plaque in the carotid (or other arteries of large and medium caliber) in patients with atherosclerotic lesions of arteries using ultrasound methods.

Ultrasound examination is a non-invasive, highly informative, inexpensive, widely used in clinical practice method that allows you to determine the localization, structure, size, shape and complications of atherosclerotic plaques, the severity of atherosclerotic lesions of the arteries of the carotid pool (V. Zwibel, J. Pellerito. Ultrasound examination of blood vessels . - M .: Vidar, 2008, p. 159-171).

The determination of the structure of atherosclerotic plaque in the carotid artery is based on plaque classifications proposed in 1983 by Reilly L.M. et al. (Reilly LM, Lusby RJ, Hughes L. et al. Carotid plaque histology using real-time ultrasonography: clinical and therapeutic implication. Am. J. Surg. 1983; 146 (2): 188-193), then amended in 1988 Gray-Weale A.C. et al. According to the classification of atherosclerotic plaques proposed by Gray-Weale A.S. et al., In B-mode ultrasound investigation, atherosclerotic plaques are distinguished: homogeneous of reduced echogenicity, heterogeneous with a predominance of hypoechogenic components, heterogeneous with a predominance of hyperechoic components, homogeneous hyperechoic (with and without it) (Gray-Weale A.C., Graham JC, Burnett JR et al. Carotid artery ateroma: comparison of preoperative B-mode ultrasound appearance with carotid endarterectomy specimen pathology. J. Cardiovasc. Surg. 1988; 29 (6 ): 676-681). The determination of the uniformity of the plaque structure during ultrasound examination in the B-mode is based on the determination of echogenicity and uniformity of the plaque, which is operator-dependent.

Atherosclerotic plaques having a heterogeneous structure (or heterogeneous plaques) largely determine the poor prognosis of patients with carotid atherosclerosis. There is a correlation between the heterogeneity of plaques and the development of symptoms of cerebrovascular insufficiency, according to which most heterogeneous plaques are symptomatic. According to numerous studies, the presence of a heterogeneous atherosclerotic plaque in the carotid artery is an independent predictor of cardiovascular events (death, myocardial infarction, stroke). Determining the uniformity of the structure of an atherosclerotic plaque using well-known non-invasive technologies, new ultrasound modes, as well as finding new ultrasonic criteria for the uniformity of the plaque structure is a very important task.

The prior art method for determining the structure of atherosclerotic plaque in the carotid artery according to complex ultrasound and histological studies (I.E. Timina, E.A. Burtseva, N.D. Skuba, A.V. Pokrovsky, G.I. Kuntsevich. Comparison of the structure of atherosclerotic plaque in the carotid artery according to complex ultrasound and histological studies. Ultrasound and functional diagnostics, No. 3, 2004, pp. 81-87). The study of atherosclerotic plaques was performed using ultrasonic B-mode, tissue harmonic mode, Nedopplerovnoy visualization of blood flow, homogeneous (anechogenic, medium, high echogenicity) and heterogeneous plaques were isolated. The authors found that homogeneous (according to ultrasound data) plaques according to the histological structure are fibrous plaques with calcium inclusions, with the deposition of cholesterol crystals and foci of hyalinosis. While heterogeneous plaques had parietal thrombosis, atheromatosis, intra-plaque hemorrhage, and fresh thrombosis. Analyzing the information content of various modes in the diagnosis of plaque structure, along with the B-mode, the authors noted the important role of the Nedoppler blood flow imaging mode in assessing fresh blood clot and plaque integrity; tissue harmonic regime in the detection of hypo- and anechogenic zones in the thickness of the plaque. However, even when using the new modes, the authors did not find additional ultrasonic criteria in the interpretation of hypo- and anechogenic zones that form an inhomogeneous plaque.

The prior art method for determining the structure of atherosclerotic plaques in the coronary artery using the method of intravascular ultrasound (IVUS) with "virtual histology" (Nair A., Kuban BD, Tuzcu EM, Schoenhagen P., Nissen SE, Vince DG Coronary plaque classification with intravascular ultrasound radiofrequency data analysis. Circulation 2002, 106: 2200-2206). The method is based on a spectral analysis of the radio-frequency characteristics of the reflected ultrasound signal obtained during the standard IVUS. To form a detailed image of an atherosclerotic plaque, not only the amplitude of the reflected ultrasound signal is used (as with the usual IVUS in the gray scale), but also the frequency of the reflected wave; these parameters are processed using autoregressive models; information is analyzed according to the classification; after which an atheroma image is formed with the determination of the composition of the plaque. IVUS with "virtual histology" allows you to identify four main components of the plaque: fibrous component (dark green color), fibrous lipid component (light green color), necrotic component (red color), calcification sites (white color). However, the IVUS method is an invasive, expensive study performed in specialized cardiological hospitals. "Virtual histology" is a post-processing technique for intracoronary ultrasound examination and is not used for large and medium caliber arteries.

