Cellular Effects - Dose/Response Flashcards
Dose received (radiation) is graphically located on the__________ axis
Horizontal
Radiation dose-response relationship
Demonstrated graphically through curve that demonstrates the dose received and the corresponding effects.
Biological effects (response) is graphically located on the _________ axis
Vertical
Four items to consider on a radiation dose-response graph:
Linear
Nonlinear
Threshold
Nonthreshold
Linear graph will represent
A straight line; dose and response are proportional
Nonlinear graph represents
A curved line; dose and response are not proportional
Threshold
A given amount of radiation (dose) must be received before biological effects occur.
A certain dose is required before a response occurs.
Nonthreshold
A radiation dose that will immediately result in biological effects occurring.
ANY exposure will cause a response.
Cancer dose curves
Both dose/curve used for most types of cancer is based upon the linear/nonthreshold curve, which implies that biological response is directly proportional to the dose and also no amount of radiation is safe.
Radiation protection - erring on the side of safety
Based upon the linear, nonthreshold curve which overestimates the risk but definitely does not underestimate.
Nonlinear threshold curve
Requires a certain dose before a specific biological action occurs.
AKA “S” shaped curve or sigmoid curve.
A nonlinear threshold curve demonstrates
A high dose cellular response and nonstochastic effects to high radiation dose such as erythema and hematologist depression.
Somatic effects
Biological damage sustained by a living organism as a result of exposure to ionizing radiation.
Early somatic versus late somatic effects
Depends on the length of time from irritation to the appearance of symptoms as a result of irradiation.
Stochastic effects
Mutational, nonthreshold, randomly occurring biologicL changes, severity not related to dose.
Examples of stochastic effects
Leukemia and other cancers and genetic alterations
Stochastic
“Doubt”
Maybe the radiation exposure caused the effect, but cannot be 100% sure
Early responses occur
In a matter of a few days.
Late effects
Occur months or years down the road.
Nonstochastic
Biological somatic effects that can be directly related to dose received.
“No Doubt”
Nonstochastic
100% sure radiation exposures caused biological effect
Early nonstochastic effects
Erythema, epilation, leukocytopenia, desquamation
Erythema
Reddening of the skin; burns to the skin
Epilation
Loss of hair
Leukocytopenia
A decrease in white blood cell count
Desquamation
Shedding of skin, peeling of skin
Late nonstochastic effects
Cataract, fibrosis, organ atrophy, reduced fertility/sterility
Cataract
Clouding of the lens of the eye, progressive from blurry to blindness
Fibrosis
Scarring
Excessive connective tissue
Organ atrophy
A decrease in size and function of an organ(s)
Ionizing radiation
Transfer of energy into living tissue
Ionizing radiation is capable of damaging living tissue by
Ionization of atoms/molecules
Electromagnetic interaction
Ionization of atoms/molecules
Imparting energy and/or removing electrons from atoms
Electromagnetic interaction
Charged particles influencing atoms/molecules
Properties of energy based ionizing radiation
Pure energy, no mass, no charge, speed of light movement (“c”), waveform movement
Matter based ionizing radiation comes from
The nucleus of unstable atoms
Properties of matter based ionizing radiation
Contain matter, have mass, can have a charge, travel slower than the speed of light, straight line movement
The quality factor for X-ray, gamma ray, and beta particles is all the same, it is…
1 (one)
Alpha particles quality factor is…
20 (twenty)
Leukemia
Aberrant proliferation of white blood cells, considered to be a blood cancer
The normal RBC (red blood cells) to WBC (white blood cells) ratio is:
1000:1
Keloid
Excessive scar tissue
Functions of skin
Protection, temperature regulation, to sense organ activity
Skin protection
Our “first line of defense”
A boundary against pathogens
Keratin
Protects against tears and cuts and excessive fluid loss
Melanin
Protects against UV radiation
Skin and temperature
Sweat glands (heat loss through evaporation)
Flow of blood close to body (heat loss through radiation)
Blushing or flushing
Reddening of skin due to increased blood flow
Cyanosis
Bluing of skin due to decrease in blood flow
Skin and sensory
Millions of nerve endings, the “antennas” of the body. Receptors for light touch, pressure touch, pain, heat, cold
1st degree burn
Occurs on the epidermis, the most common is a sunburn;
May peel
No blistering
Tissue destruction is minimal
2nd degree burn
Includes the epidermis and dermis, does NOT include complete destruction of the dermis.
Includes blistering, swelling, and fluid loss.
Scarring is common
3rd degree burn
Includes the epidermis, dermis, and subcutaneous layers.
Complete destruction of dermis and epidermis and damage to the subcutaneous layer. Damage can be deeper (muscle and bone).
Insensitive to pain as nerves are destroyed.
Loss of fluid. Infection.
__________can greatly impact the circulatory system and reduce the bodies ability to protect/heal
radiation
hematologic depression can occur with a dose of
25 rads delivered in a short period of time
__________will decrease the number of blood cells in the bone marrow and will reduce the number of cells in circulation
radiation
radiation primarily affects
the immature erythrocytes of the hematopoetic (blood) system
erythrocytes are one of the
most radiosensitive cells in the body
once mature, a RBC is
much less radiosensitive
hematopoietic system
the most radiation sensitive of all body systems
lymphocytes are the most radiation sensitive cells in the body whose lifespan is only
24 hours
lymphocytes
a type of WBC responsible for defending the body against foreign disease processes
a dose as low as 25 rads
can greatly reduce the number of lymphocytes in the blood, recovery is usually quick
a dose of 50-100 rads
will reduce lymphocyte count to zero within a few days. full recovery can take several months
neutrophils (wbc)
play a role in fighting infection, doses as low as 50 rads can decrease the number of cells, larger doses will rehire months t return back to normal ranges
granulocytes (wbc)
respond to radiation by initially increasing their number, their number then rapidly decreases.
