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89 Cards in this Set
- Front
- Back
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the radiological unit of activity is
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Curis (Ci)
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the SI units for Ci (Curie) are
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Becquerel (Bq)
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the radiological unit of exposure is
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Roentgen (R)
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the radilogical unit of absorbed dose is
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rad
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the SI unit for rad is
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Gray (Gy)
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rem =
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radiation absorbed dose (rad) x Quality Factor (QF) or biological effect factor (RBE)
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600 rad lethal toatol body radiation represents how many calories
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100
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the energy required per ionization in air is
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34 eV
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the energy required per ionization in water is
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100 eV
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the measure of energy deposition by a radiation per unit of track is
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linear energy transfer (LET)
units: KeV/mum |
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alteration of a target molecule by direct absorption of energy is called
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direct action
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alteration of a target molecule by a chemical reaction w/ a product of the radiolysis of a neighboring moleducle (such as a free radical) is called
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indirect action
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a species having an unpaired valence electron
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free radical
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the radiolysis of water results in the production of
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H and OH free radicals as well as hydrated e-
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a radical which is a mjor oxidizing species when there is not oxygen present
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OH
when oxygen is present there is HO2 and H2O2 present which are more aggresive oxygenating agents |
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when oxygen is present a pressure greater than what - cells are more radiosensitive
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5 to 10 mm
some tumor cells are hypoxic and more radioactive resistant |
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what might you use colorny forming units (CFU) for
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in vitro to make precise dose-response curves
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the inverse of the slope of the exponential region of a dose response curve
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extrapolation numbers (n)
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RBE is defined as
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dose of a standard radiation (250 KeV xrays) required to obtain a given biological effect / the dose of the test radiation required to produce the same biological damage endpoint
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LET increases as particle energy?
charge on particle? velocity of particle |
LET increases as particle energy decrease, charge increases, velocity decreases
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as LET increases, RBE
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increases, until levels of LET are reached where deposited energy is wasted as over kill.
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RBE increases as dose
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decreases
in other words the higher the RBE - the lower the dose needs to be to get a given effect |
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visible abnormalities that occur when radiation occurs on cells undergoing interphase
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swelling, pyknosis of nucleus
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the most importan reversible block or division delay produced by radiaiton appreas during what stage in the cell cycle
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G2
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why does fractionation and protraction of the radiation dose result in less cellular damage
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sublethal and potentially lethal radiation damage is repairable in a time-dependent fashion
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non-ionizing and cause the formation of pyrimidine dimers
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UV light
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disease associated with a repair deficiency
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xeroderma pgimentosum (XP)
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the principle cell renewel systems involved in radiation sickness are the
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hemopoietic and gastrointestinal systems
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lethal doses for mammalial populations of radation are close to (in rads)
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450 rads
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skin changes to radiation may be characterized by
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erythema, dry desquamination, moist desquamination, necrosis
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delayed necrosis is due to
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damage to the fine vasculature and CT
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Law of Bergoinie and Tribondeae broadly states that
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radiosensitivity varies directly with the rate of proliferation or mitotic activity and with the number of future divisions the cells with undergo, and inversely with the degree of morphologic and functional differentiation
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ALARA
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keeping doses as low as reasonalby achievable
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the incidence of malignancy increases as the dose increases upt to 300 rads, and then
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incidence rate reduces
result of cell killing at higher doses |
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this relationship is the working hypothesis on which recommendations for radiation protection are base
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simple linear dose-response curve
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two mechanisms that may explain radiation-induced cancer1.
