1

Polina A. Timoshina,a,b Denis A. Alexandrov,b Valery V. Tuchina,b,d,

aSaratov State University, Russia bTomsk State University, Russia

cSaratov State Medical University, Russia dInstitute of Precision Mechanics and Control, Russian Academy of Sciences, Russia

e-mail: timoshina2906@mail.ru

Statistics of the incidence of abdominal cavity

in the last 5 years

2

Acute pancreatitis

Gastrointestinal bleeding

Acute intestinal obstruction

Peptic ulcer

Mechanical jaundice

Acute appendicitis

Acute cholecystitis

Chronic gastritis

Hernia of anterior abdominal

wall

Ovarian cyst

3

Laser speckle contrast imaging:

The local estimation of the speckle contrast K for the fixed exposure time done

within the areas with given number of speckles makes it possible to image tissue

regions with essentially different velocity of scatterers

(1)

where k is the number of frames in a sequence of speckle-modulated images,

and are the averaged over the analyzed frame scattered light intensity and the

rms (root-mean-square) value of the fluctuation component of the pixel’s brightness,

respectively:

(2)

(3)

where M and N are the number of pixels in rows and columns of the analyzed area

of the frame.

4

The problem of quantitative velocity measurements is associated with understanding the inter­connection

between the contrast of speckles K and the velocity of scattering centers (or velocity distribution) [2].

Calibration was conducted out in the following way: the blood was passed through a channel of 3 mm in

diameter at a given velocity of 1.5 mm/s by using a dispenser of drugs (MLW Lineomat, Germany).

Recording and processing of speckle images were made by using software designed in the LabVIEW 8.5

environment (National Instruments, USA).

Under the assumption of purely ordered flow, the speckle contrast K can be defined as follows [3]:

(4)

where T is the exposure time of the camera, is time of correlation. Again, it is worth noting that the above

equation is in actuality a cumulative distribution function of a Gaussian probability distribution function,

which is characteristic to directed flows.

The simplest approach leads to a characteristic velocity defined as follows [3-4]:

(5)

where λ is the light source wavelength, k is the normalization factor which depends on the parameters of a

Gaussian curve from Eq. (4), and the scattering properties of biological tissue or phantom. Calibration

allowed us to determine the value of this coefficient as 0.14. In this regard, we can introduce the concept

of “reduced” velocity using Eqs. (4) and (5) to process phantom experimental data for contrast K at the

particular exposure time of the camera T. “Reduced” velocity can be associated with the velocity of blood

flow determined from the speckle contrast K measurements for the further assessment of blood circulation

in in vivo studies.

Calibration:

Experimental setup:

1-He-Ne laser (633 nm); 2-objective (LOMO 20x); 3 - microscope

tube lens with objective (LOMO 10x); 4-CMOS-camera Basler A602f

(656 491 pxls, pxl size 9.9 9.9 µm, 8 bits/pxl); 5- rat under study. 5

6

Animal models:

1 group Measurements of PBF were carried before ischemia, at the time

of 5 min-ischemia, and one day after the start of the experiment

2 group Measurements of PBF were carried out before ischemia, at the

time of 5 min-ischemia, and 5 days after the start of the

experiment

3 group Measurements of PBF were carried out before ischemia, at the

time of 20 min-ischemia, and one day after the start of the

experiment

4 group Measurements of PBF were carried out before ischemia, at the

time of 20 min-ischemia, and 5 days after the start of the

experiment

7

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

normal state

ischemia 5 min

reperfusion

after one day

<`>

, m

m/s

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

normal state

ischemia 5 min

reperfusion

after 5 days

<`>

, m

m/s

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

normal state

ischemia 20 min

reperfusion

after one days

<`>

, м

м/с

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0 normal state

ischemia 20 min

reperfusion

after 5 days

<`>

, m

m/s

Results:

D) C)

B) A)

The PBF was studied at different states of the experimental animal: normal functional state (free

blood flow), at the time of ischemia and after the ischemia. Time periods of cross-clamping were 5

min and 20 min. 20 experimental animals with ischemia 5 min (Fig. 5 A,B) were examined

immediately after the action, 1 day later (10 animals), 5 day later (10 animals) and 20 experimental

animals with ischemia 20 min were examined immediately after the action, 1 day later (10 animals),

5 day later (10 animals).

8

a) b) c)

Photos of the pancreas depending on the functional state: normal state (a), one day after

modeling 20 min ischemia (b); and 5 days after modeling 20 min ischemia (c).

Histological analysis: The results of histological analysis showed that in the group with 5 min of ischemia

pancreatic tissue appeared edema of the stroma, uneven blood vessel filling, single

hemorrhages, the phenomenon of separation, small foci of necrosis. In a group with 20 min

of ischemia, half of the animals died from pancreatonecrosis on the 3-4th day of the

experiment. Among the surviving animals, histologically, along with circulatory disturbances,

leukostasis was observed with leukodiapedesis in the stroma, the development of common

foci of necrosis, which indicates the development of AP.

9

Conclusion:

The results confirm that LSCI is an effective method for monitoring the

microhemodynamics of the pancreas. The method of laser speckle contrast

imaging allows to control the degree of reduction of blood flow in the vessels of

the pancreas when creating local ischemia by compression of the main vessels. In

our study was found that in the group of animals after 5 minutes of full ischemia

an increase of PBF velocity in 2-3 times, clinic of pancreatic necrosis is not

developing. After 20 minutes of full ischemia not there was a significant increase

in the rate of PBF, while in 5 days of the experiment appeared morphological and

clinical signs of pancreatic necrosis. The ability of the full-field speckle-

correlometry technique to measure blood flow velocity in a real time is prospective

feature to be used in transplantation technologies and in emergency surgery to

assess the state of internal organs by their microcirculation strength.

The research of calibration of speckle contrast imaging was supported by

the Russian Ministry of Education and Science, project #3.1586.2017/4.6 and

study of blood flow by speckle contrast imaging was supported by grant RFBR #

18-32-00587.

10