Ch. 4 & 5
Terms in this set (25)
__________ is the SI unit of electrical current.
____________ is the basic unit of electrical charge; it is the quantity of electrical charges flowing past a point in 1 second when a current of 1 ampre is used.
Freed electron with negative charged and positive charged ions
Used to measure x-ray output intensity, calibrate x-ray equipment, and radiation survey instruments
Traditional unit: Roentgen
SI unit: Coulombs/kg
-Measure of radiation intensity in air. Is the measure of kinetic energy released as a result of absorption events.
-Is used to express ionization in air or tissue.
-Unit of measure is Joules/kg
Dose area product (DAP)
Expressed as units of mGy per cm^2; represents body surface dose (NOT entrance skin dose)
-Amount of energy per unit mass absorbed by an irradiated object. It is responsible for biologic damage from exposure of the tissues to radiation
-Amount of energy absorbed depends on: atomic number of tissue, mass density of tissue, and energy of incident photon
-SI unit is Gy.
________ LET does more biologic damage
_______ LET transfers large amounts of energy into a small area
Linear energy transfer
Amount of energy transferred on average by incident radiation to an object per unit length of track through an object. Expressed in units of kev/um
Radiation weighting factor (WR)
-Used when determining Equivalent dose (EqD)
-Is a multiplier used for radiation purposes to account for differences in biologic impact among various types of ionizing radiation
-Places risks associated with biologic effects on a common scale
Equivalent dose (EqD)
-Product of the average absorbed dose in a tissue or organ in the human body and its associated WR chosen for the type and energy of the radiation in question.
-Used for radiation protection purposes when a person received exposure from various types of ionizing radiation
-May be determined or measured in Sv (or mSv)
Effective dose (EfD)
-Measure of the overall risk of exposure to ionizing radiation
-"The sum of the weighted equivalent doses for all irradiated tissues or organs"
-Incorporates BOTH the effect of the type of radiation used and the variability in radiosensitivity of the organ or body part irradiated
-Determines the overall harm to biologic components for risk of radiation induced cancer or risk of genetic damage
Tissue weighting factors (WT)
-Used in the calculation of EfD
-Accounts for the risk to the entire organism brought on by irradiation of individual tissues and organs
-Provides an indication of the working habits and conditions of personnel
-Determines occupational exposure by detecting and measuring the quantity of ionizing radiation that the dosimeter has been exposed to.
-Are lightweight and easy to carry
-made of durable materials for normal daily use
-detect and record both small and large exposures in a consistent and reliable manner
-Ensures occupational radiation exposure levels are kept well below annual effective dose limits
-Creates awareness of radiation exposure monitoring devices and their functions
-Required when radiation workers are likely to risk receiving 10% or more of the annual occupational EfD limit.
Thermoluminescent dosimeter (TLD) ring badge
Used as a second monitor when radiographic procedures require the hands to be near the primary x-ray beam; often used by nuclear medicine technologists, etc.
Optically stimulated luminescence dosimeter (OSL)
-readings as low as 1 rem (.01 mSv)
-uses aluminum oxide detector and a laser light that stimulates luminescence or flow in proportion to the radiation exposure received
-Various filters are contailed inside the badge
-They are very sensitive, tolerate eat, moisture, and pressure, can be reanalyzed and worn up to 1 year.
-Uses a film sensitive to radiation, filters, and a holder
-sensitive to 10 mrem (1mSv)
-Is economical and has a permanent record
-Is sensitive to heat, moisture and fogging; worn for no longer than 1 month.
TLD (thermoluminescent device)
-Uses lithium fluoride crystal
-reads as low as 5 mR
-Not affected by humidity, pressure and normal temp changes, can be worn up to 3 mo and can be reused after reading
-Has a high cost, can only be read once, has no permanent record
Used to detect area contamination for radioactive sources; used in nuclear medicine dept.
Used to detect alpha and beta radiation in lab environment; not used in x-ray
Used for the radiation protection surveys and to monitor the performance of equipment
-Are used to measure the radiation output from both radiographic and fluoroscopic x-ray equipment
-Types include: ionization chamber-type survey meter (cutie pie), proportional counter, and gieger-muller detector
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