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 rem = dose (rads) x Q Sv = dose (Gy) x wR

Linear Energy Transfer

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

DNA

So how does radiation effect DNA?

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

Acute Radiation Syndrome

Acute Radiation Syndrome LD50/60 = 4 Gy

Acute Radiation Syndrome Before After (3 weeks later)

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 So why don’t we just explode after drinking a cup of coffee? The thermal radiation from a cup of coffee is non-ionizing…in order for thermal radiation to be ionizing, the temperature must be sufficiently high (plasma temperatures). 5,750 calories x 4.19 J/cal = 24,092 Joules (96 J/ml of coffee) 4 Gy = 3 ml hot coffee

The Bombings of Hiroshima and Nagasaki

Radiation Effects Research Foundation, 2007

The Human Toll: What was the main cause of death/injury? 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?

Radiation and Cancer Risk:

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

The Cohort Study and ‘Relative Risk’

Dose Response Curves and Extrapolating Risk

What other populations would be appropriate for determining relative risk?

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

What is Radiation Hormesis?

Medical Benefits of Radiation

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

Gamma Knife

Bragg Peak How could this be useful in radiotherapy?

Questions?