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Dose, Biological Effects, and Exposure Models

Dose, Biological Effects, and Exposure Models. David Weisz – Nuclear Forensics. …so what exactly is dose?. 1 Gy = 100 rad = 1 J/Kg 1 Sv = 100 rem (usually) = 1 Gy x weighting factor. Rem vs. Sv. Sv = dose ( Gy ) x w R. rem = dose ( rads ) x Q. Linear Energy Transfer.

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Dose, Biological Effects, and Exposure Models

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  1. Dose, Biological Effects, and Exposure Models David Weisz – Nuclear Forensics

  2. …so what exactly is dose? 1 Gy = 100 rad = 1 J/Kg 1 Sv = 100 rem (usually) = 1 Gy x weighting factor

  3. Rem vs. Sv Sv = dose (Gy) x wR rem = dose (rads) x Q

  4. Linear Energy Transfer

  5. Cellular Radiation Effects What is the most likely target for ionizing radiation?

  6. DNA

  7. So how does radiation effect DNA?

  8. Acute Radiation Syndrome What tissues are most sensitive to radiation damage??? Tissues with high cellular reproduction rate

  9. Acute Radiation Syndrome

  10. Acute Radiation Syndrome LD50/60 = 4 Gy

  11. Acute Radiation Syndrome Before After (3 weeks later)

  12. How much radiation energy absorption needed to kill a human? LD50/60 = 4 Gy 4 Gy x 1 J/kg x 70 kg = 280 Joules • How much heat energy absorbed from drinking a cup of hot coffee? Excess temp = 60o – 37o = 23oC 250ml x 23o = 5,750 calories 5,750 calories x 4.19 J/cal = 24,092 Joules (96 J/ml of coffee) 4 Gy = 3 ml hot coffee

  13. The Bombings of Hiroshima and Nagasaki

  14. Radiation Effects Research Foundation, 2007

  15. The Human Toll: • Hiroshima: 90,000-166,000 deaths within 2 months • Nagasaki: 60,000-80,000 deaths within 2 months • (50% of deaths occurred on the first day) What was the main cause of death/injury?

  16. Radiation and Cancer Risk:

  17. How do we determine risk? Human Epidimiological Studies • Cohort Studies • Case Control Studies • Ecological Studies Animal Studies

  18. The Cohort Study and ‘Relative Risk’

  19. Dose Response Curves and Extrapolating Risk

  20. What other populations would be appropriate for determining relative risk?

  21. Extrapolating Risk John Gofman – Professor Emeritus at Berkeley: Linear No-Threshold Model

  22. What is Radiation Hormesis?

  23. Medical Benefits of Radiation

  24. Intro to Radiation Therapy Hypoxia- what is it? How can chemotherapy enhance radiotherapy?

  25. Gamma Knife

  26. Bragg Peak How could this be useful in radiotherapy?

  27. Questions?

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