usually requires 2 months to fully recover.
thrombocytes have a lifespan of
only 30 days
a dose greater than 50 rads
reduces the number of thrombocytes, doses from 100-1000 rads will require months to regain back to original numbers
thrombocytes initiate
clotting and prevent bleeding
thrombocytes AKA
platelets
neither blood or blood forming organs
should suffer damage from diagnostic radiology, the doses are too low
patients who undergo radiation therapy can
experience a decrease in blood cells
blood tests are performed on radiation therapy patients
bi weekly to monitor health as an insensitive way to measure radiation exposure due to being unable to accurately read below 10 rads
Epi/Endothelial tissue
found in/on body, constantly regenerating and considered to be highly radiosensitive.
crypt cells
stem cells to produce epithelial and endothelial tissues
spermatogonia
male genetic cells, both mature and immature exist within the male testes
sperm cells are stored and mature within the
epididymis
mature spermatogonia are less sensitive to radiation due to
being specialized
immature sperm cells are unspecialized and divide rapidly making them
more radiosensitive
Ova
female genetic cells, both mature and immature exist within the female ovary
ova do not
divide constantly
genetic damage can occur if
an irradiated ova is fertilized, the child may be born with defects/mutations
oocytes
aka ova
mature ova
are less radiosensitive
immature ova
are unspecialized and very radiosensitive
embryo-fetus nervous tissue is
more radiosensitive than the nerve cells of adults
fetal radiation can lead to
congenital anomalies
embryo-fetus is most sensitive
8-15 weeks after gestation, lower risks exist until 25 weeks
radiosensitive cells include
muscle, nerve, bone, cartilage, tendons and ligaments
muscle tissue
highly specialized, cells do not divide, very radiosensitive
adult nervous tissue
found in the brain/spinal cord, do not divide, highly specialized, a very high dose may cause damage to the nervous system
a dose of 5000 rads
may lead to death in a few hours or days
genetic effects occur as a result of
irradiation to genetic cells (meiosis) - symptoms manifest in future generations
genetic effects can only be found in
future generations (the offspring of the irradiated individual)
LD50/60
the amount of radiation dose it takes to kill 50% in 60 days
the rate of leukemia in atomic bomb survivors was
2-3 times greater than expected
fractionation
a big dose spread out over many smaller doses
protraction
a big dose all at once
females are less
radiosensitive than males
most mutations are
recessive
thyroid cancer observed due to
thymus irradiation such as rongelap, atoll nuclear test
bone cancer observed in
radium watch dial painter, radio salt treatment
skin cancer observed in patients
who received orthovoltage radiation therapy
breast cancer observed in patients
who receive TB treatment and atom bomb survivors
lung cancer observed in patients who
worked as uranium miners
liver and spleen cancer observed in patients
who were exposed to thorotrast
energy based ionizing radiation includes
X-rays, gamma rays (bundles of pure energy in transit)
matter based ionizing radiation includes
alpha, protons, neutrons, and BETA (unstable nucleus)
survival curves
a method of displaying cell sensitivity to a specific type of radiation
survival curves demonstrate
the survival rate of cells exposed to certain amounts/types of radiation by noting how many cells have the ability to divide after radiation
survival curves determine which types of cancer cells
might respond well to radiation therapy
L.E.T
linear energy transfer
O.E.R
Oxygen enhancement ratio
Low L.E.T
low dose will exhibit little to no change due to cells ability to repair/recover
High L.E.T
has no shoulder, a higher dose results in a lower survival rate
damage from high LET is usually
irreparable, does not occur in the realm of diagnostic imaging
Bergonie’ and Tribondeau
2 french scientists who discovered that radio sensitivity is a function of the metabolic state of the cell receiving the exposure
Law of Bergonie’ & Tribondeau states
the radio sensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation
Cells that are most sensitive to radiation injury or death include
least mature/specialized, high reproductive activity, and longest mitotic phase
stem cells
undifferentiated, immature cells that are yet to have a specific function, not specialized, very sensitive to radiation
White Blood Cells (WBC)
only live a few days and are highly radiosensitive
Nerve cells and those that live long lives
are least sensitive to radiation
highly specialized cells and those that divide slowly or not at all
are less radiosensitive (nerve, muscle, bone)
the more time a cell spends in mitosis
the greater the radiosensitivity
the greatest cellular damage occurs
towards the end of the M phase (telophase)
Mitotic rate
basis for radiation therapy
cancer cells are generally
immature, divide rapidly and undergo frequent mitosis
cancel cells can be destroyed by radiation while
minimizing damage to normal healthy cells
as LET increases
the occurrence of biological damage will increase also
Alpha
High LET
Gamma, Xray, Beta
low LET
OER and presence of oxygen
this will effect the cells radio sensitivity, cells with a higher aerobic state will result in an increase in cellular damage. 2-3X more damage
Lymphocytes are the most
radiation sensitive tissue in the body
Quality factor
The factor by which the absorbed dose must be multiplied to obtain a quantity that expresses the biological damage to the exposed tissue
RBE
Relative biological effectiveness
Ratio of biological effectiveness of one type of ionizing radiation relative to another given the same amount of absorbed dose
Wave particle duality
The exhibition of both wavelike and particle like properties by a single entity as of both diffraction and linear propagation by light
Radio sensitive cell examples
WBC, stem cells, non specialized cells, erythrocytes, lymphocytes, oocytes, spermatogonia, crypt cells, epithelial/endothelial tissue
Radio insensitive cell examples
Specialized cells, muscle cells, nerve cells, bone cells, cartilage, tendons, ligaments
