EXAM #1 (Ch. 35 Health Physics) Flashcards
Define: health physics
The scientific discipline of radiation protection.
Define: TVL
Tenth value layer. That thickness of material that will reduce radiation intensity to one tenth its unattenuated value.
Define: NCRP
NCRP is an acronym for National Council on Radiation Protection and Measurement.
Define: effective dose
Concept that attempts to specify the overall risk of harm to an organism by accounting for two variables with the use of appropriate weighting factors.
Define: ALARA
As low as reasonably achievable.
Define: tissue weighting factor (Wt)
A numerical index of the relative radiosensitivity of various tissues.
Define: first responder
Early people on the scene of a radiologic terrorism event who must make the first decisions.
Define: Clarence Dally
Considered to be the first x-ray fatality. An assistant to Thomas Edison.
Define: Manhattan Project
The name of the World War II project to develop the atomic bomb.
Define: LNT
LNT is an acronym for linear nonthreshold dose-response relationship.
Write the equation for the radiation dose as a function of time of exposure.
Dose = dose rate × time.
What is the function of the 5-minute reset timer on a fluoroscopy imaging system?
To help ensure that the radiologist is aware of the fluoroscopic exposure time and prevent exceeding the five-minute of exposure.
A fluoroscope emits 35 µGya/mA-minute at the tabletop for every mA of operation. What is the approximate patient entrance skin dose (ESD) after a 3.2-minute fluoroscopic examination of 1.5 mA?
(35 µGya/mA/min)(3.2 min)(1.5 mA) = 168 µGya
What are the three cardinal principles of radiation protection?
Minimize time, maximize distance, use shielding material.
The output intensity of a radiographic unit is 42 µGya/mAs. What is the total output after a 200-ms exposure at 300 mA?
(42 uGya/mAs) × (300 mA × 0.2 s) = 2.52 mGya.
At the exposure rate 42 µGya/mAs, what is the approximate patient skin dose after a 3.2-minute fluoroscopic examination of 1.5 mA?
(42 uGya/mAs) × (3.2 min × 60 s/min) × 1.5 mA = 12096 uGya. = 12 mGya.
How can the three cardinal principles of radiation protection be best applied in diagnostic radiology?
The three cardinal principles of radiation protection to be applied in diagnostic radiology are as follows: minimize the time of radiation exposure, maximize the distance from the source, wear protective apparel.
What exposure will a radiologic technologist receive when exposed for 10 minutes at 4 m from a source with intensity of 1 mGya/hr at 1 m while wearing a protective apron equivalent to 2 HVLs?
(1 mGya/hour) × (1 hour/6) × (1 m/4 m)2 × (1/4) = 2.6 uGya.
What wartime effort coined the term health physicist?
The Manhattan Project.
The collar-positioned monitor of a fluoroscopist records 0.9 mSv over the course of a month. This represents approximately what effective dose (E)?
Effective dose applies only to thyroid = 0.9 mSv × 0.05 = 0.045 mSv = 45 uSv.
Describe the change in longevity that occurred during the 20th century and the impact of radiation on that change.
Life expectancy nearly doubled, and much of that increased longevity is due to medical imaging.
How many half-value layers are included in a tenth-value layer?
1 TVL = 3.3 HVL.
What should first responders do in the event of a radiologic emergency?
First attend to the medical needs of the injured. Then attempt to determine if radioactive contamination has occurred.
Discuss the concept of effective dose.
The whole body dose that carries the same risk as a partial body exposure.
