Safety: Radiation Physics and Radiobiology Flashcards

Question

92. Which unit is used to express the absorbed dose? A. Roentgen B. rem C. rad D. Sv

Answer 1

C. rad Radiation absorbed dose (rad) is the unit of measure for absorbed dose installed on a medium. Gray (Gy) is the SI unit of absorbed dose.

Answer 2

D. Sievert The SI unit of absorbed dose equivalent is the Sievert. 1 cSv is equivalent to 1 rem, and 1 Sv is equivalent to 100 rems. Sievert is a measurement which describes the capacity of radiation to elicit a certain biological reaction in a medium.

Answer 3

A. Sievert The sievert (Sv) is the International System of Units (SI) measure for dose equivalent, representing the biological impact of ionizing radiation. It is determined by multiplying the absorbed dose in gray (Gy) by a quality factor (QF), which adjusts for the varying biological effects of different radiation types. Historically, the unit "rem" (radiation equivalent man) was used, where 1 Sv equals 100 rem. However, the sievert has become the standard unit in contemporary practice. Reference: U.S. Nuclear Regulatory Commission. (n.d.). § 20.1004 Units of radiation dose. Retrieved from [source link]. This reference provides information on radiation dose units, confirming that the gray (Gy) is the SI unit for absorbed dose and the sievert (Sv) is the SI unit for dose equivalent.

Answer 4

B. Roentgen The Roentgen is the exposure unit that will produce 2.58 × 10⁻⁴ C/kg. As an indicator of exposure, within the diagnostic range, the roentgen is unaffected by field size or area.

Answer 5

C. mGy The United States Food and Drug Administration (FDA) Code of Federal Regulations (CFR), Title 21, Volume 8 states, “cumulative air kerma means the total air kerma accrued from the beginning of an examination or procedure and includes all contributions from fluoroscopic and radiographic irradiation” and that “fluoroscopic air kerma display device means a device, subsystem, or component that provides the display of AKR and cumulative air kerma required by § 1020.32(k), which includes radiation detectors, if any, electronic and computer components, associated software, and data displays.” In compliance with the FDA CFR, Title 21, cumulative air kerma is displayed in a unit of mGy (milligray in air).

Answer 6

C. Adult nerve cells Nerve cells are the least radiosensitive in the body; in fetal life, however, nerve cells are extremely radiosensitive. Muscle cells have a relatively low level of radiosensitivity. The most radiosensitive of all bodily cells are lymphocytes, a subset of white blood cells that are involved in the immune system.

Answer 7

D. Used to plot genetic effects of radiation A linear dose-response curve is used to illustrate the genetic consequences of radiation and some somatic effects. With the linear non-threshold (LNT) model, there is no threshold for the linear dose-response curve, meaning that radiation is never completely safe below a certain level. There are also linear-threshold dose-response models, which have a known threshold below which no effects are observed.

Answer 8

B. Linear energy transfer increases Biologic effect and damage will rise in proportion to the linear energy transfer, or transferred energy (LET), which is a result of interactions between radiation and a biologic medium. Depending on the radiation type and the properties of the absorber, LET describes the rate at which photon or particle energy is transferred to (absorbed by) biologic material (via ionization processes).

Answer 9

D. Probabilistic effects A late reaction to low-dose exposure characterizes a dose-response type relationship known as probabilistic effects, also called stochastic effects. Genetic effects and radiation-induced cancer are the late (or stochastic) consequences of radiation exposure. These can happen years after surviving an acute radiation dose or during prolonged exposure to low radiation levels. Personnel who are exposed to low doses of radiation over extended periods of time must be particularly mindful of the late effects of radiation. Guidelines for occupational radiation protection are consequently founded on the late effects of radiation as determined by a non-threshold, linear dose-response curve.

Answer 10

D. Oxygenated tissue The oxygen enhancement ratio (OER) defines aerobic conditions' capacity to increase radiation efficiency. A cell's sensitivity to radiation rises with increased oxygenation; a cell which is oxygen-free is less sensitive. Tissue without oxygen is referred to as anoxic, and tissue with little oxygen is referred to as hypoxic. Because anoxic and hypoxic lesions often have little to no blood flow, they are more radioresistant.

