The document discusses the biological effects of ionizing radiation. It describes the sources of ionizing radiation, both natural and artificial. It explains the properties of different types of ionizing radiation and how they interact with living tissue on an atomic and molecular level. This can lead to direct DNA damage or indirect damage through free radical formation. A variety of cellular, tissue, and organ level effects are discussed, as well as factors that influence individual radiosensitivity. Applications of ionizing radiation such as radiotherapy and associated side effects are also mentioned.

2. The biological effect of ionizing radiation on the cell
(normal and pathologically changed)
Content
1.Biological effect of ionizing radiation
2.The sources of ionizing radiation
3.The properties of ionizing radiation
4.The dependence of biological effect of ionizing radiation from the
type, dose and energy.
5.The characteristics of ionization and excitation
6.Mechanism of the influence of ionizing radiation on the living
objects
7.The levels of metabolic changes in the organism
8.Mutagenic ability of radiation
9.Individual and specific sensitivity
10.The dependence of radiosensitivity from environmental conditions

3. Radiology consists of radiation genetics,
biochemistry, ecology, hygiene, immunology, anti-
radiation protection and treatment, cosmic radiology,
radiobiology of tumors.
Polluted air leads to respiratory system diseases;
Contaminated food and water affects GIT; Pollution
of human body surface - skin diseases;

4. Biological effect of ionizing radiation is
the reaction of organism as answer of
radiation, which manifests by
morphologic, functional, metabolic
changes in all the levels of it’s
organization: atomic, molecular
cellular, tissular, organ and organism.

5. Medical Lecture Notes – All Subjects
USMLE Exam (America) – Practice

6. The source of ionizing radiation is an object, which
consists of radioactive material, technical device that
can radiate (in certain condition) ionizing radiation.
There are natural and artificial sources of radiation.
Natural: space form (background -protons, neutrons,
nucleus of atoms has comparatively high energy
decreased with the presence of atmosphere. Low on
Earth's surface.
Artificial devices made by humans. X-ray tubes,
radioactive nuclides are formed in nuclear reactors,
generators and charged particle accelerators.


7. Ionizing radiation by nature is divided into corpuscular and
photon. And also primarily and secondary ionizing.
Corpuscular (fast moving): electrons, protons, α-particles,
neutrons
Photon – gamma and X-rays. These are electromagnetic waves.
The are the energy which is spreading without movement of
matter (like optical and thermal wave). These waves are
similar by their characteristics. But X-rays are formed by
slowdown of electrons, which were accelerated in electric field
of X-ray tube, and gamma-rays are formed by conversion of
excited nucleuses of atoms into neutral. Electromagnetic IR is
secondary ionizing. Part of it’s energy is converting into kinetic
energy of electrons, which were pushed from their orbits, and
they act as active β-particles.

8. The main ways of radionuclide entering into the organism
Air pollution
Food and water
pollution
Contamination
of the human
skin
Contamination
of wounds
Through the
respiratory
system
Through the
digestive tract
Through the
skin
Through the
wounds
Blood and lymph
Accumulation of
radionuclides in
organs and tissues

9. The artificial sources of ionizing radiation used in medicine
Radioactive substances Accelerators of the charged particles
Sealed Unsealed Linear Cyclic Roentgen devices
Gamma-
therapeutical
devices
Radioactive
medications
Solutions Suspens
ions
Cyclotron
Betatron
Synchroph
asotron
Teletherapy
Static
Brachytherap
y
Static Dyn
amic
1. Tubes
2. Balls
3. Needles
4. Darts
5. Plastic
masses
Usual
Colloid
Macro
Micro

10. Characteristics of ionizing radiation:
1. Ability to penetrate through the large and thick objects (not
transparent)
2. Ionize air and molecules of living organisms. It is because
of it’s energy (energy of light 0.5 eV, α-particle 10MeV-
ionizing ability 20.000 pairs of ions/mm-maximal ionizing
effect and biological influence)
3. Ability to activate photo materials in dosimetry
4. Scintillation
5. Ability to accumulate and cause distant effects (malignant
tumors, genetic mutations)
6. We don’t feel the radiation
7. Ionizing radiation is spreading linearly, causing
interferention and refraction