A quantitative method is known for determining the uniformity of the structure of an atherosclerotic plaque using the gray scale median or GSM (gray scale median) (M.M. Sabetai, TJ Tegos, AN Nicolaides, S. Dhanjil, GJ Pare and JM Stevens Reproducibility of Computer-Quantified Carotid Plaque Echogenicity: Can We Overcome the Subjectivity? Stroke. 2000; 31: 2189-2196). Images of atherosclerotic plaques obtained using a standard gray-scale ultrasound study are subjected to subsequent computer processing. The technique consists in quantifying the intensity (or echogenicity) of an atherosclerotic plaque. In this case, reference zones, such as the lumen of the vessel (which corresponds to the value of GSM 0-5) and its adventitious layer (GSM 185-195), are selected on the image, the image is normalized, then the echogenicity of the plaque is evaluated. By the ratio of sites with low (GSM <50) or high (GSM> 50) echogenicity, we can judge the uniformity of the atherosclerotic plaque.

Closest to the proposed is a method for determining the structure of an atherosclerotic plaque using ultrasonic compression elastography (A.R. Zubarev, I.V. Rychkova, M. B. Saratov, A.K. Demidova, E.L. Tumanova, V.N. Fedorova, V.Ya. Panko, N.V. Krivosheeva, Possibilities of ultrasound elastography for diagnosing the structure of atherosclerotic plaques of the carotid arteries. Pilot study. Medical imaging, 2011, 3, pp. 89-97). Ultrasonic compression elastography is a method for determining the mechanical properties of various tissues (thyroid, mammary, prostate, liver, etc.), which can also be used to study atherosclerotic plaques in the carotid artery. The method consists in evaluating a varying degree of tissue displacement depending on its stiffness in response to external pressure. Tissue deformation during compression elastography is formed by the operator during rhythmic manual compression by the sensor. As a result, when plaque is visualized in the elastography mode, softer plaque sections are colored green in response to the compression effect compared to denser areas with a blue color. The authors compared data from standard ultrasound, ultrasound elastography, and histological examination of plaques after carotid endarterectomy. It was found that thinning of the plaque tire, macrophage infiltration, hemorrhage in the thickness of the plaque, and areas of inflammation corresponded to the B-mode hypoechoic structure of the plaque and were stained green or red according to ultrasound elastography. Sections of necrosis, lipid and fibrous component, calcification were stained blue, which corresponded to the hypo- and hyperechoic structure of the plaque according to B-mode. It should be noted that this method is operator-dependent, since tissue deformation is created by the operator during manual compression using a sensor, has low repeatability and reproducibility of the resulting images, images contain many artifacts. To obtain well reproducible images in ultrasonic elastography mode, an experienced operator who has undergone lengthy training is required. Quantitative measurements completely depend on the quality of the image obtained in the elastography mode, which in turn leads to poor reproducibility of quantitative measurements of the compressibility of the studied tissues.

The inventive method has good repeatability seroscale patterns in the B-mode and the resulting curve parameters characterizing the mobility of the atherosclerotic plaque, in contrast to the prototype, characterized by poor reproducibility of obtaining elastographic patterns. The choice of three plaque surface segments for tracking the motion curves of these segments allows a more complete description of the plaque by considering the movement of the plaque surface relative to the base of the plaque, as well as plaque segments relative to each other, in contrast to the prototype, where the image of the plaque as a whole is analyzed. Obtaining seroscale plaque images in real time does not depend on the operator, which allows further analysis of the plaque movement using post-processing on a workstation, in contrast to the prototype, where an experienced research operator is required to obtain high-quality elastographic plaque images. The parameters are measured - the tangential velocity of the plaque segments, the shear strain and the rate of change of the shear deformation of the plaque segments, which characterize the longitudinal displacement of the plaque or its segments relative to the base, which plays an important role in detecting plaque destabilization.

