BIOLOGICAL EFFECTS OF IONIZING RADIATION

BIOLOGICAL EFFECTS OF IONIZING RADIATION

1. Biological effects of ionizing radiation D. Punitha B. Sc MIT, SRI Sathya sai medical college and research institute . GUIDED BY, PROF.DR.I.GURUBHARATH.MD.,P h.d

2. 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.

3. 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.

4. Types of biological effects

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. How to reduce radiation? We are following some rules and providing some protective material to minimize the radiation with adequate technique. Those are

13. Alara principle

14. Benefits should be more Risks should not be more

15. 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.

16. 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.

17. Protective materials

18. Food items

19. 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.