Cytoplasm
Fluid portion inside the cell
Nucleus
Controll center of the cell, contains DNA
Two functions of DNA
replication and controlling cellular activities
DNA
is the most radiosensitive target molecule in the human cell
RNA
Messanger system for DNA, located mostly in the cytoplasm
Ednoplasmic reticulum
allows the nucleus to communicate with the cytoplasm
Mitochondria
Engine of the cell
Ribosomes
dot-like structure, site of protien synthesis
Lysosomes
help to controll intracellular contaminants
1 Mrad
is required to produce a measurable change of the molecule
Nucleus is
more radiosensitve than the cytoplasm
Cell proliferation
to reproduce and multiply in number
Genetic cells
oogonium and spermatogonium cells are
Somatic cells
all other cells in the body
mitosis
somatic cell prolifeation
mitosis 1. prophase
nucleus swells, dna begins to take stucture
mitosis 2. metaphase
chromosomes appear, damage by radiation can be seen here
mitosis 3. anaphase
splitting of the chromosome at the centromere
mitosis 4. Telophase
final segment, cell division complete
2 identical daughter cells
mitosis - 1 dna replication + 1 cell division =
Meiosis
process whereby genetic cells undogo reduction division
4 Daughter cells
Meiosis - 1 dna replication + 2 cell divisions =
(LET) Linear energy Transfer
measure of the rate at which energy is transferred from a beam of radiation to the tissue through which it travels
(RBE) Relative biological efffectiveness
measuring the amount of damage caused by equal amounts of differnt types of radiation
250 KVP
0
Radiosensitizers
enhances the effects of radiation by 2x
examples of Radiosensitizers
Halogenated pyrimidines
vitamin k
Methotrexate
Radioprotecters
decreases the effects of radiation by 1/2
Hormesis
the theory that a little bit of radiation is good. Little radiation stimulates hormonal and immune response to other toxic environment.
Linear
the measured effect increases in direct proportion to the radiation dose
Nonlinear
the measured effect increases in disproportionally to the radiation dose
Threshold
the measured effect does not occur at all below a certain level
Nonthreshold
the measured effect occurs at all levels including zero
Deterministic radiation
high dose exposure and early response (burn)
Stochastic response
low radiation exposure and a late response (cancer)
radiolysis
When irradiated water dissociates into other molecule products
target theory of radiation injury
A theory that seeks to explain why some cells die when exposed to radiation and others survive.
Alpha Particles characteristics
Have 4 atomic mass units
least penetrating
Beta Particles characteristics
Have an atomic mass of zero
4-7 mev
Alpha particles energy level
0-7 mev
Beta particles energy level
in air 1-10cm
in skin up to .1 mm
Alpha particles range
in air 0 - 10 m
in skin 0-2 cm
Beta particles range
0-10 MeV
Xrays energy
0-5 MeV
Gamma rays energy
in air 0 - 100 m
in skin 0-30 cm
Xrays and Gamma range
xrays - electron cloud, gamma rays - radioactive nuclei
the only difference between gamma and xray
200 rads
minimum whole body lethal dose
200-1000 rads
Hematologic dose
1000 - 5000 rads
Gastrointestinal dose
greater than 5000 rads
Central nervous dose
LD 50/60
Dose that produces death in 50% of subjects in 60 days for human is 350 Rads
Basal
In the skin what layer is most radiosensitive?
Spermatagonia
most radiosensitive phase of male maturation
Mature follicle
most radiosensitive phase of female maturation
female and male gonad radiation doses
10 rad - reduce
200 rad - temp sterile
500 rad - sterile
Lymphocytes
most radiosensitive cells in the hematopoietic system
Granulocytes
rapidly rise, then rapidly decrease after radiation