x-ray Flashcards
What does the white or radiopaque shadows represent on an image
dense structures which have stopped the x-ray beam
What does the black or radiolucent shadows represent
Areas where the x-ray beam has passed through and not been stopped
What does the grey shadows represent
areas where the x-ray beam has been stopped to a varying degree
4 factors that quality of radiographic image rely on
contrast, image geometry (position of film + tube), characteristics of x-ray beam, image sharpness and resolution
Examples of intra-oral images
periapical, bitewing, occlusal
Examples of extra-oral images
oblique lateral, various skull, panoramic
The cathode is …….. and consists of a heated ……. of tungsten that provides the source of …..
negative, filament, electrons
The anode which is …. consists of a …….. (small piece of tungsten) set into the angled face of a large …. …….. to allow efficient removal of ……
positive, target, copper block, heat
What does the focusing device do
stream of electrons at the focal spot on the target
A ……….. flows from the …… to the ……. to measure the quantity of ……. being accelerated
current (milliamperage mA), cathode, anode, electrons
How is heat removed
by copper block and surrounding oil
The high-speed electrons bombarding the target are involved in 2 main types of collision with tungsten atoms:
heat producing collisions
x-ray producing collisions
What effects are dental professions primarily concerned about?
somatic stochastic effects
example is cancer induction which can occur with ANY amount of radiation
What is made at the end of the anode
made of metal tungsten set into a block of copper
What are stray photons responsible for
X-ray tube head leaking slightly during exposure, must never hold X-ray tube as may irradiate hand
percentage of energy which is converted to heat and x-rays
heat 99%
x-rays 1%
As the deflection increases the …..
bigger photon increased
Why are not all x-ray photons the same
because the produce different deflections
What does low and high energy photons do
low - penetrating power, will stop in patients soft tissues and absorb
high - pass through patient and hit the film
What type of energy photons are more dangerous to the patient and what are more diagnostically useful
low energy - more dangerous
high energy - more diagnostically useful
What is the energy of the incoming electrons determined by
size of the voltage applied - the bigger the voltage the greater energy given to the electrons
How are they removed from the beam so they do not hit the patient?
passing the beam through a sheet of aluminium which absorbs and filters out the lowest energy photons
What is the effect of the aluminium filter
to absorb the lowest energy most harmful photons - lack penetrating power means cannot pass through aluminium, as a result the beam which is used on patients does not contain many harmful photons
What are the advantages of being able to control the kV
allows control the eventual contrast differences between the black and white on the resultant film
What happens as Kv is increased
penetrating power of photons is increased, less absorption, dose is less to patient
BETTER advantage to use HIGHER kV for the patient
What happens if kV is low
photons have less energy, more absorption in the patient, so dose is higher to the patient, more of a NEGATIVE effect
