Lecturer: Ulyana B. Lushchyk, MD Coauthors: V. V. Novytskyy, I. P. Babiy, N. G. Lushchyk u. lushchyk@gmail. com www. lushchyk. org www. istyna. kiev. ua
Methods of the vital investigation of the vascular system may be divided in accordance with such concepts: • heart and vessel structure evaluation; • evaluation of the functional activity of the heart as a pomp; • vessel function evaluation; • evaluation of perfusion in organs and tissues; • evaluation of pressure in the vascular system; • evaluation of rheological features of the blood flow.
Methods of the vascular system diagnostics may be grouped in accordance with the character of information receiving: · direct methods of imaging – giving a visual information of structural changes related to a pathological process; · indirect – giving the information in the form of numbers of certain coefficients (parameters) known to a researcher, or in the form of diagrams; · combined – a simultaneous objectivation of structural and functional changes in the vascular system.
The problem of an adequate evaluation of the cerebral vascular system condition is inseparably connected with the evaluation of the whole hemodynamic system both at systemic and regional levels
Historically the vascular system examination was based on the global approach, i. e. they evaluated the whole vascular system condition that excluded the possibility of local pathologies diagnostics. The current level of the diagnostic equipment enables to diagnose these processes at a local level, and, if necessary, to investigate the hemodynamic and functional relevance of a local impairment for a setback in the whole circulatory system (a global level).
The arsenal of the modern diagnostic equipment is represented by vascular pathology objectivating methods used in practice: · rheography (REG); · sphygmography; · echocardiography (Echo. CG); · optic and computed capillaroscopy; · nuclear diagnostics; · angiography; · ultrasound diagnostics (color angioscanning and dopplerography); ·laser dopplerography (flowmetry of microcirculatory bloodstream); · CT; · magnetic resonance angiography (MRA); · coloring of grey-scale scanned MRA- and US-images
RHEOGRAPHY (from Greek rheo – to flow, grapheo – to describe) Indirect noninvasive dynamic method. The method is based on a biophysical principle of the registration of tissues’ electric resistance changes during the passage of the current of a high frequency (20– 40 KHz) and the low-voltage current (10 m. А) through the investigated area with a graphical registration of pulse vibrations of the complex electric resistance. A living tissue is considered as an electric conductor that has an ionic conductivity. Vibrations of the electric resistance tangently reflect changes of speed and volume of the blood that flows through vessels. Blood flow pulse vibrations are registered in the form of curved synchronized vibrations of the electric resistance.
The object of the investigation is a violation of the electric conductivity of an organ secondary to changes in its blood filling. The level of the vascular system investigation is a measurement of a value of the regional hemodynamics and the peripheral blood flow due to the rheogram analysis by the evaluation of the pulse blood filling of different vasculatures, the arterial and venous tonus.
The method of results analyzing is quantitative-qualitative (graphical). A rheographic curve reflects hemodynamic vibrations, which occur in organs and tissues during the cardiac beat. Rheovasogram is an integral tridimensional curve of all arteries and veins of the investigated area of the extremity. (according to the book: G. P. Matveikov, S. S. Pshonyk Clinical Rheography. – 1976. – p. 36).
Advantages of the method 1. The possibility of the long-lasting uninterrupted registration even on slight changes of the blood flow without a disturbance of the investigated area physiological conditions. 2. Absolutely noninvasive method, the possibility of the long-lasting control of hemodynamics. 3. Functional tests applying (with hyperventilation, hypercapnia, nitroglycerin, and nicotinic acid) offers the possibility to reveal disguised circulatory disorders and to differ functional vascular changes from cerebral vessels impairments. 4. Extended opportunities for vital organs and systems studying, timely diagnostics of blood flow disorders and the rational therapy prescribing.
Disadvantages of the method 1. A general character of analyzing the condition of arterial and venous branches of the vascular system where the blood flow function is reflected in one curve. 2. The method’s separate ability is restricted by the diagnostic level of the decrease of the vasculature blood filling, but not of a segment of a certain vessel.
