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RadBio Midterm 1

Define diagnostic efficacy The degree to which the diagnostic study accurately reveals the presence or absence of disease
What four things must occur for diagnostic efficacy to be achieved? Procedure must be justified by a referring physician, patient must undergo minimal radiation exposure, optimal images must be produced, and the presence or absence of disease must be revealed
What does ALARA stand for? What is it synonymous with? "As low as reasonably achievable", same as the "optimization of radiation protection" (ORP) principle
What is the threshold for radiation-induced cancer? It doesn't exist
What are the three cardinal rules of ALARA? Time, distance, and shielding
How does the distance rule affect patients and HCWs differently? Patients should be at the standard 100 or 180 centimeters from the x-ray tube, while HCWs should be at greatest possible distance from the beam
What does BERT stand for? "Background equivalent radiation time"
Can BERT be used to assess radiation risk? No, it only provides a means for comparison
What is the BERT for a chest x-ray? A c-spine? Hip? Abdomen? Chest: 10 days, c-spine: 2 weeks, hip: 7 weeks, abdomen: 4 months
How is ionizing radiation different from nonionizing radiation? Ionizing has enough energy to eject electrons from their atoms, while nonionizing does not
Give examples of nonionizing radiation Visible light, infrared, microwaves
What are you two main sources of radiation? Natural and artificial
What are the three types of natural radiation? Cosmic (the sun), terrestrial (radon), and internal (K-40)
Give the traditional and SI units for exposure Traditional: Roentgen (R), SI: Coulombs per kilogram (C/kg)
What replaced exposure? Define and state what units it uses Air Kerma: expresses radiation concentration transferred to a point as the kinetic energy released per unit mass (J/kg or Gy)
What is absorbed dose? Include traditional and SI units The energy transferred from ionizing radiation to tissue per unit mass (traditional: rad, SI: Gy)
What is the equivalent dose? How do we calculate it? A radiation quantity used when one undergoes various types of ionizing radiation, which takes into account radiation weighting factors (Wr) and the amount of absorbed energy (D). EqD = Wr x D
What is the effective dose? What special unit does it use? Provides a measure of the overall risk of radiation exposure to humans while taking into account tissue sensitivitis, radiation weighting factors, and the amount of energy absorbed. Measured in Sieverts (Sv)
What is the radiator weighting factor of x-rays? 1
Are the gonads or is the thyroid more radiosensitive? Gonads
Frequency of electromagnetic radiation must be what for ionization to occur? High
What is the largest amount of artificial radiation made from? Medical imaging (mainly CT)
What type of radiation are alpha and beta particles? Particulate
How many sieverts is one milisievert? 1 mSv = 1/1000th of a Sv
What are two radioactive materials found in the earth's crust? Uranium-238 and Radium-226
When did Chernobyl occur? 1986
How much radiation was released compared to the TMI incident? More than a million times more
How much radiation was released compared to the Hiroshima and Nagasaki atomic bombs? 20-40x more than the two combined
How many people were killed on site after receiving a full body dose exceeding 4 Sv? More than two dozen (>24)
What has been the greatest adverse health effect to the larger population? Thyroid cancer
List 5 people responsible for radiation protection Owner of facility, user of the equipment, equipment operator, safety officer/medical physicist, and referring physician
What is the LD-50? AKA the dose which is lethal over 30 days to 50% of the population 3.0 Sv
What contributes the most to the collective effective dose of the US population? Radon & thoron
What's the average background effective dose in the US? 3 mSv
What's the average background effective dose in Canada? 1.8 mSv
According to SC35, should radiological examinations be performed if there has been no prior clinical examination? No
According to SC35, should radiologic examinations be performed if the risk may not outweight the benefit? No, the benefit should always be great enough to outweigh the risk
What is the origin of x-rays? Emitted from the electronic cloud of an atom (so outside the nucleus) when it has been artificially stimulated
What is the origin of gamma rays? Emitted spontaneously from inside the nucleus of a radioactive atom
What are the origins of electrons and beta particles? Electrons are emitted from outside the nucleus, and beta particles are emitted from inside the nucleus
Compare a photon of x-radiation to a photon of visible light X-radiation will have a significantly higher frequency, and shorter wavelength
What is wave-particle duality? A phenomenon in which electromagnetic energy behaves like both waves and particles
Who should wear personal dosimeters? Anyone who may receive 1/20th of the annual 20 mSv limit
What is the most common type of personal dosimeter? Optically stimulated luminescent (OSL)
