64 terms

Chapter 4: Radiation Biology

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Cell
The basic structural unit of living organisms.
Cell differentiation
Individual characteristics of a cell that determine the response of the cell to radiation exposure (e.g. Cells that are immature [not highly specialized] are more sensitive to radiation).
Cell metabolism
The physical and chemical processes of a cell that determine the response of the cell to radiation exposure (e.g., cells with a high metabolism rate are more sensitive to radiation).
Coulomb
A unit of electrical charge; the quantity of electrical charge transferred by 1 ampere in 1 second.
Critical organ
An organ that, if damaged, diminishes the quality of an individual's life (e.g., skin, thyroid gland, lens of the eye, bone marrow).
Cumulative effects
The additive effects of repeated radiation exposure.
Direct theory
A theory that suggests that cell damage results when ionizing radiation hits critical areas directly within the cell.
Dose
The amount of energy absorbed by a tissue.
Dose, total
The quantity of radiation received, or the total amount of radiation energy absorbed.
Dose equivalent
A measurement used to compare the biologic effects of different types of radiation.
Dose rate
Rate at which exposure to radiation occurs and absorption takes place (dose rate=dose/time).
Dose-response curve
A curve that can be used to correlate the "response," or damage, of tissues with the "dose," or amount, of radiation received.
Exposure
A measure of ionization produced in air by x-radiation or gamma radiation.
Free radical
An atom, molecule or ion that carries a negative, positive or zero change; it exists with a single, unpaired electron in its outermost shell.
Genetic cells
Cells that contain genes; reproductive calls (e.g. Ova, sperm).
Genetic effects
Effects of radiation that are not seen in the person irradiated but are passed on to future generations through genetic cells.
Gray (Gy)
A unit for measuring absorbed dose; the SI unit equivalent to he rad; 1 gray=100 rad.
Indirect theory
A theory suggesting that cell damage results indirectly; x-Ray photons are absorbed with the cell, causing the formation of toxins; toxins, in turn, damage the cell.
Period of injury
Occurs after the latent period following exposure to radiation; can include a variety of cellular injuries.
Ionization
The production of ions, the process of converting an atom into an ion, resulting in the formation of a positive atom and a dislodged negative electron.
Latent period
The amount of time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs.
Long-term effects
Effects of radiation that appear years, decades, or generations after exposure; associated with small amounts of radiation absorbed repeatedly over a long period.
Mitotic activity
Process of cell division; determines the response of a cell to radiation exposure ( cells that divide frequently are more sensitive to radiation).
Nonstochastic effects
Somatic effects that have a threshold and increase in severity with increasing absorbed dose.
Quality factor (QF)
A factor used for radiation protection purposes that accounts for the exposure effects of different types of radiation; for x-rays, QF=1.
Radiation, background
A form of ionizing radiation that is ubiquitous in the environment; includes cosmic and terrestrial radiation.
Radiation absorbed dose (rad)
A unit for measured get absorbed dose; the traditional unit of dose equivalent to the gray(Gy); 100 erg of energy per gram of tissue; 100 rad=1Gy.
Radiation biology
The study of the effects of ionizing radiation on living tissues.
Radioresistant cell
A cell that is resistant to radiation (e.g. Bone, muscle, and nerve cells).
Radiosensitive cell
A cell that is sensitive to radiation ( e.g. Small lymphocytes; blood, immature reproductive, young bone, and epithelial cells).
Recovery period
The period during which cellular damage caused by radiation is followed by repair.
Risk
The likelihood of adverse effects or death resulting from exposure to a hazard.
Roentgen (R)
Th traditional unit of exposure for x-rays; the quantity of x-radiation or gamma radiation that produces an electrical charge of 2.58 x 10-4 coulombs in 1 kilogram of air at standard pressure and temperature conditions.
Roentgen equivalent (in) man (rem)
The traditional unit of the dose equivalent; the product of absorbed dose (rad) and a quality factor (QF) specific for the type of radiation; 100 rems=1 sievert (Sv).
Short term effects
Effects of radiation that appear within minutes, days, or weeks; associated with large amounts of radiation absorbed in a short time.
Sievert (Sv)
A unit of measurement for dose equivalent; the SI unit of measurement equivalent to the rem; 1Sv= 100rems.
Somatic cells
All the cells in the body, with the exception of the reproductive cells.
Somatic effects
Radiation injuries that produce changes in somatic cells and produce poor health in the irradiated individual (e.g. The induction of cancer, leukemia, or cataracts).
Stochastic effects
Biologic effects from radiation that occur as a direct function of dose; the probability of occurrence increases with increasing absorbed dose; however, the severity of effects does not depend on the magnitude of the absorbed dose.
The latent period in radiation biology is the time between:
Exposure to x-radiation and clinical symptoms
A free radical:
Is an uncharged molecule
Has an unpaired electron in the outer shell
Combines with molecules to form toxins
Direct radiation injury occurs when:
X-ray photons pass through the cell
Indirect radiation injury occurs when:
X-ray photons are absorbed and form toxins
Which of the following relationships describe the response of tissues to radiation?
Linear
Which of the following factors contributes to radiation injury?
Total dose
Dose rate
Cell sensitivity
Age
Which of the following statements is correct?
Long term effects are seen with small amounts of radiation absorbed in a long period.
Radiation injuries that are not seen in the person irradiated but that occur In future generations are termed:
Genetic effects
Which of the following is most susceptible to ionizing radiation?
Small lymphocyte
The sensitivity of tissues to radiation is determined by:
Cell metabolism
Which of the following is considered radioresistant?
Mature bone cells
An organ that, if damaged, diminishes the quality of an individual's life is termed a:
Critical organ
The traditional unit for measuring x-ray exposure in air is termed:
The roentgen
Which of the following radiation units is determined by the quality factor (QF)?
The rem
The unit for measuring the absorption of x-rays is termed:
The rad
Which of the following conversions is correct?
1 rad= 2.58 x 10-4 C/kg
Which of the following traditional units does not have an SI equivalent?
The roentgen
Which of the following is used only for x-rays?
The roentgen
Which of the following conversions is correct?
1 R= 2.58 x 10-4 C/kg
1 Gy = 100 rads
1 Sv = 100 rems
1 rem = rads x QF
What is the average dose of background radiation received by an individual in the United States?
150 to 300 mrads (0.0015-0.003 Gy)
What is the greatest contributor to artificial radiation exposure?
Medical radiation
The amount of radiation exposure an individual receives varies depending on:
Film speed
Collimation
Technique
Exposure factors
A single intraoral radiograph (D speed film, 70 kVp, long PID) results in a mean surface exposure of:
250 mR
Which is the dose at which leukemia induction is most likely to occur?
5000 mrads (0.05 Gy)
Which of the following statements is incorrect?
X-radiation is not harmful to living tissues.
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