11. 
Type of
radiation
Energy
MeV
Velocity
Km/h
Length of
the run in
air
Length of
the run in
tissues
Ionizing
ability
Pairs/mm
4+2He 1-10 20000 <20cm <50 mcm 10000-
20000
0 -+1 β 0.1-2 270000 <15m <1 cm 5-10
γ 0.1-20 300000 >100m >10 cm 1 p/cm

12. First stage of ionizing radiation: physical process of
the interactions between the radiation and substance
as a result of this interaction, we have excited and
ionized atoms and molecules that have high chemical
activity. They interact between each other and with
surrounding atoms, in this case a large amount of
highly active free radicals and peroxides appear. The
ionization is the separation of the electron from atom.
If the energy (E) given to the atom is not enough to
separate the electrons, this electron changes its
position to the outer orbit and becomes excited.

13. Second stage, radiation and chemical process which
leads to the charge of the structure of molecules and
as a result to the biochemistry of cell disorders.
Radiolysis -formation of free radicals, which are
highly active because they have an insufficient
number of electrons. Chain reaction. The larger the
molecule, the higher its ability to be ionized. Process
of inactivation of enzymes -OH groups, SH-groups
come together.

14. Water radiolysis
 → Н2О → Н2О+
+ e
 Н2О+
+ Н2О → Н3О+
+ ОН*
 Н2О+
+ e → Н2О*
→ Н*
і ОН*
Н*
+ О2 → НО2
*
НО2
*
+ НО2
*
→ Н2О2 + 2О

15. Tissue: The most sensitive are highly proliferating
tissues like lymphoid, haemopoietic, endocrine. They
die at a low 0-4 Gy. It causes anemia, leucopoenia,
and other disorders. The lower radioactive lesions,
which occur in the future, are in the tissues, which
have lower proliferative ability (bones, cartilage,
muscles, fat). They die at the dose of 30-100 Gy.

16. Organ level: The most sensitive organs/systems:
digestive tract, small intestine. The least sensitive is
liver. The organs, which are most sensitive, are called
"critical" organs. The critical organs, which are all
important for the organism: nervous system, bone
marrow, in the case of injury can cause death. Results
of ionizing radiation can be separated into:
Changes in somatic cells-cause malignization
Genetic mutations- affect the future generation
Affect on the embryo and fetus in case of pregnant
women radiation
Death during radiation

17. The direct effect of ionizing radiation - cases
where radiation directly causes changes:
ionization, excitation, radiolysis of water and the
formation of radicals. The direct effect of
radiation because the radiation of cell damage is
the result of the direct effects of ionizing
particles or γ-quantum is particularly sensitive to
the amount of cells, primarily in the nucleus,
resulting in its inactivation and destruction. It
could be other cell organelles.t.

18. Indirect ( mediated ) effect of ionizing radiation - when
fragments of molecules, oxidizing radicals OH, H2O2,
HO2 ions , the primary lipid peroxidation radiotoxins type
, quinones interact with intact molecules , joining them
and changing their structure and properties. Oxidative
radical steps are easy to sulfhydryl groups of enzymes and
DNA. This can cause them to rupture not contain
attachment, and the other two to form active radicals. As a
result of possible chain reaction . For example,
disintegrated molecule 1 and 2 was formed radicals. They
interact with two intact molecules, which in turn break
down into 4 radicals , etc. Therefore, a small amount of
primary energy is so great effects in the body. This is a
physical, chemical and biochemical level damage. These
processes occur in the cells , tissues and organs.

19. So functional and morphological changes in the cells
of a living organism that occur under the influence of
ionizing radiation can be caused by two mechanisms:
 direct action of radiation / - ionization and
excitation of atoms and molecules irradiated cells of
the body / and indirectly - influence of radicals
formed in the area of exposure.​​

20. Speaking about the mechanism of the indirect effects
of ionizing radiation, it must be emphasized that the
radiation response of water is largely dependent on
the content of oxygen . Established that lack of
oxygen is important in the direct irradiation, ie at the
time when the formation of free radicals and there .
Lack of oxygen or decrease its partial pressure in the
tissues reduces the effectiveness of ionizing radiation.
Thus , the degree of radiation reactions depends on
the concentration of oxygen in a biological substrate.
This phenomenon is known in radiobiology "called
oxygen effect .

