Radiology Flashcards
What is the SLOB rule in radiology?
used in the parallax technique. Same lingual, opposite buccal. Used to locate position of tooth
What is the name of the UK legislation that requires a radiographic report to be recorded for every radiograph
IRMER; Ionising Radiation (Medical Exposures) Regulations 2017
What is cervical burnout on a radiograph and what causes it?
It is caused by the varying attenuation of the x-ray beam by the normal anatomy present.
The dentine in the crown is surrounded by enamel, and the dentine in the more apical parts of the root are surrounded by bone, but the dentine in the cervical region is surrounded by neither and so there is less attenuation of x-ray photons. This results in a radiolucent band around the neck of the tooth, and this band is more radiolucent at the mesial and distal aspects of the tooth because roots have a round cross section and are therefore narrower at the edges.
What is the main benefit of rectangular collimation and why is this important?
It reduces the radiation dose to the patient by around 30%
This is important as ionising radiation in dentistry carries a small risk of carciogenesis.
In radiology, outline the steps in the bisecting angle technique.
*Place image receptor as close to subject as possible.
*Estimate the angle between the long axis of the subject and receptor.
*Bisect this angle with an imaginary line
*Aim the x-ray beam perpindicular to this bisecting line
From the OPT what is your assessment of this patients development in relation to his chronological age (12 yo boy)
Delayed lower premolars. Lower 5s developing ahead of lower 4s. Would normally expect lower first premolars at 10-11 and second premolars at 11-12 years.
This may be happening because of crowding in the lower arch. Also, lower 5s appear to be larger than normal.
ULQ is delayed in comparrison to URQ. UL4 expected to have erupted by now. Upper first premolars tend to erupt around 10-11
What is the purpose of quality assurance in dental radiology?
To ensure consistently adequate diagnostic information, whilst radiation doses to patients (and other persons) as kept ALARP, taking into account the relevant requirements of IRMER17 and IRR17
What checks are required for digital image receptors?
* Formally checked every 3 months or sooner if issue suspected.
* Receptor; visible damage to casing, wiring. Ensure cleanliness
* Image uniformity; expose receptor to unattenuated x-ray beam and check if resulting image is uniform
* Image quality; take radiograph of test object and assess the resulting image against baseline
How can damage affect a phosphor plate?
Scratches will appear as white lines
Cracking will appear as a network of white lines
Delamination will appear as white areas around the edges
How can damage effect a solid state sensor?
White squares or straight lines
What constitutes a diagnostically acceptable radiograph?
No errors or minimal erros in either patient preparation, exposure, positioning, image (receptor) processing or image reconstruction and of sufficient image quality to answer the clinical question.
Digital no less than 95%
Film no less than 90%
What consittutes a radiograph being diagnostically unacceptable?
Errors in either patient preparation, exposure, positioning, image (receptor) processing or image recontruction which render the image diagnosically unacceptable
What are the requirements of a bitewing to be diagnostically acceptable?
* Show entire crowns of upper and lower teeth
* Include the distal aspect of the fore standing posterior tooth an the mesial aspect of the last standing tooth (may require more than one image)
* Every aproximal surface shown at least once without overlap (where possible)
What are the requirements of a PA radiograph to be diagnostically acceptable?
Shows entire root
Shows periapical bone
Shows crown
Must also have adequate contrast, sharpness and resolution as well as minimal distortion
Give 2 examples of each type of bone pathology for; developmental, inflammatory, neoplasm, metabolic
Developmental; tori, dysplasia
Inflammatory; dry socket, osteomyelitis
Neoplasm; osteoma, osteosarcoma
Metabolic; osteoperosis, ricketts, Pagets, Giant cell lesion
Give 4 differential diagnosis for multilocular radiolucency
* Ameloblastoma
* KCOT
* Giant cell lesion
* Odontogenic myxoma
* Cherubism
* Aneurysmal bone cyst
What is the reason for distorted anteriors in an OPT?
Pt was not in the focal trough
What is the reason for a blurry image in an OPT?
Patient moved during exposure
What is the reason for an OPT image being too wide?
Canine guide set in front of the canines
When taking an OPT how can positioning errors be limited?
Use guides; temple rest, chin rest, bite block, hand rest, guide lights
Give 3 characteristics of a ghost image
Appears higher than the true image
Shows on opposite side
Appears larger/wider
Give 3 ways to reduce patient dose
* Beam diameter no greater than 60mm at end of spacer
* Rectangular collimation 40x50mm
* Focal skin distance 20-30cm
* 60-70kV
* Fast film F
* Aluminium filtration
* Lead absorption
* Limit exposure
What is compton scatter vs photoelectric effect?
