Radiation Protection (Biological aspects of radiation) ARRT
Which acute radiation syndrome requires the largest exposure before any effects become apparent?
Central nervous system (CNS) Radiation effects that appear days or weeks following exposure (early effects) are in response to high radiation doses; this is called acute radiation syndrome.
Usually occurs with high-LET radiations and when ionization occurs at the DNA molecule itself.
The direct effect
Which of the following types of adult tissues is (are) relatively insensitive to radiation exposure? 1. Muscle tissue 2. Nerve tissue 3. Epithelial tissue
1. Muscle tissue 2. Nerve tissue
Which of the following cell types has the lowest radiosensitivity? 1.Nerve cells 2.Muscle cells 3.Spermatids 4.Lymphocytes
1.Nerve cells Muscle cells have a fairly low radiosensitivity, and nerve cells are the least radiosensitive in the body (in fetal life, however, nerve cells are highly radiosensitive). Lymphocytes, a type of white blood cell concerned with the immune system, have the greatest radiosensitivity of all body cells. Spermatids are also highly radiosensitive, although not to the same degree as lymphocytes.
Biologic material is least sensitive to irradiation under which conditions?
Anoxic Anoxic refers to tissue without oxygen; hypoxic refers to tissue with little oxygen. Anoxic and hypoxic tumors typically are avascular (with little or no blood supply) and, therefore, more radioresistant.
The interaction between ionizing radiation and the target molecule that is most likely to occur is the
Indirect effect
Biologic material is most sensitive to radiation exposure under which of the following conditions?
Oxygenated Tissue is most sensitive to radiation exposure when it is in an oxygenated condition.
The dose of radiation that will cause a noticeable skin reaction is referred to as the
SED Erythema is the reddening of skin as a result of exposure to large quantities of ionizing radiation. It was one of the first somatic responses to irradiation demonstrated to the early radiology pioneers. The effects of radiation exposure to the skin follow a nonlinear, threshold dose-response relationship.
What is the term used to describe x-ray photon interaction with matter and the transference of part of the photon's energy to matter?
Scattering occurs when there is partial transfer of the proton's energy to matter, as in the Compton effect.
How are LET and biologic response related?
They are directly related.
Isotopes are atoms that have the same isos ("equal") and topos ("place"), meaning "the same place";
atomic number but a different mass number Isotopes are atoms of the same element (the same atomic number or number of protons) but a different mass number. They differ, therefore, in their number of neutrons.
Somatic effects of radiation refer to effects that are manifested
during the life of the exposed individual Somatic effects of radiation refer to those effects experienced directly by the exposed individual, such as erythema, epilation, and cataracts.
constantly regenerate through mitosis they are very radiosensitive.
epithelial cells
Of these, red blood cell precursors, are the most radiosensitive.
erythroblasts,
Which occurs most frequently, happens when ionization takes place away from the DNA molecule in cellular water.
indirect effect
The effects of radiation on biologic material depend on several factors. If a large quantity of radiation is delivered to a body over a short period of time, the effect
will be greater than if it were delivered in increments
Which of the following dose-response curve characteristics represent genetic and some somatic responses to radiation? 1. Linear 2. Nonthreshold 3. Sigmoidal
1. Linear 2. Nonthreshold Genetic effects of radiation and some somatic effects, like leukemia, are plotted on a linear dose-response curve. The linear dose-response curve has no threshold, that is, there is no dose below which radiation is absolutely safe.
Which of the following anomalies is (are) possible if an exposure dose of 40 rad (400 mGy) were delivered to a pregnant uterus in the third week of pregnancy? 1.Skeletal anomaly 2.Organ anomaly 3.Neurologic anomaly
1.Skeletal anomaly 2.Organ anomaly Skeletal and/or organ anomalies can appear if irradiation occurs in the early part of this time period, and neurologic anomalies can be formed in the latter part; mental retardation and childhood malignant diseases,
Which of the following statements regarding the human gonadal cells is (are) true? 1.The female oogonia reproduce only during fetal life. 2.The male spermatogonia reproduce continuously. 3.Both male and female stem cells reproduce only during fetal life.
1.The female oogonia reproduce only during fetal life. 2.The male spermatogonia reproduce continuously. The development of male and female reproductive stem cells has important radiation protection implications. Male stem cells reproduce continuously. However, female stem cells develop only during fetal life; women are born with all the reproductive cells they will ever have. It is exceedingly important to shield children whenever possible because they have their reproductive futures ahead of them.
