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RADT 465 Safety

ARRT registry review covering radiation safety content area

QuestionAnswer
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
Created by: CarolAR
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