Compton fogs and decreases image quality due to the xray hitting outer electrons and losing direction and energy.
Photoelectric complete absorption giving a white image as xray doesnt reach film
Besides lead, what metal is used in the xray tube head?
Aluminium, tungsten, copper
Regarding IRR17 give 5 safety features advised
* Controlled area
* Warning sign for controlled area
* A sign that lights up to indicate when equipment is on
* Light and audible sound during exposure
*Exposure with continuous pressure only
* Exposure stops automatically
What is ALARP
As low as reasonably practicable. Minimises exposure and dose
How is ALARP achieved?
Rectangular collimation 40-50mm, FSD 20-30cm, Fastest film available F speed or digital, 60-70kV. Aluminium filtration. Beam diameter no greater than 60mm at end of spacer
What is a radiation protection supervisor?
Ensures regulations and training are followed
What is a radiation protection advisor?
Advises on risk, regulations, training, quality etc
Compare and contrast the paralleling technique and bisecting angle technique
Paralleling; no contact but object and receptor are parallel and beam perpendicular to receptor.
Bisecting angle; in contact but not parallel and beam perpendicular to receptor
Why should radiographs be reported?
Medico-legal
Best practice
IRMER17
Records
Audit
According to IRMER17 what is the role of the employer
legal person, safety, make sure equipment in line with IRR17, staff follow regulations
According to IRMER17 what is the role of the referrer?
Check patient demographics, clinically justify radiograph, be trained
According to IRMER17 what is the role of the practitioner
Justifies exposure, benefits vs risks, check no recent relevant radiographs
According to IRMER 17 what is the role of the operator
Check patient demographics, ALARP, takes exposure, processes and reports
Identify this structure
Maxillary sinus
Identify this
Pneumatized maxillary sinus. When the sinus extends into an old extraction site
Identify
Pterygomandibular fissure. The space between the posterior border of the maxilla and the lateral pterygoid plate
Identify this structure
Lateral pterygoid plate; thin bony extension of the spenoid bone
Identify
Hamulus; small bony spine extending downward below the lateral pterygoid plate
Identify
Glenoid fossa
Identify
Articular eminence
Identify
Zygomaticotemporal suture
Identify
Zygomatic air cells
Identify
Zygomatic process
Identify
External auditory meatus
Identify
Mastoid process
Identify
Middle cranial fossa
Identify
Orbit
Identify
Infra orbital foramen
Identify
Infra orbital canal
Identify
Nasal cavity
Identify
Nasal turbinates
Identify
Incisive foramen
Identify
Ghost image of hard palate
Identify
Palatine torus (Hard palate appears thicker than normal)
If a cyst is suspected, what would be the initial radiographic investigations taken?
Periapical.
OPT
Occlusal
Supplemental include
CBCT
PA mandible
Occipitomental view
How should the radiographic features of a cyst be described?
Location
Shape (often spherical or egg shaped, most grow by hydrostatic pressure)
Margins (often well defined, often corticated)
Locularity (unilocular, multi, pseudo)
Multiplicity (single, bilateral, multiple, multiple may indicate a syndrome)
General overview of odontogenic cysts
Occur in tooth bearing areas.
Most common cause of body swelling in the jaws.
Account for 90% of all cysts in the oral and maxillofacial region.
All lined with epithelium
What are the three odontogenic sources of epithelium?
Rests of malassez - remnants of hertwigs epithelial root sheath
Rests of Serres - remnants of the dental lamina
Reduced enamel epithelium - remnants of the enamel organ
What is a radicular cyst and what is its clinical presentation?
Inflammatory odontogenic cyst.
Always associated with a non vital tooth
Initiated by chronic inflammation at apex of tooth due to pulpal necrosis
Incidence; more common in 4th and 5th decades, affects males and females equallly, 60% occur in maxilla, can involve any tooth
Often asymptomatic unless infected.
Typically slow growing with limited expansion
What are the radiographic features of a radicular cyst?
Well defined round/oval radiolucency
Corticated margin continuous with lamina dura of non vital tooth
Larger lesions may displace adjacent structures.
Long standing lesions may cause external root resorption and/or contain dystropic calcificaiton
What are residule and lateral cysts?