Which of the following types of radiation is (are) considered electromagnetic? 1.X-ray 2.Gamma 3.Beta
1.X-ray 2.Gamma Alpha and beta radiation are particulate radiations; alpha is composed of two protons and two neutrons, and beta is identical to an electron. Gamma and x-radiation are electromagnetic, having wave-like fluctuations like other radiations of the electromagnetic spectrum (e.g., visible light and radio waves).
LET is best defined as 1.a method of expressing radiation quality 2.a measure of the rate at which radiation energy is transferred to soft tissue 3.absorption of polyenergetic radiation
1.a method of expressing radiation quality 2.a measure of the rate at which radiation energy is transferred to soft tissue When biologic material is irradiated, there are a number of modifying factors that determine what kind and how much response will occur in the material. One of these factors is LET, which expresses the rate at which particulate or photon energy is transferred to the absorber. Because different kinds of radiation have different degrees of penetration in different materials, it is also a useful way of expressing the quality of the radiation.
The photoelectric effect is more likely to occur with 1.absorbers having a high Z number 2.high-energy incident photons 3.positive contrast media
1.absorbers having a high Z number 3.positive contrast media The photoelectric effect occurs with high-atomic-number (Z) absorbers such as bone and with positive contrast media.
The late effects of radiation are considered to 1.have no threshold dose. 2.be directly related to dose. 3.occur within hours of exposure
1.have no threshold dose. 2.be directly related to dose. Late effects of radiation exposure, such as carcinogenesis, are considered to be related to the linear nonthreshold dose-response curve. That is, there is no safe dose; theoretically, even one x-ray photon can induce a later response.
Somatic effects resulting from radiation exposure can 1.have possible consequences on the exposed individual 2.have possible consequences on future generations 3.cause temporary infertility
1.have possible consequences on the exposed individual 3.cause temporary infertility It is well established that sufficient quantities of ionizing radiation can cause a number of serious somatic and/or genetic effects. Somatic effects of radiation are those that affect the irradiated body itself.
The law of Bergonié and Tribondeau states that cells are more radiosensitive if they are 1.highly proliferative 2.highly differentiated 3.immature
1.highly proliferative 3.immature Bergonié and Tribondeau were French scientists who, in 1906, theorized what has now become verified law. Cells are more radiosensitive if they are immature (undifferentiated or stem) cells, if they are highly mitotic (having a high rate of proliferation), and if the irradiated tissue is young. Cells and tissues that are still undergoing development are more radiosensitive than fully developed tissues.
The dose-response curve that appears to be valid for genetic and some somatic effects is the 1.linear 2.nonlinear 3.nonthreshold
1.linear 3.nonthreshold
Which of the following is (are) possible long-term somatic effects of radiation exposure? 1.Blood changes 2.Cataractogenesis 3.Embryologic effects
2.Cataractogenesis 3.Embryologic effects Formation of cataracts or cancer (such as leukemia) and embryologic damage are all possible long-term somatic effects of radiation exposure. A fourth is life-span shortening.
Which of the following types of adult tissue is (are) comparatively insensitive to effects of ionizing radiation? 1.Epithelial tissue 2.Nerve tissue 3.Muscle tissue
2.Nerve tissue 3.Muscle tissue Because muscle and nerve tissues perform specific functions and do not divide, they are relatively insensitive to ionizing radiation exposure.
The principal late effects of ionizing radiation on humans include 1.local tissue damage 2.genetic effects 3.malignant disease
2.genetic effects 3.malignant disease Late or long-term effects of radiation can occur in tissues as a result of chronic exposure or tissues that have survived a previous irradiation months or years earlier. These late effects, such as carcinogenesis and genetic effects, are "all-or-nothing" effects—either the organism develops cancer or it does not.
Stochastic effects of radiation are those that 1.have a threshold 2.may be described as "all-or-nothing" effects 3.are late effects
2.may be described as "all-or-nothing" effects 3.are late effects Late effects of radiation can occur in cells that have survived a previous irradiation months or years earlier. These late effects, such as carcinogenesis and genetic effects, are "all-or-nothing" effects—either the organism develops cancer or it does not. Most late effects do not have a threshold dose; that is, any dose, however small, theoretically can induce an effect.
