Ionizing radiation can damage biological cells and tissues through direct or indirect action. Direct action involves radiation directly ionizing molecules like DNA, while indirect action involves radiation ionizing water molecules to form free radicals that then damage cells. The biological effects of radiation can be deterministic or stochastic. Deterministic effects have thresholds and increase in severity with higher doses, like tissue damage. Stochastic effects have no threshold and probability increases with dose, like cancer induction. Radiation exposure can cause somatic effects in the exposed individual or genetic effects passed to offspring. Protective measures aim to reduce radiation exposure according to the ALARA principle and use time, distance, shielding.

1. BIOLOGICAL EFFECTS OF
IONIZING RADIATION
Reddy varun kumar
Group – 9
Semester – 9
Guided by : Skorobogatova mam

3. WHAT IS IONIZING RADIATION?
• Ionizing radiation is radiation with enough energy to detach electrons from atoms and
molecules so that during an interaction with an atom, it can remove tightly bound electrons
from the orbit of an atom, causing the atom to become charged or ionized.

4. WHY RADIATION IS HARMFUL ?
• Radiation can cause biological damages on cells either indirect or direct
action. If radiation falls on a human body, it produces moving electrons. The
electrons cause further ionization, excitation, resulting in chemical and
molecular changes. Radiation can also pruduce free radicals, which are
unpaired electrons that are chemically reactive.
• Human body consist of 70% water, most of the radiation damage is caused by
water especially by OH radicals.
• These radicals can further interact with DNA, RNA or protein molecules and
cause damage tissue and affect its normal function.
• E. g : chromosome break and aberration.

5. TYPES OF BIOLOGICAL EFFECTS
BIOLOGICAL
EFFECTS OF
RADIATON
STOCHASTIC
EFFECT
SOMATIC EFFECT GENETIC EFFECT
DETERMINISTICE
EFFECT

6. DETERMINISTIC EFFECT
• Deterministic effect is one in which “ severity increases with
increasing absorbed dose”.
• Deterministic effects have a threshold below which the effect
does not occur. The threshold may be very low and may vary
from person to person.
• However, once the threshold has been exceeded, the
severity of an effect increases with dose.

7. PROPERTIES OF DETERMINISTIC EFFECT
• The main mechanism of
deterministic effect is Cell killing.
• It has threshold dose
• This effect occurs only at high dose.
• It can be completely avoided.

8. STOCHASTIC EFFECT
• A stochastic effect is one in which “the probability of occurrence
increases with increasing absorbed dose rather than its severity”.
• The stochastic effect is further classified into SOMATIC and
GENETIC effect .
• Stochastic means random and the severity of this effect is
independent of the radiation dose.

9. PROPERTIES OF STOCHASTIC EFFECT
• The main mechanism of this effect is
cell modification.
• It has no threshold dose.
• It occurs at even at low doses.
• It can’t be completely avoided.

11. SOMATIC EFFECT
• Radiation effect occurs on an exposed individual
during his life time is called somatic effect .
• Cancer induction is the largest risk of radiation
exposure encountered in radiology.
• Cancer risk is generally higher for children than adults.
• It may induce both benign and malignant tumor.

12. GENETIC EFFECT
• The genetic effect is not seen in the person
irradiated but is passed on to future
generations.
• The radiation induced mutations affect the
health of off –spring.
• Genetic damage can not be repaired.

13. FETAL RISK
• The effect of radiation on embryo and fetus are
• Lethal effects
• Malformation
• Growth disturbance with malformation.
• Pre – mature stage is the most sensitive stage, which may cause lethal effect.
• The fetal risk depends on the gestation period of the pregnant women.
• Mother exposed to diagnostic x rays in the third trimester, resulted in excess childhood
leukemia.
• Diagnostic x ray can increase the risk of childhood cancer by 40%
• To avoid radiation induced congenital anomalies, an abortion may be advised only when dose
exceed 100 mGy.

14. HOW TO REDUCE RADIATION?
• We are following some rules and
providing some protective material
to minimize the radiation with
adequate technique.
• Those are

15. ALARA PRINCIPLE

16. Benefits should be more Risks should not be more

17. TEN-DAY RULE
• ICRP is introduced this rule and its mainly
applied to the women Who are in child
bearing age(11-55)
• To avoid irradiating to a fetus before the
mother realized that she was pregnant or
not.
• Care must be taken to protect the fetus
from radiation when the examination is not
avoidable.
• When the technologist unsure of pregnancy
10 day rule must be used.

19. TIME –DISTANCE –SHIELDING
• TIME :
• Lesser the time spent near the radiation
source, lesser will be the radiation dose.
• Distance :
• Increasing the distance between you and
the source wil reduce the exposure by
square of distance
• Shielding :
• Larger the shielding thickness, lesser the
radiation exposure.

20. PROTECTIVE MATERIALS

21. FOOD ITEMS

22. SOME COMMON THINGS
• Only essential investigations should be taken .
• Avoid the necessity of retakes.
• Use anti scatter grid or air gap technique .
• Don’t perform any examination which has not been
prescribed.
• X ray beam must be well collimated.
• The focal spot to skin distance must be as long as
possible with good radiographic technique.
• Don’t spend more time in radiation area.
• Before performing any x ray investigations on female
of childbearing age (11-55) the patient must be asked
whether there is any chance to be pregnant.
• The person who’s presence is needed they only
present in x ray rooms.