SPHYGMOGRAPHY Noninvasive indirect graphical dynamic method. Sphygmography is a mechanic-cardiographic method of a dynamic record of the arterial pulse in the form of a diagram and its analysis. The pressure increases in arteries on every cardiac beat and the vessel transection growth is observed, then the vessel resets. The whole cycle of transformations is called an arterial pulse that is caused by the arterial wall pulsation during the passage of the stroke volume through the arterial bed, and its recording in dynamics is known as sphygmogram.
Advantages of the method 1. The simplicity of the investigation technique. 2. The possibility of the long-lasting uninterrupted registration of slight changes in the distribution speed of the pulse wave over arteries. 3. Absolutely noninvasive method, the possibility of controlling in dynamics. Disadvantages of the method 1. It is seldom used in the practical medicine as it needs the deep knowledge in peculiarities of the pulse wave distribution. 2. It is better an analytic method than a pour diagnostic one.
The method is based on piezoelectric sensors applying. The object of the investigation is a graphical imaging of arterial pulse characteristics in dynamics, defining the distribution speed of the pulse wave over vessels of elastic and muscular types. The level of the vascular system investigation – sphygmograms are: of the central pulse (investigation of major arteries) and of the peripheral pulse (registration from arterioles). The method of results analyzing is quantitative-qualitative (graphical).
Sphygmogram has determined points on the synchronic recording either with electrocardiogram (ECG) or with phonocardiogram (PCG) that allows to analyze cardiac cycle phases separately for right and left ventricles. Mostly two or more piezosensors are simultaneously attached or the synchronic record with electro- and phonocardiograms ECG and PCG is carried out. Curves recorded from major and peripheral vessels are different.
ECHOENCEPHALOGRAPHY (Echo. EG) Indirect noninvasive method. The method is based on the one-dimensional ultrasonic radiation applying. The object of the investigation is the cerebral ventricular system. The level of the vascular system investigation is a dislocation of cerebral medial structures (M-echo), ventricular system sizes, and hydroencephaly. The method of results analyzing is quantitative-qualitative (graphical).
Advantages of the method 1. Screening noninvasive technique for the urgent diagnostics of disorders of the liquordynamic balance and the dislocation of cerebral medial structures. Disadvantages of the method 1. A little informative method in comparison with modern neuroimaging methods.
Smart optic CAPILLAROSCOPY
Direct noninvasive dynamic method. The method is based on applying the optic method of imaging with using modern computer technologies of the received image reflection on the monitor. The object of the investigation is imaging and analysis of the form, calibre, length and blood filling of capillaries, and the character of erythrocytes stream in them. The level of the vascular system investigation is imaging of the blood perfusion at the microcirculatory level. The method of results analyzing is a direct imaging with a quantitative-qualitative analysis.
Nuclear diagnostics (SCINTIGRAPHY) Direct noninvasive method. The method of radiodiagnosis based on the registration of the radiation from injected artificial radioactive substances with tropism to one or another organ. An isotopic tag of the radiopharmmedication allows to supervise the character and the way of the medication accumulation and elimination from investigated organs and tissues. The object of the investigation is the permeability of the vascular system of a separate organ or tissue.
The level of the vascular system investigation is defining parameters of the regional blood flow in the evaluation of organ functioning (quantitative hepatobiliary scintigraphy, radiocardiography, radiopulmonography, radiorenography, radioencephalography). The method of results analyzing is quantitative-imaging due to the evaluation of life-span.
Advantages of the method 1. This is an applied technique for dynamic investigations of the organ functioning. 2. It reflects the organ vascular system functioning on the whole without explaining reasons of the contrast agglomeration absence. Disadvantages of the method 1. Results of this technique applying have an ascertaining character and do not point at pathogenic mechanisms of one or another pathology origin.
X-RAY CONTRAST ANGIOGRAPHY Direct invasive static method. The method is based on puncture or catheterization of different peripheral arteries, injection of X-ray contrast substance that is followed by the series of X-ray pictures (in modern angiograms the series of pictures is registered on magnetic record mediums). The object of the investigation is a stream of erythrocytes per tissue volume. The level of the vascular system investigation is imaging of the regional arterial (arteriography) and/or venous vascular system (venography, phlebography), and lymphatic system (lymphography). The method of results analyzing is visual, quantitative.