21. Examining the relationship between dose and effect
of biological, be aware that the smaller the dose of
ionizing radiation, the later clinical manifestations
may occur biological effect, they are often 30-40 years
after the exposure .
With increasing doses, increases the degree of
biological effect, reduced the timing of its discovery,
however, may change the quality of the effect.
Increasing the degree of biological effect with
increasing dose proportionally occurs only in certain
ranges of doses.

22. The least sensitive to ionizing radiation and bacteria are
simple, the most sensitive - mammals. In a nuclear reactor,
where the dose reached 10 million in the glad day, were
discovered bacteria that not only killed by the powerful
radiation flux, but divided, multiplied, Different
radiosensitivity and radiostiykistyu have not only different
kinds of organisms, but animals of one species. This
difference is already for the minimum, average and absolute
lethal doses. After all these experiments matched animals of
the same sex, age and weight. People are also inherent in
the individual radiosensitivity. It is well known radiation
therapist. Some patients tolerate the entire course of
treatment without any complications, but other radiation
reactions begin just after the first session of
radiotherapy.and "feel" great.

23. Important role to play radiosensitivity overall health
and his age. The most radiosensitive organisms in the
embryonic period, especially during the active
bookmarks organs in humans - in 2-6 weeks after
conception, that is when a pregnancy may be not yet
installed. The dose is harmless for the mother, can
cause serious violations of fetal development. Young
organisms are more radiosensitive and after birth.
Therefore, exposure of young women and children are
allowed only in cases of emergency.
.

24. Many years of experimental and clinical studies make
it possible schematic classification of radiosensitivity
of normal cells and tissues by decreasing the degree
on the basis of radiation damages. The high
radiosensitivity have: embryonic, lymphatic tissue,
spleen, thymus gland, RE system, testes, ovaries, bone
marrow, small intestine, where the first signs of
damage are observed at a dose of 25-100 x-rays, and
severe lesions - a dose of 400-600 x-ray.

25. Average, radiosensitivity was found in the skin,
mucous membranes, eyes, growing bones,
cardiovascular system, to achieve serious injuries they
needed dose 850-2000 x-rays, and the first signs
appear at a dose of 300-800 x-rays,?
The low radiosensitivity own tissue endocrine
secretions, liver, kidney, ts.n.c., lung, skeletal and
smooth muscle of the heart. The minimum dose that
causes certain defeat - 1000 - 4000 X-ray, severe
lesions arise from 3000-6000 X-ray radiation

26. Radiotherapy
The medical use of ionizing radiation as art of cancer
treatment to control malignant tumors. It's for
curative cancer treatment or as a pain alleviating
treatment. It's also used as a therapeutic treatment.
Total body irradiation — a technique used to prepare
the body to receive a bone marrow transplant. To
spare normal tissues, shaped radiation beams are
aimed from different angles of exposure to interact at
the tumor, providing a larger absorbed dose than in
the surrounding healthy tissue.

27.  Side -effects: Acute (arising during treatment) cause damage to
epithelial surfaces. Edema- swelling of soft tissues may cause
problems during radiotherapy. Surgical intervention may be
considered prior to treatment or steroids may be used during
radiotherapy to reduce swelling.
 Infertility (gametes won't be produced after direct exposure of
gonads to most normal doses). And also generalized fatigue.
 Medium and long-term side effects. It depends on tissue being
treated. Fibrosis—tissue becomes less elastic over time due to a
diffuse scarring process. Hair loss-radiation induced is more likely to
be permanent, limited to the area of treatment. Dryness-xerostomia
and xerophalmia, dryness of vaginal mucosa after pelvic irradiation.
Cancer-secondary malignancy seen in a minority of patients.