Term
| Do all xrays reach the dental receptor? |
|
Definition
| no, some are absorbed by the patient tissue causing chemical changes |
|
|
Term
| What do these chemical changes in the cells cause? |
|
Definition
|
|
Term
| What are the two mechanisms of radiation injury that are possible? |
|
Definition
1.ionization
2.free radical formation |
|
|
Term
| What are the two ways xrays are absorbed into the patients tissue? |
|
Definition
1.photoelectric effect
2.compton scatter |
|
|
Term
| What are the percentages that these two make up? |
|
Definition
photoelectric effect-30%
compton scatter-62% |
|
|
Term
| What happens in ionization? |
|
Definition
| photon is deflected from its path and looses energy, it them interacts with other atoms within the absorbing tissues causing chemical changes int he cell resulting in biologic damage |
|
|
Term
| What does cell damage occur primarily though? |
|
Definition
| the formation of free radicals |
|
|
Term
| When are free radicals formed? |
|
Definition
| when an xray photon ionizes water |
|
|
Term
|
Definition
| neutral atom that exists in a single unpaired electron in its outermost shell |
|
|
Term
| What are free radicals like? Do they have a long lifespan? |
|
Definition
| highly reactive and unstable, no they have an extremely short lifespan |
|
|
Term
| How does xradiation cause cell damage? |
|
Definition
| through the production of free radicals |
|
|
Term
| What three things will a free radical do to achieve stability? |
|
Definition
1.Recombine without causing changes in the molecule
2.combine with other free radicals, cause damage
3.combine with ordinary molecules, forms a toxin |
|
|
Term
| What is a radical commonly formed that can cause widespread cellular damage? |
|
Definition
|
|
Term
| What two things may cause damage to living tissue by exposure to ionizing radiation? |
|
Definition
1.A direct hit and absorption of an xray photon within a cell
2.absorption of an xray photon by water within a cell accompanied by a free radical formation |
|
|
Term
| What is the direct theory of radiation injury? |
|
Definition
| cell damage results when ionizing radiation directly hits critical areas(DNA) within the cell |
|
|
Term
| Does the direct theory happen frequently? |
|
Definition
| no, it occurs infrequently because most dental xray photons pass through cells causing little or no damage |
|
|
Term
| What is the indirect theory of radiation? |
|
Definition
| xray photons are absorbed within the cell and cause the formation of toxins which in turn damage the cell |
|
|
Term
| What do free radicals combine to form? |
|
Definition
|
|
Term
| What percentage of cells is H2O? What are the chances of free radical formation and indirect injury? |
|
Definition
-cells 70-80% water
-chances are great |
|
|
Term
|
Definition
| the measure of ionization produced by air in xradiation |
|
|
Term
|
Definition
| the amount of xray energy absorbed in tissue |
|
|
Term
| What is a dose response cure? |
|
Definition
| determines what level of radiation is acceptable |
|
|
Term
| What does the dose response curve correlate? |
|
Definition
| the response(damage) of tissue with the dose(amount) of radiation recieved |
|
|
Term
| What is a linear relationship? |
|
Definition
| tissue response directly proportional to dose |
|
|
Term
| What is a threshold curve? |
|
Definition
| below the threshold level, no response is seen in tissue |
|
|
Term
| What is the linear nonthreshold relationship? |
|
Definition
| no matter how little the radiation there is some tissue damage |
|
|
Term
| What are the possible outcomes of radiation exposure? (5) |
|
Definition
1.Cell is unaffected by the exposure
2.Cell is damaged but repairs itself and functions at prexposure levels
3.Cell dies, but is replaced through normal biological processes
4.Cell is damaged, repairs itself, but not functions at a reduced letter
5.cell is damaged, repairs itself incorrectly or abnormally, result-biophysical change(tumor or malignancy) |
|
|
Term
| What are stochastic effects? |
|
Definition