The task is to develop a new method for assessing the uniformity of the structure of an atherosclerotic plaque using a new set of parameters characterizing the displacement of the contours of the selected segments of the surface of the atherosclerotic plaque relative to its base over the period of the cardiac cycle.

The technical result is achieved by increasing the accuracy of diagnostics by increasing the objectivity of the interpretation of the information obtained according to the results of the studies. A traditional ultrasound study of the structure of a plaque by its echogenicity is an instrumental method in which each operator interprets the result in his own way. The inventive method for determining the uniformity of the plaque structure objectifies the data, thereby increasing the accuracy of the diagnosis.

In addition, the set of parameters used in the claimed method allows monitoring the changes in the mobility of the plaque and its segments in dynamics.

In addition, the inventive method expands the arsenal of known tools used to study atherosclerotic plaques.

The problem is solved in that the method for determining the uniformity of the structure of the atherosclerotic plaque located in the artery includes the following sequence of actions:

- obtaining a series of successive frames of an ultrasound image of an atherosclerotic plaque in a longitudinal section of an artery during one cardiac cycle,

- processing an ultrasound image of an atherosclerotic plaque, as a result of which the base and surface of the plaque are contoured on one of the initial frames of the cardiac cycle and the selection on the contour line of at least three segments - distal, proximal and central,

- subsequent measurement of the motion parameters of the contours of the selected segments of the plaque surface relative to the base for the period of the cardiac cycle and obtaining the curves of the tangential velocity of the plaque segment, the shear deformation of the plaque segment, the rate of change of the shear deformation of the plaque segment, the relative position of which determines the uniformity of the plaque structure.

The listed parameters of the movement of the contours of the selected segments of the plaque surface (the tangential velocity of the movement of the plaque segment, the shear deformation of the plaque segment, the rate of change of the shear deformation of the plaque segment) are measured for each segment of the plaque and graphs of the measured values versus time from frame to frame are plotted from the measured values of the listed parameters the period of the cardiac cycle, while the uniformity of the plaque structure is examined by the relative position of the movement curves of the plaque segments. In this case, the tangential velocity of the plaque segment is determined as the projection of the velocity vector of the center of mass of the contour of the surface of the plaque on the X axis, which is determined by the direction of the base contour, while assessing the minimum and maximum values of speed per cycle; the shear deformation of the plaque segment is calculated by the ratio of the displacement of the center of mass point of the contour of the plaque surface segment in the tangential direction (dX) to the height of the plaque (N); the rate of change of the shear deformation of the plaque segment is determined as the first derivative of the shear strain of the plaque segment with respect to time.

Single-frame ultrasound images of an atherosclerotic plaque can be obtained using an ultrasound device configured to save the resulting image in DICOM format. Ultrasound image processing can be carried out using a workstation - MultiVox computer. In this case, tracking the change in the position of the selected segments of the contour lines in ultrasound images is carried out according to an algorithm based on the technology for tracking speckles of ultrasound images.

The invention is illustrated by drawings, where in FIG. 1 shows an image of an atherosclerotic plaque in an artery: red (1), orange (2) and yellow (3) lines indicate the surface of three segments of the plaque; the blue line (4) marks the base of the plaque; in Fig 2. presents an example of the selection of a coordinate system attached to the base of the plaque; in FIG. 3 shows a diagram for determining the displacement of the center of mass of the contour of the plaque surface Δx as the projection of the displacement of a point from frame to frame on the X axis; in FIG. 4 is a diagram for determining plaque height as the distance between the centers of mass of the contours of the base and surface of the plaque; in FIG. 5 is a graph of the tangential velocity of plaque segments; in FIG. 6 is a graph of shear deformation of plaque segments; in FIG. 7 is an example of a graph of the rate of change of shear deformation of plaque segments; in FIG. 8 shows co-directional curves of the tangential velocity of the plaque segments and the rate of change of the shear deformation of the plaque segments; in FIG. 9 shows multidirectional curves of the tangential velocity of the plaque segments and the rate of change of the shear deformation of the plaque segments; in FIG. 10 is an image of the station desktop in the "Plaque Movement" mode; in FIG. 11 - an example of a table with quantitative indicators of the movement of the plaque displayed on the screen of the MultiVox workstation; in FIG. 12 is an image of a “uniform” atherosclerotic plaque processed in the “Plaque Movement” mode; FIG. 13 shows an image of a “heterogeneous” atherosclerotic plaque in the “Plaque Movement” mode.

