Chapter 3 Flashcards
true or false: in the law of bergonie and tribondeau, stem/immature cells are more radiosensitive than mature cells
- true
true or false: younger tissues are more radiosensitive than older tissues
true
true or false: the higher the metabolic rate (the energy the cells use), the more radiosensitive it is
true
true or false: the greater the proliferation (rate of cell division) and growth rate for tissues, the greater the radiosensitivity is
true
why are our bodies not created equal?
because our cells are not created equally
what does the law of bergonie and tribondeau conclude?
that compared to a child or mature adult, the fetus is the most radiosensitive
define radiosensitivity
- the effects that our cells undergo and the probability of damage or recovery when irradiated
define radioresistance
- how resistant the cell is to radiation
what is one main factor of determining radiosensitivity?
- the proliferation (rate of cell division) rate of that cell and the rate of cell division (mitosis) rate
true or false: the faster the cell divides, the less time it must repair itself from damage before dividing into another damaged cell
true
define proliferation
- the rate of cell division is
what cells have the highest sensitivity?
- cells that are immature, undifferentiated, precursor or stem cells
define direct effect
- ionization occurs directly with a molecule
define indirect effect
- ionization occurs with water and transfers ionization to target molecules
define fraction theory
- radiation dose broken into smaller doses spread out over a period rather than given all at once
what are the highly radiosensitive cells?
- lymphocytes
- spermatogonia
- erythroblasts
- intestinal crypt cells
- DNA
what are intermediate radiosensitive cells?
- endothelial cells
- osteoblasts
- spermatids
- fibroblasts
- RNA
what are low radiosensitive cells?
- muscle/nerve cells
- chondrocytes
true or false: cell radiosensitivity depends on what part of the cell cycle they’re in
true
define irradiated
- exposed to radiation
what occurs when a cell is irradiated in the cell cycle?
- mitosis is slowed down
- interphase death = cell death occurs before entering mitosis
- cell death occurs
what part of the cell cycle is most radiosensitive?
- M phase/mitotic phase (prophase, metaphase, anaphase, and interphase)
- G1 phase (1st growth phase)
- early S phase (where DNA replication occurs)
When looking at a graph that deals with age factors consisting of the fetus in the uterus, childhood, adult, and age, which portion has the highest radiosensitivity?
- fetus in the uterus (womb)
- this is due to the fetus having immature cells, which makes them vulnerable to radiation
define LET
- linear energy transfer
- a measure of the rate at which energy is deposited as a charged particle travels through matter
- units of measurement: keV/mm (micrometer)
- is the function of the physical characteristics of radiation (mass and charge)
explain low LET
- contains electromagnetic x-rays (x-rays and gamma rays)
- they produce few and thinly dispersed interactions due to their fast moving electrons
- lose their energy at a low rate when passing through tissues
explain high LET
- consists of alpha particles and neutrons
- highly ionizing
- more likely to interact with tissues
- lose their energy quickly
- produce several ionizations with a short distance
true or false: a diagnostic x-ray with an LET of 3kev/mm are considered to be low when compared to other radiations
true
how much RBE (relative biologic effectiveness) does a diagnostic x-ray have?
- approximately 1
define division delay
- slowing down of cell mitosis
- low radiation dose = delay cell mitosis
define RBE
- relative biologic effectiveness
- a comparison of a dose of test radiation to a dose of 250 keV x-ray that produces the same biologic response
- measures the biologic effectiveness of radiations having different LET’s
- comparing dose of test radiation to a dose of 250keV x-ray, which produces the same biologic response
what’s the formula for RBE?
RBE = dose in rads from 250 keV x-rays necessary to produce a given effect / dose in rads of test radiation necessary to produce the same effect
RBE = dose in rads from 250KeV x-rays / dose in rads of test radiation
what factors influence RBE?
- radiation type
- cell or tissue type
- physiology condition
- biologic result being examined
- radiation dose rate
what’s the relationship between LET and RBE?
