Radiology Flashcards
what are the principles of radiation protection?
justification- must be beneficial to the patients
optimisation - ALARP
dose limitation
define processing of an image, how are the ways of doing this?
conversion of the latent image to the permanent visible image.
digital
chemical
list the 3 ways x-rays can interact?
no effect
complete absorption - transfer of energy to the patient
absorption and scatter - partial absorption and direction of beam changes
What colour does a material that completely absorbs the x-rays appear as on a radiograph?
white
define attenuation.
combination of absorption and scatter and how it reduces the intensity of the beam in some areas.
list the types of radiographs.
intra-orals
bite wings
periodicals
occlusal
extra-orals
panoramic
cephalometric
cone beam CT
what teeth are bitewings used on?
premolars
molars
what do we aim to capture In bitewings?
Symmetry of uppers and lowers - equal image of upper and lowers.
Mesial side of first premolar to the most distal contact point/surface of the last tooth.
Minimal overlap of teeth.
Enamel-dentine junction Coronal pulp morphology
Interdental bone
when using the paralleling technique, what beam is perpendicular/at a right angle to the image receptor?
the central ray/beam
the others are slightly divergent
what occurs if there is a short focus to skin distance?
outer beams are more divergent = increased magnification
what occurs if there is a long focus to skin distance?
less magnification
what is the recommended focus to skin distance?
20cm
how are film packets held in place?
rinn holders
what radiographs are the blue rinn holders used for?
anterior perioapicals
what radiographs are the yellow rinn holders used for?
posterior periapicals
what radiographs are the red rinn holders used for?
bitewings
what occurs if the rinn holder is not assembled correctly?
coning off
what is collimation?
equipment that allows you to control the shape, size and reduce the dosage of the x-ray beam
according to the law what is the maximum beam diameter of circular beam measured at the patient end of the spacer cone?
60mm
why is a focus to skin distance of 20cm used?
to reduce magnification and divergent beams
when is a size 0 bitewing image receptor used?
small children
deciduous teeth
when is a size 2 bitewing image receptor used?
used in adults
used in permanent dentition
where must the image receptor be in relation to the line of arch?
parallel to the line of arch
what is the ideal vertical angle for a radiograph?
5-10 degrees (related to the curve of monson)
what occlusal plane curve is buccolingual?
curve of monson
what occlusal plane curve is anteroposterior?
curve of spee
what legislation protects the exposure of patient to radiation?
IRMER 17
what legislation protects the exposure of healthcare workers and the general public?
IRR17
According to IRR17 how far away must everyone in the room be for the primary beam whilst the x-ray is being taken?
1.5m
According to IRR17 what is the dose limit for unclassified staff for the whole year?
6mSv/yr
According to IRR17 what is the dose limit for the public for the whole year?
1mSv/yr
who is the referrer?
registered healthcare professional, supervising dentist/clinician.
what is the responsibility of the referrer?
provide sufficient medical data to the practitioner to enable justification.
who is the practitioner?
registered healthcare professional
what is the responsibility of the practitioner?
Decides if exposure is justified - ensures benefits outweighs the detriment.
Ensure dosages are ALARP
Complies with the employers procedures.
= authorises the radiograph
a radiograph must be justified by a practitioner, what must be considered?
Efficacy
Benefits - directly and in society
Risk to the individual
Alternatives
who is the operator?
anyone who carries out the practical aspects that can affect patient dose
is there a dose limit for patients?
no, as if the dose is justified and optimised then it is of benefit to the patient
what does the practitioner require before authorising the radiograph?
patient ID - name, DOB, CHI number
clinical info
unique identifying signature
is pregnancy a contraindication to taking a radiograph?
no - some woman air on the side of caution however and decide not to.
how often should bitewings be taken in a high caries risk patient?
6 months
how often should bitewings be taken in a moderate caries risk patient?
annually
how often should bitewings be taken in a low caries risk patient?
primary = 12-18 months
permanent = 2 years
what metal absorbs excess heat when taking a radiograph?
copper
list the ways we can reduce patient dose? (3)
FSD 20cm
Using a faster film speed
rectangular collimation
what positioning factors would make anterior teeth appear horizontally magnified? explain (3)
Canine BEHIND the vertical canine guideline
= teeth are closer to the x-ray source than expected
= the speed of beam is slow and the speed through the IR is fast
= unmatched speeds causes distortion
what factor would make posterior teeth on one side appear horizontally magnified? (1)
patient movement
