Medical applications of physics

1. What do x-rays form part of? The electromag- netic spectrum 2. What sort of waves are x-rays? Transverse (their oscillations are perpendicular to the direction of en- ergy transfer) 3. What are the properties of x-rays? -they have a very short wavelength (about the same size as the diame- ter of an atom -they have a very high frequency -they cause ionisa- tion (adding or re- moving electrons in atoms and mol- ecules) -they affect photo- graphic film in the same way as visi- ble light (turning it black) -they are absorbed by metal and bone -they are trans- mitted by healthy body tissue 4. What are some uses of x-rays? -Form images of bones on photo- graphic film -Dental problems 5. What is used in modern x-ray devices instead of pho- tographuc film? Charged Coupled Devices (CCD's) 6. How do CCD's work? They convert lights to electrical sig- nals which can be recorded in a com- puters memory 7. Why is using A CCD sometimes better than using photographic film? 8. How is a CT scan different from a normal x-ray image? Why is this useful in diagnosing some medical condi- tions? The image is saved onto a com- puter -CT takes images that are slices through the body -They can be reconstructed to make a 3D image of the body -This is useful be- cause it produces a clearer image 9. What does radiotherapy treat? Cancer 10. What is the difference between x-rays used in diagno- sis and the x-rays in radiotherapy? They x-rays used in radiotherapy provide a higher dose of radiation than those used in diagnosis 11. How does radiotherapy affect cells? -Ionising radiation damages cells, and high enough doses kill them -The cells in can- cerous tissue are dividing very rapid- ly, maing them more susceptible to damage by radi- 12. When are cells more likely to be damaged and why is this important in treating tumors? ation -Healthy cells are also able to re- generate if they are only slightly damaged, cancer- ous cells can't -Cells are more likely to be dam- aged when they are in cancerous tissue -Important when treating tumors be- cause it means there is a higher chance if getting rid of it 13. How is damage to healthy tissue reduced? -By creating a treating plan that lists the direc- tions the x-rays will come from -Calculating the radiation does to the tumor and the rest of the body -Lead sheeting 14. What was Prof. W. Roentgen experimenting with that led him to accidentally discovering x-rays? 15. What dense substance could be injected into to pro- duce a radiograph of the stomach of small intestine? 16. What substance could be injected to investigate blood vessels in the body? Cathode rays Barium Iodine 17. What do workers using x-radiation have to do as a safety precaution? -Wear a lead apron -Stand behind a lead glass screen 18. Why must the film badge be plastic and not metal? Metal would ab- sorb ALL of the x-rays 19. Despite x-rays being dangerous to living cells, give a use of this property of x-rays. How are healthy tissues protected? -They can kill can- cerous cells -Healthy tissues are covered in lead 20. What does CT stand for? Computerised To- mography 21. What is an advantage of x-rays? They give more re- liable results than ultrasound 22. What is the frequency range of human hearing? 20Hz-20,000Hz 23. Why can't humans hear ultrasound waves? -They are beyond our hearing range -They can be any- where from 20KHz to several GHz 24. What are the properties of ultrasound waves? -Humans can't hear them -They have a very high frequency -They are lon- gitudinal waves (the oscillations are paralled to the direction of energy transfer) 25. What is ultrasound used for? -Detecting cracks in metals/pipe lines -High frequencies can be used for cleaning delicate items e.g. fancy jewellery -Powerful ultra- sounds can break up kidney stones 26. Why is ultrasound better than x-rays for pre-natal scanning? 27. What does the transducer contain and what do they do? 28. What does the gel that is applied before placing the transducer on the surface do? -Non ionsing (harmless) -Not as clear an image as x-rays -Partially reflected from tissue -Amount reflected depends on densi- ty -Piezoelectric crystals -They vibrate to create the waves Reduces reflec- tions from the pa- tients skin 29. What are some uses of CT scans? -Diagnose condi- tions -Guide further tests or treatments -Monitor condi- tions 30. What is refraction? -When light changes direction as it moves into a different sub- stance -This is because the density of the substance is differ- ent so light travels at different speed 31. Ray diagrams LOOK IN BOOK 32. What is refractive index? A measure of how much the sub- stance can reflect a light ray 33. What is the symbol for refractive index? n 34. Convex lens (converging) diagram 35. Concave lens (diverging) diagram 36. What is the point where the rays meet called? Focus point or principle focus 37. When is an angle small? When i is smaller than the critical an- gle 38. When is an angle big? When i is bigger than the critical an- gle 39. What is the critical angle? A property of a material 40. What is total internal reflection? Where the angle of incidence is greater than the critical angle 41. What do fibreoptic cables use? Total internal re- flection 42. What are endoscopes used for? To see inside the body, especially stomach ulcers 43. Why do enodscopes have two bunches? Light travels up one and down the other 44. How is an image formed by an endoscope? -Light is shone through one bun- dle into the stom- ach -When the light reaches the stom- ach some of the light is reflected -The reflected light travels back along the other bundle -The light is then directed into an eyepiece or a screen -The medical pro- fessionals can 45. What is the advantage of having bundles of fibre optic cables? 46. What is the name of the phenomenon that allows light rays to travel from one end to the other? 47. What other key term must you always include when describing total internal reflection? then see an im- age of the patient's stomach -If a strand breaks it will still work -They will pro- duce clear images because there is more light Total internal re- flection Critical angle 48. What do lasers do? They use light to perform a va- riety of different functions, some of them being medical, including laser eye treat- ment? 49. What does LASER stand for? Light Amplification by Stimulated Emission of Radiation 50. What is special about laser light in comparison with normal light? Laser light all have the same colour wavelength, fre- quency and colour 51. What are some uses of lasers? -Laser eye surgery -Cancer diagnosis and treatment 52. Describe how the image formed by the lens in a cam- era is different from the image formed by a lens used as a magnifying glass -Cauterising wounds The image formed by the lens in a camera is dimin- ished