What type of detector material does an OSL use? Aluminum oxide (Al2O3)
How are OSLs read? Using a laser light that causes sensing material to become luminescent
What 3 filters are used in an OSL? Aluminum (weakest), tin, and copper (strongest)
Will a high or low kVp cause consistent luminescence in an OSL? High
What is the dynamic range of an OSL? 10 ┼│Sv to 10 Sv; 5 keV to 40+ meV
How often is an OSL replaced? Every 3 months
Can an OSL be reread? Yes (because electors remain trapped in sensing material)
What is the measure of radiation intensity called? Dosimetry
Give two circumstances when an individual might wear 2 dosimeters When pregnant, or when working with fluoroscopy
What does TLD stand for? "Thermoluminescent Dosimeter"
What type of detector material does a TLD use? Lithium fluoride (LiF)
Describe how a TLD is read with heat Electrons which became trapped in higher energy levels by ionizing radiation are returned to their valence bands by heat, releasing light in the process. The light is captured and used to measure radiation as they're directly proportional
Can a TLD be reread? No (electrons have been released)
Can the crystals in a TLD be reused? Yes
What is on a personal monitoring report? Group #, date of report, period start/end dates, dosimeter serial #, full name, multiple group status, type and location of dosimeter, current dose, annual dose, lifetime dose, any anomalies
What are ionization chambers filled with? Xenon gas
Why are ionization chambers good in a diagnostic setting? They're fast and sensitive to the diagnostic x-ray range
Are ionization chambers used in area survey? What about as cumulative exposure devices? Yes to both
What is proportional to the radiation that's being measured in an ionization chamber? The current (generated by freed electrons which are drawn to the anode as voltage is applied)
What classification is VIM? Most radiosensitive; rapidly divides and undifferentiated; spermatogonia, erythroblasts
What classification is DIM? Relatively radiosensitive; actively divide and partially differentiated; intermediate spermatogonia, myelocytes
What classification is MCT? Intermediate; irregularly divides; endothelial cells, fibroblasts
What classification is RPM? Relatively radioresistant; don't normally divide (but can) and high differentiated; lymphocytes, bone, muscle cells
What classifications is FPM? Most radioresistant; don't divide and highly differentiated; spermatozoa, erythrocytes
Via what three modes in radiation energy transferred to tissues? Excitation, ionization, and thermal heating
Are biologic effects of radiation unique? What does that entail? No, the same effects could be caused by other means
What is the name of the time gap which precedes the appearance of damage caused by radiation? The latent period
What three things determine radiation energy transfer? Linear energy transfer (LET), relative biological effectiveness (RBE), and the oxygen-enhancement ratio (OER)
What is LET? Explain the difference between high and low LET The average energy transferred per unit length of track. High has many interactions over a short distance traveled and is more damaging. Low has fewer interactions over a long distance traveled and is less damaging (x-rays are low LET)
What kind of damage is more commonly caused by x-rays? Indirect (from free radicals) because it's low LET
Can x-rays induce single-strand breaks in DNA? Technically yes, but it doesn't occur frequently because it's low LET
What is RBE? Relative capabilities of radiation with differing LETs to produce a particular biologic reaction
Do equal doses of radiation with different LETs produce the same biologic responses? No
What is RBE used to calculate? Radiation weighting factors (Wr) and thus equivalent and effective doses
What is RBE dependent on? Dose size and rate of administration
What is protraction? The continuous administration of radiation at a lower dose
What is fractionation? Breaking up radiation doses with time in between each
Why do protraction and fractionation decrease RBE? They allow more time for intracellular repair and tissue recovery
What is the RBE of x-rays? 1
What is the oxygen fixation hypothesis? Biologic tissues are more sensitive if oxygenated because free radicals combine to form harmful organic peroxides
How do you calculate OER? (dose required to cause biological response without oxygen) / (dose required to cause biological response with oxygen)
What's the average OER for low-LET mammalian cells? 2-3
What's the average OER for high-LET mammalian cells? 1
What's the relationship between LET and RBE? As one increases so does the other
What's the relationship between LET and OER? As one increases the other decreases
What is the law of Bergonie and Tribondeau The radiosensitivity of living tissue varies with maturation and metabolism
What is the photoelectric effect? When a photon removes electrons from an inner shell (electrons from outer shells will fall in to replace it)
What is the compton effect? When a photon removes electrons from the outer (valence) shell
Created by: Ewood61