Which type of dose-response relationship represents radiation-induced leukemia and genetic effects? 1.Linear, threshold 2.Nonlinear, threshold 3.Linear, nonthreshold 4.Nonlinear, nonthreshold
3.Linear, nonthreshold Radiation-induced malignancy, leukemia, and genetic effects are late effects (or stochastic effects) of radiation exposure. These can occur years after survival of an acute radiation dose or after exposure to low levels of radiation over a long period of time. Radiation workers need to be especially aware of the late effects of radiation because their exposure to radiation is usually low level over a long period of time.
Examples of stochastic effects of radiation exposure include 1.radiation-induced malignancy 2.genetic effects 3.leukemia
ALL...
Possible responses to irradiation in utero include 1.spontaneous abortion 2.congenital anomalies 3.childhood malignancies
ALL...
The effect of ionizing radiation on tissue depends on which of the following? 1.Type of tissue interaction(s) 2.Amount of interactions 3.Biologic differences
ALL...
Which of the following is (are) considered long-term somatic effect(s) of exposure to ionizing radiation? 1.Life-span shortening 2.Carcinogenesis 3.Cataractogenesis
ALL...
Which of the following radiation exposure responses exhibit a nonlinear threshold dose-response relationship? 1. Skin erythema 2. Hematologic depression 3. Lethality
ALL... The nonlinear/sigmoidal dose-response curve has a threshold and is thought to be generally correct for most somatic effects
Which of the following is (are) considered especially radiosensitive tissues? 1.Bone marrow 2.Intestinal crypt cells 3.Erythroblasts
ALL... All the tissues listed are considered especially radiosensitive. The intestinal crypt cells of Lieberkühn are responsible for the absorption of nutrients into the bloodstream. Because these cells are continually being cast off, new cells must continually arise.
In 1906, Bergonié and Tribondeau theorized that undifferentiated cells are highly radiosensitive. Which of the following is (are) characteristic(s) of undifferentiated cells? 1.Young cells 2.Highly mitotic cells 3.Precursor cells
ALL... Cells that are termed undifferentiated are immature or young. They have no specific function and/or structure. They are usually precursor cells; their most important function is to divide. Mitosis is the most radiosensitive part of the cell cycle.
Examples of late effects of ionizing radiation on humans include: 1.leukemia 2.local tissue damage 3.malignant disease
ALL... Occupationally exposed individuals are concerned principally with late (i.e., long-term or delayed) effects of ionizing radiation such as radiation-induced genetic effects, leukemia, and cancers (e.g., bone, lung, thyroid, and breast), as well as local effects, such as skin erythema, infertility, and cataracts—these can occur many years following initial exposure to low levels of ionizing radiation. The long-term/delayed effects usually are chronic, and many are represented by the linear, nonthreshold dose-response curve.
The radiation dose to an individual depends on which of the following? 1.Type of tissue interaction(s) 2.Quantity of radiation 3.Biologic differences
ALL... Photoelectric interaction in tissue involves complete absorption of the incident photon, whereas Compton interactions involve only partial transfer of energy. The larger the quantity of radiation and the greater the number of photoelectric interactions, the greater is the patient dose. Radiation dose to more radiosensitive tissues, such as gonadal tissue or blood-forming organs, is more harmful than the same dose to muscle tissue.
Which of the following factors can affect the amount or the nature of radiation damage to biologic tissue? 1.Radiation quality 2.Absorbed dose 3.Size of irradiated area
ALL... Radiation quality determines degree of penetration and the amount of energy transferred to the irradiated tissue (LET). Certainly, the larger the absorbed radiation dose, the greater is the effect. Biologic effect is increased as the size of the irradiated area is increased. The nature of the effect is influenced by the location of irradiated tissue (bone marrow vs. gonads).
What is (are) the major effect(s) of deoxyribonucleic acid (DNA) irradiation? 1.Malignant disease 2.Chromosome aberration 3.Cell death
ALL... If the damage happens to the DNA of a germ cell, the radiation response may not occur until one or more generations later.
Irradiation of macromolecules in vitro can result in 1.main-chain scission 2.cross-linking 3.point lesions
ALL... Irradiation damage is a result of either the effects of irradiation on water (radiolysis) or its effects on macromolecules. Main-chain scission breaks the DNA molecule into two or more pieces. Cross-linking is incorrect joining of broken DNA fragments. A point lesion is the disruption of a single chemical bond as a result of irradiation.
Late radiation-induced somatic effects include 1.thyroid cancers 2.cataractogenesis 3.skin cancers
ALL... Late somatic effects are those that can occur years after initial exposure and are caused by low, chronic exposures. Occupationally exposed personnel are concerned with the late effects of radiation exposure. Bone malignancies, thyroid cancers, leukemia, and skin cancers are examples of carcinogenic somatic effects of radiation.
