Biological effects of radiation

pathophysiology IIPHARM-D

1. Biological effects of radiation

2. BIOLOGICAL EFFECTS OF RADIATION Definition: The harmful effects caused to human being and other living beings due to their exposure to radiation is called as biological effects of radiation.

3. Content MECHANISMS : How does radiation inflict biological damage? DOSIMETRY : How do we quantify a ‘dose’ of radiation? EFFECTS : What are the potential biological effects of radiation? RISKS & LIMITS : What level of risk is associated with working with diagnostic radiation?

4. MECHANISM

5. MECHANISM DIRECT ATTACK MECHANISM - Incident radiation directly attacks the DNA of the water molecule and ionises water molecules; electrons are released. - Biologic chain reaction occurring. - The ionised water molecules can react further - forming highly reactive molecules such as hydrogen peroxide, or radicals such as hydroperoxyl .

6. Indirect EFFECT mechanism When free radicals produced by the interaction radiation with water molecules act on a vital molecule such as DNA, the damaging action of the ionisation radiation is indirect.

7. - Absorbed dose (Measured ingrays; Gy) : - The ‘gray’ is a measure of the energy in a material by incident ionising radiation. - (1 Gray = 1 Joule of energy deposited in 1kg of tissue) deposited DOSIOMETRY

8. EFFECTS 1). RADIATION EFFECTS ON CELLS Basically, there are three things that can happen: The radiation may pass through the cell without doing any damage to cell. 2. The radiation may damage the cell so that the cell not only form to repair itself but reproduces itself in the damaged form – Biological Response. 3. The radiation may cause so much damage, cells dies.

9. 2).EFFECTS OF LOW DOSE RADIATION Low-Dose Radiation The low dose or “stochastic” effects (statistical), which could be seen are: Carcinogenesis (i.e. induction of cancer ) and Genetic effects (i.e. damage seen in offspring )

10. 3).Deterministic Effects They are dose related ,The injury increases in severity as dose increases. They are generally not an issue in diagnostic imaging – the doses are too low. They are predictable Mechanisms are relatively well understood e.g. in radiotherapy - Repair and recovery can occur.

11. Other toxic dose effects Hair Loss Sterility Cataracts Skin Burns

12. Sensitivity In a malignant tumours the cell system will be much sensitive. Outer layer of cells reproduce rapidly and has a good supply of blood and oxygen The cells become more sensitive when they are reproducing and the presence of oxygen increases sensitivity to radiation. In anoxic cells it tend to be less reactive .

13. As the tumour is exposed to the radiation ,outer layer of rapidly dividing cells are destroyed,ceasing it to the shrunken image. In tumour if massive dose is given the patient may die hence small dose is given each day which gives a healthy tissue ,a chance to recover from damage.

14. WHOLE BODY SENSITIVITY FACTORS Total dose Type of cell Type of radiation Stage of cell division Part of body exposed General state of health Tissue volume exposed Time interval over which dose is received

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