Radiation Biology

1. Radiation Biology Cellular Level Cell Sensitivity Radiolysis of Water Direct Effect/Indirect Effect Target Theory Radiation Effect Early Effects Prodromal/Latent period/Manifest Illness Hematologic Syndrome GI Syndrome CNS Syndrome Local tissue damage Late Effects Local Tissue Effect Life Span shortening Radiation Protection Time Distance Shielding Shield Types ALARA

2. Radiation Biology

3. Largest sources of man-made radiation are medical and dental x-rays.

4. THE EARLY YEARS

6. Radiation Biology

7. Cellular Level

8. Cellular Levels

9. Cell Sensitivity • Early Effect: • radiation response occurs within minutes/days after exposure • acute radiation syndrome • local tissue damage • Late Effect: • radiation response not observable for months or years • leukemia • cataracts • other cancers • local tissue damage • Life span shortening • genetic damage

10. Cell Sensitivity

11. Cell Sensitivity

12. Linear Response to radiation: • Non-threshold • Assumes no dose is safe • Threshold assumes • Minimum dose needed to produce a response A B A dose response relationship is produced by extrapolating high dose experimental data to low doses.

14. Diagnostic radiology is almost exclusively concerned with the late of effects for radiation exposure. This assumes a linear non-threshold dose-response relationship. However, no dose is considered safe. Cell Sensitivity

15. Basic Cell Structure • Two parts: • Nucleus- contains DNA • Cytoplasm is 80% water • DNA is at risk when a cell is exposed to ionizing radiation

16. Two Basic Cell types Cell Structure

17. Radiolysis of Water Ionization radiation interacts with a water (H2O). Water dissociates into 2 ions. This process creates free radicals. These are uncharged molecules containing as single unpaired electron in outer shell.

18. H 2 O molecules - • Ejection of electron = free radical • H2 0 2 = hydrogen peroxide Radiolysis of Water

19. HOH+ recombine to H2O

20. Direct/Indirect Effect

21. Let’s Play Jenga !!

22. Target Theory Target theory suggests that a key molecule must be inactivated. The key molecule is assumed to be DNA. • When interaction occurs between radiation and target molecule, it is • considered a “hit” • An indirect hit has a larger target area because of the mobility • of the free radicals • Radiation acts randomly.

23. B3…..miss……..A4…..hit…….You sunk my Battleship!!!

24. Early Effect • Prodromal/Latent/Manifest Illness • Hematologic syndrome • GI syndrome • CNS syndrome • Late Effects • Local Tissue Effect • Erythema • Cataracts • Life Span Shortening • Cancers/Malignancies • Genetic Effects Radiation Effects

25. Early Effect • Prodromal/Latent/Manifest Illness • Hematologic syndrome • GI syndrome • CNS syndrome • Local Tissue Damage

26. Each stage has 3 main sub-stages prodromal stage latent stage manifest illness cell death/repair Early Effects

27. Acute Radiation Syndromes – full body exposure given in a few minutes. • 3 stages of response: 1. Prodromal -NVD stage (nausea, vomiting, diarrhea) 2. Latent Period-Feels well while undergoing biological changes 3. Manifest Illness-Full effects felt, leads to recovery or death Total Body Response to Radiation

28. Hematologic : results in infection, hemorrhage & anemia • Gastrointestinal : results in diarrhea, nausea & vomiting, fever • Central Nervous System : results in convulsions, coma, & eventual death from increased intracranial pressure. CNS least sensitive in ADULTS – MOST sensitive in the FETUS 3 Radiation Syndromes

29. Cherynobyl Fall out

30. 11,000 mrem- current background in red zones • 12 mrem is your average background radiation. • This is a thousand times greater than the normal background level of radiation • Approximately 15-20% of babies are born healthy. Exposure in soil & water

31. Late Effects • Local Tissue Effect • Erythema • Cataracts • Life Span Shortening • Cancers/Malignancies • Genetic Effects Late Effects

32. Somatic Effects: develop in the individual who is exposed • Most common: • Skin Damage, Cataract formation & Carcinogenesis • Genetic Effects: develop in future generations as a result of damage to germ cells. Late Effects of Radiation

33. Cardinal Principles of Radiation Protection Time Distance Shielding • ALARA Radiation Protection

34. Cardinal Principles of Radiation Protection Time Distance and Shielding

35. Triad of Radiation Safety 1. Time 2. Distance 3. Shielding *Apply to the patient & Technologist Cardinal Principles of Protection

36. Time

37. Time Skin burns from 30 min of beam on time Over Radiation to SkinToo much time under beam

38. Acute Localized Radiation Effects The Table 2-2 provides examples of possible radiation effects to skin caused by typical fluoroscopy exposures. Note that patient and technique factors can substantially increase exposure rates, significantly reducing the time necessary for the subsequent effect. Table 2-2: Dose and Time to Initiate Localized Radiation Effects .7 of an hour is approximately 42 miutes

39. Distance

40. This is an actual arm tatoo. Now that’s dedication ! Inverse square law Inverse square law Inverse square law

41. Shielding

42. Shielding A lead protective shield is placed • Between the x-ray tube and the individuals exposed • Absorbs unnecessary radiation

43. Contact • Shaped • Shadow TYPES OF SHIELDING

44. SHIELD TYPES

47. Shadow Shields Breast ShieldShadow shields

48. 1. TECHNOLOGIST . 25 mm LEAD • Lead apron • Gloves • Thyroid shield • Glasses 2. PATIENT – . 5 mm LEAD • Gondal Shielding SHIELDING

49. ALARA As Low As Reasonably Acheivable

50. Primary Barriers