| biological response based on the probability of occurrence rather then the severity of the change, ex cancer |
|
|
Term
| What are nonstochastic effects? (deterministic effects) |
|
Definition
| the severity of the change is dependent on dose |
|
|
Term
| What occurs as a direct function of the dose? |
|
Definition
|
|
Term
| Do stochastic effects have dose thresholds? |
|
Definition
| no(ex: cancer, genetic mutations) |
|
|
Term
| What are somatic effects that have a predictable threshold? |
|
Definition
| nonstochastic effects, ex: erothema(redness), loss of hair, cataracts, decreased fertility |
|
|
Term
|
Definition
| elapsed time between exposure to ionizing radiation and the appearance of clinical signs |
|
|
Term
| What do latent periods depend on? |
|
Definition
| depends on the total dose of radiation and the amount of time it took to receive the dose |
|
|
Term
| What is the sequence of radiation injury? |
|
Definition
1.Latent period
2.Period of injury |
|
|
Term
| What occurs in the period of injury? |
|
Definition
| a variety of cellular injuries may result, changes in cell occur(size, function, abnormal activity, death of the cell) |
|
|
Term
| Are all cellular radiation injuries permanent? |
|
Definition
|
|
Term
| Can cells repair damage done to then by radiation? |
|
Definition
|
|
Term
| Do you see the effects of radiation after one exposure? |
|
Definition
| no, the effects are collective |
|
|
Term
| Where does unrepaired damage from radiation exposure accumulate? What can this lead to? |
|
Definition
| in the tissues, this can lead to health problems |
|
|
Term
| What are the determining factors of radiation injury? (5) |
|
Definition
1.total dose
2.dose rate
3.amount of tissue irradicated
4.cell sensitivity
5.age |
|
|
Term
|
Definition
| how much radiation one is being exposed to, more is bad |
|
|
Term
|
Definition
| the time frame, in rapid delivery there is no time for cell repair |
|
|
Term
| What is "amount of tissue irradated"? |
|
Definition
| the areas exposed, total body vs. local area |
|
|
Term
| What is cell sensitivity? |
|
Definition
| young vs. mature cells, rapidly developing cells |
|
|
Term
| What are four areas to consider for radiation effects? |
|
Definition
1.short and long term effects
2.somatic and genetic effects
3.radiation effects on cells
4.radiation effects on tissues and organs |
|
|
Term
| What is short term effects? |
|
Definition
| Associated with large doses of radiation in a short amount of time |
|
|
Term
| What is ARS? What are the side effects? |
|
Definition
-acute radiation syndrome
-nausea, vomiting, hairloss, hemorrhage (like side effects of excessive sun exposure) |
|
|
Term
| What are long term effects? |
|
Definition
| small doses absorbed repeatably over a long period of time |
|
|
Term
| When are long term effects seen? What are some long term effects? |
|
Definition
-seen after years, decades, generations
-includes cancers, birth abnormalities, genetic disorders |
|
|
Term
|
Definition
| all cells in body besides reproductive cells |
|
|
Term
| What are genetic cells? How are they passed on? |
|
Definition
-reproductive cells
-passed on in DNA |
|
|
Term
| Who are somatic effects seen in? |
|
Definition
| the person irridiated, not future generations |
|
|
Term
| Who are genetic effects seen in? |
|
Definition
| not in the person exposed to radiation, it is passed on in future generations |
|
|
Term
| What is an ulcerated lesion? |
|
Definition
| early carcinoma on the finger of a dentist who holds film in the mouth while exposing patient |
|
|
Term
| What is cells response to radiation determined by? (3) |
|
Definition
1.mitotic activity(cells with frequent division)
2.cell differentiation
3.cell metabolism |
|
|
Term
| What are radiosensitive cells? |
|
Definition
| cells that are sensitive to radiation |
|
|
Term
| What are some examples of radiosensitive cells? |
|
Definition
-lymphatic cells
-erythrocytes
-immature reproductive cells
-young bone cells |
|
|
Term
| What are radioresistant cells? |
|
