SUMMARY 2 Flashcards
What does position indicating device provide?
collimation
what do electrons contact that produces x-rays?
tungsten target
what dissipates heat?
copper rod
where do x-rays lie on the electromagnetic spectrum?
between ultraviolet radiation and gamma rays
what are electromagnetic waves packaged in to?
photons
what happens to photons?
produced by x-ray tube, scattered and absorbed by tissue.
what is attenuation?
how the x-ray beam weakens as it travels through matter
what are receptors?
digital sensors that produce image
what is a form of energy that acts by removing electrons from atoms and molecules to create ions?
ionising radiation
in the x-ray tube, what is the cathode?
tungsten filament that produces electrons
in the x-ray tube, what is the anode?
tungsten target that converts electrons to photons
99% heat
1% photons
what is the glass for in an x-ray tube?
insultation
what is aluminium for in an x-ray tube?
filtration
what is lead for in an x-ray tube?
collimation - maintains a singular beam
what does exposure time impact?
beam intensity
what is mA?
tube current - flow of electrons through tube from filament to anode and then back
what is kVp?
tube potential - electrons from cathode to anode (generate photons)
what does aluminium do to act as a filter?
filters out low energy photons, reducing beam intensity - reduces dose, increasing image quality
how does collimation work?
lead barrier that reduces scatter by limiting the size of the beam to either circle or rectangle
what does a SOD increase result in?
intensity decrease
what does an IOD decrease result in?
sharper image, less magnification
what is it called when incident photon contacts outer shell electron and becomes shattered photon, changing direction?
coherent scattering
what is the result of coherent scattering?
decrease contrast
what is it called when incident photon contacts inner electron and forms an ion pair?
photoelectric absorption
what is the result of photoelectric absorption?
increase contrast
what is it called when incident photon contacts an outer electron and forms an ion pair?
compton scattering
what is the result of compton scattering?
decrease contrast
explain the bisecting angle technique?
x-ray aimed perpendicular to bisector between long axis of tooth and long axis of receptor
explain the paralleling technique
receptor placed parallel to long axis of tooth
x-ray perpendicular to long axis of tooth
what intra oral technique is a bit more magnified?
paralleling
what are the layers of an x-ray film?
base - flex plastic
film emulsion - silver halide crystals in gelatine
intensifying screen (in DPT) - coated with fluorescent phosphor
what reaction results in a latent image?
silver halide crystals to reduced to neutral silver atoms
what is a latent image?
invisible image
what is converted into a visible image through chemical processing?
metallic silver
what is radiolucency?
dark - photons pass through tissue to reach the film
what is radioopacity?
light - photons attenuated and dont reach the film
what is developing?
turning latent image to visible image
what does the developing solution do?
converts crystals into metallic silver grains that are seen as dark on the image
what does developing solution contain?
phenidone and hydroquinone
what does phenidone do?
first electron donor that reduces silver ions to metallic silver at latent image
what does hydroquinone do?
provides an electron to reduce oxidised phenidone to its original active state
what is fixing?
washing away unexposed/ undeveloped silver grains
what does fixer solution do?
removes unexposed silver halide crystals from emulsion, keeping the black metallic silver
what does fixer solution contain?
ammonium thiosulphate - cleaning
aluminium salts - hardener
acetic acid - neutraliser
sodium sulphite - preservative
water - solvent
what does washing do?
washes away residual chemicals
what part of CCD/CMOS captures x-rays and displays image?
silicon sensor chip
what part of the PSP plate captures x-rays?
barium fluorohalide
