RAD BIO TEST 2 Flashcards
How is lethal dose expressed?
% of of population to die
__________________________
# of days it would take
most late effects follow which dose response curve?
linear non-threshold
most early effects follow which dose response curve?
threshold
when would a sigmoid response curve be likely?
Deterministic effects at high levels. high levels is an important key word here
What is the order of mitosis cell phase?
Prophase, Metaphase, Anaphase, Telophase
PMAT
When are cells more radiosensitive?
During mitosis. rapidly dividing cells are more radiosensitive
When are cells more radio resistant?
Mid to Late S phase. (DNA replication)
What is the law of Bergonie and Tribondeau?
Cells are more sensitive to radiation if they are “primitive and prolific” (ex: lymphocytes) cells that divide more/less highly differentiated are generally more sensitive to radiation
In interphase cell death, how many Gy is needed to kill a cell before it can divide?
Several Hundred Gy
How quickly dose is delivered.
Dose rate
^dose rate, ^effect
How slowly a dose is delivered
protraction
^ protraction, v effect
Delivering dose in discrete portions with a recovery period inbetween.
Fractionation.
^ fractionation v effect.
90% repairable
Systemic effects of radiation to an individual.
Somatic. (SELF)
characterized into deterministic and stochastic
Biological effects that can be directly related to the dose recieved
Deterministic
What are some early deterministic effects?
Erythema (2Gy), epilation-hair loss, infertility.
happens within hours or weeks. 90% repairable
Would deterministic be considered threshold or non threshold?
Threshold
What are the late deterministic effects?
Cateracts, temporary sterility (100 mSv)
Would Deterministic effects occur from digital or fluoro?
most likely fluoro
Deterministic or stochastic:
occurs after a large dose
deterministic
Randomly occurring biological effects of radiation
Stochastic
would stochastic be considered threshold or non-threshold?
non-threshold
What are some late stochastic effects?
cancer, genetic abnormalities
stocastic probability increases or decreases with dose?
INCREASES.
theoretically can occur in diagnostic radiology
Occurs en-utero to a developing embryo or fetus?
Teratogenic effects
At what period of development for an embryo/fetus would congenital abnormalities likely be caused by radiation?
2-8 weeks
During mid to late fetal growth, ________ results from radiation exposure.
Lukemia
At what week of gestation would skeletal defects occur from radiation exposure?
3rd week of gestation.
A fetus receives ____ dose of the mother’s skin exposure to the abdomen?
1/3
How sensitive to radiation is a 10 day old embryo compared to adults?
10x more sensitive
How many pairs of chromosomes are in the typical human?
23 pair
What does the genetic code consist of?
sequence of nitrogenous bases found in DNA
Transfer RNA (tRNA) is attached to:
a specific amino acid
A theory that describes certain molecules are critical for the survival of the cell:
target theory
Deactivation of a target molecule from an x-ray photon is considered:
Direct effect. (ex: x-ray photon directly damages a key gene on a chromosome)
Radiation ionizes water which in return deactivates a target molecule:
Indirect effects
is most damage done by direct or indirect effects?
indirect
Where does indirect effect most commonly occur?
cytoplasm of the cell
What is a free radical?
Any uncharged atom with a single, unpaired electron in its outermost shell
radiolysis:
ionization of water
hydrogen peroxide can be the end result of this
What is the oxygen effect?
Tissue is more sensitive to radiation when irradiated in an oxygen rich environment.
indirect hits
What is acute radiation syndrome?
Radiation sickness that occurs at large doses over a short period of time
What are the 4 stages of ARS?
Prodomal- within hours. Nausea vommiting, Diarrhea.
Latent- 1 week. no symptoms, false sense of recovery
Manifest illness- >1 week. syndrome effects
Death (or recovery with some long term effects)
3 main symptoms/syndromes related to Acute Radiation Syndrome
Hematopoietic
Gastrointestinal
Cerebrovascular
Describe Hematopoietic:
What is it-
dose-
death-
Decreased blood cells in bone marrow. (body susceptible to infection and organ failure)
1-10Gy
death in 6-8 weeks.
early radiologist suffered from leukemia
Describe Gastrointestinal:
What is it-
dose-
death-
Damage to epithelial cells that line the GI tract. Dehydration and severe diarrhea.
6-10 Gy
Death in 4-10 days
Describe Cerebrovascular:
What is it-
dose-
death-
Fluid leaks into brain, intracranial pressure. central nervous system failure.
50+ Gy
Death in hours-days
Single strand DNA breaks associated with high or low LET?
Low LET. more susceptible to cancer
Linear Energy Transfer. (LET)
amount of energy deposited by radiation into a material per unit path.
LET is an expression of radiation quality
Low LET =
High LET=
high or low penetration?
Low LET = high penetration
x-ray & gamma rays
High LET= low penetration
alpha particles
X-ray LET is low due to its:
high penetration
High LET=
HIGH OR LOW RBE?
HIGH LET=HIGH RBE
Relative Biological effectiveness (RBE) is the effectiveness of a certain type of radiation causing a specified effect or disease
All stages of Acute Radiation Syndrome are ____________ proportional to the dose received
inversely.
higher dose= shorter time period of each stage
What are the only instances we have data from regarding large population Radiation Sickness?
Hiroshima and Nagasaki (atomic bombs)
Generate tissues for specific organs:
Destroy particular cells that are “worn-out”
- blast cells
rapidly dividing= more radiosensitive.
-clast cells
Genetic cells=
Reproduction or Beginning
ex: sperm or ova
-genesis
rapidly dividing= more radiosensitive
