Physics 2 test 3 Flashcards
At nearly every stage in the sequence of events after radiation exposure to human cells, it is possible or not possible to repair radiation damage and recover?
Possible
The study of the effects of ionizing radiation on biologic tissue
Radiobiology
Radiation interacts in the human body at what level
Atomic level
What percent of the body consist of hydrogen and oxygen?
85%
What percent of the body is water?
80%
What does it mean to fractionate radiation exposure?
To give small amounts over a period time, versus all at once in one setting.
What does it mean to Protract radiation exposure?
Spread out a single large dose continuously at a slower and lower rate.
What is extrapulation?
Scientifically theorizing results to exposure
Very large molecules that sometimes consist of hundreds of thousands of atoms
Macromolecules
Four of the five principle molecules found in the body are
Proteins
Lipids (fats)
Carbohydrates (sugars and starches)
Nuleic acids
What type of molecules are life supporting and contain carbon?
Organic Molecules
Which molecules make up Organic Molecules?
Proteins
Lipids
Carbohydrates
This molecule is one the rarest molecules, a nucleic acid concentrated in the nucleus of a cell and is the most critical and radiosensitive target molecule.
DNA
Most abundant molecule in the body and simplest
Water
The body’s attempt to maintain a constant internal environment through perspiration and replacement
Homeostasis
The breaking DOWN of molecules ending in water an carbon dioxide
Catabolism
The PRODUCTION of large molecules
Anabolism
Catabolism + Anabolism
Metabolism
Long chain macromoleucles that consist of a linear sequence of amino acids connected by peptide bonds
Proteins
Proteins make up what percent of the human body
15%
Name the variety of uses Proteins provide the body
Structure and support
Function as Enzymes, hormones and antibodies
A catalyst which speeds up reactions
Enzymes
Molecules that excersise regulatory control over some body functions such as growth and development
Hormones
Hormone molecules are produced and secreted by what?
Endocrine glands:
Pituitary, adrenal, thyroid, parathyroid, pancreas and gonads
The body’s defense system
Antibodies
Molecules that consist of one molecule of gycerol and three molecules of fatty acid
Lipids
Lipids are composed of what?
Carbon, hydrogen and oxygen
Lipids are a part of cell membrane in what body tissue?
EVERY body tissue
Lipids are
Thermal insulation ( just under the skin) and a Secondary energy source-easier to get to energy from than carbohydrates
What is the cheif function of carbohydrates in the body?
To provide fuel for cell metabolism
Carbohydrates are also called
Saccharides
What are the two sugars in Carbohydrates
Monosaccharides and Disaccharides
Plant startches and Animal Glycogen
Polysaccharides
Chief cell function of carbohydrates
Cell Metabolism
A simple sugar, is main fuel for body
Glucose
Glucose is composed of what?
Carbon, Hydrogen and Oxygen
What is the ratio of hydrogen to oxygen in glucose?
2:1 same as water molecules, hydrated water
Two principle Nucleic Acids important to human metabolism
Deoxyribonucleic Acid- DNA
Ribonucleic Acid- RNA
Resides in the nucleus, control center for cell and contains cell hereditary info
DNA
Extrememly large and complex macromelecules are
Nucleic Acids
Mostly in cytoplasm, there are two types of this and messenger and transfere
RNA
Describe Nucleotides
Base-sugar-phosphate combinations strung together. two chains attach at bases and then spiral to form DNA
Bases of Nucleotides are allowed in only two combinations
Adenine + Thymine
or
Cytosine + Guanine
The order of base combinations in DNA carries what
Genetic code
Basic component of all living material
Human Cell
The two major structures of the human cell are
Nucleus and Cytoplasm
The principle molecular component of the nucleus is
DNA
Other than DNA what else if contained in the nucleus
RNA
Protein
Water
(Blank) makes up the bulk of the cell and contains great quantities of all molecular components except (blank)
Cytoplasm
DNA
The (blank) is a channel or series of channels that allows the nucleus to communicate with the cytoplasm.
Endoplamic Reticulum
Located in the cytoplasm (blank) are large bean-shaped structures. Their purpose is to provide (blank) for the cell
Mitochondria
Energy
These small dot like structures are located throughout the cytoplasm or the (blank). (blank) are the site of protein synthesis.
Endoplasmic reticulum
Ribosomes
(blank) are small pea-like sacs that contain (blank) that help with cellular digesting.
Lysosomes
enzymes
The normal number of chromosomes in a human cell
46
Ocupational radiation is measured in what?
mR milli rad
Mammalian cells may be killed by doses of less than (blank) rad or (blank) Gy
100 rad
1 Gy
What part of the cell is most sensative to radiation and why
DNA because you only have to much
If radiating cytoplasm and not the nucleous, how much radiation in rad and Gy could it take for cellular death
1000 rad or 10 Gy
If something is avascular it means what in relation to blood supply and radiation treatment and why?
