Radiation Biology Flashcards
Somatic Cells
Cells in the human body - i.e. skin, muscle,)
chromosomes
clusters of DNA molecules
DNA
Central nucleus of a human cell holds the genetic code
large macromolecule = DNA
Hereditary information
Double helix
Base pairs = adenine, guanine, thymine, cytosine
genetic cells
Cells of reproductive organs
females = oogonium
males = spermatogonium
Under go meiosis
germ cells
immature cell
contain all hereditary information for an individual
LET
how the ionizing radiation energy is deposited along a track or path in tissue.
High LET = passes thru tissue depositing large amount of energy in a short distance (greater biologic effect) = Alpha & Beta particles
Low LET = spreads energy over a large distance (does not cause significant damage in any one cell) - x-ray & gamma rays
meiosis
reduction and division of genetic cells
Number of chromosomes is reduced to half 46 to 23
mitosis
Division of somatic cells Phases: 1- Prophase 2- Metaphase 3- Anaphase 4- Telophase
RNA
Contained in both cell nucleus and cytoplasm
Similar to DNA but with a single strand of nucleic acid
Messenger RNA
Transfer RNA
cataracts
cloudiness or opacity of eye
single acute dose of 2 Gy
threshold dose of 10 Gy
latent period = several years
epilation
temporary hair loss
threshold above 3 Gy
erythema
redness of skin
dose level of 6 Gy (600 rad)
gastrointestinal syndrome
6 - 10 Gy
kills most stem cells in the Gi tract
All hematologic effects and…
severe nausea, vomiting and diarrhea
Death in 2 weeks
GSD
measures effect on the genetic pool of radiation exposure to the gonads
Medical exposures contribute to about 200 uGy (20 mad)
hematologic syndrome
affects blood forming tissues
depression of bone marrow
decrease in WBC, RBC, thrombocytes and lymphocytes
death in 3 weeks
3 Gy
latent period
2nd stage of high dose effects
no clinical or visible symptoms
few hours to several days
manifest stage
3rd stage - three syndrome become manifest, hematologic, GI and CNS
OER
oxygen enhancement ratio of the radiation doses necessary to produce the same effect w/ and w/o oxygen
high LET value of 1 = so effective in producing damage that the presence or absence of oxygen does NOT matter
low LET value of 2 to 3 = oxygen enhances the effect of radiation
prodromal stage
Initial stage of radiation response
less than 1Gy may show symptoms
varying degrees of nausea, vomiting and diarrhea
RBE
biological effect of radiation with different LET value are compared by comparing their RBE
Ratio of dose standard to produce the same biological effect
X-rays have an RBE close to 1
High LET have have higher RBE