The red (1), orange (2), and yellow (3) curves in the figures correspond to three plaque segments — distal, middle, and proximal, while the proximal portion of the plaque is considered to be the site closest to the vessel, where the distal is the site farthest from place of departure of the vessel, middle - the area located between the proximal and distal.

The method is as follows.

The study of the patient is carried out in a supine position after a 10-minute rest.

An ultrasound duplex scan of the carotid artery is performed in B-mode according to the standard protocol on an ultrasound system equipped with a linear sensor with a frequency of at least 7.0 MHz, an ECG synchronization module and the ability to save the received images in the DICOM format (used to store and process medical images in world practice).

An atherosclerotic plaque is considered to be a structure protruding into the lumen of the artery by 0.5 mm or 50% of the surrounding thickness of the intima-media complex of the artery, or a structure with an increase in TIM of more than 1.5 mm (Touboul PJ et al. Mannheim Carotid Intima-media thickness and Plaque Consensus (2004-2006-2011). Cerebrovasc Dis 2012; 34: 290-296).

In the process of ultrasound scanning, a series of single-frame ultrasound images of an atherosclerotic plaque in an artery is visualized in B mode in a longitudinal section of the vessel within one or more cardiac cycles. Image recording frequency is 50 Hz and higher. Real-time images of an atherosclerotic plaque in the presence of synchronization with an ECG are stored in the memory of the ultrasound system. Then a series of ultrasound images in the DICOM format is stored on any medium (for example, a DVD-ROM or a flash card) to enable their analytical processing using a personal computer.

Moreover, for analytical processing, two contours are interactively distinguished on one of the initial images of the series — the base of the plaque and its surface, each of which can be divided into one or more segments. Optimal for obtaining a reliable result is the use of three selected plaque segments - distal (A1), middle (A2) and proximal (A3).

The contour is a set of points, the distance between which is 0.5 mm. In this case, the contours are distinguished only in one image, on the remaining images the contour points are determined by the method of tracking the speckles of ultrasonic images. At each tracking stage, the contour is smoothed by a Gaussian filter so that the contour points do not shift significantly relative to each other in noisy sections of ultrasound images. An image of an atherosclerotic plaque in an artery is shown in FIG. 1, where red (1), orange (2) and yellow (3) lines indicate the surface of three plaque segments; the blue line (4) marks the base of the plaque.

The base contour defines a coordinate system relative to which the movement of the surface contour of the plaque is considered. Using the least squares method, the coordinate system is determined along the contour of the base of the plaque so that the contour lies in the best way on the X axis of the Cartesian coordinate system. The origin of the system’s coordinates is associated with the center of mass of the contour (Fig. 2), which is calculated as the arithmetic mean of the coordinates of the contour:

where N is the number of points, C _o are the coordinates of the point of the center of mass of the base contour of the plaque.

The coordinate system is determined on each frame of a series of ultrasound images. The movement of the contour of the surface of the plaque is considered as the movement of the center of mass of the contour of the surface of the plaque relative to the coordinate system C _o .

The method proposes to use the following set of parameters of the motion of the plaque contour:

- Δx is the displacement of the contour along the X axis, the determination circuit of which is clearly shown in FIG. 3 (as the projection of the displacement of a point from frame to frame on the X axis). This value is used only to calculate the following indicators;

- тангенциальная скорость движения контура поверхности бляшки;-

- tangential velocity of the surface contour of the plaque;

- сдвиговая деформация бляшки;-

- shear deformation of the plaque;

- скорость изменения сдвиговой деформации бляшки;-

- the rate of change of the shear deformation of the plaque;

where t is the time between frames in a series of ultrasound images, and the value H - corresponds to the height of the plaque and is determined by the distance between the centers of mass of the contour of the surface of the plaque and the base contour (Fig. 4).

Since each value is calculated on each image of the series, it becomes possible to construct graphs of the curves of the change in these values over time (see Fig. 5-7). Moreover, in FIG. 5. shows an example of a graph of the tangential velocity of the plaque segments, FIG. 6. - an example of a graph of shear deformation of plaque segments; in FIG. 7. - an example of a graph of the rate of change of shear deformation of plaque segments.

