Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
radiobiology module2
| Question | Answer |
|---|---|
| Radiolysis of water | The interaction of x-radiation with water. |
| Linear energy transfer (LET) | Average energy deposited per unit length of the path or track of radiation or the rate at which energy is transferred from ionizing radiation to soft tissue. |
| Relative biologic effectiveness (RBE) | The relative capability of radiations with different linear energy transfers (LETs) to produce a particular biologic reaction. |
| Oxygen Enhancement Ratio (OER) | Ratio of the dose necessary to produce a given effect under anoxic conditions to the dose necessary to produce the same effect under aerobic conditions |
| Classical Scattering | A process that is most likely to occur with low-energy x-rays (below 10 keV) |
| Compton scattering | A process that is most likely to occur with x-rays in the energy range of 30 to 50 keV |
| Characteristics photon | The result that occurs when an electron in an inner shell is knocked from its orbit by a projectile electron and another electron jumps down to fill its place |
| Photoelectric | The process that occurs when an incident x-ray photon is absorbed by the atom it strikes, and an electron is ejected from the inner shell of that atom. |
| Binding energy | The energy that holds protons and neutrons together in the nucleus through the force of attraction; the amount of energy needed to break up the nucleus. |
| Photoelectron | The electron that is ejected during the process of photoelectric interaction. |
| Pair production | A photon with at least 1022 keV (or 1.02 MeV) of energy may penetrate the electron shells of the atom and reach the nucleus, where its energy is converted into the production of an electron and a positron. |
| Positron | A positively charged electron. |
| Annihilation process | A process that occurs after pair production. The positron that is created in pair production travels until it strikes an electron with which it interacts |
| Photodisintegration | The process that occurs when x-rays with extremely high energy (above 10 MeV) strike the nucleus of the atom and make it unstable |
| During a typical exam the radiographer is most likely to be exposed to which of the following? A)Compton B)Classical C)Pair production | A) Compton |
| Which interaction results in excitation of the tissue atom but not ionization? A)Compton B)Photoelectric C)Classical D)Pair production | C)Classical |
| Prior to 1990, Medical sources of radiation contributed less than half of the total exposure to radiation in the United States. True or False? | True |
| Photodisintegration is a common interaction in diagnostic radiography. True or False? | False |
| Which type of ionization radiation is from the same family as microwaves? | Electromagnetic |
| What involves an inner shell interaction and total absorption of the photon? | Photoelectric |
| 1.02 MeV is required for what interaction? | Pair production |
| Biologic damage resulting from ionizing radiation occurs on what three levels? | Molecular, Organic, Cellular |
| Atoms are the basic building blocks of all matter, including human tissue | |
| When a patient is irradiated, the primary photons may do one of three things. First, they may penetrate the body and pass through the patient to reach the radiographic image receptor, contributing to the x-ray image | These photons are termed exit or image-formation radiation. |
| Second, some photons may be absorbed in biologic tissue by interacting with the atoms or molecules as described in the previous section | These photons do not reach the radiographic image receptor but contribute to patient dose. |
| Third, the photons may be scattered as described in Section 2. Some scattered photons may reach the image receptor and cause radiographic fog. Others may be deflected away from the image receptor and present a hazard to imaging personnel. | |
| After the x-ray energy enters the patient, absorption can occur in molecules at any level. Some energy may interact in the skin, in bone, or in any other tissue or organ. | |
| absorbed dose | The measurement of radiation absorbed inside the patient. An absorbed dose is the amount of energy per unit mass absorbed by the irradiated object |
| Direct action | Process by which ionized particles directly transfer energy to important macromolecules, resulting in the breaking of chemical bonds, which may cause biologic damage. |
| Indirect action | Process by which ionized particles interact initially with noncritical molecules, which are then broken down into smaller molecules, producing both ions and free radicals that can recombine to form toxic substances, which can produce biologic damage. |
| the positively charged water molecule (HOH+) and the negatively charged electron (e-), are unstable. | |
| Once the water molecule is ionized, several different things may occur | Minimal biologic damage, is for the electron and ionized water molecule to recombine. If the positively charged water molecule, called HOH+, recombines with the ejected electron, water (H2O) is formed again and no biologic damage occurs |
| Once the water molecule is ionized, several different things may occur | If the positively charged water molecule does not recombine, the instability created by the missing electron causes it to separate into two components, a positively charged hydrogen ion and a hydroxyl free radical |
| During the interaction of water and ionizing radiation, there is minimal danger of biologic damage from the hydrogen and the hydroxyl ions because these two ions can easily recombine to form a molecule of water. | |
| Point Lesion | Damage resulting when the chemical bonds of molecules are disrupted; also known as molecular lesion. |
| when a hydrogen free radical interacts with molecular oxygen | Hydroperoxyl radical : A combination that can occur during radiolysis of water. |
| One of the most dangerous interactions resulting from the radiolysis of water occurs when two hydroxyl radicals bond to form | Hydrogen Peroxide |
| One micron is one-millionth of a meter. Human cells are about 10 to 30 microns in diameter | |
| Remember that as the LET of radiation increases, the potential biologic damage also increases | |
| Remember also that different types of radiation have different LETs. For instance, 1 gray of neutron radiation is more biologically damaging than 1 gray of x-radiation | |
