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
Does of radiation that can cause death in 24 hours
> 10 Sv
What kind of radiation causes genetic effects (i.e could be passed onto future children)?
non-deterministic
Dental workers radiation dose
<0.1mSv (never exceed 1)
What speed film has lowest radiation (D speed or F speed)?
F speed is best (fastest).
The younger the patient, the _____ the risk of radiation.
The worst
What collimator is best for reducing dose: rectangular vs round?
Rectangular
Controlled area size
1.5 metres (always 2 metres at DDH)
What is wrong with this radiograph?
Light damage. Large black area shows the over exposed area from light seeping in.
What is wrong with this radiograph?
Light damage. Fogging is visible as well as over-exposed black area.
What is wrong with this radiograph?
Film is back to front. Lead foil pattern visible on the left hand side.
Film
B: Super coat
C: Emulsion
A: Adhesive layer
D: Base
S, E, A, B - super coats emulate afgan blankets.
Emulsion layer in film
Silver halide crystals suspended in gelatin.
Image formation on dental film
Silver halide crystals are sensitised by x-ray photons, reducing them to black metallic silver.
Larger silver halide crystals…
Produce film faster but at lower quality.
Indirect film is sensitive to _________ rather than __________
Indirect film is sensitive to light rather than x-rays.
Intensifying screens pros and cons
Less radiation, less detail on radiograph
What’s wrong with this radiograph?
It’s been bent.
5 stages of image developing
- Develop
- Wash
- Fix
- Wash
- Dry
Components of an automatic processor
A - Feed in rollers
B - Developer rack
C - Fixer rack
D - Wash rack
E - Dryer
Developing the image allows you to see the latent image with the naked eye…
as the developing agents phendone and hydroquinone act upon sensitised silver halide crystals to reduce to black metallic silver.
How does fixing allow the unexposed silver halide crystals to be removed?
The fixing agents change the unexposed silver halide crystals to a soluble compound that can be washed away.
What causes this green brown tinge?
under fixing
Legislation meaning employers had a legal duty to ensure their staff were safe and risk free at work.
Health and safety at Work act 1974
How would you position your bite block for a bitewing radiograph?
Place the block on the centre of the 6th molar.
Comment
Just OK
Comment
Repeat, no upper bone levels visible posterior to the 7.
Comment
Repeat, because 8 collimate off.
Comment
Repeat, receptor size too small.
Comment
Repeat, vertical angulation causing elongation and lower bone level projected off.
Comment
Perfect
Comment
Repeat, cone-cutting (collimation is cover lower bone levels).
Comment
Good
Comment
Repeat, number 4 and receptor squint.
Comment
Good
Comment
Repeat, corner of film bent over so large area not exposed.
Comment
Repeat, too much overlap
Comment
Repeat, patient not biting on block
IR (ME) R
The ionising radiation (medical exposure) regulation 2017 to protect the patient.
IRR
The ionising radiation regulation 2017 protect both staff and public but also deal with patient protection in relation to the equipment we use.
The employer
the boss, must ensure that their establishment is complying with IRMER.
The practioner
The person who justifies the exposure. They must be aware of and adhere to the correct referral criteria for dental exposures. The practitioner assumes legal responsibility for the exposure when they put their name to it.
The operator
Anyone who is involved in the production of a radiograph. That includes the person who asks the patient to simply sit in the chair, to the nurse who develops the film.
The referrer
The person who has clinically examined the patient and referred them for the radiographs and who is responsible for viewing that radiograph and recording the findings in the patient’s notes
The dentist
Dentists are quite unique in the fact that they can be every single one of these roles, therefore need to pay close attention to this document.
Two main IRMER regulations
- Quality assurance programmes for standard operating procedures.
- Practioner and operators have undertaken CPD.
Training
5 hours of CPD every 5 years
Basic SOPs
How we justify the exposure
How we correctly identify the patient
How we collect the equipment
How we expose the patient
How we clean the phosphor plates and develop them.
So what exactly do we look at in QA programme?
Image quality
X-ray equipment
Image processing (film and digital)
Working procedures
Training
Audit
X-ray equipment requirements
Inventory must be kept.
Regular testing (every 3 yrs or so)
- this includes checking representative patient doses.
*at DDH we QA test our equipment every 3 months.
What happens to the equipment annually?
Annual service by a suitably qualified engineer (company called MI Healthcare).
What is the main method of checking performance known as?
Sensitometry
What does sensitometry involve?
A daily check of the developer, the idea is to compare a film developed with fresh chemistry with a new film taken every day to check image quality has not deteriorated as the developer becomes exhausted.
What image can you expect to see if the developer has become exhausted?
Will give you a pale image.
What causing film fogging?
Exposure to light
How often should you perform a visual check on solid state sensors and PSP plates?
Weekly: for any signs of damage, and x-ray the sensor once a month and study the resultant image.
Bent
Thumb print
Scratch/crack
Bite
Who can take radiographs?
