Download Macro- and Microlevel of Noninvasive Examination of the Vascular

Lecturer: Ulyana B. Lushchyk, MD
Coauthors: V.V. Novytskyy,
I.P.Babiy, N.G. Lushchyk
[email protected]
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 (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
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 mА) 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 longlasting 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
qualitative (graphical).
analyzing
is quantitative-
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 (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).
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 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.
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,
3D-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
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.
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).
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.
6.
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.