How do fractionation and protraction affect radiation dose effects? 1.They reduce the effect of radiation exposure. 2.They permit cellular repair. 3.They allow tissue recovery.
ALL... influence the effect of radiation on tissue. Larger quantities, of course, increase tissue effect. The energy (i.e., quality and penetration) of the radiation determines whether the effects will be superficial (erythema) or deep (organ dose). If the dose is delivered in portions (fractionation) and/or delivered over a length of time (protraction), the less the tissue effects.
______ occurs when an x-ray photon interacts with matter and disappears, as in the photoelectric effect.
Absorption
What is the relationship between LET and RBE?
As LET increases, RBE increases.
a high-energy incident photon uses some of its energy to eject an outer-shell electron. In doing so, the incident photon is deflected with reduced energy, but usually retains most of its original energy and exits the body as an energetic scattered photon.
Compton scatter In Compton scatter, the scattered radiation will either contribute to image fog or pose a radiation hazard to personnel, depending on its direction of exit.
The x-ray interaction with matter that is responsible for the majority of scattered radiation reaching the image receptor (IR) is
Compton scatter In doing so, the incident photon is deflected with reduced energy, but it usually retains most of its energy and exits the body as an energetic scattered ray. This scattered ray will either contribute to image fog or pose a radiation hazard to personnel depending on its direction of exit.
Which interaction between x-ray photons and matter involves partial transfer of the incident photon energy to the involved atom?
Compton scattering the high-energy incident photon uses only part of its energy to eject an outer-shell electron. It retains most of its original energy in the form of a scattered x-ray. The outer-shell electron leaves the atom and is called a recoil electron. Compton scatter is the interaction between x-ray photons and matter that occurs most frequently in diagnostic x-ray and is the major contributor of scattered radiation fog.
Occupational exposure received by the radiographer is mostly from
Compton scattering Radiologic personnel can be exposed to that high-energy scattered radiation, especially in fluoroscopy and mobile radiography. Lead aprons are used to protect us from exposure to scattered radiation during these procedures.
All the following radiation-exposure responses exhibit a nonlinear threshold dose-response relationship except A.skin erythema B .hematologic depression C.radiation lethality D. leukemia
D. leukemia The genetic effects of radiation and some somatic effects, such as leukemia, are plotted on a linear dose-response curve. The linear dose-response curve has no threshold; that is, there is no dose below which radiation is absolutely safe.
The target theory applies to
DNA molecules The target theory specifies that DNA molecules are the targets of greatest importance and sensitivity; that is, DNA is the key sensitive molecule. However, since the body is 65% to 80% water, most interactions between ionizing radiation and body cells will involve radiolysis of water rather than direct interaction with DNA.
Which of the following ionizing radiations is described as having an RBE of 1.0?
Diagnostic x-rays The RBE [sometimes called quality factor (QF)] of diagnostic x-rays is 1, the RBE of fast neutrons is 10, the RBE of 5-MeV alpha particles is 20, and the RBE of 10-MeV protons is 5.0.
Which of the following defines the gonadal dose that, if received by every member of the population, would be expected to produce the same total genetic effect on that population as the actual doses received by each of the individuals?
Genetically significant dose The genetically significant dose (GSD) illustrates that large exposures to a few people are cause for little concern when diluted by the total population. On the other hand, we all share the burden of that radiation received by the total population, especially as the use of medical radiation increases, so each individual's share of the total exposure increases
Low-energy photon interacts with an atom but causes no ionization; the incident photon disappears in the atom, then immediately reappears and is released as a photon of identical energy but changed direction.
In classical scatter Thompson scatter is another name for classical scatter.
Which interaction between ionizing radiation and the target molecule involves formation of a free radical?
Indirect effect which occurs most frequently, happens when ionization takes place away from the DNA molecule in cellular water. However, the energy from the interaction can be transferred to the molecule via a free radical (formed by radiolysis of cellular water).
For exposure to 1 rad of each of the following ionizing radiations, which would result in the greatest dose to the individual?
Internal source of alpha particles Alpha particles are large and heavy (two protons and two neutrons), and although they possess a great deal of kinetic energy (approximately 5 MeV), their energy is lost rapidly through multiple ionizations (approximately 40,000 atoms/cm of air). As an external source, alpha particles are almost harmless because they ionize the air very quickly and never reach the individual.
