Shared Flashcard Set

Details

Chapter 4- Radiation Biology
Radiation Biology
94
Anthropology
6th Grade
11/08/2012

Additional Anthropology Flashcards

 


 

Cards

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
biologic damage
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
What is a free radical?
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
H2O2
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
toxins
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
What is exposure?
Definition
the measure of ionization produced by air in xradiation
Term
What is dose?
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
stochastic effects
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
What is a latent period?
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
no
Term
Can cells repair damage done to then by radiation?
Definition
yes
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
What is total dose?
Definition
how much radiation one is being exposed to, more is bad
Term
What is dose rate?
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
What are somatic cells?
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
no
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
100 rads
Term
How many Gy does one rad equal?
Definition
0.01 Gy
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
REM and sievert
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
How many Gy=1 Sv?
Definition
1
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
medical radiation
Term
What product causes the most background radiation?
Definition
Radon-55%
Term
What is risk?
Definition
likelihood of adverse effects of death resulting from exposure to a hazard
Term
What is the potential risk in dental radiography?
Definition
3 in 1 million
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
6000 mrads (0.06 Gy)
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
5000 mrads(0.05 Gy)
Term
How many dental films would it take to cause leukemia?
Definition
2000-5000 films
Term
Which film speed is the best to reduce absorbed dose?
Definition
F, reduces by 60%
Term
How much does collimation reduce the absorbed dose?
Definition
by 70%
Term
Which technique reduces skin dose?
Definition
parallel technique, uses longer sources to film distance
Term
Which exposure factor reduces absorbed skin dose?
Definition
kVp(higher)
Supporting users have an ad free experience!