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Radiobiology4307

QuestionAnswer
What is radiobiology? The study of the sequence of events following absorption of energy from ionizing radiation.
What are the two general classifications for ionizing radiation? Electromagnetic and particulate radiation.
What are three common charged particles associated with beam interactions? Alpha particles, protons and electrons
A direct ionization reaction occurs when what composes the primary beam? Neutrons; Secondary particles produced from neutrons interaction with nucleus of atom may cause direct damage to the DNA.
An indirect ionization reaction occurs when what composes the primary beam? X-rays or gamma rays.
Radiolysis is an indirect effect. What occurs? Splitting of water; ionization or ejection of an electron from a water molecule producing a water ion.
During radiolysis, a chemically unstable pair of water ions tend to rapidly break down into another ion and what else? Free radical; atom or atom group in a highly reactive transient state that is carrying an unpaired electron with no charge.
What is LET and what is its relationship to charge and velocity? Linear energy transfer is an average value calculated by dividing the energy deposited in keV by distance traveled in micrometers. It is directly proportional to the square of the charge and inversely proportional to the square of velocity.
What is RBE and how is it related to LET? Relative biologic effectiveness equals dose from 250 keV x-ray divided by dose from test radiation to produce the same biologic effect. The RBE relates the ability of radiations with different LETs delivered under same conditions.
DNA is a large molecule that has four nitrogenous bases. What are the bases? Adenine (A), thymine (T), cytosine (C), guanine (G).
What are the four phases of mitosis? Prophase, Metaphase, Anaphase and Telophase
What is division delay in regards to cellular response to radiation? Irradiated cells are delayed from going through division. Fewer daughter cells will be reproduced.
What is interphase death in relation to cellular response to radiation? Cell death caused by radiation during G1, S or G2 phase. This is death before the cells reach mitosis.
What is reproductive failure? Most common end point for cell response to radiation. Decrease in reproductive integrity or cell's ability to undergo a limited number of divisions after radiation.
How is the extrapolation number (n) of a cell survival curves determined? The extrapolation number or target number is determined by drawing the linear portion of the curve back until it intersects the y-axis.
The quasithreshold dose (Dq) is a measure of cell response at low dose. What else does the Dq measure? The quasithreshold dose also measures the cells ability to accumulate and repair sublethal damage.
What are two physical factors that affect cellular response to radiation which changes the overall cell survival curve? One is the response of cells to high-LET radiation compared to exposure after to low-LET radiation. The second factor is dose rate.
What are the two major chemical factors that influence cellular response to radiation? Radiosensitizers (enhance cellular response) and radioprotectors (decrease cellular response).
What is the OER and what two things does it compare? Oxygen Enhancement Ratio; Compares response of cells with radiation in the presence and absence of oxygen.
Biologic factors affect cellular response. During what phase are cells most sensitive? M phase.
The Law of Bergonie and Tribondeau states that ionizing radiation is more effective against cells that are actively mitotic, have a long mitotic future and are __________? Undifferentiated.
Out of the 5 basic cell populations, which is the most radiosensitive? Radioresistant? Groups: vegetative intermitotic (VIM), differentiating intermitotis (DIM), multipotential connective tissue cells, reverting postmitotic (RPM), fixed postmitotis (FPM) Radiosensitive: differentiating intermitotic (DIM) Radioresistant: fixed postmitotic (FPM)
What are the four R's of radiation response and healing? Regeneration, Repair, Repopulation, Reoxygenation.
The hematopoietic syndrome occurs between total-body doses of 100 to 1000 cGy. How long does the patient have until death and what organ does it damage? 3 weeks to 2 months. It damages the bone marrow.
The gastrointestinal syndrome affects the small intestine. At which total-body dose does this occur and how long does the patient have to live? It occurs between 10-50 Gy. The patient is given 3-10 days.
What syndrome occurs from a total-body dose of over 50 Gy, a time of death under 3 days and causes damage to the brain? Cerebrovascular Syndrome.
Nausea, vomiting and diarrhea are major symptoms for which stage of the total-body syndrome? And what is it's duration? The prodromal stage and days-minutes.
The latent and manifest syndromes have the same duration of time. Which syndrome has no symptoms? The latent phase.
What is the estimated lethal dose (LD 50/60) for humans? 350-450 cGy.
What are 2 common acute changes experienced after irradiation? Inflammation and edema.
What is the most severe late response an organ will experience after irradiation? Necrosis or death.
During what stage of gestation will the embryo/fetus have radiation damage causing death to the embryo and resorption? Preimplantation
During organogenesis, what is the risk for microcephaly and mental retardation from radiation? Very high risk.
During the fetal stage of gestation, what is the status of growth retardation from radiation? Permanent damage.
What is the most important late effect that is also an example of a stochastic effect? Carcinogenesis.
Leukemia is a somatic effect. Hiroshima and Nagasaki provide us with evidence of this. About how long is the latent period for leukemia? 4 to 7 years.
Radiologist used to place their hands in the x-ray beam to check its efficiency. What two most common types of skin cancers are associated with this radiation exposure? Basal cell carcinoma and squamous cell carcinoma.
Watch painters from 1915-1930 are associated with radiation-induced osteosarcoma because they used what radioactive element? Radium.
Which naturally occurring radioactive deposit is associated with lung cancer and a large exposure of annual background radiation? Radon gas.
H. J. Muller irradiated male and female fruit flies in 1927 to research what potential of radiation? The mutagenic potential.
Well oxygenated, oxic cells, are actively dividing. What are hypoxic cells? Hypoxic cells do not have normal levels of oxygen. However, they are viable and capable of dividing.
Oxic cells are highly radioresistant or radiosensitive to low-LET radiations? Highly radiosensitive.
True/False. Reoxygenation gets rid of all hypoxic cells. False; If this was true, low-LET fractionation would be highly curative.
The Strandquist Isoeffect curve was the first attempt to establish a relationship between what two things? Radiation dose and treatment time.
What is the definition of a TD 5/5? The TD 5/5 is the tolerance dose delivered by a fractionation schedule that causes a minimal (5%) complication within 5 years.
What is the tolerance dose (TD 5/5) of the spinal cord at 20 cm? 4500 cGy.
What is the difference between an acute response and a latent response? Acute responses are observed within a short time frame where latent responses are seen after a long time period following radiation exposure.
What is the difference between meiosis and mitosis? Meiosis is cell division in terms of germ cells. Mitosis is cell division in other types of cells.
The cell survival curve describes the relationship between the proportion of cells surviving and what else? Radiation dose.
What phase of the cell cycle is the most resistant to radiation? S phase.
What is the relationship between OER and LET, direct or indirect? Directly proportional; as the OER increases, so does the LET.
True/False. More cells are killed in the resistant phase of the cell cycle. False; More cells are killed in the sensitive phase of the cell cycle.
On a cell survival curve for alpha particles and low-energy neutrons, how is the curve displayed? (straight line, up and down, straight up or straight down) The cell survival curve for alpha particles and low-energy neutrons is a straight line.
Another name for an acute effect is what? Nonstochastic effect.
Particulate radiation has a high LET because of what two things? Their charge and heavy mass.
There are four types of dose response curves. What are they? Linear, nonlinear, threshold and no threshold.
When the dose response curve is no threshold and linear, what effect is it showing? (deterministic or stochastic) Deterministic.
At what dose does skin erythema occur? 20 Gy.
What acute effect occurs at 40 Gy to the skin? Wet desquamation.
During the first trimester of a pregnancy, a dose as low as ____ could be lethal to the embryo? 0.05 Gy.
Created by: anbrickner