EXAM Flashcards
is it true or false that xray photons have electrical charge
false
what is the correct ring holder to use when taking a paralleling periapical radiograph of tooth 11
blue
is it true or false that the xray beam is aimed upwards at approx 8 degrees
true
when positioning a patient for a panoramic radiograph which anatomical reference should be horizontal?
Frankfort plane
it should be standard practice for the patient to wear a lead apron for which intramural dental radiograph?
none of them
list 2 specific anatomical features that can hinder the positioning of the image receptor holder when attempting to take a paralleling periapical radiograph of a first molar tooth in an adult?
strong tongue
lack of adjacent teeth
shallow or high hard palate
lack of opposing molar teeth
tight cheeks unable to hold receptor
intra oral dental xray units, with an operating potential of 60-70kv, must include a spacer cone to ensure a minimum “focus to skin distance”. state the minimum distance and explain why the UK guidance depends it?
focus to skin distance 200mm
ensures xray beam is parallel as more parallel beam means you have less distortion of the anatomy, maintains high quality and can be replicated
what does the Compton effect cause?
scatter which results in a lower quality image very little diagnostic information.
which end of the spectrum has photons which are not useful for image formation?
what material is used to filler these out of the xray beam?
low end of spectrum
aluminium
who can be the referee for radiographs?
qualified dental professionals
operators
practitioners
what are ghost shadow son a radiograph?
earrings
facial peircings
salivary stones
tonsil stones
dental restorations
dentures
what radiographs would you use for a patient with a BPE of 4 in all sextants?
Full mouth of periapicals
What is the numbers of the radiograph receptors and what colours are they and what type of radiographs would be take with these and what colour of xray holder would be used?
0- Anterior periapical- yellow receptor - blue Xray holder
2- bitewing, posterior periapical- green receptor - red xray holder.
4- occlusal - blue receptor
what are advantages and disadvantages of intraoral radiographs?
advantages :
low exposure, detailed image, quick and easy
dis adv:
uncomfortable for the patient, might need to retake, patient positioning
what would you you see on a periapical radiograph?
what are the advantages
and disadvantages?
the entire tooth crown root and apex of the tooth
periodontal bone loss
apex of the tooth for any infection
caries
endodontic treatment
dis adv:
just 1 or 2 teeth at a time so limited view
technique sensitive
overlapping
what would you see on a bitewing radiograph? what are the advantages and disadvantages?
molars and pre molars of upper and lower arch crown and root of the tooth
periodontal bone loss
interdental caries
advantages:
detect inter dental caries, bone loss, minimal radiation exposure, fast exposure
dis adv:
may be uncomfortable for the patient
if patient has over lapping teeth may need to take 2
doesn’t show other anatomy
the quality of the image may nit be great
what does an OPT show you and what are advantages and disadvantages?
opt shows you the entire dentition, and other surrounding anatomy such as TMJ maxillary sinuses and wisdom teeth.
adv
good for patients with gag reflex
can see full dentition
Other anatomy
dis adv
higher radiation exposure 5x more
Longer exposure time
What is the ideal projection geometry?
Non divergent xray beam
Tooth immediately next to receptor
Xray beam exactly perpendicular to both the tooth and receptor
How you achieve the best possible projection geometry?
Keep patient still
Maintain focus to skin distance
Ensure the receptor is as close to the tooth as possible
The uk guidance recommends at least how much distance for focus to skin distance? For intra oral X-ray units
And what is this distance maintained by using ?
200mm
Spacer cone
What is the curve of spee?
The occlusal plane rises as you move distally
What is the curve of Wilson?
Teeth don’t sit on the jaws completely vertically maxillary teeth tilt buccal labial mandibular molars tilt lingully
What is the bisecting angle technique?
When the subject and receptor are tilted at equal but opposite angles the two effects counteract one another
When is the bisecting angle used and who would we use it on?
Used when unable to position the receptor parallel to the tooth
Edentulous patient
Bad gag reflex
Child can’t tolerate receptor in mouth
Shallow palate
What is the match band effect?
Optical illusion created by the retina can make areas look brighter and areas look darker
How would you assess image quality?
Over exposure or underexposed
If the receptor is the wrong way around
What is caries seen as on a radiography and where can it be seen?
Radiolucent
Pits and fissures, smooth surfaces, interdental, root surface, secondary caries under restorations
What are the requirements of a controlled area for standard dental radiography?
Within 1.5m of the xray tube head and patient
Who is in charge of radiographs and who governs radiography?
FGDP
Why do we need safety regulations put in place?
To keep patients and staff safe
There is risk associated with X-rays
Exposure levels were higher in the past
What are local rules?
Rules put in place to ensure there is safe working in the xray area
What is a radiation protection adviser ?What matters should the employer consult a radiation protection advisor on?
A Radiation protection adviser is a specialist who advises employers to comply with IRR17 regulations.
Investigations
Radiation risk assessments
Regular equipment checks
The basic principles of the ICRP system are that all radiation exposures should be ?
Justified
Optimised
Limited
Who does IIR17 regulate
And what are some examples of what they regulate?