- direct relationship
- when LET increases, RBE increases
define OER
- oxygen enhancement ratio
- dose of radiation that produces a given biologic response under anoxic (no oxygen) conditions divided by the dose of radiation that produces the same biological response under aerobic (with oxygen) conditions
define anoxic
- no oxygen
define hypoxic
- lacking oxygen
what’s the formula for OER?
OER = dose that produces a given biologic response under anoxic conditions / dose that produces the same biologic response under anaerobic conditions
true or false: OER is most effective with low LET radiation
true
true or false: OER is less effective with high LET radiation
true
true or false: an increase in OER increases LET
true
what happens when cell mature?
- radiosensitivity declines
- as we mature, we become radioresistant
- once we hit old age, we become radiosensitive again
define direct interaction
- takes place when an original ionization incident happens on that macromolecule
- Ex.) DNA, RNA, protein, enzymes
- if a macromolecule is ionized, it’s considered abnormal and is damaged
define indirect interaction
- ionization incident that takes place on a distant non critical molecule, which then transfers that energy to another molecule
true or false: radiation interactions with humans are mostly indirect
- true
- this is due to the human body being 75% of water
define radiolysis
- when water is irradiated, it gets ionized, producing a free radical
- human body containing 75% of water
what’s the principal cause of effects from radiation?
- the irradiation of water that causes indirect effects
define free radical
- an uncharged molecule containing a single unpaired electron (ion) in the outermost shell/valence shell
- chemically unstable
- highly reactive
- can quickly interact with other molecules and interfere with their bonds
what are the results of radiolysis?
- H+ and OH- (ion pair)
- H* and OH* (free radicals)
- the free radicals can either create a water molecule or damage other macromolecules
true or false: if OH* and H2O2 (hydrogen peroxide) causes 2/3rds radiation damage
true
define vitro
- outside of the body or cell
- irradiating macromolecules requires a significant dose of radiation to create a measurable effect
define vivo
- inside the cell
- irradiating macromolecules show cells in their natural state
- more radiosensitive
define main-chain scission
- occurs when the thread or backbone of a long chain molecule is broken
- reduced to smaller molecules
- viscosity (thickness) is reduced
define cross-linking
- causes the macromolecules to connect to another macromolecule, or to another section of the same molecule
- viscosity is increased
define point lesion
- may cause slight molecular changes, which in turn cause the cell to function incorrectly
- occur in low doses of radiation
- responsible for the late radiation dose
define dose -response relationships
- graphical relationship between observed effects (response) from radiation and dose of radiation received
1. they’re either linear or nonlinear
2. they’re either threshold or non-threshold
define linear
- an observed response is directly proportional to dose
- doubling the dose of radiation will double the response
define nonlinear
- an observed response is not directly proportional to the dose
- doubling the dose of radiation does not double the dose of the response
define threshold
- a point where biologic response occur
- implies there is a “safe” amount of dose delivered
- curves can be linear, sigmoid, or curvilinear
- doesn’t start at zero
define nonthreshold
- any radiation exposure is harmful/causes a response in the body
- no safe level
- curves can be linear, curvilinear
- all start at zero
define linear quadratic dose-response curves
- low doses of low LET radiation follow a linear quadratic dose-response
- low dose = linear curve
- high dose = curvilinear curve
- curve is nonthreshold
define nonlinear dose-response relationships
- sigmoid
- contains threshold with no observable effects occuring
- with sigmoid dose-response, there a nonlinear relationship between dose and effect
- not directly proportioned
define target theory
- effect of radiations by direct hits on sensitive cellular targets
- DNA is considered a critical molecule (because it’s not abundant)
- target interactions occur randomly
define hit
- when chromosomes (or target) is/are irradiated
- interactions can either be direct or indirect
- represent critical damage to DNA
define how target theory depends on LET
- with an aerobic condition, the indirect effect is intensified due to more free radicals formed
- this increases the likelihood of a hit
define bystander effect
Treatment of cells with low doses of radiation results in the release of specific factors outside the cell that seem to be responsible for biological changes in cells not directly exposed to radiation.
define repopulation
- allow cells to replenish and repopulate following injury or interaction to ionizing radiation to lessen the likelihood of damage
define protraction
- the time during which a course of radiation is given (spread out dosage)
when were x-rays discovered?
