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?
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
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:
• 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?