Radiation safety to members of the public and staff
Controlled areas
Local rules
Risk assessments
Who does IRMER17 govern?
medical exposures of patients and others
Exposures must be justified
And staff must be trained
What is the xray beam made up of?
Millions of xray photons directed in the same direction
what are radiographs?
Images created by X-rays which have been through an object then interacted with receptor
what is the xray production?
Electrons go towards atoms at a very high speed as they collide kinetic entry from the electrons is converted to heat and electromagnetic radiation
Xray units have generations which modify the alternating current so that it mimics a constant direct current what is this process known as?
Rectification
What are the electricity fundamentals?
Current - flow of electric charge
Voltage - different electrical potential between 2 points in electric field
Transformers - alter voltage from one circuit to another
what is electromagnetic radiation?
X-rays are a form of electromagnetic radiation
The flow of energy represented as a sine wave
What are properties of electromagnetic radiation?
No mass
No charge
Can travel in vcuum
Travels at speed of light
EM radiation involves the movement of energy as “packets of energy” known as what?
Wat are they usually measured in ?
Photons
Electron volts
What are properties of X-rays
Form of electromagnetic radiation
No mass
No charge
Travel in vaccum
Man made
What is an electron shell ?
When electrons spin around the nucleus in discrete shells
What is the dental xray unit made up of?
Tube head
Collimator
Spacer cone
Positioning arm
Control panel
Circuitry
Xray units have generators which modify the alternating current so that it mimics constant direct current what is this process known as?
Rectification
The dental Xray unit requires what type of current? And what type of voltages?
Requires a direct current
Requires 2 voltages
One as high as 10s of thousands
One as low as 10 volts
What way to photons travel?
Photons effectively travel in straight lines but diverge from the xray source
Not parallel
What are xray photons aimed at?
A subject
What removes the lower energy (non diagnostic X-rays) from the beam?
Aluminium absorbs the photons
What is the precise area on target where electrons collide and X-rays are produced?
Focal spot
What is the penumbra effect?
Blurring of radiograph image due to the focal spot not being a single point
What are the main components of a tube head ?
Xray tube
Metal shielding
Aluminium filtration
Oil
Spacer cone
How much Focus to skin distance should the tubehead be from the patient
How is this effective?
200mm
Reduces magnification of image
How much can rectangular collimation potentially reduce surface area irradiated and reduce effective dose to the patient by approximately?
50%
How would you assess image quality ?
Over exposure
Under exposure
Elongation
Cone cutting
Receptor placed back to front
Who is IRMER17 Enfored by?
Health Improvement Scotland
IRMER17 defines particular roles during medical exposures called duty holders what are these ?
Referrer
Practitioner
Operator
Employer
What is distortion and what are common causes of it?
a false size or shape of structures being imaged
Incorrect distances
Angulation of xray beam
Patient movement
What are double shadows and ghost shadows on OPT?
Double shadows are structures which are captured twice on the image due to the way in which the radiograph was taken
Such as 2 soft palates
Ghost shadows are faint blurry parts of an image that shouldn’t be there
can happen due to patient movement
Double exposure by accident
Jewelery such as lip pearcing, earrings
When would you take an OPT?
you wouldn’t routinely take these
Only for generalised gross caries
Periodontal bone assessment
Assessment of 3rd molars
Assessment of anatomy such as TMJ & maxillary sinus
When would you take an OPT?
you wouldn’t routinely take these
Only for generalised gross caries
Periodontal bone assessment
Assessment of 3rd molars
Assessment of anatomy such as TMJ & maxillary sinus
Why are radiographs useful?
Can show anatomy
Help diagnosis
Help monitor
Help treatment plan
What is rectification?
Xray units have generators which modify the alternating current so that it mimics a constant direct current
How many volts is the electrical supply to xray unit ?
220-240 volts
What results in the xray beam intensity ?
The quality of photon energy passing through a cross section area of the beam
What causes divergence of the xray beam?
When the dose decreases with the distance from xray source
What does electron volts measure?
Kenetic energy gained by electrons
How are the xray photons emitted from the focal spot?
lead shielding
Attenuated by aluminium filtration
Exit tubehead to form xray beam
What ways does xray photons interact with matter ?
Transmission
Absorption
Scatter
What does attenuation lead to?
The radiographic image
What are specific attenuation interactions?
Photoelectric effect is when an xray photon and gets completely absorbed leads to a high contrast image
Compton effect is when the xray photon hits an outer body electron and leads to less absorption and scatter creating a bur or fog in the image
The majority of scatter from an xray beam produced by an xray tube operating at what KV and what scatter ?
70kv
Forward scatter
The controlled area should extend at least how far from the Xray tube and patient?
1.5m
What digital receptor checks would you carry out?
Check receptor
Image
Image quality
What does the step wedge test check ?
To check image quality and contrast
What teeth would you aim to see on a bitewing radiograph ?
Distal of the canine and medial aspect of the last tooth
What are potential faults you may see on a radiograph
Receptor damage
Bad contrast
Too dark too pale