A residule cyst is when a radicular cyst persists after loss of tooth (of after successful RCT) Clinical history important to avoid mis diagnosis.
A lateral radicular cyst is related to a lateral canal. Located at the side of the tooth instead of the apex.
What is a dentigerious cyst?
A developmental odontogenic cyst. Associated with crown of unerupted (and usually impacted) tooth eg mandibular 3rd molar or maxillary canine.
Cystic change of dental follicle.
Most common in 2nd to 4th decades.
Affects males more than females
More common in the mandible
What are some clinical and radiological features of a dentigerous cyst?
Corticated margins attached to cemento-enamel junction of tooth.
Larger cysts may begin to envelope root of tooth.
May displace involved tooth
Tend to be symmetrical initially.
Larger cysts may begin to expland unilaterally.
Variable displacement of cortical bone ie bony expansion
How can you identify a dentigerous cyst vs an enlarged follicle
Consider cyst if follicular space >4mm (measure from surface of crown to edge of follicle)
Assume cyst if >10mm
Consider cyst if radiolucency is asymmetrical.
What is an odontogenic keratocyst?
A developmental odontogenic cyst. No specific relationship to teeth.
Most common in 2nd and 3rd decades
More common in males than females
More common in the mandible, and more common posteriorly
Often have scalloped margins.
25% are multilocular
Often cause displacement of adjacent teeth.
Root resorption uncommon.
Characteristic expansion (can expand mesio distally without bucco lingual expansion)
High chance of recurrance due to thin friable lining and difficulty of surgery
What syndromes can be associated with odontogenic keratocysts?
Basal cell naevus syndrome;
multiple OK
multiple carcinomas
plamar and plantar pitting
Calcification of intracradial dura mater known as Gorlin-Goltz syndrome
What is a naso palatine duct cyst?
Developmental non odontogenic cyst.
Arises from nasopalatine duct epithelial remnants
Most common in 4th to 6th decades
More common in males than females
Often asymptomatic
Pt may note a salty discharge
Larger cysts may displace teeth or cause swelling in palate
Always involve the midline but not always symmetrical
Non keratinised stratified squamous and modified respiratory
What is the radiographic presentation of a nasopalatine duct cyst?
Need a PA and/or standard maxillary occlusal radiograph.
Corticated radiolucency between/over roots of central incisors
Often uniloclear
May appear heart shaped due to superimposition of anterior nasal spine.
CBCT indicated for surgical planning
If radiolucency <6mm assume it is the incicive fossa
Incisive fossa not visibly corticated
What is a solitary bone cyst?
Non odontogenic cyst without an epithelial lining.
AKA simple/traumatic bone cyst
Most common in 2nd decade
Males more than females
Mandible more than maxilla
Can occur in association with other bone pathology eg fibro-osseous lesions
What is the clinical presentation of a solitary bone cyst?
Usually asymptomatic and an incidental finding
Rarely pain or swelling
Radiologically;
Majority in premolar/molar region of mandible but can also occur in non tooth bearing areas
Variable definition and cortication
May have scalloped margins giving a pseudoloclear appearance
May project up between the roots of adjacent teeth
What is a stafne cavity?
Not a cyst but commonly mistaken as one. It is actually a depression in the bone. (cortical bone preserved)
Only occur in mandible and almost exclusively lingual.
Contains salivary or fatty tissue
Most common in 5th and 6th decades
Often in angle or posterior body
Often inferior to IAC
Asymptomatic
Well defined, often corticated radiolucency
Rarely displaces adjacent structures
What are the 3 options for obtaining material from a cyst for histology?
Aspirational biopsy (drainage of contents)
Incisional biopsy (partial removal)
Excisional biopsy (complete removal)
Describe an aspiration biopsy
Wide bore needle
5-10ml syrings
Can get; air, blood, pus or cyst fluid
Cyst fluid can be clear straw coloured fluid in inflammatory or developmental cysts. White or cream semi solid may indicate keratocyst
May be unable to withdraw plunger
Describe an incisional biopsy
Taken to obtain a sample of the lining for histological analysis
Usually under LA
Select area where lesion appears superficial.
Raise mucoperiosteal flap
Remove bone as required using rongeurs or a round bur
Incise and remove a section of linin
Procedure may be combined with marsupialisation
What is enucleation of a cyst
All of the cystic lesion is removed.
Treatment of choice for most cysts.
Advantages; whole lining can be examined pathologically, primary closure, little aftercare needed.
