1. Radiation Biology – 2
Dr Rupak Sethuraman

2. FORMAT INTRODUCTION DIRECT EFFECT INDIRECT EFFECT STOCHASTIC EFFECT
DETERMINISTIC EFFECT

3. DIRECT EFFECT
When the ionizing radiation directly interacts with the cell DNA,RNA,Chromosome the effect that occurs is called as Direct Effect.

4. Photon +H2O H+ + OH- HO 2- +H+ H2O 2 HO2 -+HO2- O2 + H2O2
INDIRECT EFFECT
Photon +H2O H+ + OH-
H+ + O HO2-(Hydroperoxyl)
HO 2- +H H2O 2
HO2 -+HO O2 + H2O2

5. Accumulative Effect
DIRECT EFFECT
INDIRECT EFFECT
ACCUMULATIVE EFFECT

6. Factors Affecting Effect of Radiation
Radiation Factors
Host Factors
Type of radiation
Total Dose
Penetrating ability of radiation
Acute/chronic exposure
Threshold dose
Type of tissue
Sensitivity of the tissue
Stochastic/deterministic effect
Local area/whole body

7. Based on sensitivity:
Vegetative inter mitotic cells eg – spermatogenic cells, erythroblastic, OMM
Differentiating inter mitotic cells eg – Inner enamel epithelium of developing teeth, hematopoetic cells,
Multi potent connective tissue cells – eg – vascular endothelial cells, fibroblasts, mesencymal cells
Reverting post mitotic cells – eg – acinar cells, ductal cells, parenchymal tissue of organs
Fixed post mitotic cells – eg – neurons, muscles,

8. Relative Radio sensitivity of Cells, Tissues and Organs
Blood-forming
Organs
Reproductive
Organs
skin
Vascular
Organs
Bone
Teeth
Muscles & Connective Tissue
Nervous
System
Respiratory System
Digestive
Organs
Extremely
Radio
sensitive
Radio
sensitive
Moderately
Radio
sensitive
Moderately
Radio
resistant
Radio
resistant
Relatively
Radio
resistant
Very
Radio
resistant
Extremely
Radio
resistant

9. Stochastic Effect – Genetic Effect
Definition – in which the probability (chances) of biologic damage increases with increasing absorbed dose but the severity (effect) in the affected individual does not depend on the magnitude (level) of absorbed dose.

10. Deterministic Effect – dose dependent
Those effects which increases in severity with increasing absorbed dose in affected individuals.

11. Quiz – 21 – 09 – 14/26 – 11 - 1435 Radiation Physics – 1
Topics Covered
Topics For Quiz
Introduction to Radiology
Radiation Physics – 1
Radiation Physics – 2
Practicals –
Components of X ray Machine
Radiation Protection
X Ray Films
Radiation Physics – 1
Radiation Physics – 2
Radiation Protection

12. Thank You
Any Questions???