UNIT 1: Radiation Quantities and Units Flashcards
Somatic damage
damage to the biological tissues directly related to the dose of ionizing radiatin received
Occupational exposure
radiation exposure received in the course of exercising professional responsibities
Early tissue reactions
reactions that appeared within minutes, hours, days, or weeks of the time of radiation exposure
Threshold dose
A dose of radiation lower than which an individual has a negligable chance of sustaining specific biologic damage
Late tissue reactions
nongenetic consequences of radiation exposure that appear months or years afterwards
Stochastic effects
mutational or randomly occuring biologic changes, independent of dose, that occur months or years after high level (possibly low level) radiation exposure
DAP (Dose Area Product)
the sum total of air kerma over the exposed area of the patients surface (a measure of the amount of radiant energy that has been thrust into a portion of the patients body surface)
tissue weighing factor (Wt)
-A value that denotes the percentage of the summed stochastic (genetic and cancer) risk stemming from irradiation of specific tissues to the all inclusive risk when the entire body is irradiated in a uniform fashion
-Takes into account the relative detriment(harm) to each specific particular organ and tissue
radiation weighting factor (Wr)
a dimensionless factor (a multiplier) that was chosen for radiation protection purposes to account for differences in biolagic impact among various types of lonizing radiations. This factor places risks associated with biologic effects on a common scale
When were x-rays discovered, and who discovered them?
November 8, 1895, Wilhelm Conrad Roentgen
What was imaged in the first x-ray?
Wilhelm’s wifes hand (Anna Bertha ludwig)
Who is Clarence Madison Dally, and what is his significance to the subject of radiation protection?
First person to die from x-ray exposure (radiation induced cancer), he was Thomas Edison’s assistant.
What is the purpose of the International System of Units (SI)?
makes possible the interchange of units among all branches of science throughout the world
What was the first unit for measuring radiation exposure? Why was this a poor method to quantify exposure?
-Skin erythema: received quantity of radiation that causes diffused redness over an are of skin after irradiation
-Amount of radiation required to produce an erythema reaction varied from person to person
Early tissue reaction examples
• nausea
• diffuse redness of the skin
• loss of hair
• fever
• fatigue
• shedding of outer layer of skin
• intestinal disorder
• blood disorders
Late tissue reaction examples
-Cataract formation
-Fibrosis
-Organ atrophy
-Loss of parenchymal cells
-Reduced fertility
-Sterility
Stochastic effect examples
-Cancer
-Genetic(hereditary) effects
Abbreviation used for exposure
X
Define exposure
Number of photons that interact with air molecules. lonization produced in air.
In what location is Exposure measured
Occurs in air outside the X-ray tube
Exposure unit of measure
C/kg
Air kerma
-Quantifies the amount of energy in the air
-DAP → sum total of air kerma over the surface of the patients skin that has been exposed to radiation (may be seen with fluoroscopic procedures)
Where is Air Kerma location measured
occurs in air outside the X-ray tube
Exposure unit for Air Kerma
Joule per kilogram (J/kg) or Gray (Gy)
Absorbed dose abbreviation
D
Absorbed dose
-Deposit of ionizing radiation energy per unit mass in ANY material
-How much radiahon is absorbed in the patient or health care worker
Absorbed dose unit of measure
Gray (Gy)
formula to determine absorbed dose
1 gray= 1 joule/kilogram
Where is absorbed dose location measured?
Biological tissue
Formula to convert Gray to milligray?
Number of gray X 1000 = # of milligray
Formula to convert milligray to Gray?
Number of milligray / 1000 = # of gray
Formula to convert Gray to centigray?
Number of gray x 100 = # of centigray
Formula to convert centigray to Gray?
Number of centigray / 100 = # of gray
How many Gray equals 1 rad?
1/100 Gy
How many rads equal 1 cGy?
1 rad
Practice problems: Convert 1 Gy to milligray:
1 Gy x 1000 = 1000 mGy
Practice problems: Convert 10 centigray to Gray:
10 cGy/100 = 0.1 Gy
If a patient received 20 mGy of radiation from an exam, how many Gy does this equal?