- November 8, 1895
who found x-rays?
- Wilhem
what year was radium discovered?
- 1898
who discovered radium?
- Pierre and Marie Curie
who invented the fluoroscope?
- Thomas Edison
what year was the fluoroscope invented?
- 1898
who was Thomas Edison’s assitant?
Clarence Dally
How did Clarence Dally die?
- due to cumulative exposure to radiation
who discovered mutations through experiments with fruit flies?
- Herman Muller
what did Herman Muller discover?
- mutations through experimenting with fruit flies
define rad
- Radiation absorbed dose
- also known as Gray
- patient dose
define rem
- radiation equivalent man
- also known as sievert
- occupational dose
define roentgen
- exposure in air
- also known as Coulumb/kilogram
- x-ray in air
define curie
- radioactivity
- also known as becquerel
- x0ray quantity
define NCRP
- national council of radiation and protection
- sets the standard for dose limitations for occupational workers and the public exposure
what’s the formula for occupational dose and patient dose
1 RAD = 1 REM
100 RADS = 1Gy (Gray)
define epilation
- hair loss
define erythema
- skin reddening
define desquamation
- skin peeling
define inflammation
- skin swelling and reddening
define tissues
- collection of cells
define organs
- collection of tissue
define systems
- collection of organs that work together
define organisms
- all systems working together
- Ex.) human
what are the functions of cells?
- metabolism
- growth
- irritability
- adaptability
- repair
- reproduction
what’s the normal number of chromosomes in a human?
- 46
- diploid or 2n
define haploid number?
- the number of chromosomes in germ cells
define germ cells
- reproductive cells
- also known as somatic or gamete cells
what’s the name of a male germ cell?
- spermatozoa
what’s the name of a female germ cell?
- oocytes
When are cells most radiosensitive?
- during division
- cells are immature
when are cells radioresistant?
- after division is complete
- when the cell is mature
define interphase
- subdivided into G1, S, and G2 phase
define G1 phase
- “resting phase”
- 1st growth phase
- normal metabolic roles
define S phase
- cell cycle is completed and “mature” (radioresistant)
- DNA replication
define G2 phase
- gap or growth phase
- the process of mitosis
- 2nd growth phase
what happens after G2 phase?
- the cell DNA replicates itself and begins a cell cycle M phase
- mitotic phase
define prophase
- first stage
- chromosomes migrate towards opposite poles of the cell
- produce spindle fibers that extend across the equator
define metaphase
- 2nd stage
- the cells are lined up at the equator
- lined up in the middle of the
define anaphase
- 3rd stage
- the centromeres divide and the sister chromatids detach as they are pulled to opposite poles
define telophase
- 4th final stage
- the sets of chromosomes become longer, thinner and indistinct as they reach the poles of the cell
- cell division is complete
define mitosis
- the process of cell division in which nucleus and the cytoplasm divide
define meiosis
- the process of cell division in which the nucleus and the cytoplasm divide to form 2 identical cells
- cells divide twice
- chromosomes duplicate once
What happened in 1896
- antoine and henri becquerel observance being given off by uranium containing substances
As LET ____________, the RBE ______________
increase; increase
Tissue is _______ radiosensitive under high oxygen conditions and _________ radiosensitive under hypoxic conditions.
more; less
A _________ response to radiation is directly proportional to the dose received.
linear
If a response to radiation is expected, no matter how small the dose, then that dose-response is ________________
nonthreshold
Radiation induced genetic damage follows a ___________________ dose-response relationship
linear nonthreshold