Which of the following cells is the least radiosensitive? A. Myelocytes B. Myocytes C. Megakaryocytes D.Erythroblasts
Myocytes There are several types of stem cells in bone marrow, and the different types differ in degree of radiosensitivity. are mature muscle cells and are fairly radioresistant
Which of the following interactions between x-ray photons and matter is most responsible for patient dose?
The photoelectric effect
What contributes most to patient dose?
The photoelectric effect a relatively low-energy photon uses all its energy to eject an inner-shell electron from the target atom, leaving a vacancy in that shell. An electron from the shell beyond drops down to fill the vacancy and, in doing so, emits a characteristic ray.This type of interaction contributes most to patient dose, because all the x-ray photon energy is being transferred to tissue.
response curve has a threshold and is thought to be generally correct for most somatic effects
The sigmoidal dose
If 600 rad or more is received as a whole-body dose in a short period of time, certain symptoms will occur; these are referred to as
acute radiation syndrome Radiation is most hazardous when it is received in a large dose, all at one time, to the whole body. When 600 rad or more is received as a whole-body dose in a short time, biologic effects will appear within minutes to weeks (depending on the dose received).
The photoelectric effect is an interaction between an x-ray photon and
an inner-shell electron a relatively low-energy incident photon uses all its energy to eject an inner-shell electron, leaving a vacancy.
Stochastic effects of radiation include
genetic alterations radiation are nonthreshold and randomly occurring. Examples of stochastic effects include carcinogenesis and genetic effects. The chance of occurrence of stochastic effects is directly related to the radiation dose; that is, as radiation dose increases, there is a greater likelihood of genetic alterations or development of cancer.
Atoms having the same mass number but different atomic number are
isobars
Atoms with the same atomic number and mass number are.
isomers
Atoms having the same neutron number but different atomic number are.
isotones
Which radiation-induced conditions is most likely to have the longest latent period?
leukemia Radiation-induced malignancy, leukemia, and genetic effects are late effects (or stochastic effects) of radiation exposure. These can occur years after survival of an acute radiation dose or after exposure to low levels of radiation over a long period of time.
Platelet precursor cells, are even less radiosensitive.
megakaryocytes
White blood cell precursors
myelocytes
Early signs of acute radiation syndrome include
nausea, vomiting, diarrhea, fatigue, and leukopenia (decreased white blood cells count); these occur in the first (prodromal) stage of acute radiation syndrome.
Which interaction between x-ray photons and matter results in total absorption of the incident photon?
photoelectric effect The photoelectric effect and Compton scattering are the two predominant interactions between x-ray photons and matter in diagnostic x-ray. In the photoelectric effect, the low-energy incident photon uses all its energy to eject an atom's inner-shell electron. That photon ceases to exist—it has used all its energy to ionize the atom.
Irradiation of water molecules within the body and their resulting breakdown is termed
radiolysis Radiolysis has to do with the irradiation of water molecules and the formation of free radicals. Free radicals contain enough energy to damage other molecules some distance away. They can migrate to and damage a DNA molecule (indirect hit theory).
The most radiosensitive portion of the GI tract is the
small bowel The most radiosensitive portion of the GI tract is the small bowel. Projecting from the lining of the small bowel are villi, from the intestinal crypt cells of Lieberkühn, which are responsible for the absorption of nutrients into the bloodstream. Because the cells of the villi are continually being cast off, new cells must continually arise from the crypts of Lieberkühn.
Late effects of radiation, whose incidence is dose related and for which there is no threshold dose, are referred to as
stochastic
Linear energy transfer (LET) may be best described as
the amount of energy delivered per distance traveled in tissue. The velocity and charge of particulate radiation determine the amount of energy transferred (and, therefore, the number of ionizations) to the tissue traversed. A greater LET (number of ionizations) is delivered by particles with a slower velocity and greater charge. The greater the LET and the number of ionizations, the greater is the biologic effect.
If a quantity of radiation is delivered to a body in a short period of time, its effect
will be greater than if it were delivered over a long period of time.
The effects of radiation on biologic material depend on several factors. If a quantity of radiation is delivered to a body over a long period of time, the effect
will be less than if it is delivered all at one time The effects of a quantity of radiation delivered to a body depend on several factors—the amount of radiation received, the size of the irradiated area, and how the radiation is delivered in time. If the radiation is delivered in portions over a period of time, it is said to be fractionated and has a less harmful effect than if the radiation were delivered all at once. With fractionation, cells have an opportunity to repair, so some recovery occurs between doses.