| Radiation with an RBE of less than 1 has lower LET than diagnostic x-rays. Radiation with an RBE greater than 1 has a higher LET than diagnostic x-rays. | |
| Calculate the RBE from this information: the plant dies after irradiation by 6 gray of x-radiation or by irradiation of 4 gray of fast neutrons. What, then, is the RBE of fast neutrons? | The calculation of the RBE is expressed as the ratio of 6/4 or 1.5 RBE. |
| If a dose of radiation is delivered over a shorter period of time, the biologic effect will be greater than the same dose delivered over a longer period of time, because with more time there is an opportunity for cellular repair and tissue recovery | |
| Protracted Dose | A dose delivered continuously at a low-dose rate. |
| Fractionated Dose | A radiation dose delivered over time in equal fractions. |
| Main-chain scission | The condition resulting from breakage of the thread or backbone of a long-chain molecule. |
| The most serious damage to a cell occurs when there is damage to a cell's nucleus. The reason for this is that the nucleus contains the DNA that controls all of the cell functions | |
| Instant death of large numbers of cells can occur when the cells are irradiated with a high 1000 gray (100,000 rad) dose of x-rays or gamma rays over a period of a few seconds or minutes | |
| Reproductive death can happen when cells are exposed to a moderate dose of 1 to 10 gray (100 to 1000 rad) of ionizing radiation | |
| The Law of Bergonie and Tribondeau was developed in 1906 to help explain and predict cell radiosensitivity. | According to the Law, radiosensitivity is directly proportional to a cell's reproductive activity and inversely proportional to its degree of differentiation |
| What unit is used to compare the different types of radiation with their biologic effect at different doses? | RBE (Relative Biological Effectiveness) |
| What occurs after cell division? | Mitotic death |
| According to the Law of Bergonie and Tribondeau, Cell radiosensitivity is directly proportional to reproductive activity? | True |
| Which of the following is the term used to describe the average energy deposited along the path of radiation? | LET (Linear Energy Transfer) |
| OER is significant with? | Low LET radiation |
| Radiation can effect organic molecules in the same manner as inorganic molecules. | True |
| What is the process called when ionizing radiation transfers its energy to important macromolecules? | Direct action |
| Radiation interacting with DNA would be a? | Subcellular effect |
| Most biologic damage from ionizing radiation is a result of what? | Indirect action |
| LET is the term used to describe the average energy deposited per? | Unit length of track (micron) |
| X-rays are what form of ionizing radiation? | Electromagnetic |
| Which type of radiation originates from a radioactive nucleus? | Particulate |
| CT scanning in now a major source of medical radiation exposure. | True |
| Which interaction interacts photons generally below 10keV? | Classical |
| Interaction between higher energy photons and outer shell electrons of tissue atoms results in? | Compton |
| Most of the scatter produced during radiography procedures results from which interactions? | Compton |
| Photoelectric absorption increases as the effective atomic number of matter increases. Which of the following has the highest atomic number? Water, Bone, Air, Soft tissue? | Bone |
| What is the ejected electron called in a photoelectric event? | Photoelectron |
| Photodisintegration involves an interaction with the nucleus of a tissue atom | True |
| What interaction produces a positron and an electron? | Pair production |
| What first happens when an x-ray interacts with and ionizes a molecule of water? | Ion pair is created |
| If HOH+ and an electron combine, which of the following occurs? | H2O |
| When does radiolysis of water occur? | When water is ionized |
| During irradiation, which of the following is more biologically dangerous? Dense ionization or Sparse ionization? | Dense ionization |
| Which of the following is used as the standard for RBE? Gamma, X-rays, Beta, Alpha?? | X-rays |
| The presence of which of the following with low LET radiation will increase biologic damage? | Oxygen |
| Which subcellular effect may involve the breaking of one side rail of DNA? | Main-Chain scission |
| Which cellular effect would result from 1000 gray over a very short period? | Instant Death |
| According to the Law of Bergione and Tribondeau, cell radiosensitivity is directly proportional to the degree of differentiation. | False |
| Classical scattering is low energy X-ray photons with less than 10 keV | |
| Pair production occurs only with very high-energy photons of 1.02 MeV or greater | In this interaction, two particles are produced: a positron (positively charged electron) and an electron. For these particles to exist, they must each have energy of 0.51 MeV (the energy equivalent of an electron). |
| Photodisentigration Photons with extremely high energies above 10 MeV may strike the nucleus of the atom and make it unstable | |
| A free radical (denoted by *) is a molecule that has no charge but that has a single electron in the outer shell. The hydrogen ion is H+ and the hydroxyl radical is OH*. | |
| if the positively charged water molecule and the free electron do not recombine, the electron may join with a different molecule. If it joins another H2O water molecule, a negatively charged water molecule HOH- is created. This molecule, too, is unstable | This instability can cause the HOH- molecule to dissociate into two smaller compounds, a hydrogen radical (H*) and a negatively charged hydroxyl ion (OH-). |
| The LET is also inversely related to the speed of an ejected electron. This effect is opposite of what you might expect. The probability of ionization increases as a particle moves more slowly. | |
| LET is a function of both mass and charge | |
| The LET of diagnostic x-rays is about 3 keV/μm | |
| Low-LET radiation includes x-rays and gamma rays, which do not cause much ionization along their track | |
| High-LET radiation includes alpha particles, ions of heavier nuclei, and charged particles released from interactions between neutrons and atoms | |
| Keep in mind that an x-ray photon in the beam has no LET until it interacts with matter. Remember that no LET can be calculated until a photon interacts with tissue and sets an electron in motion. |
Created by:
volcomgrl12