Definition
| cells that are resistant to radiation |
|
|
Term
| What are some examples of radioresistant cells? |
|
Definition
-mature bone cells
-muscle cells
-nerve cells |
|
|
Term
| What are some examples of radiosensitive organs? |
|
Definition
-lymphoid tissue
-bone marrow
-testes
-intestines |
|
|
Term
| What are some examples of radioresistant tissues? |
|
Definition
-salivary glands
-kidney
-liver |
|
|
Term
| What is a critical organ? |
|
Definition
| an organ that if damaged, reduces the quality of life |
|
|
Term
| What are some critical organs exposed during dental radiographs? (4) |
|
Definition
1.skin
2.thyroid gland
3.lens of the eye
4.bone marrow |
|
|
Term
| What are the traditional units of radiation measurement? (3) |
|
Definition
1.Roentgen (R)
2.Radiation absorbed dose (rad)
3.Roentgen equivalent man (rem) |
|
|
Term
| What are the SI(international system) units of radiation measurement? (3) |
|
Definition
1.Coulombs/kilogram (C/kg)
2.Gray (Gy)-like RAD
3.Sievert (Sv)- like REM |
|
|
Term
| How does Roentgen measure radiation? |
|
Definition
| by determining the amount of ionization that occurs in air |
|
|
Term
| Does Roentgen describe the amount of radiation absorbed? |
|
Definition
|
|
Term
| Is there an SI equivalent to R? What is R exposure stated in? |
|
Definition
| no, exposure stated in C/kg |
|
|
Term
| What is dose measurement? What are two units that measure this? |
|
Definition
-the amount of energy absorbed by the tissue
-RAD and GY |
|
|
Term
| How many rads does 1 GY equal? |
|
Definition
|
|
Term
| How many Gy does one rad equal? |
|
Definition
|
|
Term
| What is a dose equivalent measurement? |
|
Definition
| used to compare biological effects of different types of radiation |
|
|
Term
| What are the units that measure dose equivalent? |
|
Definition
|
|
Term
| How many rems does 1 seivert equal? How many Sv does one rem equal? |
|
Definition
-1 Sv=100 rems
-1 rem=0.01 Sv |
|
|
Term
|
Definition
|
|
Term
| What are the factors that determine radiation risks? (5) |
|
Definition
1.Source of radiation exposure
2.Risk and risk estimates
3.Dental radiation and exposure risks
4.Patient exposure and dose
5.Risk versus benefit of dental radiographs |
|
|
Term
| What is natural/background radiation? |
|
Definition
| ionizing radiation that is everywhere in the enviornment |
|
|
Term
| What are the two types of natural radiation? |
|
Definition
1.Cosmic radiation(stars/sun)
2.Terrestrial radiation(radioactive material in earth/air) |
|
|
Term
| What is the average dose of background radiation received by someone in a year? |
|
Definition
| ranges from 150-300 mrads per year |
|
|
Term
| What is artificial or man-made radiation? |
|
Definition
| resulting from modern technology(nuclear plants, medical radiation) |
|
|
Term
| What is the greatest contributor to artificial radiation? |
|
Definition
|
|
Term
| What product causes the most background radiation? |
|
Definition
|
|
Term
|
Definition
| likelihood of adverse effects of death resulting from exposure to a hazard |
|
|
Term
| What is the potential risk in dental radiography? |
|
Definition
|
|
Term
| Is the risk of someone spontaneously developing caner higher or lower than the risk of dental radiography? |
|
Definition
| much higher, 3300 in 1 million |
|
|
Term
| How much radiation must the thyroid gland be exposed to before carcinoma induction? |
|
Definition
|
|
Term
| How much mrads does a FMX equate to? |
|
Definition
| 6 mrads, 1/1000th of a dose to induce thyroid cancer |
|
|
Term
| How many mrads are needed to induce bone marrow cancer?(leukimia) |
|
Definition
|
|
Term
| How many dental films would it take to cause leukemia? |
|
Definition
|
|
Term
| Which film speed is the best to reduce absorbed dose? |
|
Definition
|
|
Term
| How much does collimation reduce the absorbed dose? |
|
Definition
|
|
Term
| Which technique reduces skin dose? |
|
Definition
| parallel technique, uses longer sources to film distance |
|
|
Term
| Which exposure factor reduces absorbed skin dose? |
|
Definition
|
|
