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RADT 465 Safety
ARRT registry review covering radiation safety content area
Question | Answer |
---|---|
What are the two mechanisms through which x-ray production occurs? | Bremsstrahlung radiation and Characteristic radiation Page 252 |
Which type of radiation is this: a high speed electron is deflected from its path and the loss of kinetic energy is emitted in the form of an x-ray photon. | Bremsstrahlung "Braking" radiation Page 252 |
What percentage of the primary beam is made up by Bremsstrahlung radiation? | 70%-90% Page 252 |
What type of radiation is this: a high speed electron encounters a tungsten atom, ejects a K-shell electron, leaving a vacancy. An electron from a higher energy shell fills the vacancy, ejecting an x-ray photon. | Characteristic radiation Page 252 |
What percentage of the primary beam is made up by Characteristic radiation? | 10%-30% Page 253 |
What is the energy of a K-characteristic x-ray? | 69 keV Page 253 |
The gradual decrease in exposure rate as ionizing radiation passes through tissues is called what? | Attenuation Page 253 |
In which effect does the incoming (low energy) photon release ALL of its energy to eject an inner shell electron? | Photoelectric effect Page 253 |
As atomic number increases, the photoelectric effect _________. | Increases Page 253 |
In which effect does the incoming (high energy) photon use PART of its energy to eject an outer shell electron and change the direction of the photon (scatter) | Compton Scatter Page 253 |
Wavelength and frequency are inversely/directly related. | Inversely related Page 254 |
Name a few examples of late effects. | Cataractogenesis, carcinogenesis, Embryologic effect, and life-span shortening Page 256 |
Which type of risk is characterized by nonlinear dose responses and are associated with a threshold (safe) dose below which no effect is observed? | Nonstochastic/deterministic Page 257 |
Which risk generally has no threshold and no safe dose? | Stochastic/probabilistic Page 257 |
Which Law states that that stem cells, immature cells, and highly mitotic cells are particularly radiosensitive? | Law of Bergonie and Tribondeau Page 258 |
What is the formula for Equivalent dose (EqD)? | Absorbed dose x radiation weighting factor Page 258 |
What is the formula for Effective dose (EfD)? | Absorbed dose x radiation weighting factor x tissue weighting factor Page 258 |
What is the radiation weighting factor for x-rays and gamma rays? | 1 Page 258 |
What is the rate at which radiation deposits energy as it passes through tissue? | LET (Linear Energy Transfer) Page 259 |
As the LET of radiation increases, the radiations ability to produce biologic damage increases/decreases? | Increases Page 259 |
LET and RBE are directly/inversely related? | Directly RBE=Relative biologic effectiveness Page 259 |
Diagnostic x-rays are considered to be high/low LET radiation? | Low-LET radiation Page 259 |
What percentage of the body is composed of water? | 65%-80% Page 259 |
What are the two types of ionizing effects that occur? | Direct effect and indirect effect Page 259 |
Which ionizing effect occurs with high-LET radiation and interacts directly with the key molecule (DNA). | Direct effect Page 259 |
Which ionizing effect occurs with low-LET radiation (x-rays), happens more frequently, and happens when ionization takes place in cellular water instead of the DNA? | Indirect effect Page 259 |
What is the term called when ionization of water molecules in the body causes the molecules to break into smaller molecules (free radicals)? | Radiolysis Page 259 |
Free radicals occur with which ionizing effect? | Indirect effect Page 259 |
DNA replicates during which stage of interphase cell cycle? | Synthesis (S) phase. which is the least radiosensitive stage of the cell cycle Page 260 |
Which cells are extremely radiosensitive? | Lymphocytes, epithelial tissue, genetic cells (the most radiosensitive cell is the lymphocyte) Page 260 |
Which cells are not as radiosensitive? | Muscle and nervous tissues (nervous tissue is the most radioresistant) Page 260 |
The greater the oxygen content of tissues the lesser/greater their radiosensitivity? | Greater Page 261 |
The oxygen enhancement ratio (OER) can be determined by what formula? | divide the dose required to cause an effect without oxygen by the dose required to cause that effect with oxygen Page 261 |
During which part of pregnancy, if fetal irradiation occurs, can embryonic resorption or spontaneous abortion happen? | During the first two weeks of gestation Page 262 |
What is the 10 Day Rule in regards to scheduling procedures for pregnant women? | This rule identifies the first 10 days following onset of the menses as the safest time to schedule a radiographic procedure. Page 263 |
What are the 3 acute radiation syndromes? | Hematopoietic, Gastrointestinal, and Cerebrovascular Page 266 |
What is ARS? | Acute radiation syndrome (radiation sickness). This is an acute condition caused by a large exposure of ionizing radiation to all or most of the body. Page 266 |
What amount of radiation does the hematopoietic syndrome appear? | Doses between 1-10 Gy. It can cause nausea, vomiting, diarrhea, decreased blood count, infection and hemorrhage. Page 266 |
What amount of radiation does the Gastrointestinal syndrome appear? | Occurs between 6-10 Gy. It causes damage to the stem cells lining the GI system resulting N, V, D, blood changes, and hemorrhage. Death usually occurs within 2 weeks Page 266 |
What amount of radiation does the Cerebrovascular syndrome appear? | Occurs at doses above 50 Gy. There is a collapse of the circulatory system, increased cranial pressure, vasculitis, meningitis, ataxia, and shock. Death occurs in 3 days. Page 266 |
What are the four stages of ARS? | Prodromal, Latent, Manifest illness, and Recovery or death Page 267 |
What are the symptoms of the prodromal stage? | Nausea, vomiting, and diarrhea that occur 1-2 days following the exposure Page 267 |
What are the symptoms of the Latent stage? | Symptoms disappear for a few weeks. The length of the latent stage depends on the amount of exposure received (inversely related) Page 267 |
What are the symptoms of the Manifest illness stage? | Symptoms depend on the specific syndrome and can last up to several months depending on severity. Page 267 |
What is LD50/30? | The whole-body dose of ionizing radiation that can be lethal to 50% of the exposed population within 30 days of exposure Page 267 |
What is the recommended method of choice for determining patient radiation skin dose during imaging? | DAP meter (Dose area product) Page 270 |
What is the most important consideration in reducing patient exposure? | Good patient communication Page 274 |
What is the single most important factor in reducing patient dose? | Beam restriction Page 274 |
What are the 3 basic types of beam restrictors? | Aperture diaphragms, cones, and collimators. Page 274 |
What is one disadvantage of the aperture and the cone restrictors? | They have one fixed opening size. You would have to change the entire aperture or cone to change the irradiated field. Page 274 |
Which is the most practical and efficient beam restricting device? | The collimator Page 275 |
What angle is the mirror in the collimator assembly? | 45 degrees Page 275 |
True/False: For the light field and x-ray field to correspond accurately, the x-ray tube focal spot and the light bulb must be exactly the same distance from the center of the mirror. | True Page 275 |
The NCRP guidelines state the collimators must be accurate to within what percentage of the source-to-image-receptor distance (SID)? | 2% Page 276 |
What feature allows the collimator to open or close automatically according to the IR size being used in the Bucky tray? | Positive Beam Limitation (PBL) Page 276 |