Contraindications/disadvantages; Risk of mandibular fracture with very large cysts
Dentigerous cyst? May wish to preserve tooth
Old age/ill health
Clot filled cavity may become infected.
Incomplete removal of lining may lead to recurrance
Damage to adjacent structures
What is marsupialisation of a cyst? and what are the indications?
Creation of a surgical window in the wall of the cyst, removing the contents of the cyst and suturing the cyst wall to the surrounding epithelium.
Encourages the cyst to decrease in size and may be followed by enucleation at a later date.
Idications; if enuculeation would damage surrounding structures eg IAC
Difficult to access area
May allow eruption of teeth affected by the dentigerous cyst.
Elderly or medically compromised patients unable to wishtand extensive surgery
Very large cysts that would risk jaw fracture if enucleation was performed
Can combine with enucleation as a later procedure
What are some advantages of marsupialisation?
Simple to perform
May spare vital structures.
What are some contraindications/disadvantages of marsupialisation?
Opening may close and cyst may reform
Complete lining not available for histology
Difficult to keep clean, lots of aftercare needed.
Long time to fill in
An obturator is used to keep marsupialisation window open
Identify
Condyle of mandible
Identify
Coronoid process
Identify
Sigmoid notch
Identify
Ramus of mandible
Identify
Styloid process
Identify
Styloid ligament ossicles
Identify
Inferior border of mandible
Identify
External oblique line
Identify
Posterior border of ramus
Identify
Submandibular fossa
Identifyy
Genial tubicles
Identify
Body of hyoid bone superimposed on mandible
Identify
Tongue
Identify
Palatoglossal air space
Identify
Soft palate
Identify
ear
What is the incidence of odontogenic tumours?
1% of all lesions sent to histopathology come back as OT
Benign>malignant 100:1
Most asymptomatic and discovered investigating unerupted teeth
Pain usually secondary to infection
Most arise within bone
What are the three classifications of odontogenic tumours?
Epithelial
Mesenchymal
Mixed
ONLY mixed tumours can have dentine/enamel formation
Give description of ameloblastoma
Benign epithelial tumour
Locally destructive but slow growing
Typically painless
Most common in 4th to 6th decades
80% occur in posterior mandible
Male more than Female
Radiologically 85% multicystic. Unicystic carries lower recurrance rate
Histilogica
What types of tumours can fall into the different classifications?
Epithelial; ameloblastoma. Adenomatoid odontogenic tumour. Calcifying epithelial odontogenic tumour
Mesenchymal; odontogenic myxoma
Mixed; odontoma
Give the incidence and some features of ameloblastoma
Benign epithelial tumours
Locally destructive but slow growing
Typically painless
Most common in 4th to 6th decades
80% occur in posterior mandible
male more than female
Radiological; 85% multicystic, unicystic lower rate of recurrence
Histological; follicular, flexiform, desmoplastic
Margins well defined and corticated. Potentially scalloped
Adjacent structures can be displaced, thinning on bony cortices ‘knife edge’ extended root resorption
What is the management of an ameloblastoma/
Surgical resection with margin
Recurrance relatively common, up to 15%
Risk of malignant change <1% Ameloblastic carcinoma
AOT Adenomatoid Odontogenic Tumour
Benign epithelial tumour
Classic presentation - unilochlear radiolucency with internal calcifications around crown of unerupted maxillary canine
Incidence/presentation;
3% of odontogenic tumours
Most common in 2nd decade
female more than male
Mostly anterior maxilla
75% associated with unerupted tooth
Similar to dentigerious cyst but attached to CEJ
Impedes eruption
Unilocular
Majority have internal calcifications
External root resorption is rare
CEOT
Benign epithelial tumour
Most common in 5th decade
male more than female
Post mandible most common
Slow growing
50% associated with UE tooth
Internal radiopacities
Odontogenic myxoma
Benign mesechymal tumour
Most common in 3rd decade
female = male
mandible more than maxilla
well defined
small lesions unilocular
larger soap bubble appearance
slow growth m-d
scallops between tooth, may displace if large
management; curettage or resection. 25% recurrance rate
Odontoma
Benign mixed tumour
Malformation of dental tissue
Similarities to teeth; do not grow indefinitely, surrounded by dental follicle, lie above IAC
Most common in 2nd decade
Female = male
Compound; ordered dental structures (resembles multiple mini teeth) more common in maxilla
Complex - disorganised mass more common in post mandible