Not a good blood supply
Not very responsive to treatment such as Chemo, meds etc
Oxygen is carried through the blood, if the blood supply is low, oxygen is low and oxygen is key for treatment
Because DNA is the most radiosensative part of the cell, the faster a cell replicates the (blank) radiosensative it is.
More
Describe Mitosis
Cell swells up, chromosomes lines up, Chromosomes split and migrate toward nucleus
In radiology what process of cell reproduction are we most concerned with
Interphase
Describe interphase
The part of cell reproduction that varries in time from cell to cell. Ths is where DNA is replicating.
Most radiosensative cells are and whats different about them from other human cells
Sperm and Ovary
Spermatogonium and Oogonium
They go through Meiosis versus mitosis
The less mature a cell or cell system the (blank) sensative
More
Reproductive cells go through regualar mitosis where you have two cells alike, then those two cells do what…and the end result is what?
Divide again without going the “S” phase so they do not synthesis DNA. End result you have four cells with 23 chromosomes each
46-46-23/23 and 23/23
Undifferentiated, presursor or stem cells are concidered what kind of cells? Are these cells more or less radiosensitive than mature cells?
Immature cells
More
Cells, tissues and organs that are highly sensative take more or less radiation
Less
What type of cells have low sensativity?
Muscle, brain and Spinal (Nerve)
High metabolic acitivty means what in relation to reproduceability and radiosensitivity?
Rapid reproduction
Highly sensitive
If you are fractionating radiation you are doing what?
Giving small doses over an extended period of time.
If you are protracting radiation you are doing what?
Giving continuous radiation over a longer period of time.
List the 9 things that affect radiation response
LET RBE Fractionation Protraction OER Age Sex Recovery Chemical agents
Define LET
Linear Energy Transfer: How much energy a given photon deposits in the tisue over distance (micrometer)
The more energy a photon gives up, the (blank) the LET
Higher
As LET increases, bioligic damage produced (blank)
Increases
About the rate at which diagnostic x-rays give up energy
3 keV per micrometer
Degine RBE
Relative biologic effectiveness: The effectiveness of LET radiation
As LET (ability to transfer energy to tisue) goes up, RBE goes (blank). Is this directly proportional?
Up
no
When do RBE levels, level out? can’t get any higher
3, triple the effect of diagnostic
What is the RBE of diagnostic x-rays and in what kVp range is this
1
20-130
How can you increase radiation tolerance? What effect if any do these have on biological effectiveness?
Use protraction or fractionation
Either would reduce the biological effect of the exposure
As RBE goes up, LET goes (blank) and OER goes (blank)
Up
Down
As OET goes up, RBE goes (blank) and LET goes (blank)
Down
Down
Define OER
Oxygen Enhancement Ratio: A numerical descriptin of the effect oxygen has on tissue damage
What does the presence of oxygen do the the effectiveness of radiation?
Effectiveness goes up
Cells that duplicate faster are more radiosensitive-they have less time for repair before time to divide again. This means they are more likely to to be hit during what cell division phase?
Mitosis
In vitro irradiation occures (blank) the body or (blank) the cell
Outside
In vivo irradiation occures
In the living cell
In vitro or In vivo are more radio-sensitive
In vivo
Major radiation responses of DNA (5) and viscosity results
Main-chain scission: sever one side rail-thinner sever both side rails-thinner with cross-linking-thicker Point lesions Change or loss of base
Which radiation response to DNA is more likely to cause a mutation?
Main-chain scission with cross-linking
Difference between direct and indirect hits of radiation to DNA
Direct-hit the actual DNA
In direct-hit water and then effected the DNA
Doesn’t matter which is hit, the end result is the same.
3 types of damage to DNA
Cell death
malignant disease
genetic damage
Describe radiolysis of water
Water that has been irradiated dissociates into other molecular products.
Breakingdown of water
What happens to an atom of water that is irradiated?
It ioizeses and dissociates into two ions-an ion pair H+ and OH- and two free radicals
Describe a free radical
Unchaerged molecule that contains a single unpaired electron in the outer shell. Short life span.
How is hydrogen peroxide in relation to free radicals
The OH* free radical can join with a similar molecule to form hydrogen peroxide.
Hydrogen peroxide can also be formed with two hydroperoxyl free radicals
The principal damaging products after radiolysis of water
Hydrogen peroxide and hydroperoxyl radical
Describe a hydroperoxyl radical
H* interacting with an oxygen molecule
Priciple action of radiation on humans is (blank)
Indirect
Target Theory
There are key sensitive molecules that no other colecules can pick up the work of if damaged to the point of non-function.
What is the target molecule
DNA
What must happen for cell death to occur
The target molecule must be damaged to the point it ceases to function
Describe a “hit”
An ionization that inactivates the target molecule (DNA)
What probability of a “hit” does high LET radiation ionization have?
