Health Physics Flashcards
Who was the first American fatality that resulted from radiation exposure
Thomas Edison’s assistant, Clarence Dally
Define health physics
It is concerned with providing occupational radiation protection and minimizing radiation dose to the public and workers.
What year was the first dose limiting recommendations made
1931
NCRP
National Council on radiation protection and measures is today’s advisory committee for radiation protection
Name three jobs of a health physicist
- Design equipment
- Calculate and construct barriers
- Develop administrative protocols to maintain radiation exposures as low as reasonably achievable
ALARA
As low as reasonably achievable
- it does not mean zero
When was the term health physics coined
In the 1940s while the Manhattan project, which was a secret WW2 development of the Atomic Bomb.
The group of physicist and doctors responsible for radiation safety of people involved in the production of the atomic bombs were the first health physicist
1 employee died ARS
We practice ALARA because of
The LNT linear NoN treshold radiation dose response for stochastic effects: cancer, leukemia, genetic effects
What are three cardinal principles of radiation protection
Time
Distance
Shielding
How is dose related to radiation exposure
The dose to a person is directly related to the duration of radiation exposure.
If the time during which a person is exposed to radiation is doubled, the exposure will be?
Doubled
Exposure =
Exposure rate x exposure time
How can ALARA principles be used in fluoroscopy
- Last image hold
- Pulse fluoro rate: fast or slow
- 5-minute reset timer
Describe the use of pulse-progressive fluoroscopy
The radiologist depresses the fluoroscopy foot switch in a repeated up and down motion
Point source of radiation means
source of radiation (as light) that is concentrated at a point and considered as having no spatial extension.
If the distance from the source of radiation exceeds five times the source diameter, it can be treated as
A point source
Isoexposure Lines
Lines on a plot plan represent positions of equal radiation exposure in the fluoroscopy room
During portions of a fluoro exam when possible you should take two steps back why?
Two steps back, the exposure rate is only 50 uGy/hr
Why does the reduction in exposure during fluoro, not follow the inverse square law?
Because the patient is an extended source of radiation because of scattered x-rays generated within the body.
HVL
Half value layer is the amount of material required to reduce intensity by one half.
TVL
TVL is the 10th value layer.
The thickness of absorber that reduces radiation intensity two 1/10 it’s original value.
How can you estimate the amount that a protective barrier reduces radiation intensity?
If the half value layer or the 10th value layer of the barrier material is known.
1 TVL=
3.3 HVL
Protective aprons usually contain
0.5 eqPb
