Radiobiology Flashcards
What is radiobiology?
Branch of science concerned with the methods of interaction and the effects of ionizing radiation on living systems
Erythema
Skin redness
Desquamation
The shedding of the outer layers of the skin
Epliation
Hair loss
Who was Clarence Dally and what did he do?
Thomas Edison’s assistantDocumented the side effects of xraysHelped prove the dangers of radiationDied from radiation
Law of Bergonie & Tribondeau (1906)
younger, immature tissues and organs are more radiosensitive than older tissues and organsas the metabolic activity increases within a cell, the more radiosensitive the cell is
Fractionation
give radiation treatment slowly rather than a large dose at one time
Repopulation
ability of normal tissues to replenish themselves following injury
Protraction
time during which a course of radiation is given
Rad
energy ABSORBED in matter from any type of radiation
Rem
unit of DOSE EQUIVALENT of occupational exposure
Roentgen
unit of radiation QUANTITY (measure of ionization of air)
What is a Rad in SI units?
Gray (Gy)
1 Rad = ? Grays
0.01 Grays (Gy)
What is a Rem in SI units?
Sievert (Sv)
1 Rem = ? Sievert
0.01 Sieverts (Sv)
What is a Roentgen in SI units?
Coulomb/kg
What is ICRP?
International Commission of Radiological Protection
What is NCRP?
National Council on Radiation Protection and Measurement
What is the occupational exposure limit per year?
5 rem
What is the cell?
Basic unit of structure and function of all living things composed of a cell membrane, cytoplasm, organelles, and a nucleus -each has a distinct function
Water makes up about what % of a person’s total body weight?
80%
What are somatic cells?
non-sexually reproducing body cells
What are germ cells?
Sexually reproducing cells
What is mitosis?
process of cell division in which the nucleus and the cytoplasm divide to form two identical cells
What is meiosis?
process of cell division for the purpose of reproduction
What is LET?
Linear energy transfer- measure of the rate at which energy is deposited as a charged particle travels through matter (kigher kVp=less energy loss)Diagnostic x-rays have an LET of 3
What is RBE?
Relative biologic effectiveness - A comparison of a dose of test radiation to a dose of 250 keV x-ray that produces the same biological effect (relative effect of LET )As LET increases = RBE increasesDiagnostic x-rays have an RBE of 1
What is OER?
Oxygen enhancement ratio - dose of radiation that produces a given biologic response under anoxic conditions divided by the dose of radiation that produces the same biologic response under aerobic conditions
What is the most critical target of radiation?
DNA
What is LD 50/60?
lethal dose required to kill 50% of the population within 60 days (250-300 rads)
What are the 4 response stages?
prodromallatentmanifestdeath/recovery
What is Bone Marrow Syndrome?
Exposure 200-1,000 RDeath within 10-60 daysReduction of red blood cells, white blood cells, & plateletsDeath results from anemia or infection
What is Central Nervous Syndrome?
exhibited by nervousness, confusion, nausea, vomiting, loss of consciousness and burning sensations of the skin; which are a result of damage to blood vessels and increased intracranial pressure
What is Gastrointestinal Syndrome?
exhibited by nausea, vomiting, cramps and diarrhea as a result of damage to the villi in the small intestine, which leads to a lack of absorption. Dehydration and infection are the result
What are the types of radiation interactions?
coherent scatteringcompton effect/scatteringphotoelectric effectpair productionphotodisintegration
What are the 4 populations that are used as sources of data on the incidence of radiation-induced cancers?
1) atomic bomb survivors2) medically exposed patients3) occupationally exposed personnel4) populations that receive high natural background exposure
Name some radiation induced malignancies.
LeukemiaSkin carcinomaThyroid cancerBreast cancerOsteosarcomaLung cancer
What did Russell do/conclude?
1) radiation is a powerful mutagenic agent2) the majority of mutations are unhealthy to the organism3) there are no unique mutations produced by radiation4) radiation-induced genetic damage can occur as a result of a single mutation
What are the 3 stages of development of the fetus?
Pre-implantationMajor organogenesisFetal or growth stage
What is radiation hormesis?
The theory that ionizing radiation is benign at low levels of exposure, and that doses at the level of natural background radiation can be beneficialscientific consensus is NOT to accept radiation hormesis
Name the 4 types of personnel radiation detectors/monitors?
Pocket dosimeter (most sensitive)OSL (Optically Stimulated Luminescence)TLD (Thermoluminescent Dosimeter - rings)Film Badge
What are some mobile exam considerations?
wear a lead apronbe at least 6 feet away from the patientposition yourself at right angles to the patienttake a position around a corner from the patient if possible
Ancel and Vitemberger
determined that radiation damage is determined by the amount of biological stress the cell receives & the conditions the cell is exposed to before and after radiation
Muller
discovered radiation’s role in mutation (mutagenesis)no new mutations, etc.
What is the limit for infrequent public exposure?
