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Theoretical and practical elaboration of cryotherapy by Medical Technique

Department of RMAPO

Prof. Dmitry I. TsyganovDr. Natalia V. Morozova

Russian Medical Academy of Postgraduate Education

Russian Medical Academy of Postgraduate Education Studies - the largest educational, scientific and methodical center of additional and postgraduate professional education of health care staffs of the Russian Federation. Was established since 1931 as Institute of improvement of medical personnel.

The Rector of Russian Medical Academy of Postgraduate Education Studies, Academician of the

Russian Academy of Medical Sciences, Professor

Larisa K. Moshetova

The main building of Academy

One of prospective directions developing by department’s experts is

Cryotherapy (cryosurgery)

It is the application of extreme cold to destroying abnormal or diseased tissue. Cryotherapy has been historically used to treat a number of diseases and disorders, especially a variety of benign and malignant skin conditions.

Cryotherapy is a minimally invasive procedure, and is often preferred to more traditional kinds of surgery because of its minimal pain, scarring and cost; however as with any medical treatment there are risks primarily due to of damage of nearby healthy tissue.

Uses

Warts, moles, solar keratoses, and small skin cancers are candidates for cryosurgical treatment. Several internal disorders are also treated with cryosurgery, including: liver cancer, prostate cancer, lung cancer, oral cancers, hemorrhoids.

Cryosurgery acts by the destructive effect of freezing temperatures on cells. At low temperatures, ice crystals form inside the cells and destroy them apart.

Damage resulting of cryoinfluence at tissue level represents quickly arising, not bleeding and accurately outlined necrosis. Only capillaries and small vessels was destroying but big vessels and veins are highly resistive to freezing.

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Main question of cryosurgery is:

How long is necessary for the necrosis temperature at the required depth (border of pathological and normal tissue) establishing?

Advantages of cryodestruction is:

anesthetizing, haemostatic and anti-inflammatory effects; keeping of ablastica principle; minimum of perifocal reaction; cosmetic effect.

Disadvantages is:

complexity of control and forecasting of cryoinfluence results; necrosis area always is less than a freezing zone;necrosis temperature is individual for each body or tissue.

cryotool

1 zone

Formation of the tissue freeze zones in dependence on speed and temperature of process (experimental data)

On the depth of 300-400 μm: breaks of tissue, necrosis of cells and vessels

On the depth of 0.4-10 mm: vacuoles dystrophy of cells, breaks and thromboses of the blood vessels

2 zone 3 zone

Mathematical modeling

f

z

TrzT

zr

TrzTr

rr

TrzTС z

эфrэф ),,(),,(

1),,(

For successful application of cryotherapy methods it is necessary not only to calculate correctly parameters of local cryoimpact on biological tissue but also to be able to predict its results.

Our model of temperature field in biotissue is described by means of the heat conductivity equation. The effective coefficient of heat conductivity considers increase of a thermal flow as a result of biological thermal emissions. The last component in the right part of equation describes a thermal emission as a result of the phase transition of the water containing in biotissue as function of temperature.

с – specific thermal capacity, J / (kg · K);ρ – density of biotissue, kg/m3; r – radial coordinate; z – axial coordinate; T – temperature, К; τ – time coordinate, seс; χ – specific warmth of phase transition during the freezing of water, J/kg; f – concentration of not frozen water in biotissue, %.

The algorithm of the model's usage is based on a large number of experimental data and measurements of thermal-physical properties for various biotissue types, is computerized and described in the monograph and technical regulations.

Necrosis temperature

The handpiece of cryotool diameter Dн > D0 mm

Handpiece of cryotool temperature

Necrosis depth h=h0 mm

Size of formation:diameter - D0 mm

thickness - h0 mm

CTk0 f

Freezing time sec

CTn0

By the modeling was provided the possibility to make the choice of cryoinfluence tactics:

By the modeling was provided the possibility to make the choice of cryoequipment:

- children's surgery - oncology - cosmetology- gynecology - urology

- gynecology- otorhinolaryngology

- ophthalmology - cosmetology- physical therapy- traumatology- neurosurgery

Due to our investigations Portable cryodevice KM-1 (temperature of working

part -1750С) was created

Normative documents (technical regulations) deals with operation of medical equipment are developed

Many thanks for your attention!

Contacts: 10/12 Polikarpova St., Moscow, Russia

Phone: +7 (495) 946-07-23

E-Mail: innat.m@mail.ru