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1. somatic mutaiont
2. makes cellular environment mroe compatible for viral-induced or chemical malignant transformation |
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X-rays induce high incidence of what kind of mutaitons
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point
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the mutation doubling dose for humans is approx
measured in rems |
60 rems
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in the testis and female what are the most sensitive cells
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spermatogonia
granulos cells in growing follicles |
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a dose of what may be harmful to the human fetus
in rads |
5 to 10 rads
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in addition to carcinogenesis, the late effects of radiation included (4 things)
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aplastic anemia
lifespan shortening cataracts retinal dysplasia |
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how does radiation affect eh immunity response of mammals
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suppresses it
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represent the larges man-made source of radiation exposure
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medical diagnosit x-rays
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the gonadal dose that, if received by every member of the population would be expected to produce the same total genetic effect on the population as the sum of the individual dose actually received is called the
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genetically significant dose (GSD)
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deposited in the environment, can be concentrated at various stages i the food chain, used in therapy, etc... (e.g what causes radiation)
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radionuclides
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reside in lungs or in bones of many man may produce very high internal doses since all of the energy of the particles emitted will be depositid w/in organ of localization
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alpha particle emitters
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acute radiation syndrome
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when the whole body or a major part of it is exposed to a large acute dose of penetrating radiation
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three stages of acute radiation syndrome
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1. Prodromal phase (1-2 days)
2. Latent period (days-wks) 3. manifest illness at high doses - CNS is involved |
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if the prodromal phase which includes nausea, vomiting, anorexi, etc occured w/in two hours then dose is probably
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more than 200 rem
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a dose of what might lead prodromal phase to lead directly to manifest illness (w/o latent period)
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600 rem -
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epilation (loosing hair) occurs at what rem
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350 for some
700 for all |
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pancytopenia
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lymphocyte counts fall w/in first day or two w/ max depression after 200 rem
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a lymphocyte count of 1200 over 48 hours suggest
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less serious exposure
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what does a neutraphil count near zero by the 4th or 5th day suggest
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poor prognosis and irrepairable damage
platelet counts parallel neutrophils |
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what heralds recovery of blood production
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return of reticulocytes into circulation
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a marrow mitotic index of zero on the 4h day may mean a dose in excess of (in rem)
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200 rem
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diarrhea occurs how soon after exposure
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about 4 days
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if the dose is in the order of thousands of rems and CNS is involved what is the most likely outcome
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death w/in hours
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mortality reaches 50% at what rem and 100% at what rem
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50 at 400 and
100% at 600 rem |
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if the prodromal symptoms are still present on the third and fourth days, the dose is most likely
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400-600
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hospitilization should be carried out where the exposure dose is suspected of having been what or more (rems)
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100 rem
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treatment of prodromal symptoms should be prompt and may consist of
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sedatives and antimetics
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changes in the blood picture will be developing in spite of the absense
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symptoms
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type of particle stopped by a sheet of paper, does not penetrate skin. consists of a neutron and two proteons.
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alpha
problem arises when material gets inside body by inhalation, ingestions etc |
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stopped by a layer of clothing or less than an inch of sustance
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B
electron ejected from the nucleus of a radioactive atom. may causes skin injury if exposed for a long time. protective clothing as precaution |
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travel many feet in air and many inches in human tissue - "penetrating" radiation
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Gamma rays and x-rays
(photons) gamma and x radiation frequently accompanies the emission of beta and alpha radiation |
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how does alpha, beta, and gamma differ in their LET
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alpha - high LET
beta and Gamma - low LET |
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which particle is more potent and causes more tissue damage
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alpha
only 5 rad of alpha particles produced the same effect (in rem) as 100 rad of gamma and beta particles |
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absorbed dose weighted by type of radiation
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rem
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to calculate rem you are multiplying rad by a radiation weighting factor - the radiation factor for x-rays, gamma rays, and beta particles is
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1
QF might be higher for other types of radiation |
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about how much is the annual natural background radiation
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200mrem annually
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physical half life
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time required for the activity of a radioactive material to decrease by one half due to radioactive decay
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biological half life
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time required for the body to eliminate half of the radioactive material (depends on chemical form)
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the net effect of the combination of the physicial and biological half-lives in removing the radioactive material from body
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effective half life
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metal which insulates radioactive material
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lead
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in a case w/ a pt who has been exposed - what comes first decontamination or patient stabilit?
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pt stability
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the latent period (interval) is affected how by dose
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decreased latent period w/ increased dose
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a dose over 3,000 will cause damage to the
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CNS
vomitting, diarrhea, confusion, severe hypotensiont w/in minutes. collapse of cardiovascular and CNS - fatal 24 to 72 hours |
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what is the effect on skin after less than 100 rem
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no visible injuries
at over 500 = erythema, epilation over 1,800 = desquamation |
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1 Sy =
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a "doubling dose" = (1Gy)
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percentage change in risk for given dose (relative change rate)
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excess relative risk (EER)
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LD50/30
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about 450 rads - death for mammals usually
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EER and EAR can vary w/
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age at exposure, gender, attained aga, etc..
EER is excess relative risk which is the percentage change in the risk for a given dose EAR is the absolute change in rates for a given dose |
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what is the effect for doses less than the threshold on a dose response curve re cancer
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none -
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how does ERR change as you get older
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decreases with age at exposure and age
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EAR is affected by age how
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EAR increases w/ age
age specific excess rates decrease with age at exposure |
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life saving actions guidance (NCRP-116) in mrem
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50,000
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pts are said to be contaminated when
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radioactive material is on their skin or in their bodies. radiation safety precautions are not needed for patients who have only been exposed and are not contaminated
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placing the radioactive source in a lead container is a type of
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shielding
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