0.5 Rem
What are the 4 types of organic compounds?
proteinscarbohydrateslipidsnucleic acids
What do proteins do?
assist in cellular growth and repair
What do carbohydrates do?
provide energy in the cell
What do lipids do?
provide energy storage and insulation
What do nucleic acids do?
comprise the DNA and RNA of the cell
What are 2 inorganic molecules vital to cell life?
potassium and sodium
What do potassium and sodium do in relation to cells?
maintain osmotic pressure within the cell
What effect does radiation have on mitosis?
slowdown in cell mitosisinterphase death prior to mitosiscell death
When are cells are most radiosensitive?
when they are young and when they are undergoing mitosis
What is direct radiation?
occurs when the ionizing incident occurs on a particular macromolecule
What is indirect radiation?
occurs on a macromolecule distant from the macromolecule affected by the radiation
The majority of interactions involving radiation in the human are the result of what?
irradiation of water in the cells that becomes ionized and separates into other molecular products
Radiation of macromolecules has what 3 effects?
Main-chain scissionCross-linkingPoint Lesions
What is Main-chain scission?
when the macromolecule is reduced in size and thickness due to radiation
What is Cross-linking?
when the spurs on the macromolecule adhere to other macromolecules, enlarging and thickening the original due to radiation
What are Point Lesions?
when slight molecular changes occur that cause the cell to function incorrectly due to radiation
Linear dose-response relationships show what?
effects of radiation are exhibited regardless of the dose
Nonlinear dose-response relationships show what?
effects that are not directly proportional to the dose
What is the target theory?
theory that there are sensitive critical molecules that are essential to cell survival and that radiation to these cells will result in cell death
Radiation damage to eyes causes what?
cataracts
Local tissue damage to the skin at lower doses results in what?
inflammation, redness and a breakdown of the tissues layers
Local tissue damage to the skin at higher doses results in what?
hair loss, changes in pigmentation, ulcers, tissue death and cancer
Tissue damage to the reproduction system as a result of radiation exposure may result in?
immature reproductive cell death leading to infertility and the possibility of genetic mutations in offspring
Radiation effects on the hematologic system does what?
reduces the # of stem cells produced by the bone marrowdecreases the # of white & red blood cells & platelets
Cytogenic effects as a result of radiation exposure result in?
damage and mutation of chromosomes
The epidemiology of radiation exposure determines what?
the incidence, distribution and control of disease in a particular population
Risk estimation models measure what?
the amount of risk in a particular population at a particular point in time related to a particular disease
Stochastic effects occur?
randomly; the probability of being affected increases with the dose
Nonstochastic effects are?
deterministic; the severity of the injury increases with the dose, not the chance of it occurring
How is the recommended radiation dose limit for personnel calculated?
multiplying one’s age in years by 1 rem
Factors to consider when developing structural shielding construction?
distancetime of occupancyworkloaduse
To minimize exposure of the radiographer during a fluoroscopic exam, the radiographer should try to?
increase their distance from the table
Radiation exposure during fluoroscopic procedures can be limited by?
using intermittent fluoroscopy and reducing the size of the exposed field
Describe the Prodromal stage.
1st stageNausea/vomitting/diarrheaCan occur with doses as low as 100 rads
Describe the latent stage.
2nd stageAppear symptom freeSometimes mistaken for early recovery
Describe the manifest stage.
3rd stageVisually illOrgan system has been damaged
Describe death or recovery stage.
Final stagePatient will die or recover depending on the dose and which organs have been damaged
What is coherent scattering?
incident x-ray interacts with a target atom causing it to be excited; results in a change in direction of the x-Ray without a change in its energy
What is the Compton effect or Compton scattering?
Incident x-ray interacts with an outer shell electron and ejects it from the atom therefore ionizing the atomone of the 2 primary interactions in the diagnostic ranges
What is the photoelectric effect?
The incident x-ray interacts with an inner shell electron and it is completely absorbedthis is one of the 2 primary interactions in the diagnostic ranges
What is pair production?
Incident x-Ray has enough power to interact with the nuclear field of the atom it hits
What is photodisintegration?
Incident x-Ray is absorbed directly by the nucleus of the atom it interacts with; releases a nuclear fragment
Describe pre-implantation stage.
From conception to 9 daysRadiation has an all or nothing effect
Describe major organogenesis.
2nd thru 8th weekIncidence of congenital abnormalities more frequent during this stageDifferent organs at risk during different points throughout the stage
Describe fetal growth stage.
9th week thru end of pregnancyMostly affect the nervous/sensory organsDamage may not manifest until later on in life
What does diagnostic radiography mostly deal with re: dose-response relationships?
Linear, non-threshold dose-response relationships
Line begins at zero =
Nonthreshold
Line begins above zero =
Threshold
Curved line =
Nonlinear
Straight line =
Linear
What does nonlinear mean?
The observed effect is NOT proportional to the radiation dose received
What does nonthreshold mean?
assumes that any radiation will produce an effect
What does threshold mean?
Assumes that there is a radiation level reached below with there are no effects observed
What does linear mean?
An observed response is directly proportional to the dose
Which interaction is most common: direct or indirect?
indirect
