radiology 2 Flashcards
When assessing radio graphs what is involved in step 1 - the overview
is it suitable
is it diagnostically acceptable
any technique errors e.g positioning, tilting, excessive contrast
any foreign bodies, movement artefacts?
are the proportions normal ?
When assessing radio graphs what is involved in step 2 - assessing teeth
number, position , development, caries, restoration , resorption, roots, developing teeth
When assessing radio graphs what is involved in step 3 - apical tissues
lamina dura - intact / lost?
periodontal ligament space - normal/ widened ?
abnormal radiolucencies/ radiopacities at apices
When assessing radio graphs what is involved in step 4 - periodontal tissues
bone levels/ calculus deposits/ furcation involvement
When assessing radio graphs what is involved in step 5 - bone
bone levels, shape/size/symmetry, bones other than mandible and alveolar
abnormal radiolucencies/ pacities
What are the 5 stages of assessing a radiograph
overview
teeth
apical tissues
periodontal tissues
bone
if assessing specific structures/ pathologies on a radiograph what should be described
site - crown/ alveolar bone/ roots
radiodensity - paque/lucent/ combo
shape - round/ irregular/ scalloped
margins - corticated/ well defined/ irregular
size - 10 x5mm/ spanning 13 to 23
multiplicity - few/ solitary/ many
how often should bitewings be taken for high risk caries patients
every 6 months
how often should bitewings be taken for moderate caries risk caries patients
annually
how often should bitewings be taken for low caries risk patients with a primary dentition
every 12-18 months
how often should bitewings be taken for a low caries risk patient with a permanent dentition
every 2 years
what type of radiation are x rays
electromagnetic radiation
why are x rays a risk to humans
they can cause ionisation which is the displacement of electrons from atoms/molecules
what 3 things are contained within the tubehead of an x ray
cathode (+ve)
transformer
anode (-ve)
function of the cathode in x ray tubehead
compromised of filament (coiled metal wire that when heated releases electrons) and a focusing cup (metal plate around filament that repels released electrons from filament towards anode)
purpose of transformers in x ray tubehead
change the mains electrical supply to the machines required voltage
purpose of anode in x ray tubehead
compromised of target (metal block (tungsten) that is bombarded with electrons released from cathode filament) (contains focal spot where electrons hit) and a heat discipating block (ensures machine doesn’t overheat by absorbing heat produced - usually copper)
penumbra effect
blurring of radiographic image due to focal spot being a small area rather than a single point
ideally focal spot should be as small as possible
what are the benefits of having an angled focal spot within the x ray tubehead
larger impact area therefore decreased heat production whilst still achieving an x ray beam with a small area therefore reducing the penumbra effect
(diagram in notes)
purpose of the glass envelope within an x ray tubehead
made of leaded glass and surrounds cathode and anode so that photons can escape except for one small window where they escape and form the x ray beam
contains vaccum to ensure no air molecules within the space
filtration
done using a thin sheet of aluminium placed over the path of the x ray beam
this removes low energy x ray photons which would not contribute to image quality but would increase the patient dose
collimator
lead diaphragm attached to the end of spacer cone which crops beam to the shape and size of the receptor therefore ensuring minimal patient dose
where is the fsd measured from
focus to skin distance
measured from focal spot NOT where x ray beam exits tube head
for modern equipment usually 200mm
what is the x ray anode made of (target/focal spot)
tungsten