A state registered dentist or hygienist
dental nurses with a post-qualification certificate in dental radiography or radiographers. Must also be able to provide evidence that they are competent to use the equipment in the practice.
What is cervical burnout?
Overexposure of the film can “burnout” the thinner sections of enamel, giving the false appearance of cervical caries.
Radiographing caries in children: risk
High - 6 months
Moderate - 12 months
low - 12-18 months (deciduous), 24 months (permanent)
Radiographic baseline
Outer canthus of the eye to the external auditory meatus, and this represents the base of the skull (red)
Frankfort plane
The inferior orbital margin to the upper border of the EAM. (green)
Maxillary occlusal plane
the ala of the nose to the tragus of the ear (yellow)
Landmark for a CT scan?
Maxillary occlusal plane
Landmark for extra-oral radiography?
Radiographic baseline
Landmark for DPT?
Frankfort plane
Positioning for anteroposterior
Positioning for postero-anterior
Positioning for a lateral cephalgram
Connie is suspected to have a cyst or malignancy on her jaw due to the media-lateral expansion.
PA mandible
Ryan thinks he broke the posterior body of the mandible and ramus in his rugby match.
PA mandible
When requesting a PA, you would usually…
request in conjunction with a DPT.
Positioning for lateral oblique mandible
Rob has a potential mandibular fracture on the ramus.
Lateral oblique mandible using a skull unit or conventional x-ray unit.
Kiki has infected molars.
Lateral oblique mandible using a dental tube with either horizontal or vertical angulation.
lateral oblique mandible using horizontal angulation
lateral oblique using vertical angulation
Rachel is about to undergo orthognathic surgery.
Cephalometric radiograph
Daniel is about to get invasive orthodontic treatment.
Cephalometric radiograph
Rohan broke his orbits and wall of maxillary sinus and potentially the body of the zygoma in a bar fight
OM10
Positioning for Occipital mental views
OM10 or OM30
Medical physicist or specialist company. Consult this person planning new surgery etc. radiation over dose. Establishing the controlled area. Their name and details can be found in the Radiation Protection File.
RPA: Radiation protection adviser
How do the RPA and the Medical Physics Expert differ?
They could be the same person.
RPA - IRR2017
MPE - IRMER2017
This person is usually a dentist or senior member of staff. Ensures compliance with IRR 2017 and local rules. Closely involved in radiography. Has authority to carry out their duties.
RPS: Radiation Protection Supervisor.
Highest radiation dose to lowest (of various scans)
- CT mandible and maxilla
- Craniofacial CBCT
- Dento-alveolar CBCT
- PA skull
- Lateral skull
- Chest PA
- Maxillary occlusal
- Lateral cephalometric
- DPT
- Bitewing/periapical
mA
Amperage = tube current.
Increasing amperage (mA)
Higher production of electrons inside the X-ray tube, increase radiation = higher exposure/darkening of film.
Green - soft palate
Yellow - hard palate
Red - anterior nasal spine
orangey-yellow - maxillary sinus (medial wall)
green - maxillary sinus (floor)
blue - maxillary sinus (posterior wall)
yellow - zygomatic arch
purple - zygomatic buttress
pink - pterygoid plates
Comment
Faulty; incorrect selection of exposure factors – not enough radiation equals an underexposed image.
Film didn’t spend enough time in the developer tank
Developer is exhausted or at too low a temperature.
Incorrect dilution of chemicals
Comment
incorrect exposure factor
Comment
Tube isn’t sitting right with all 4 corners.
Film is damaged with several scratched and marks and its under exposed.
Comment
Insufficient washing, residual chemicals.
Comment
Static electricity discharging on the film. Caused when film is pulled too quickly from packet in a dry atmosphere.
Comment
Chin too far down, patient is also rotated.
Comment
Narrow incisors = patient too far into the machine
Comment
Wide incisors = patient too far out of the machine
Simon has intracranial bleeding from being hit on the head by a bat.
CT scan
Increase of mA or S
S – seconds; increasing the time of exposure enhances the ‘sharpness’ or definition of x-ray this is typically reported on alongside mA.
mAs – milliampere-seconds; current going through the x-ray tube, should take into account radiographic density (i.e. higher mAs for a abdomen scan versus for a hand scan as there are less structures so its less necessary for contrast between the different structures).
mA (current) x S (time) = mAs —> changes in this will effect contrast and an increase in mAs will increase radiation dose.
Increasing kV
increases the exposure given to the film, potentially darker image (may need a greater exposure depending on what is being x-rayed if there are more structures = increase the Kv).
The dentist is trying to locate sam unerupted maxillary canine
CBCT
Susan has a cleft palate
CBCT
Roxy needs to an assessment of her resorpted unerupted molar
CBCT
Lewis has disc issues with his TMJ and potentially a salivary gland problem.
MRI
Rodrick has a neck swelling that is suspicious
Ultrasound
Inverse square law