A qualitative analysis of the movement of an atherosclerotic plaque is based on the study of the multidirectionality of the curves of the tangential velocity of the plaque segments (or the rate of change of the shear deformation of the plaque segments). Three plaque segments can move synchronously relative to the vessel wall, then we talk about the co-directionality of the motion curves of the plaque segments (Fig. 8.) or can move asynchronously, then we talk about the multidirectionality of the motion curves of the plaque segments (Fig. 9). Considering that the curve of the rate of change of the shear deformation of the plaque segments qualitatively coincides with the curve of the tangential velocity of the plaque segments, but quantitatively takes into account the size of the plaque, we can talk about the parameter "multidirectional curves of movement of the plaque segments."

Thus, the proposed method for determining the uniformity of the structure of an atherosclerotic plaque includes the following indicators:

1. The tangential velocity of the plaque segments, which is defined as the projection of the velocity vector of the center of mass of the contour of the surface of the plaque on the X axis, which is determined by the direction of the base contour, while assessing the minimum and maximum values of speed per cycle.

2. The relative shear deformation of the plaque segments, which is calculated from the ratio of the displacement of the center of mass point of the contour of the plaque surface segment in the tangential direction (dX) to the plaque height (H).

3. The rate of change of the shear deformation of the plaque segment, which is defined as the first derivative of the shear deformation of the plaque segment with respect to time.

4. Omnidirectionality of the motion curves of plaque segments.

The implementation of the proposed method for determining the mobility of an atherosclerotic plaque was tested using an expert-grade ultrasonic system Philips IU 22, equipped with a linear sensor with a frequency of 7-12 MHz, an integrated ECG module, and a workstation - MultiVox computer. In this case, the claimed technology was implemented in software. The MultiVox workstation is an original domestic development of the Laboratory of Medical Computer Systems of the Research Institute of Nuclear Physics, Moscow State University M.V. Lomonosov (registration certificate of the Federal Service for Supervision of Health and Social Development FS00262006 / 4783-06). The computer software module makes it possible to take measurements, see a graphical representation of the obtained curves, save and load measurements in the database of the MultiVox workstation.

In FIG. Figure 10 shows the desktop image taken from the MultiVox workstation monitor in the "Plaque Movement" mode, which contains an ultrasound image (in the center of the screen), graphs of the analyzed parameters (on the right of the screen), a series of instrumental virtual keys for processing the ultrasound image (on the left of the screen ), at the bottom of the screen there is a tab with the image of this patient indicating the name, age, card number, date of visit, visit history, image modality. In FIG. Figure 11 shows the table from the MultiVox workstation’s desktop, which contains the values of the measured angular momentum of the plaque maximum (Rot max) and minimum (Rot min), the tangential velocity of the plaque maximum (TVel max) and minimum (TVel min), shear deformation of the maximum plaque (ShDef max) and minimum (ShDef min), the rate of change in the shear deformation of the plaque maximum (ShDefSpeed max) and minimum (ShDefSpeed min) for three plaque segments (A1 - distal, A2 - middle, A3 - proximal) and averaged values over three segme there (Am).

In FIG. 12 is an image of a “homogeneous” atherosclerotic plaque in the carotid artery processed at the MultiVox workstation in the “Plaque Movement” mode; FIG. 13 shows an image of a “heterogeneous” atherosclerotic plaque in the carotid artery processed at the MultiVox workstation in the “Plaque movement” mode.

The development of the proposed method for assessing the uniformity of the structure of an atherosclerotic plaque was carried out on the basis of a study of the mobility parameters of an atherosclerotic plaque in groups of patients with acute coronary syndrome (ACS) and coronary heart disease (CHD).

We examined 35 patients with ACS hospitalized in the Department of Emergency Cardiology of the IKK them. A.L. Myasnikov RKNPK Ministry of Health of the Russian Federation, 23 patients with chronic coronary artery disease. The inclusion of patients with chronic coronary artery disease was carried out on the basis of the clinical departments of the IKK them. A.L. Myasnikov RKNPK Ministry of Health of the Russian Federation.

Criteria for inclusion in the ACS group: the presence of myocardial infarction and / or unstable angina no later than 3-5 days before inclusion in the study; men and women over 18 years old; patient consent for examination.

Exclusion criteria: cardiogenic shock; recurrent heart rhythm disturbances of high gradations; myocardial rupture; severe concomitant diseases: chronic renal (creatinine> 200 μmol / l) and / or liver failure (ALT> 200 IU / l, malignant neoplasms, etc.).

