Dose, Biological Effects, and Exposure Models

David Weisz – Nuclear Forensics

…so what exactly is dose?

1 Gy = 100 rad = 1 J/Kg1 Sv = 100 rem (usually) = 1 Gy x weighting factor

Rem vs. Sv

Sv = dose (Gy) x wRrem = dose (rads) x Q

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 SyndromeLD50/60 = 4 Gy

Acute Radiation Syndrome

Before After (3 weeks later)

• How much radiation energy absorption needed to kill a human?

4 Gy x 1 J/kg x 70 kg = 280 Joules

• How much heat energy absorbed from drinking a cup of hot coffee?

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

Excess temp = 60o – 37o = 23oC

LD50/60 = 4 Gy

The Bombings of Hiroshima and Nagasaki

Radiation Effects Research Foundation, 2007

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?

Radiation and Cancer Risk:

How do we determine risk?

Human Epidimiological Studies

Animal Studies

• Cohort Studies

• Case Control Studies

• Ecological 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?