chapter 5 Flashcards
x rays have the ability to detach and remove electric charges from the complex atoms that make up the molecules of body tissues; delicate balance of structure is altered, and a cell may be damaged or destroyed
ionization
what are the two theories for how radiation damages biological tissues
direct and indirect
one third of biological alterations from x radiation exposure result from a direct effect; most dental x ray photons probably pass through a cell with little or no damage
direct theory
x ray photons collide with important cell chemicals and break them apart by ionization, causing critical damage to large molecules; a healthy cell can repair any minor damage that might occur
direct theory
based on the assumption that radiation can cause chemical damage to a cell by ionizing the water within it; before it enters the cell
indirect theory
two thirds of biological alterations from x radiation exposure result from___ effects
indirect
radiolysis of water
indirect theory
indicates threshold amount of radiation, below which no biological response would be expected
threshold dose response curve
indicates that any amount of radiation, no matter how small, has the potential to cause a biological response
non threshold dose response curve
As low as reasonably achievable
ALARA
sequence of events following radiation exposure
latent period , period of injury recovery period
following initial radiation exposure, and before the first detectable effect occurs
latent period
follows latent period stoppage of mitosis breaking or clumping chromosomes abnormal mitosis formation of multinucleated cells associated with cancer(giant cells; large tissue clumped together, could be cancerous)
period of injury
following exposure to radiation, recovery can take place(short term effects);
may be a certain amount of damage from which no recovery occurs(later or long term effects)
recovery period
greater dose, more severe the probable biological effect
total dose