In the group of chronic ischemic heart disease, the diagnosis was confirmed on the basis of clinical data, identification of objective signs of ischemia (ECG monitoring, stress tests, isotope studies) or when hemodynamically significant stenosis of coronary arteries was detected according to coronarography.

The clinical characteristics of patients with ACS / CHD are presented in table 1.

Groups of patients with ACS and chronic coronary artery disease were comparable by sex, age, body mass index, history of arterial hypertension, diabetes mellitus, biochemical parameters (TG, LDL cholesterol, HDL cholesterol, glucose) and blood pressure levels. Smokers predominated in the ACS group, which was significantly different from the chronic coronary heart disease group, the level of total cholesterol was significantly higher in the ACS group compared with coronary heart disease.

All patients underwent ultrasound duplex scanning of the extracranial section of the brachiocephalic arteries on the PHILIPS IU22 ultrasound system with recording of the atherosclerotic plaque image in OCA / ICA in B-mode in real time with synchronization of the image with ECG, with saving in DICOM format for subsequent computer processing at the workstation MultiVox and obtaining the motion parameters of an atherosclerotic plaque. The presence of atherosclerotic plaques (ASB) in the following arterial segments was assessed: common carotid artery along the course (OCA), bifurcation area of the OCA, internal carotid artery (ICA) on the right and left (a total of 6 segments). According to the criteria of ultrasound research in B-mode (gray scale), plaques of various structures were distinguished: homogeneous (uniform) ASB - atherosclerotic plaques, mostly of the same echogenicity, heterogeneous (heterogeneous) ASB - atherosclerotic plaques with areas of different echogenicity.

A total of 94 ASB were detected in patients with ACS, 50 ASB in patients with stable coronary artery disease. The study material of the parameters of the movement of the plaque were 119 atherosclerotic plaques OCA / ICA in real time (B-mode) with synchronization with ECG. 25 atherosclerotic plaques were excluded from the analysis of the parameters of plaque mobility, as they had a small percentage of vessel stenosis (20–25%), which did not allow obtaining well reproducible curves of the movement of plaque segments and their qualitative analysis.

So, 87 out of 119 plaques were heterogeneous (heterogeneous) according to ultrasonic duplex scanning, which amounted to 73.1%; 32 of 119 plaques were homogeneous (homogeneous), which amounted to 26.9% (Table 1). In the group of patients with ACS, 79.7% were heterogeneous, 20.3% were homogeneous; in the group of patients with coronary heart disease, 62.2% were heterogeneous, 37.8% were homogeneous.

When assessing the mobility of a plaque during the passage of a pulse wave, a set of parameters was considered, including the relative expansion of the vessel, the normal deformation of the plaque, the deviation of the internal normal distribution of the plaque, the tangential velocity of the plaque, the angular momentum of the plaque, the shear deformation and the rate of shear deformation of the plaque. To determine the uniformity of the structure of the atherosclerotic plaque, we performed a qualitative analysis of the curves of two parameters — the tangential velocity of the plaque and the rate of change of the shear deformation of the plaque.

The analyzed parameters of ASB movement were considered for three plaque sites - A1 (distal plaque site), A2 (middle plaque site), A3 (proximal plaque site). The codirectionality and / or multidirectionality of the tangential velocity (and / or shear strain rate) curves of three plaque segments (Al, A2, and A3) were evaluated.

According to the results of a study of 119 plaques, it was found that heterogeneous (heterogeneous) ASBs in the studied groups of patients had predominantly multidirectional motion curves, homogeneous (homogeneous) ASBs had co-directional motion curves. According to the analysis of the movement curves of the plaque, 76 out of 119 atherosclerotic plaques had multidirectional motion curves, which amounted to 63.9%; 43 of 119 plaques had co-directional motion curves, which amounted to 36.1%.

In the group of patients with ACS, heterogeneous plaques had mainly multidirectional curves of movement of the plaque segments, the frequency of the sign of “multidirectional motion curves” was 76.3%; in the group of patients with coronary heart disease - 85.7%; in the general group of patients - 79.3% (see table. 3). Homogeneous plaques had predominantly unidirectional plaque segment motion curves; the frequency of “multidirectional plaque motion curves” in the subgroup of homogeneous ASB in patients with ACS was 20%, in patients with coronary artery disease 23.5%, in the group as a whole, 21.9%. When analyzing the contingency of signs, significant differences were revealed between heterogeneous and homogeneous ASB in all groups of patients (Table 3).

