Dose Limits Flashcards
1
Q
UNSCEAR and RERF
A
- UNSCEAR and RERF - Research and Report
- Est 1955
- Collects, evaluates, and reports on radiation exposures
- perform epidemiological (study of observing) research
- monitor Japanese and Chernobyl survivors
- Monitor background radiation levels (radon, cosmic)
- Make predictions concerning bio effects
- Collective equivalent dose calculations
2
Q
NAS BEIR
A
- 1955
- Analyze epi data collected concerning the bio effects related to radiation exposure
- BEIR V (1990) - Established and identified the non threshold linear dose response relationship
- No perfectly safe dose - even low doses have potential to cause damage
- ALARA - based on report
3
Q
ICRP
A
- International Commision on Radiological Protection
- leading international group responsible for providing clear and consistent radiation guidance through its recommendations on dose limits
- bases information on reports by UNSCEAR and NAS BEIR
- Only makes recommendations, does not enfore
4
Q
NCRP
A
- National Council on Radiation Protection
- determines the way the ICRP recommendations are incorporated into the US
- Not an enforcement agency, only recommends
5
Q
Agreement States
A
- These states assume responsibility for enforcing radiation protection regulations through their respective health departments
- Must adhere to rules and regulations of NRC
6
Q
EPA
A
- Environmental Protection Agency
- Facilitates the developement and enforcement of regulations pertaining to the control of radiation in the environment
7
Q
Nuclear Regulatory Commission (NRC)
A
- has authority to enfore federal radiation protection laws in all states
- x ray tube calibration
- radioisotope disposal
- in majority of states they have own Radiation Bureau’s who take care of this - Agreement States
8
Q
FDA / CDRH
A
- regulates the design and manufacture of electronic products including x ray equipment
- Given authority by 1968 law
- CDRH is a subdivision of FDA, specifically for x ray equipment
9
Q
OSHA
A
- monitors places of employment
10
Q
The Radiation Control for Health and Safety Act (1968)
A
- Recognized the need to protect all of us from potential hazards of unnecessary radiation exposure from electronics and x ray machines
- established CDRH (overseer of all things x ray equipment)
- established code of standards for x ray equipment
- Code of standards took effect in 1974, made our profession much safer
- Standards :
- PBL
- minimal permanent filtration of x ray beam, provided reduction in intensity of x ray beam
- x ray units to duplicate certain exposures for any given kvp, mas
- inclusion of beam limitation devices for spot films taken during fluoro
- presence of “beam on” indicators to give visible warning when using xrays
- manual back up times for AEC
11
Q
Reproducibility
A
- consistency in output in radiation intensity for identical generator settings from one exposure to others after it
12
Q
Linearity
A
- ratio of the difference in mR/mas values between two successive generator stations to the sum of those mR/mas values. Must be less than 0.1
13
Q
Consumer Patient Radiation Health and Safety (1981)
A
- Calls for minimum standards and education as well as certification for those who administer radiation to public
- Compliance is not mandatory, many states have not complied
14
Q
CARE bill
A
- would ensure that patients undergoing all types of radiologic procedures have the same assurance of quality
- ASRT has introduced House and Senate bills that pursue basic educational and certification standards for health care workers who administer radiologic procedures in every state in the union
15
Q
Dose Limiting Systems - MPD (Maximum Permissable Dose) system
A
- implies there is an acceptable dose of radiation that could be received year after year with little or no bio injury
- introduced concept of annual and cummulative dose limits for occupationally exposed
- Dose limit 1960 - 12 rems/year
- Dose limit 1971 - 5 rems/year
- Cummulative dose limit -
- H = 5(N-18)
- Rem Bank - extra rems from each working year were stored
- worker allowed to exceed 5 rems/yr by as much as 15 rems/yr, if enough rems were in their rem bank
- Critical Organs - deemed some organs more radiosensitive
- in 1987 when NCRP introducted EDE it ended MPD
16
Q
Effective Dose Equivalent Limiting system (EDES)
A
- Defintion: upper boundary dose of ionizing radiation that a person can receive in a year time, or in a single exposure in a given yr with negligble risk of sustaininly bodily damage
- dose limiting system currently used
- Replaced MPD because of BEIR V. A trend towards stricter radiation protection standards
- possible link towards low doses and carcinogeneois
- dose limits set for occupational and public
- eliminated concept of critical organs - all organs exposure contributes bio damage
17
Q
Difference in MPD and EDE dose calculations
A
- MPD System
- H = 5 (N - 18)
- H = 5(40-18)
- H = 110 rems
- EDE System
- E = (1 rem) x (age)
- E = (1 rem) x 40)
- E = 40 rems
- EDE system much more concerned with reducing dose over an entire work career
- Average dose a radiographer in this country is 100 mRem
18
Q
Specific doses to certain organs
A
-
Mean Marrow Dose :
- 25% of active bone marrow were in the beam received an average dose of 0.8 mGy, the mean marrow dose is 0.2 mGy
- Gonadal Dose: depends on gender. Certain exams are higher for women and men
- Fetal Dose
- Mean Glandular Dose (breasts)
Why are we concerned about these?
Because of long term effects (Stotastic Effects)
19
Q
Entrance Skin Dose
A
- measurement of the air exposure just above the pt’s skin nearest the primary beam
- unit of measurement = R
- most common measurement because it is easy to measure
- Measured two ways :
- Direct : tape a TLD to a pt’s skin. Group them in the middle of the light field. 95% accurate
- Indirect: Use output intensity charts. Has to be posted by each x ray room
