Biological Effects of Ionizing Radiation (V. 1) Flashcards
dose to air, as radiation comes out of x-ray tube
exposure, air kerma
dose to tissues, as radiation enters body of patient
absorbed dose, equivalent dose, effective dose
a measure of the ionization produced in the air by x-rays or gamma rays
exposure
traditional unit of exposure; SI unit
roentgen (R); air kerma (Gy or Gray)
what does “kerma” stand for?
kinetic energy released in matter
air kerma measures _______ transferred from ____ to _____ of the absorber
kinetic energy, photons, electrons
kerma values in the is called….
air kerma
absorbed dose is energy transferred from ionizing radiation per ________ of _____
unit mass, irradiated material
traditional unit of absorbed dose; SI unit
rad (radiation absorbed dose); Gray (Gy)
absorbed dose varies with __________ and __________
type/energy of radiation, type of absorbing material
equivalent dose is used to compare the ______ of different types of radiation on a _______
biologic effects, tissue/organ
equivalent dose depends on ____
LET
high LET radiation causes (more/less) harm than low LET radiation
more
tradition unit for equivalent dose; SI unit
rem (roentgen equivalent man); Sievert (Sv)
1 Sv = __ Gy
1 Gy
effective dose is used to estimate risk of ______
radiation in humans
true/false? not all tissues respond identically to radiation
true
effective dose is the ________ of the _________ of a tissue and ________ applicable to each of the tissue irradiated
sum of the products, equivalent dose, weighting factors
unit of effective dose
Sv
a measurement of decay or disintegration of a sample radioactive material
radioactivity
traditional unit of radioactivity; SI unit
Curie (Ci), Becquerel (Bq)
a badge special film that is particularly sensitive to x-rays
film badge
_______ on exposed and processed film is related to exposure received by operator
optical density
what does TLD stand for?
thermoluminscence dosimeter
when TLD is exposed, it absorbs energy and stores it as _______
excited electrons
_______ of TLD provides the dose received by operator
intensity of light
OSL is stimulated with ____
LED
radiation produces ionizations/excitations of essential molecules, such as…
DNA, enzymes, ATP, etc.
damage to ____ is much worse than damage to _____
DNA, cell membrane
effect in which damage/mutation occurs at the site where radiation is deposited
direct effect
effect in which radiation initially acts on water molecules to cause ionization
indirect effect
____ direct effects; __ indirect effects
1/3; 2/3
direct effects of radiation characteristics…
- generates free radicals
- free radicals either dissociate or cross link
- altered biological molecules differ from original molecules (structure/function)
indirect effects of radiation characteristics…
- body is 70% water
- high likelihood that x-ray photons will interact with water in body
- radiolysis of water
indirect effects of radiation produces (from radiolysis of water)
hydroperoxyl, hydrogen peroxide (both are oxidizing agents and toxins)
do you need to know the direct/indirect effect equations on the PPT?
no, you don’t. don’t stress! :)
radiation effects types (2); which is more damaging?
short term, long term: long term more damaging
types of long term effects
cancer, genetic mutation, mental/physical retardation of children
cancer may occur ____ years later from exposure
10-30
histologically, radiation induced cancers are _______ than other cancers
not different
probability of cancer/genetic mutation increases with ________, but severity does not depend on ________
increasing the dose, the amount of the dose
random; having a random probability distribution that may not be predicted precisely; unpredictable
stochastic
a somatic effect that increases in severity with increasing absorbed dose
deterministic effects
examples of deterministic effects
cataract, skin erythema, fibrosis, abnormal growth
deterministic effects are not by ____ but are a _____
chance, “will-happen” event
deterministic effects usually (are/are not) from diagnostic radiology
are not
if radiation damage to DNA is severe enough, __________ may be detected, but DNA molecules can be damaged ______
visible chromosomes aberration; without chromosome aberration
effect of radiation on individual gene
point mutation
result of point mutation
- loss of gene/set of gene
- mutation in gene/set of genes
…and the cell may exhibit abnormal function
several kinds of alterations in the chromosomes have been described
chromosome alteration
effect of chromosome alterations
- breaking of one or more chromosome
- broken ends seem to possess ability to join together again after separation
in chromosome aberration…
if damage is after DNA synthesis, then _____
if damage is before DNA synthesis, then ____
after = only one arm of chromosome is broken before = both arms of chromosome are broken
chromosome repair without errors
restitution
chromosome “repair”/error with loss
deletion (losing part of structure)
if there is more than one break in chromosome, _____ may occur
broken fragments joining in different combinations
illegitimate union characteristics…
- defectively repaired chromosome
- pre-replication
- 1 break in each chromosome
- causes U-shaped and extra
ring formation, acentric fragment characteristics…
- defectively repaired chromosome
- pre-replication
- breaks in each arm of the same chromosome
translocation characteristics…
- defectively repaired chromosome
- 2 different pre-replication
- 1 break in each chromosome
- “swapped” appearance
a large proportion of damage will result in mis-repair which can result in the formation of _______ that cause _____
gene/chromosomal mutations, malignant development (cancer)
ionizing radiation also affect cell division, resulting in _____, and thus _____. This is the basis of ____
arrested mitosis, retardation of growth, radiotherapy of neoplasms
cells are more sensitive to radiation during the _____________
last part of resting phase, early part of prophase
to stop cancer cells from repairing themselves (in radiotherapy), you must give ________
fractionated dose (multiple doses/not all at once)
Bergonie/Tribondeu key statement: “cells are sensitive to radiation ____________ and in _____________”
in proportion to their proliferative activity, inverse proportion to their degree of differentiation
rapidly dividing are ____ than more differentiated, slowly dividing cells
more sensitive
____ are radiosensitive, ____ are radioresistant
stem cells, mature cells
younger tissues/organs are _____
radiosensitive
tissues with high metabolic rate are ____
radiosensitive
high proliferation/high growth rate are ______
radiosensitive
notable Bergonie/Tribondeu
lymphocyte
lymphocyte is…
- not capable of proliferative activity
- is a differentiated cell
- one of the most radiosensitive cells in body
highly radiosensitive
- lymphoid organs
- bone marrow
- testes
- intestine
- mucous membrane
intermediate radiosensitive
- fine vasculature
- growing cartilage
- growing bone
- salivary glands
- lungs
- kidney liver
low radiosensitive
- optic lens
- mature erythrocytes
- muscle cells
- neurons
cell death for differentiated (nerve, muscle, secretory, etc.) cells = _____
loss of function
cell death for proliferating cells (stem cells, intestinal cell) =
loss of capacity for proliferation (also known as reproductive death)
densely ionizing =
sparsely ionizing =
densely = neutrons, alpha rays sparsely = x-rays
cytoplasmic changes play a _____ in arrested mitosis and cell death
minor role
