9/30: Radiation Biology Flashcards
What are the radiation measurements?
Exposure dose
Absorbed dose
Equivalent dose
Effective dose
This is a measure of the capacity of radiation to ionize air
Exposure
What is the traditional and Metric unit for exposure?
Traditional: roentgen
Metric: air kerma
This is the sum of the kinetic energy released in matter in exposure
Air kerma
How is air kerma measured? What is the conversion?
coulomb/kg
1 R → 2.58 x 10^-4 coulomb/kg
Roentgen produces how many ion pairs?
2.08 x 10^9
What is RAD an acronym for?
Radiation absorbed dose
What is the traditional and metric unit for absorption?
Traditional = RAD
Metric = Gy
What is the conversion of RAD to Gy?
1 Gy→ 100 RAD
This is to compare the biological effects of different types of radiation
Equivalent
Radiation weighting factor depends on what?
Type and energy of the radiation involved
What is the equation for equivalent dose?
Equivalent dose = absorbed dose + radiation weighting factor
This is a measure of the biological effectiveness of a radiation to ionize matter
Quality factor
What is the QF for x-radiation?
1
REM is equivalent to what?
RAD x QF
What are the traditional and metric units for Equivalent dose?
Traditional = REM
Metric = Sv
What is the conversion for equivalent dose?
1 Sv = 100 rem
This is used to calculate risk of radiation to human tissues on a common scale. The calculation is a product of the sum of dose equivalence to the specific tissue exposed and the biological tissue weighting factor
Effective dose
What is the equation for effective dose?
Effective = W x H (tissue weight factor x equivalent dose)
The use of the effective dose allows comparisons of what?
Different imaging techniques or be made on a common scale
This is used to assess risk of non-uniform radiation to localized part of body and degree to which this would increase a person’s “whole body” risk of cancer induction and/or induction of genetic mutations
Effective dose
Area exposed related to what?
Maximum size of the beam
This is the interaction of X-radiation with matter
Ionization
List all the types of ionization
No interaction: 9%
Coherent scattering: 7%
Photoelectric absorption: 27%
Compton scattering: 57%
What ionization has the most effect?
Compton scattering
This is when the x-ray photon enters object and exits with no change
No interaction
This is when x-ray photon collides with an electrons and losses its energy, atoms state is altered
Photoelectric
This is when an Xray photon collides with an outer orbital electron losing some energy, photon continues with less snergy, creating more scatter until all energy is lost
compton scattering
This is when a photon interacts with an electron and changes directions, no change
Coherent scattering
This ionization directly ionizes biological macromolecules
Direct effect
This ionization has its photons absorbed by water → free radical → damage
Indirect effect
How does direct and indirect contribute to biological effects?
Direct = ⅓
Indirect = ⅔
What is the outcome of the direct effect of UV light on skin DNA?
Repair
Inaccurate repair
No repair
What is the primary method of cell damage that results from radiolysis of water?
Indirect effect
This is a free atom or molecule carrying an unpaired orbital electron in the outer shell
Free radical
How do you get toxic substances from free radicals?
Want a stable structure so that causes toxic substances
What are the types of dose-response curves?
Non-linear threshold
Linear non-threshold
Non-linear, non-threshold
Describe non-linear threshold
Small doses have no effect until a threshold is met, then you get rapid response
Describe linear, non-threshold curves
No threshold and dose is proportional to response
Describe non-linear, non-threshold curves
Dose does not require threshold and it is not proportional to response
Deterministic effects of radiation have a
Threshold and severity is proportional to dose
This is a side-effect of head and neck cancer treatment
Radiation erythema
Stochastic effects of radiation have
No dose threshold and probability of occurrence is proportional to dose but severity not on dose
1 day of background radiation is how much exposure?
8.5 microSv
Stochastic effects to somatic cells cause what?
malignancies
Stochastic effects to germ cells cause what?
Genetic mutations that are inheritable
This effect is only seen in the person affected, NOT future generations
Somatic mutations/effects
This effect is not seen in the person affected, ONLY in future generations
Genetic effects/mutations
What is the sequence of radiation injury?
Latent period
Period of injury
Period of recovery
How can you have a shorter latent period?
Larger dose
What factors modify effects on radiation?
Total dose
Dose rate
Oxygen
Area exposed
Cell type and function
Age
Who is at risk for radiation in terms of age?
Pediatric patients