Answer 11

A. Somatic effects Short-term early somatic effects may manifest if a significant dose of radiation is applied to the entire body at once. For example, acute radiation syndrome results from bodily exposure to 600 rad (6 Gy) at one time. Leukopenia, exhaustion, nausea, vomiting, diarrhea, and other symptoms are early indicators of acute radiation syndrome and appear during the prodromal phase of the condition.

Answer 12

E. A, B, and C Early somatic effects require a very high dosage of radiation administered to the entire body in a little amount of time. Consequently, doses derived from proper use of diagnostic radiologic procedures cannot cause early somatic effects. Though, technologists still need to be aware of early somatic effects. Certain high dose CT scans or fluoroscopy procedures may have early somatic repercussions, such as erythema or epilation, if they are not performed carefully. Following radiation exposure, early somatic symptoms may appear minutes, hours, days, or weeks later. Depending on which system or systems are affected and what symptoms occur, whole body reactions can be classified as either hematologic, gastrointestinal, or central nervous system responses.

Answer 13

C. Late somatic effect The long-term repercussions of radiation exposure are a concern for individuals who are employed in environments where radiation is present. Low, prolonged doses might result in late somatic consequences, which can manifest years after initial exposure. Radiation can cause cancerous somatic consequences, such as skin cancer, leukemia, thyroid tumors, and malignancies of the bones. A further example of the late somatic consequences of radiation is the development of cataracts on an individual's orbital lenses following chronic radiation exposure.

Answer 14

E. A and B In addition to local effects like skin erythema, infertility, and cataracts, occupationally exposed individuals are primarily concerned with late effects of ionizing radiation, such as radiation-induced leukemia, genetic effects, and cancers, like bone, thyroid, breast, and lung malignancies; these effects can manifest years after initial exposure to low levels of ionizing radiation. The radiosensitivity of a cell is directly related to its rate of reproduction and is inversely proportionate to its degree of differentiation, according to the law of Bergonie and Tribondeau.

Answer 15

C. Skin erythema Infertility, skin erythema, and cataracts are examples of delayed local effects of radiation exposure, following a linear, threshold, dose-response curve. The linear, non-threshold dose response curve signifies long-term (delayed) somatic effects.

Answer 16

D. A and B The effects of radiation on the irradiated tissue(s) are known as somatic effects. The timing of somatic effects (i.e., early, late) is determined by the amount of time that passes between radiation exposure and the onset of symptoms. The reproductive organs of humans are very radiosensitive. The germ cells that are generated in the ovaries (oogonia) and testes (spermatogonia) have a significant impact on inheritance and fertility. Genetic alterations and/or temporary or permanent infertility can result from excessive radiation exposure to the gonads. While genetic changes have an impact on future generations, infertility is a somatic condition because it affects the exposed individual.

Answer 17

E. A and C Leukemia, which is a cancer of the body's blood-forming tissues, or a reduction in life expectancy can result from excessive radiation exposure to the bone marrow or other blood-forming organs. Erythroblasts are young, immature, highly radiosensitive embryonic cells, and lymphocytes are the body's most radiosensitive cells.

Answer 18

D. 5 mSv The NCRP suggests a 5 mSv maximum total equivalent dosage for the embryo or fetus. This can also be expressed as 500 mrem or 0.5 rem. For the duration of the gestational period, this dosage limit applies. For each month during pregnancy, the maximum allowable dose is 0.5 mSv, also expressed as 50 mrem or 0.05 rem.

Answer 19

C. Acute radiation dermatitis Carcinogenesis, cataractogenesis, embryological effect, and a reduction in longevity are four categories of late radiation exposure

Answer 20

B. Erythropenia The gonads may have transient sterility, and the skin may experience erythema and epilation as an immediate localized consequence of excessive radiation exposure. Erythropenia refers to an atypical reduction in the quantity of red blood cells circulating throughout the body and would be considered a hematologic somatic effect.

Answer 21

E. A and C Effects that are nonstochastic, or deterministic, have a threshold dose that needs to be exceeded in order for them to manifest. Greater doses cause nonstochastic effects to become more severe. Erythema, cataracts, and infertility are a few instances of nonstochastic effects. To prevent nonstochastic effects, dose limits have been defined.