X-ray contrast angiography of carotid arteries (general, interior, and exterior). The defect of contrast filling in the proximal segment of the interior carotid artery proves the constrictive lesion.
Advantages of the method 1. A long-lasting observability of the vascular system region with a consecutive reflection of the passage of the X-ray contrast substance from the place of its injection through the arterial system with moving to the venous system through the capillary phase. 2. It reveals impairments and defects of vessels development and disorders in their patency. 3. It offers the possibility not only to control separately arterial, capillary and venous phases of the cerebral blood circulation and to reveal their duration in different areas of the organ vascular system, but to investigate hemodynamics of separate vasculatures and the vasculature of pathological focal lesions (tumors and arteriovenous malformations) due to the contrast selective injection. 4. A high diagnostic informativity in case of tumors with a well developed vasculature, traumatic and spontaneous hemorrhages, obstructive-stenotic impairments of magistral arteries, arterial aneurisms, arteriovenous and arterio-sinus pathological shunts.
Advantages of the method 5. Catheterizing angiography in the course of diagnostic investigations may be transformed into the treatment technique of the endovascular surgery; due to different bomb-catheters aneurisms and arteriovenous lesions are “switched off”, angioplastics in case of the arterial stenosis and the regional infusion of medicamental vehicles are carried out. 6. Recently a new technique of the angiography procedure has appeared – the digital subtracting angiography – a contrast vascular investigation followed by the computed analyzing. The change for digital technologies in angiography has received (provided) a list of advantages: - a high quality with certain vessels separation from a general bulk and the imaging’ high informativity, - a minimal dose of the contrast substance during the examination, - a comfortable archiving and data selection, - absence of X-ray films and chemicals and a low price of an examination; - it offers the possibility to reduce the examination traumatism due to the chance of refusing from catheterization and/or decreasing the quantity of the X-ray contrast substance that is injected. This substance may be injected less traumatically for a patient – intravenously, without applying the arterial catheterization.
Disadvantages of the method 1. Invasiveness. 2. A high risk of complications caused by contrast injecting (an allergic response to the contrast, hematoma, thrombembolia), a large number of contraindications in case of acute inflammatory and infectious diseases, a grave condition of a patient, psychiatric diseases, allergic responses to iodine, evident cardiac, hepatic and renal insufficiency. 3. Time delimitation of arterial and venous phases of blood flow, inability for a simultaneous examination of arteries and veins in a real time. 4. Imaging only in one vessel projection considerably restricts method possibilities in case of the vessel sinuosity, stenotic impairments, and mild atherosclerotic plagues. 5. A restricted time of the investigation is caused by a fast passage of the contrast substance portion through the vascular system, and that is why arterial, capillary and venous phases of this substance expansion are distinguished.
6. A received angiographic image is static, i. e. it corresponds to a single-step slice and disables functional tests and controlling in the dynamics. Venography is conducted on special indications: chronic thrombophlebitis, thrombembolia, suspected venous scapus development anomaly, different disorders of the venous blood flow. Venography is carried out in two ways: direct and indirect. In case of the direct venography the contrast substance is injected directly into the vein by its puncture, sometimes catheterization. The direct venography is carried out in three ways: · injecting the contrast substance into arteries, after which it flows into veins through the capillary system; · injecting the contrast substance into organ tissues, during this time veins, abducting the blood from this organ, is observed on the screen; · injecting the contrast substance into the medullary space. Contraindication for venography is thrombophlebitis.
ULTRASOUND VASCULAR DIAGNOSTICS Ultrasound vascular diagnostics includes two complementary techniques – these are ultrasound color angioscanning (USAS) and ultrasound dopplerography (USDG). USAS visualizes the structure of the vessel wall, the vessel lumina and function in the process of the blood flow organization and provision, and USDG graphically reflects the blood flow speed in vessels and characteristics of the vessel wall functioning, and interrelation of all branches of the blood circulation at a local level.
