CH. 41 Flashcards
This is the study of disease in a population with little control over variables. Large populations are required for statistical reliability.
Epidemiology
Long time periods of tracking are difficult for what?
Epidemiology
This is projecting unknown results from known data based on assumptions that conditions and responses above or below the know data will be consistent with known data.
Extrapolation
DIrect experimentation occurs in labs and the benefits of this type of experimentation are what?
- tight control over variables
2. control groups for comparisons increase validity as to cause and effect.
What are the disadvantages of direct experimentation?
- animal results cannot always be validly applied to humans.
What are the 3 types of risk?
- Absolute Risk
- Relative Risk
- Excessive Risk
This is the raw number of cases of a particular disease or condition. Expressed as the number of cases per million per year.
Absolute Risk
This is a ratio of the number of cases occurring in a population exposed to radiation to the number of cases occurring in a control population of identical size. Always given in ratio form.
Relative Risk
This is the number of cases beyond the normal occurrence expected in a particular group of people.
Excess Risk
This is an increase in severity with increasing dose above a threshold curve due to an increased number of cells damaged. Also called nonstochastic.
Deterministic Effects
Deterministic Effects follow which type of response?
non-linear threshold
When do deterministic effects occur?
Only after large doses such as radiation therapy possible in c-arm fluoro and angiography
What are some examples of early effects from radiation therapy from deterministic effects?
- Erythema
- Epilation
- Fibrosis
- Atrophy
- Sterility and decreased gamete
This is the increase in probability with increasing dose while severity is independent of dose level causing an “all or nothing “ response. This is usually random and measured statistically within a population.
Stochastic Effects
Stochastic Effects may occur at what dose levels?
Low dose levels such as diagnostic radiography
Stochastic Effects follow what type of response curve?
Linear non threshold
What are common late effects of radiation from stochastic effect?
- carcinogenic
- genetic/hereditary effects
Both diagnostic radiography and radiation therapy are generally limited to specific portions of the body by what?
Beam Collimation
Stochastic effects can be thought also as what?
Statistical effects
Stochastic effects take how long to manifest?
Months or years
Deterministic stems from the fact that these effects are certain to occur to whom?
Exposed Individuals
What is the threshold dose for decreased blood cell counts in whole body early effects?
25rem
What is the threshold dose for 50% loss of lymphocytes in whole body early effects?
50rem
What is the threshold dose for human death in whole body early effects?
100rem
What is the threshold dose for Human LD 50/30 in whole body early effects?
350-400rem
What is the threshold dose for lethal dose for the human population in whole body early effects?
600-700rem
What is the partial body early effect threshold dose for chromosome aberrations?
5 rem
What is the partial body early effects of erythema threshold dose?
200rem
What is the partial body early effects of epilation threshold dose?
300rem
What is the lowest radiation dose resulting in any measurable biological effect which can cause visible chromosome aberrations.
5rem
This is expressed as LD x/y where x is the percentage of the population that will die and y is the number of days over which this is measured.
Lethal Doses