In the general group, a noticeable statistically significant correlation of the sign of multidirectionality / unidirectionality of the motion curves and the structure of the atherosclerotic plaque was revealed (correlation coefficient r = 0.53, p <0.000001, table 4). In the group of patients with ACS, the correlation coefficient was 0.47 (p <0.0002), the most noticeable correlation was found in the group of patients with coronary artery disease (r = 0.62, p <0.00005).

The obtained correlation dependences and analysis of the occurrence of “multidirectional plaque motion curves” in the subgroups of heterogeneous and homogeneous ASB indicate a close relationship between the sign of multidirectional plaque motion curves and the heterogeneity of its structure.

When checking the feasibility of the proposed method, a statistical analysis of the data was carried out using the program Statistica 7.0. Distribution hypotheses were tested using the Shapiro-Wilk test. Comparison between the subgroups was carried out using nonparametric criteria - Mann-Whitney and Kolmogorov-Smirnov. When comparing the frequency of occurrence of the trait, the corrected Chi-square test with Yates correction was used. An analysis of the relationship between the two qualitative features was performed using the non-parametric Spearman correlation method.

A method for determining the uniformity of the structure of an atherosclerotic plaque is illustrated by an example.

A method for determining the mobility of an atherosclerotic plaque is illustrated by an example.

Patient K., 75 years old. Diagnosis: ischemic heart disease. Myocardial infarction anterior localization. Early post-infarction angina pectoris. Atherosclerosis of the aorta and coronary arteries (stenosis of the PNA in the proximal segment of 90%, in the middle segment of stenosis up to 90%). Condition after TBA with stenting PNA. Arterial hypertension 2 tbsp. Art. risk 4. Type 2 diabetes, art. compensation.

Duplex scanning of the extracranial part of the brachiocephalic arteries revealed stenoses of 40-45% in the bifurcation region of the right OCA, 50-55%) in the bifurcation region of the left OCA. In FIG. 14 is an image of “heterogeneous” according to ultrasonic duplex scanning of an atherosclerotic plaque located in the bifurcation of the right OSA processed in the MultiVox workstation “Plaque movement” mode. According to duplex scanning, the plaque is heterogeneous or heterogeneous, contains areas of different echogenicity - the distal portion of the plaque is characterized by increased echogenicity, medium and proximal - reduced echogenicity. Attention is drawn to the multidirectional plaque motion curves of the distal plaque segment A1 (red curve) with respect to two other plaque segments, middle A2 and proximal A3 (yellow and orange curves), which indicates its heterogeneity.

Claims (6)

1. A method for determining the uniformity of the structure of an atherosclerotic plaque located in an artery, according to which a series of successive ultrasound images of an atherosclerotic plaque are obtained in a longitudinal section of an artery during one cardiac cycle, the base and surface of the plaque are contoured at one of the initial frames and three are selected on the contour line segments - distal, proximal and central, followed by an assessment of the motion parameters of the selected plaque surface segments relative itelno base for the period of the cardiac cycle by determining the tangential velocity plaques segment and / or the speed of movement of the shear deformation segment plaques with subsequent plotting the measured velocity and the time when receiving codirectional curves Segment plaques conclude a homogeneous structure plaque. 2. The method according to p. 1, characterized in that the tangential velocity of the plaque segment is determined as the projection of the velocity vector of the center of mass of the contour of the surface of the plaque on the X axis, which is determined by the direction of the base contour, while evaluating the minimum and maximum values of speed per cycle. 3. The method according to p. 1, characterized in that the rate of change of the shear deformation of the plaque segment is determined as the first derivative of the shear deformation of the plaque segment with respect to time. 4. The method according to p. 1, characterized in that the single-frame ultrasound images of an atherosclerotic plaque are obtained using an ultrasound device configured to save the resulting image in a DICOM format. 5. The method according to p. 1, characterized in that the processing of ultrasound images is carried out using a workstation - computer MultiVox. 6. The method according to claim 1, characterized in that the tracking of the change in position of the selected segments of the contour line in the ultrasound images is carried out according to an algorithm based on the technology for tracking the speckles of the ultrasound image.

Images