Noninvasive dynamic method (USAS is direct visual, USDG is indirect graphical). The method is based on ultrasound radiation applying with using Doppler effect: the ultrasound wave changes its frequency on recoiling from movable blood elements, in particular erythrocytes. The object of the investigation is a segment of the magistral artery or vein. The level of the vascular system investigation is magistral vessels. The method of results analyzing is quantitative-qualitative (digital and/or graphical).
US-angioscanning (USAS) is available in several modes of the ultrasound system work depending on its type and kind: modes of black and white imaging, the effect of color blood flow mapping (color angioscanning) and the energetic color blood volume coding, and the tissue perfusion colorization: · using the modern US-system with the color coding and dopplerography, it is possible to receive more information about circulation state in magistral arteries and veins. In the mode of Doppler color mapping a qualitative evaluation of the lumina size, elastic-tonic and pulse features of the investigated segment of the artery, the vascular wall thickness, the organized nature of the blood flow with the diagnostics of disorganized areas in the form of turbulence and prognostication of the danger of the possible cerebral arteries embolia are carried out;
· the modern US-system with the color coding of energetic Doppler effect offers the possibility of receiving the one-color picture of the circulation in organs, but it does not analyze the tissue type in organs, especially in zones of the intensive circulation, and does not differentiate the arterial and venous discirculation that is important for the individual pathogenic approach to the treatment policy. The mode of energetic Doppler mapping allows to visualize cerebral arteries during the transcranial scanning and to evaluate the character of the arterial angioarchitectonics and the sinuosity of proximal segments.
Ultrasound dopplerography (USDG) with the help of the pencil sensor allows to receive the graphical signal from a separate point in the projection of one or another vessel. The graphical profile of the linear blood stream speed change during the cardiac cycle reflects the stream character – laminar or turbulent, uninterruption or evidence of the interrupted blood flow, elastic-tonic features of the certain vessel, the level of the intravascular resistance more distal from the location place and the dependence of the blood stream on signs of the hydrodynamic conflict. The specificity and main advantages of the dopplerography method lie in the generalization of all local data from investigated segments of arteries and veins, and the information from separate points is analyzed from the view of the evaluation of all regional systems hemodynamics.
Advantages of the method 1. Noninvasiveness 2. Safety and possibility of applying in dynamics. 3. USAS is sensitive to a slight change of the vessel diameter, it localizes stenosis zones, atherosclerotic plagues, blood flow swirling in the areas of vasoconstrictions. 4. Transcranial angioscanning offers the possibility of arteries of the circle of Willis imaging, revealing ways of the collateral formation of the blood flow changeover in cases of stenosis and magistral arteries occlusions. 5. Echocardiography is a method of cardiac structure investigation, valve apparatus and hemodynamic alterations in cardiac cavities with the aid of US-scanning, USDG, and M-mode. 6. The possibility of receiving the dynamic image unlike the static image in cases of AG and MRA. 7. The possibility of the simultaneous investigation of arterial and venous beds.
8. The possibility of the experimental modeling of different pathologic conditions and applying various provocative factors for the objectivation of the reason of the vascular-cerebral insufficiency: · tests with arm abducting for the diagnostics of the thoracic output syndrome evidence; · respiratory tests; · tests with head switching; · compressive Matas’ tests; · ortho- and antiorthostatic tests; · tests with a dosed physical load; · acute pharmacological tests.
Disadvantages of the method 1. Disability for the observation imaging of all vessels: unlike MRA and X-ray contrast angiography (AG), US-method allows to investigate one or another vessel segmentally only. Today the absence of the observability effect is compensated by a new method – the panoramic scanning. 2. The method of USDG is restrictedly sensitive for stenotic arterial impairments up to 50% lumina reduction.
LASER DOPPLER FLOWMETRY (LDF) The graphical image received due to the LDF-method offers the possibility of evaluating the tissue microcirculation per 1 sq. mm quantitatively
Noninvasive indirect graphical method. The method is based on laser radiation applying with using Doppler effect. The object of the investigation is the tissue microcirculation in superficial dermostrata and mucus membranes. The sample volume: 1 sq. mm contains about 200 microvessels. The level of the vascular system investigation is the measurement of the blood perfusion value in the tissue at the microcirculatory level. The method of results analyzing is quantitativequalitative (digital and/or graphical).
