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Radiation biology and protection in dental radiology.

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Presentation on theme: "Radiation biology and protection in dental radiology."— Presentation transcript:

1 Radiation biology and protection in dental radiology

2 Dose units and dosimetry Radiation-absorbed dose (D) This is a measure of the amount of energy absorbed from the radiation beam per unit mass of tissue SI unit: Gray,(Gy) measured in joules/kg conversion: 1 Gray=100 rads

3 Contd Equivalent dose (H) -This is a measure which allows the different radio-biological (RBE) effectiveness of different types of radiation to be taken into account. -equivalent dose(H)=radiation-absorbed dose(D)*radiation weighting factor (Wr) SI unit: Sievert (Sv)

4 Contd Effective dose (E) This measure allows doses from different investigation of different parts of the body to be compared by converting all doses to an equivalent whole body dose Effective dose(E)=equivalent dose(H)* tissue weighting factor(Wt)

5 Typical effective doses X-ray examination mSv CT head 8.0 Dental pan dental intraoral films Using 70 kV rectangular Collimation and long cone 0.02

6 Various sources of radiation Natural background radiation -Cosmic -Gama form the rocks -Radiation from ingested radioisotops -Radon

7 Contd Artificial background radiation Medical and dental diagnostic radiation Radiation from occupational exposure

8 The biological effects and risks associated with X-rays Somatic Deterministic effects Somatic Stochastic effects Genetic Stochastic effects

9 Somatic deterministic effects They are definitely produced by the high dose of radiation Threshold dose Examples- skin reddening

10 Somatic stochastic effects They may develop Examples- leukemia and certain tumors No threshold dose

11 Contd Every exposure to ionizing radiation carries the possibility of inducing a stochastic effect The severity of the damage is not related to the size of the inducing dose

12 Genetic stochastic effects Mutations result from any change in the chromosome May result from radiation or occur spontaneously No threshold dose

13 Effects on the unborn child Large dose of radiation- congenital abnormalities Mental retardation- low doses of radiation

14 Harmful effects important in dental radiology In dentistry the size of the doses are relatively small Somatic stochastic effects are the damaging effects of most concern

15 How do X-rays cause damage Direct damage Indirect damage

16 Direct damage Incoming X-ray photon An ejected high-energy electron Effects Inability to pass on information Abnormal replication Cell death Only temporary damage

17 Factors to be considered The type and number of nucleic acid bonds The intensity and type of radiation The time between exposure The ability of the cell to repair the damage The stage of the cells reproductive cycle when irradiated

18 Indirect image The damage to cells result from the free radicals produced by the ionization process The hydrogen peroxide damages the cell by breaking down DNA or proteins

19 Estimating the magnitude of the risk of cancer induction Dental intraorals (2) Dental panoramic 1 in Lateral ceph ALARA principle

20 Radiation protection measures X-ray equipment Processing equipment Position and distance from the patient ALARA Guidelines for prescribing of radiographs Digital radiography

21 X-ray equipment Collimation- maximum 6 cm of an x-ray beam Filtration-aluminium filter to remove long waves x-rays from the beam Beam-indicating device (BID)- the legal focus to skin (fsd) distances are: -200 mm for sets operating above 60 kV -100 mm for sets operating below 60 kV

22 Inverse square law

23 Ways to reducing radiation exposure to the patients ALARA concept -As Low As Reasonably Achievable Digital radiography-80 % dose reduction

24 Guidelines for prescribing dental radiographs Clinical examination must be performed first Adhere to departmental protocols for x- raying patients in the School

25 Safety measures for operator protection Only the operator and patient are permitted in the x-ray room The operator will stand in a safe place: -6 feet away NOT in direct beam -behind an appropriate barrier -outside the room if you cannot get 6 feet away Never hold the film or tubehead during exposure

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