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radiobio review

review of 32, 33, 34

QuestionAnswer
Ionization of living tissue can cause this chemical and biologic damage to somatic and/or genetic cells
Non-threshold dose-response(dose effect) curve indicates this there is no safe dose of radiation below which there will be no effects
Linear non-threshold dose response curve indicates this stochastic responses (cancer, genetic effects)
linear non-threshold is the curve of choice for occupational exposure
Stochastic "all or nothing"
Late effects of radiation carcinogenesis and genetic effects
Radiobiology the study of the effects of ionizing radiation on biologic material at the cellular level
law of bergonie and tribondeau stem (undifferentiated or precursor) cells, young, immature tissues, and highly mitotic cells are particularly radiosensitive
1906 bergonie and tribondeau
the most highly radiosensitive very young cells stem cells and cells having the most reproductive activity
examples of highly radiosenstive tissues intestinal epithelial cells, and cells of the rapidly developing embryo and fetus
energy this is what radiation deposits as it passes through tissue
let the rate at which energy is deposited as it passes through tissue (another means of expressing radiation quality and determining the radiation weighting factor)
as the let of radiation increases, the radiations ability to produce biological damage also increases
rbe relative biologic effectiveness
let and rbe are directly related
diagnostic x rays are considered low let radiation
the approximate let of x-rays 3 keV/um
the target theory specifies that DNA is the day sensitive molecule
direct effect occurs with high let radiations and when ionization occurs at the dna molecule itself
indirect effect occurs most frequently, happens when ionization takes place away from the dna molecule
single main chain/ side rail scission (break) on the DNA molecule is repairable
double main chain/side rail scission may repair with difficulty or may result in cell death
double main chain/side rail scission on the same "rung" of the DNA ladder results in irreparable damage or cell death
faulty repair of main chain breakage cross-linking
damage to the base itself or to the rungs connecting the main chains can result in alteration of base sequences causing molecular lesion/point mutation
the majority(90%) of cell damage is repairable
multiple hits to same cell are likely to leave permanent damage
are somewhat insensitive to radiation exposure muscle and nervous tissues
the longer the period of time over which a dose of radiation is delivered the less its effect
the greatest effect or irradiation will be observed large quantity of radiation is delivered in a short time to the whole body
the greater this content of tissues, the greater the radiosensitivity oxygen
this is most radiosensitive fetal tissue and lympocytes
as an individual ages, tissue sensitivity decreases
somatic effects early or late, depending on the length of time between irradiation and manifestation of effects
late somatic effects occur years after initial exposure cause by low, chronic exposure
examples of late somatic effects bone malignancies, thyroid cancer, leukemia, skin cancers
cataract formation one more example of somatic effects
Created by: hseratt