Tissue blood flow vibrations, which are physiologically important, are subdivided into low-frequency, high-frequency and pulse. Low-frequency vibrations (LF) from 4 to 12 vibrations per minute are caused by the activity of smooth cell myocytes in the wall of microvessels and precapillary sphincters. LF-vibrations are the reflection of the active microcirculatory change mechanism – vasomotion. High-frequency vibrations of the blood flow (HF) from 13 to 30 vibrations per minute are caused by periodical pressure changes in the venous part of the vasculature due to respiratory vibrations. Such a compensatory mechanism is observed in case of ischemic disorders of the dermal blood flow.
Pulse vibrations of the blood flow (CF) is evaluated as the main, but passive mechanism of the blood flow in the microvasculature that is formed far beyond it. Modern laser analyzers are supplied with mathematic wavelet-transducers of amplitudes and frequencies of blood flow vibrations related to the endothelial, neurogenic, and biogenic activity. The influence of respiratory cardiac rhythms on the microcirculatory level is also taken into account.
Advantages of the method 1. In contrast to ultrasound Doppler methods, applying the probing shortwave laser radiation offers the possibility of receiving the reflected signal of the biggest amplitude from the thinner layer (about 1 mm) (Fagrell B. , 1994) that contains microvasculature structures: arterioles, capillaries, venules and arteriovenular inosculations. 2. The possibility of functional tests conducting for the investigation of the vasoconstriction and vasodilatation, endothelial activity and neurogenic regulation.
Disadvantages of the method 1. The general character of the gathered information: the absence of the differentiation of the information about certain microvessels – arterioles and venules. 2. The LDF-method is a relative method of the microcirculation control as measurements calibrating sharply depends on heterogeneity of erythrocytes distribution in the tissue, the epidermis pigmentation and thickness, which are not controlled during noninvasive investigations. 3. In contrast to the optic capillaroscopy, the method is indirect, without the imaging of capillary form and size and the density of capillaries per unit area that considerably influences the final interpretation of received data.
COMPUTED TOMOGRAPHY Direct noninvasive method of imaging. The method is based on applying the X-ray radiation. The object of the investigation is a layered investigation in the axial plane. The level of the investigation is the condition of the cerebrospinal fluid circulation, in case of the contrast – the condition of the regional angioarchitectonics. The method of results analyzing is a quantitative-qualitative imaging method.
Advantages of the method 1. It differentiates more than hundred degrees of the density change in investigated tissues – from zero (for water and liquor) up to hundred and more (for bones and calcioliths) that allows to differentiate densitometric distinctions of normal and pathologic tissue areas within 0, 5– 1%, i. e. 20– 30 times more than on ordinary X-ray images. 2. The minimal slice thickness 2– 5 mm makes it possible to differentiate reactive changes in surrounding tissues (zones of the perifocal edema of the brain, ischemic focuses, degree of hydrocephaly and ways of the spinal fluid circulation). 3. The separating power – focuses of up to 0, 5 cm in diameter. 4. In cardiology electrocardiogram gates are sometimes used during CT, which allow to receive images at a certain phase of the cardiac cycle. This offers the possibility of evaluating sizes of atriums and ventricles, and also the cardiac work according to many functional parameters. 5. Spiral computed tomography is a new method of receiving CT-images by spiral radiator movements around the patient’s body. Due to this it is possible to receive the information about the layered structure of the certain body area in several seconds. On the base of this method the computed angiography, which allows to reveal vascular pathologies effectively, 3 D-X-ray study (three-dimensional X-ray study), and even the virtual endoscopy have appeared.
Disadvantages of the method 1. The necessity of the intravenous infusion of X-ray contrast substances for vessels imaging. 2. It underperforms the informativity and image resolution in comparison with the MRT-method.
