Radiation Health, Safety And Protection Flashcards
What is maximum possible dose (MPD)?
Maximum dose of radiation that a person or body part is allowed to receive in stated period of time
Determines the amt. of radiation you can receive without harming yourself
What is whole body radiation?
5 rem/year for radiation workers
What is latent period?
Period of time between exposure to radiation and clinically observable symptoms
What is output?
Amount of radiation produced by a dental machine and measured at the end of the cone (X-ray machine should have .7R to 1R/sec)
What is secondary radiation?
Radiation being given off by any matter being irradiated
After the primary radiation has been absorbed by the tissue some E will be emitted as secondary radiation
What is primary radiation?
Original radiation that emanate from the focal spot in the tube of the X-ray unit
What is useful radiation?
Part of primary beam that is permitted to emerge from the housing of the tube and is limited by the opening, lead diaphragm or other collimating devices determined by the size of the opening of the collimating
What is scattered radiation?
Form of secondary radiation
Radiation that has been deflected from its path by impact during its passage through matter
Presents the most serious danger to the operator
What is leakage radiation?
Form of radiation that originates at the target inside the tube and escapes in all directions through the protective shielding of the tube and tube head
What is remnant radiation?
Primary beam passes through the patient and continues until it interacts, or absorbs another object
What material is being used to replace the aluminum filters in some new x-ray machines? What is in our machines at school?
Samarium
We still have aluminum filters in our machines at school
How much of a % reduction in radiation is there what samarium is used instead of an aluminum filter?
20% reduction in radiation
Mechanical safeguards in radiation
Filtration
Collimation
Protective shielding
If unable to be shielded, how far away from the patients head should the operator stand? At which degrees should the place themselves to the patient/x-ray beam?
6 feet away
Should stand at 90-135 degrees out of the primary beam
How thick should a lead apron be?
0.5mm thickness
What speed of film exposes the patient to the least amount of radiation?
ASA speed E or F
What is most unwanted radiation in dental offices due to?
Overexposure
Under-development of film (conventional)
What is the purpose of a radiation monitoring device?
Periodic or continuing measurement to determine the dose rate in an area or the dose received by a person
What are monitoring devices the only method to assess?
If x-ray equipment is emitting too much radiation
If individual is receiving more than the maximum permissible dose
What would state personnel from the DEP be brought in to monitor/measure?
Output of the dental x-ray machine
Radiation leakage
To determine if any radiation is passing through walls
What is the name of the device that may be worn by personnel to measure radiation levels? What exactly does it measure?
Dosimeter
Measures radiation that has been received, the amt. of radiation, type of radiation
What is a more practical device that may be worn by personnel working directly with radiation?
Modern receptor badge
What organization developed radiation protection guidelines for the maximum permissible dose? When was it formed?
NCRP- National Council on Radiation Protection.
Formed in 1929
What was the purpose of creating the MPD?
To protect radiation workers/general public
Guides represent doses far below those at which any effect have ever been observed
General public is allowed less exposure than radiation workers
Reason for MPD being created
Workers are a small % of the pop
Damage to heredity material will be diluted in gen pop so will not cause diasterous mutation levels
Radiation for medical/dental diagnostocs not counted in the permissible amt.
What are the permissible exposure limits for radiation workers?
May not exceed 5 rems/yr (50mSv)
How much radiation exposure is allowed for pregnant women
.5mSV per month
How much radiation is generally received by the public every year?
1mSv/year
What does ALARA stand for?
As low as reasonably achievable
Direct effects of ionization
When ionization radiation alters or destroys cells that lie in the direct path of the radiation beam (striking the DNA)
Indirect effects of ionizing radiation
Impaired function because radiation is absorbed in cells and formation of toxins, damage not due to direct hit of radiation
Cell recovery
Not all radiation induced changes in tissue cells are permanent.
Cells repair process may be sufficient to recover. Depends on total does and rate
What is dose rate?
Amount of time of exposure. The more radiation and faster the rate, the shorter the latent period
WHAT DETERMINES TISSUE SENSITIVITY?
The degree os sensitivity is directly related to the AGE of the cells and the rate of cellular reproduction
Young, rapidly growing cells are more sensitive to radiation (young children, pregnant women)
According to the DHNB what are the most to least sensitive organs and tissues to radiation?
Blood forming cells and reproductive organs
Immature bone
Epithelium and muscle
Mature bone and nerve
What are the critical organs of the head and neck region that are exposed during dental radiology procedures??
Skin, thyroid gland, lens of the eye, bone marrow
What are somatic cells?
All cells in the body with the exception of the reproductive cells (sperm and ova)
Changes in these cells are not passed on to the succeeding generations
What happens when there are changes in genetic cells?
Chromosomes are passed on to succeeding generations called mutations. Can be recessive and carried on for generations before clinically evident
What is the average background radiation in population?
3.1 mSv/year
What are the 4 major sources of background radiation?
Cosmic rays (sun)
External radiation- radioactive materials from the earth used in building materials
Internal radiation- radioactive materials ingested (potassium 40)
Fallout- radiation from nuclear exposure
What is localized exposure?
2.75 inches in diameter to a particular area of the face
What is total body exposure?
Fraction of the facial exposure that reaches all parts of the body.
TBE from a dental radiograph is 1/10,000 of the facial exposure
What may be caused by excess radiation to the patient?
Erythema Cataracts Hair loss Hematonic changes Gonads- sterilization 400R males, 625R females Pregnancy
Ways to reduce patient exposure
Collimator Filtration Fastest speed film Lead shielded open ended cone Lead shield
What is a collimator?
Reduces exposure by lessening the opening on the cone
Xray beam should not be more than 2.75 inches
What is filtration?
1.5mm of aluminum if operation at less than 70 kVp
What does a lead shield open ended cone do?
Decreases scatter radiation
