Macro- and Microlevel of Noninvasive Examination of the Vascular System

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Macro- and Microlevel of Noninvasive Examination
of the Vascular System

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Lecturer Ulyana B. Lushchyk, MD Coauthors
V.V. Novytskyy, I.P.Babiy, N.G. Lushchyk
u.lushchyk_at_gmail.com www.lushchyk.org
www.istyna.kiev.ua
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• 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.

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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.

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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
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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).

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The arsenal of the modern diagnostic equipment is
represented by vascular pathology objectivating
methods used in practice rheography (REG)
sphygmography echocardiography (EchoCG)
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

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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 (2040 KHz) and
the low-voltage current (10 m?) 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.

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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.
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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).
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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.

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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 methods 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.  

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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.  

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• Advantages of the method
• The simplicity of the investigation technique.
• The possibility of the long-lasting
  uninterrupted registration of slight changes in
  the distribution speed of the pulse wave over
  arteries.
• 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.
• It is better an analytic method than a pour
  diagnostic one.

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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).

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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.

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ECHOENCEPHALOGRAPHY (EchoEG)
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).

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• Advantages of the method
• Screening noninvasive technique for the urgent
  diagnostics of disorders of the liquor-dynamic
  balance and the dislocation of cerebral medial
  structures.
• Disadvantages of the method
• 1.      A little informative method in comparison
  with modern neuroimaging methods.  
•  

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Smart optic CAPILLAROSCOPY

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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.

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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.

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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.
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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.  

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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.
  
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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.
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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.

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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.

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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.

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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.

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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.

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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).


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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  



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        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.    




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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.

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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.        

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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.  
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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.
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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  

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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 quantitative-qualitative (digital
and/or graphical).

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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.

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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.

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Advantages of the method 1.      In contrast to
ultrasound Doppler methods, applying the probing
short-wave laser radiation offers the possibility
of receiving the reflected signal of the biggest
amplitude from the thinner layer (about 1mm)
(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.
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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.  
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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.

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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 0,51, i.e. 2030
times more than on ordinary X-ray
images. 2.   The minimal slice thickness 25 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 patients 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, 3D-X-ray study
(three-dimensional X-ray study), and even the
virtual endoscopy have appeared .
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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.
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MAGNETIC RESONANCE ANGIOGRAPHY(?R?)

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 (?. ?.
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
1980s 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.
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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 short-time
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.

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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.

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Advantages of the method 1.      Mostly harmless
method for the patients 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).     

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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.

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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.

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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.  


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Color-coding of grey-scale CT-MRI-images
MRA- and US-images Despite a rather high level of
imaging during MRA and US-studies, today a new
methodological approach to the improvement of the
separating power of received scanned grey-scale
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.