High
Will adding or increasing oxygen with a high LET dose increase the liklihood of a “hit”?
No
Low LET radiation ionization does or does not get many “hits”
Does not
What happens to the likelihood of a “hit” when you add oxygen to low LET?
Increases the liklihood giving a greater area of effectiveness
As dose increases inactivity damage likelihood (blank)
increases
How are lethal effects of radiation determined?
By observing cell survival NOT cell death
What is D37
The amount of radiation that if uniformly distributed would be enough to inactivate ALL the cells exposed (kill all the cells)
The 37 represents 37% of the cells hit would survive
A specimen with a LOW D37 is (blank) radiosensitive.
Highly-doesn’t take a large dose to kill 63% of cells
A HIGH D37 means the specimen has (blank) radiosensitivity
Low-takes a good bit of radiation to inactivate 63% of cells exposed
Complex organisms like human cells require two or more “hits” to inactivate a cell. This is known as
Multitarget, single “hit” theory
In what phase of mitosis are cells most resistant to radiation exposure? and why?
Late S phase-have double/extra DNA
3 stages of Acute Radiation Syndromes
Prodromal
Latent
Manifest Illness
What happens in Prodromal?
Immediate, brief, acute symptoms seen at min dose of 100 rad (1gy)
What happens in Latent?
Symptom free hours to weeks with from greater than 5000 rad, to 100-500 rad
Manifest Illness
Acute, lethal symptoms
Hematologic effects of radiation exposure
200-1000 rad (2-10 Gy) reduced cell count manifested by vomiting, mild diarrhea, malaise, lethargy, and fever pt MAY recover 4-60 days (dose Depentent)
Gastrointestinal effects of radiation exposure
1000-5000 rad (10-50 Gy)
Death within 4-10 days (Dose Independent)
nausea, vomiting, and diarrhea
Central Nervous System (CNS)
Over 5000 rad (50 Gy)
Death within hours to 3 days (Dose Dependent)
Disoriented, seizures, lethargy, coma, death
elevated fluid in brain increases intracranial pressure
What is LD 50/30
Dose response for human lethality
threshold, nonlinear
Dose that will kill 50% of subjects within 30 days
For humans about 300 rad (3 Gy)
Damage to (blank) cells results in the earliest manifestation of radiation injury to the skin
Basal Cell
Erythema
Sunburn like reddening
Desquamation
Ulceration and Denudation
Epilation/Alopecia
Hair loss
could temporary or permanent
Erythema dose that will be created in 50% of the people irradiated
@600 rad (6Gy) for humans
Gonadal exposure
Responses documented at doses as low as 10 rad (.1 Gy)
Ovarian exposures:
(blank) may suppress menstruation
(blank) may increase genetic mutations
(blank) temporary sterility
(blank) permanent sterility
10 rad (.1 Gy) 25-50 rad (.25-.5 Gy) 200 rad (2 Gy) 500 rad (5 Gy)
Testicular Exposure: Sperm replace every (blank) (Blank) reduces sperm count (Blank) temporary sterility (Blank) Permanent Sterility
Every 3-5 weeks 10 rad (.1 Gy) 200 rad (2 Gy) 500 rad (5 Gy)
Most Radiosensitive
Lymphocytes and Spermatogonia
Radiation-induced Chromosome aberrations follow a (blank) dose-response relationship
Nonthreshold
What is Cytogenetic analysis
The study of the genetics of cells, particularly cell chromosomes
What is a karotype
Chromosome map
Single hit chromosomes are (blank) and nonthreshold
Linear
Multihit chromosomes are (blank) and nonthreshold
Nonlinear
Reciprocal Translocations (Chromosomes)
No loss of genetic material, rearranged
Chromosome hit
Visible derangement, by then multiple DNA have been severed
Radiation safety guidelines and practices are based on linear or non linear, and threshold or nonthreshold dose-response
Linear
Nonthreshold
Chromosome linear nonthreshold exposures can continue to show abnormalities for how many years after exposure?
20+
What can skin look like at the linear nonthreshold exposure dose?
Weathered, discolored and callused
Threshold for radiation induced cataracts?
1000+ rad (10+ Gy)
What pattern do radiation induced cataracts follow?
Threshold, nonlinear
What is the latent period for Radiation induced cataracts?
5-30 yrs of apparent well-being
1 rad is equal to how many MR
1000
What pattern does life span shortening follow with radiation exposure?
Linear, nonthreshold (no amount of radiation is safe)
What is the worse case senario for life span shortening?
Reduction of 10 days for every rad
Explain Relative Risk in relation to Radiation induced malignancies and genetic effects
One population was exposed, all the details of exposure are not known
Explain Absolute Risk in relation to Radiation induced malignancies and genetic effects
Two groups, one known exposure one “control” or non effected group, compare to each other
Explain Excess Risk in relation to Radiation induced malignancies and genetic effects
Cases above what would be expected in general population
