Radiation Biology Flashcards
(31 cards)
What is radiation biology?
the study of the effects of ionizing radiation on living tissue
Dr. Rollins
was researching harmful effects of radiation in 1898
Absorption
total transfer of energy from the x-ray photon to patient tissues
What is the overall concept of radiation injury?
chemical changes occur due to exposure to radiation and biological damage results
Ionization mechanism
result in formation of a positive atom and a dislodged negative electron, occurs when x-rays strike patient tissues
*kinect energy of electron results in further ionization, excoriations or breaking of molecular bonds
*chemical changes resulting in biological damage
What is a free radical?
uncharged/neutral atom or molecule existing with a single unpaired electron in its outermost shell
*highly reactive and unstable
Free radical formation mechanism
when xray photon ionizes water (primary component of living cells)
result in formation of hydrogen and hydroxyl free radicals
*free radicals combine with each other to form toxins
What is the primary mechanism that x-radiation causes damage through?
Free radical formation
Direct theory of radiation injury
ionizing radiation directly hits critical areas within the cell, causes cell damage (DNA damage)
*occurs infrequently, most photons pass through the cell and cause little or no damage
Indirect theory of radiation injury
xray photons absorbed within the cell and cause formation of toxins
occurs frequently since 70-80% cell is water
*free radical formation and combining to form toxins results in indirect injury
Dose-response curve
relationship between an effect of an drug and the amount of drug given
-linear NONTHRESHOLD relationship
-determines hazardous level of drug
-drug=x-radiation
-response= damage of tissues produced
-dose=amount of radiation received
Threshold dose
point at which effects are first seen
*threshold dose level does not exist for xradiation, no matter how small the amount, some biological damage will occur
Herman Joseph Muller
-researched radiation induced mutations
-studied how radiation produces its biological effects
-Nobel prize in physiology/medicine in 1946
Stochastic effects
-direct function of the dose
-no dose threshold; doesn’t depend on magnitude
ex// cancers, genetic mutations
Nonstochastic/deterministic effects
-somatic effects
-has a DOSE THRESHOLD; effects increase in severity with increase of absorbed dose
ex// skin erythema, loss of hair, radiation sickness, decreased fertility, cataract formation
Latent period
elapsed time between exposure to radiation and appearance of clinical signs
-depends on total dose received and amount of time it took to receive dose
Period of injury
variety of cellular injuries may result including…
-cell death
-changes in cell function
-abnormal mitotic activity
Recovery period
cells can repair damage caused by radiation, not all cellular injuries are permanent
Cumulative effects of radiation
-effects of radiation exposure are additive
-body never returns to original state
-leads to health problems such as cancer, cataract formation, birth defects
List the determining factors for radiation injury
-total dose
-dose rate
-amount of tissue irridated/exposed
-cell sensitivity
-age
Short-term effects
larges doses of radiation absorbed within short period of time
-effects are seen within minutes day or weeks after exposure
-acute radiation syndrome (ARS): nausea vomiting diarrhea hair loss hemorrhage
*usually NOT applicable to dentistry
Long-term effects
small doses of radiation absorbed over a long period of time
-effect are seen years, decades, or generations after cumulative exposure
-cancer, birth anomalies, genetic defects
Somatic effects
somatic cells: all the cells in body except reproductive cells
occurs in an irridated person, changes in somatic cells, cancer, leukemia, and cataracts
*do NOT transfer to future generations
Genetic effects
not seen in irradiated person
passed on to future generations
cannot be repaired
