RESIT: Radiology Flashcards
How would you describe an x-ray?
Identical to gamma rays - with lower energy values.
No charge, weight or mass.
Very fast.
Cause ionisation.
Visible light range
400-700nm
What view is this?
Intra-oral occlusal (maxilla)
What view is this?
Intra-oral occlusal (mandible)
What view is this?
Extra-oral: lateral cephalogram
What view is this?
Extra-oral: postero-anterior mandible
What view is this?
Extra-oral: lateral oblique mandible
What view is this?
Occipital-mental view of facial bones
Jack is under doing orthodontic treatment, they need to visualise the relationship of the teeth to the jaws and the mandible to the rest of the facial skeleton.
Lateral cephalogram
Olivia has fractured her mandible playing rugby.
Postero-anterior mandible
Olivia has fractured her mandible playing rugby.
Postero-anterior mandible
Tommy (a child) cannot tolerate a bitewing and keeps crying.
Lateral oblique mandible
Ron is in a dental surgery that doesn’t have a DPT, he broke his mandible falling over on a night out.
Lateral oblique mandible
Susie is in A&E with facial trauma after tripping on her heels dancing on a table.
Occipital-mental views of facial bones
Adam has fought the bouncer at aura and is suspected to have damage his orbits, maxilla and zygomatic arches.
Occipital-mental view of facial bones
Which radiograph may require multiple takes?
OM views are taken twice from two angles: first at 10 degrees, second at 30 degrees.
Adam had to stand for his OM view radiograph, why?
Taking the films erect can help demonstrate the fluid levels the antra.
What is the standard intra-oral technique with the receptor parallel to the tooth called?
Paralleling technique
When would you take an intra-oral radiograph without a holder from an angle, and what is this called?
When the patient can’t tolerate a holder in their mouth or during endodontic procedures. Bisected angle technique
What colour holder would you select for anterior teeth?
Blue
What colour holder would you select for posterior teeth?
Yellow
What colour holder would you select for bitewing?
Red
What makes to tooth appear elongated?
Vertical angulation downwards
What can make the tooth appear shorter?
Vertical angulation upwards
What is the prime positioning when taking an x-ray?
Short object to film distance, and a long source to object distance.
Is this a bad x-ray?
Yes, vertical angulation of the beam has foreshortened the teeth and separated the cusps.
Is this a bad x-ray?
Yes, horizontal overlap of the teeth caused by horizontal angulation of either the receptor or the beam.
Is this a bad x-ray?
Yes, vertical angulation and cone-cutting (collimator has cut off the image).
Is this a bad x-ray?
Bottom right: vertical angulation is wrong giving foreshortened teeth.
Film size: anterior periapical
0 (only use a 1 if unique anatomy/long canine)
Film size: posterior periapical
2 (typically won’t do posteriors on young children as periapical pathology is uncommon)
Film size: bitewing (8-10 years old)
0
Film size: bitewing (<10 years)
Just <10 maybe = size 1
Film size: bitewing (adult)
Adult = size 2
What is able to be altered by the control panel?
the time of the exposure
the area of the exposure
the type of film we are taking (e.g bitewing etc)
white
cathode (-ve)
black
anode (+ve)
brown
aluminum filter
pink
X-rays
blue
lead collimator
purple
Copper stem
orange
glass housing
yellow
tungsten target
green
tungsten wire
red
molybdenum (focussing cup)
Basics of how dental x-ray works
Current gets passed along tungsten wire, electrons are excited and wire gets hot.
Basics of how dental x-ray works
Current gets passed along tungsten wire, electrons are excited and wire gets hot.
Continuous spectrum
Bremsstrahlung/breaking radiation.
Electrons fired across from the wire with heat the tungsten target, some of the electrons will penetrate the atoms of the target material being attracted to the nucleus of the atom.
This caused slowing down or deflection of electrons from the atom’s electron shell. There’s a wide range of x-ray wavelengths produced.
Continuous spectrum (or bremsstrahlung/breaking radiation)
- Electron from cathode comes in and decelerated as a result of pull from the nucleus.
- The kinetic energy of that electron is transferred to x-ray photon energy.
Hence there is no specific energy produced its continuous
Line spectrum
- Electron from cathode comes in and knocks out an electron from L or K shell (innermost).
- The shells balance themselves by an electron dropping down to replace the knocked-out one.
- This movement to a “lower” energy level means the electron loses energy.
- This energy is in the form of an x-ray photon.
Photon energy is directly related to
kV across the X-ray tube
The higher the kV…
the more capable it will be to penetrate through material (dark image).
Kv needed for characteristic x-ray to be produced
69.5kV
Large wavelength, low energy
Radiowaves/microwaves
Medium-shortish wavelength, medium-lowish energy
Infrared
Medium-longish wavelength, medium-highish energy
ultraviolet
Wavelength and energy: X-ray compared to gamma rays?
X-rays: lower energy, longer wavelength
Gamma ray: higher energy, shorter wavelength
At what point does the electromagnetic spectrum become ionising?
moving from ultraviolet radiation to x-ray and gamma rays.
Attenuation
reduction in intensity of beam due to scattering & absorption
What type of energy photons are absorbed by soft tissues?
Low energy photons.
Film type: intra-oral radiograph
Direct film: x-rays act directly on silver halide crystals on the film.
Film type: extra-oral radiograph
Indirect film: x-rays ‘hit’ intensifying screens producing light photons which then acts on silver halide crystals on the film.
PSP vs solid state
PSP more commonly used in DDH.
Solid state shows better image but requires specific holder and is less well tolerated by patients. Has the black wire coming from it
How do PSP work?
- X-ray hits the plate: stable exited state.
- Plate is scanned by red laser: unstable excited state.
- Blue light is emitted and this is collected by a scanner (vista) which converts it’s to an image.
Solid state sensor
A: back cover
B: Silicon wafer (converts light to electrical signal)
C: Scintillator layer (converts x-ray to light)
D: front cover
Solid state sensor: how does CCD work?
X-rays hit scintillator layer, producing light which reacts with the silicon wafer.
Electrons released produce charge which is converted to the image.
Solid state sensor: CCD vs CMOS system
CCD is better but more expensive, more commonly used.
Where are images stored from DDH?
PACS (picture archiving communication system) - Livingstone.
T113H - unique accession number for images taken at DDH.
Deterministic effects of radiation
Non-stochastic - those we know will occur, threshold dose (known), somatic effects (this is utilised in radiotherapy for cancer patients)
Non-deterministic effects of radiation
Stochastic - those which may occur, down to chance, no threshold known.
Dose of radiation that is harmful
2-10 Sv