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Radiation physics
- 1. Radiation physicsRadiation physics PRESENTEDBY LEEMA RK FIRST YEAR PG ORAL MEDICINE & RADIOLOGY 08/17/18 1
- 2. contents History Physics Basic model ofan atom Binding energy@ ionization Nature of radiation Properties Radioactivity Units of measurement Dental xray unit Interaction of Xrays with matter 08/17/18 2
- 3. HISTORY Wilhelm Conard Roentgen08/17/18 3
- 4. EARLY X RAYMACHINE 08/17/18 4
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- 6. BASIC MODEL OFAN ATOM 08/17/18 6
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- 12. properties 1.MASS 2.Charge 3.Speed 4.Travel 5.Electric field 6.Energy 7.Effect onliving tissue 8.propagation 9.Free space 08/17/18 12
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- 14. Wave theory Refraction diffractioninterference polarization 08/17/18 14
- 15. Quantum theory EM energycannot be radiated or absorbed in any arbitrary amounts, but only in discrete “quantum” amounts. The energy of a “quantum” depends on frequency as Equantum = h f h = 6.6 x 10-34 Js “Planck’s constant” 08/17/18 15
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- 17. Natural radioactivity Spontaneous disintegrationof nucleus of an unstable naturally occurring isotopes. Emission of alpha,beta,gamma radiation. Associated with only heavy nucleus. Cannot be controlled. Tremendous amount of energy is released. Artificial radioactivity Changing common stable nuclei of atoms into unstable radioactive nuclei. Emission of positron,electron. Induced in heavy or light nuclei. Can be controlled. Small amount of heat energy is released. 08/17/18 17
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- 20. DENTAL X RAYMACHINE 08/17/18 20
- 21. Wall-mounted type or fixedto the floor Portable handheld X- ray units Mobile units mounted on a stand a 08/17/18 21
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- 23. Exposure time (ms) Increasing ordecreasing exposure time Type of film selector Patient size selector Warning light CONTROL PANEL 08/17/18 23
- 24. TUBE HEAD -inherent filtration -addedfiltration 08/17/18 24
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- 26. SHAPE Conical Closedpointed cone Scattered radiation Rectangular Not much scatter Round Not much scatter LENGTH Short 8 inches Long 16 inches Position indicating device 08/17/18 26
- 27. X ray tube 08/17/18 27 Glass vaccumtube 1.High atomic number 2.High melting point(3380degree celsius) 3.Low vapour pressure 4.High specific heat
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- 30. • Each tubehas rating specification that describes the operating limits of the tube • Tube rating describes the longest exposure time the tube can be energized for a range of kVp and mA values without risk of damage to target from overheating • Duty cycle – refers to how frequently successive exposures can be made Tube rating and duty cycle Hu=kVp X mA X sec 08/17/18 30
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- 32. BREMSSTRALUNG RADIATION CHARACTERISTICRADIATION 08/17/18 32
- 33. INTERACTION OF XRAY WITH MATTER 08/17/18 33
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- 39. 1.Textbook of Dentaland Maxillofacial Radiology-2E- Freny R Karjodkar MDS 2.Oral Radiology principles and interpretation-6E- WHITE AND PHAROAH, DDS 3.Dental Radiology-third edition –Sikri 4.Textbook of Oral Radiology-Pillai 5. Essentials of Dental Radiography & Radiology – Eric Whaites 5ed 08/17/18 39 References
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