Answer 22

A. A late effect of radiation exposure which exhibits no threshold dose Stochastic effects are defined as those which happen by chance, without a dose threshold, whose severity is dose-independent and whose probability is dose-proportional. Cancer and genetic impacts are the two main stochastic consequences in the context of radiation protection.

Answer 23

C. Linear no-threshold model Experts contend that radiation exposure causes cancer to develop in a stochastic way, meaning that there is no threshold, and the risk rises proportionately with dose. According to the linear-no threshold model, the risk of inducing cancer increases linearly and does not have a threshold. The International Commission on Radiological Protection presently recognizes this concept.

Answer 24

A. Cataractogenesis Short-term, early somatic effects of acute radiation syndrome may occur if a significant dose of radiation is applied to the entire body at once (i.e., whole body dose of 600 rad [6 Gy]). Severe nausea, vomiting, diarrhea, leukopenia, and fatigue are early symptoms of acute radiation syndrome that appear in the prodromal stage of the condition. Cataractogenesis is a chronic somatic effect relative to radiation exposure.

Answer 25

A. Central nervous system syndrome Although certain symptoms can appear after a dose as low as 20 Gy, or 2000 rads, central nervous system syndrome usually manifests with a dose larger than about 50 Gy, or 5000 rads. After such a significant exposure, death typically results within three days. An increase in pressure in the constraining cranial vault because of an elevation in fluid content from edema, vasculitis, and meningitis, along with expected collapse of the circulatory system, are the primary causes of death. Gastrointestinal (GI) syndrome generally results from an exposure between 6 and 10 Gy. Bone marrow syndrome, which is also called hematopoietic syndrome, results following a dose of between 0.7 and 10 Gy.

Answer 26

E. Quantum mottle The image designated "A" was acquired using 2 mAs and the image labeled "B" was reacquired at 160 mAs. The primary observation is the significant rise in quantum mottle associated with the low exposure in the image labeled "A" (observe pixel value variation in the circled area).

Answer 27

D. Increase mAs The image designated "A" was acquired using 2 mAs and the image labeled "B" was reacquired at 160 mAs. The primary observation is the significant rise in quantum mottle associated with the low exposure in the image labeled "A" (observe pixel value variation in the circled area).

Answer 28

The computed radiography sample frequency and the line frequency "To stop scattered x-ray photons from lowering the quality of images, antiscatter grids are frequently utilized. Lead strips and aluminum strips, which are x-ray absorbing and transmitting materials, respectively, make up these grids. A grid artifact may arise if the frequency of these lines per centimeter in the grid is near the computed radiography sample frequency."

Answer 29

An electrical discharge that causes lightning-like black densities on the radiograph is the source of static artifact.

Answer 30

B. Reduce scatter This diagram illustrates the usage of an air gap technique to minimize scatter. There are less scattered photons that come into contact with the detector in image B because there is a larger air gap between the patient and the detector in comparison to image A. Due to the patient's closer proximity to the source of photons, the patient will receive a higher dose of radiation

Answer 31

A. Dead pixel artifact "Even when the patient’s position changes, there is a spherical artifact that remains in the same place on all radiographic images. A burned-out or dead pixel caused this artifact."

Answer 32

E. A and B In this instance, an exposure of 80 kVp over 80 mAs (EI 2611) has produced an oversaturated (unduly dark) 'burnt out image.' A swimmer's lateral cervical spine radiograph frequently needs high exposures to penetrate through substantial amounts of soft tissue. Overexposure should be suspected if the radiographer is unable to window the soft tissue and bony features into an ideal image. A filter helps prevent lower density areas from being overexposed in a swimmer's lateral cervical spine radiograph. Alternatively, decreased mAs may be necessary.

Answer 33

B. Moiré pattern A moiré pattern on a digital radiograph appears as an interference pattern, typically resulting from the misalignment of the grid used during image acquisition and the pixel array of the digital detector. This misalignment creates an optical illusion, manifesting as alternating light and dark bands or patterns superimposed on the radiographic image, potentially obscuring diagnostic information. Adjusting the alignment of the grid or employing software corrections can help mitigate or eliminate moiré artifacts.

Safety: Radiation Physics and Radiobiology Flashcards

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