MAGNETIC RESONANCE ANGIOGRAPHY(МRА) Magnetic resonance imaging (MRI) or in the identical definition nuclear magnetic resonance (NMR) is a relatively new kind of organs image receiving, which is based on the effect of the nuclear magnetic resonance. The phenomenon of NMR was discovered by E. K. Zavoiskyi in 1944 in the form of the paramagnetic resonance and irrespective of him – by Bloch and Purcell (Е. М. Purcell, F. Bloch) in 1946 in the form of the resonance phenomenon of magnetic moments of atomic nuclei, and in 1952 they won the Nobel prize for this discovery. Clinical samples of MR-tomographs appeared at the beginning of the 1980 s for the investigation of inner organs and the head. Later MRI possibilities were extended for vascular and cardiac investigations as it became possible to receive images of the real time with applying the image synchronization.
Direct noninvasive method of introscopy. The method is based on applying the radio-wave band radiation of the wave length from 1 up to 300 m with using the phenomenon of the shorttime proton resonance in the electromagnetic field for the tissues imaging depending on different water contents in them. The object of the investigation is the vascular system imaging of the virtual organ slice. The level of the vascular system investigation is the regional angioarchitectonics. The method of results analyzing is the vascular system imaging built on the principle of the automated computer-controlled scanning and analyzing and receiving the layered image of the inner structure of organs.
The MRI-method (magnetic resonance angiography) visualizes the circulating blood and creates additional possibilities for the vascular impairments revealing. Magnetic resonance angiography allows to receive the selective image of vessels (similar to the image of ordinary angiograms), but without applying contrast substances, and to evaluate the degree of magistral head arteries and veins sinuosity safely for the patient, and also to reveal stenosis and occlusion. So, due to the leading method of the observation diagnostics – MRA – it becomes possible to visualize impairments of magistral head arteries and cerebral arteries by receiving their static (immovable) image secondary to the MRI-structural impairment of the medullary substance.
Advantages of the method 1. Mostly harmless method for the patient’s health as it erases the question of the gamma-radiation load on a patient and a doctor (in contrast to CT). 2. A high sensitivity of the method to some vital isotopes and hydrogen that provides the high contrast of received images. 3. The possibility of receiving images of the vasculature without injection of the contrast substance and with defining blood flow parameters. 4. A high separating power – it is possible to see objects of fractions of a millimeter in size. 5. It is possible to receive not only transverse, but also longitudinal slices and images of vascular structures in different planes, and to form tridimensional organ and tissue constructions of a high separating power and a higher contrast (in comparison with CT).
6. The high separating power of the tonality of a black and white image, with the ability to differentiate tones’ gradation from white (fat tissue) up to black (air, bones, calcioliths) that almost do not reflect MRI-signals. 7. The resolute imaging of the vessel wall, atherosclerotic plagues, intracranial aneurisms, arteriovenous malformations, and arterio-sinus pathologic shunts. 8. To investigate extremely small biologic objects special equipments are adjusted for the separating power of 10 mkm, i. e. it is possible to receive an image of the cell and its inner structures. For this reason a new term and investigations field evolved – MR-microscopy.
Disadvantages of the method 1. The necessity of creating the magnetic field of a high tension requires a large energy consumption and the usage of expensive technologies for providing the superconductibility. 2. Disability for examining patients with cardiostimulators, metal implants, and pregnant women. 3. Disability for revealing focuses of ossification and calcification. 4. To increase the diagnostic informativity, the intravenous injection of magnetic-forcing contrasts (such as magnevist, omniscan etc. ) is necessary.
PERFUSION MRI The method of the positron emission tomography (PET) offers the possibility of the simultaneous receiving of tomographical slices, the investigation of the regional blood circulation and metabolism with the help of the registration of short-lived radioindicators preinjected intravenously. Imaging is provided by the color scale of the quantitative perfusion level.
Color-coding of grey-scale CT-MRI-images MRA- and US-images Despite a rather high level of imaging during MRA and USstudies, today a new methodological approach to the improvement of the separating power of received scanned greyscale images of the brain and vessels due to applying the effect of coloring has been created. The method of coloring lies in the division of the grey-scale image according to the level of the ultrasonic density and the appropriate image coloring 4 – 64 – by the color scale. It is this mode that offers the possibility of, in particular, imaging slices of arterioles and venules walls and the microcirculatory character, and coloring blood flows applying the optic caustic effect.
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