20 mGy/1000 = .02 Gy
Equivalent dose abbreviation
EqD
Equivalent dose
takes into account the type of ionizing radiation that was absorbed by the tissue and the associated damage it could cause
*radiation weighting factor (Wr)is associated with this
Equivalent dose location measured
- digsostic imaging: x-ray
- environment: radioisotopes
- radioactive materials: nuclear reactors
- particulate radiation
- provides overall dose value
Equivalent dose unit of measure
millisievert (mSv)
formula to determine equivalent dose
EqD = (D)(Wr)
Which radiation type(s) have a weighting factor of 1?
• X-ray photons
• gamma ray photons
• electrons (every energy)
Which radiation type(s) have a weighting factor of 2?
Protons
Which radiation type(s) have a weighting factor of 5?
-Neutrons
-Energy <10 keV
Which radiation type(s) have a weighting factor of 20?
-Alpha particles
-100 keV–2 MeV
Formula to convert Sievert to millisievert?
Number of Sievert ×1000
Formula to convert millisievert to Sievert?
Number of millisievert / 1000
How many mSv equal 1 rem?
10 mSv
How many rem equal 1 Sv?
100 rem
Practice problems: Convert 10 centisievert to millisieverts
100 mSv
Practice problems: Convert 2.5 Sieverts to millisieverts
2,500 mSv
Practice problems: A patient received a dose of 6mGy from a radiographic exam.
What is their equivalent dose (inc. units of measure)?
What amount of background exposure does this equate to?
• (6mGy)(1) = 6 Sv
• 2 years of background exposure
Effective dose abbreviation
EfD
Effective dose
-Best estimate of overall harm
-the best measure of overall risk of exposure to humans from ionizing radiation
-takes into account: radiation type (Wr) and tissue (Wt)
Effective dose unit of measurement
mSv
formula to determine effective dose
EfD = (D)(Wr)(Wt)
Which tissue/ organ has the highest weighting factor? What is its Wt?
-Gonads
-0.20
Which tissue(s)/ organ(s) has a Wt of 0.12?
- red bone marrow
- colon
- lungs
- stomach
Which tissues)/ organ(s) has the lowest weighting factor? What is its Wt?
-skin and bone surface
- Wt is .01
Collective Effective Dose (ColEfD)
represents an attempt to describe the radiation exposure of a population or group from low doses of different sources of ionizing radiation
How is ColEfd determined/ calculated & what is its unit of measurement?
-The radiation unit of measurement for this quantity is person-sievert
-formula: # Of people x average effective dose
-Example:
if 200 people receive an average effective dose of .25 Sv, the collective effective dose (ColED) is (200)(0.25) = 50 person-sieverts
What is the purpose/ usefulness of Total Effective Dose Equivalent (TEDE)?
a radiation dosimetry quantity that was defined by the Nuclear Regulatory Commission (NRC) to monitor and control human exposure to ionizing radiation
Practice Problem: A patient with lung cancer is undergoing radiation therapy. At their appointment, they had a chest x-ray (CXR) performed that resulted in an absorbed dose to the bones of 0.01 mGy, an absorbed dose of 0.08 mGy to the lungs followed by inhalation alpha particle therapy with an absorbed dose of 10 mGy.
• What is the effective dose they received at this visit (inc. units of measure)?
• Approximately, what amount of background exposure does this equate to?
What is the effective dose they received at this visit (inc. units of measure)?
• (0.01mGy) (1)(0.01) = 0.0001 mSv
• (0.08 mGy) (1)(0.12) = 0.0096 mSv
• (10 mGy) (20)(0.12) = 24 mSv
Approximately, what amount of background exposure does this equate to?
• <1.5 days
• <1.5 days
• >4.5 years
What comprises the largest share of the natural background radiation exposure to the average U.S. citizen?
Radon
radioactive decay
naturally occurring process by which instability of the nucleus is relieved through various types of nuclear spontaneous emissions
