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Dental Radiology > Advanced Oral and Maxillofacial Imaging > Flashcards

Advanced Oral and Maxillofacial Imaging Flashcards

1
Q

What are the indications for Computing Tomography? (4)

A
  • Excellent for fine bone detail so very useful in mid-facial trauma
  • Cranio-facial reconstruction planning
  • Assessment of bony expansion or destruction caused by large cysts or tumours
  • Assessment of intra-cranial trauma or disease
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2
Q

What is a Cone Beam CT? (7)

A
  • Sometimes known as digital volume tomography
  • Uses a cone shaped x-ray beam
  • Scan time ranges from 20-40 seconds
  • Larger field of view results in greater radiation dose
  • Dose is much lower than a “medical” CT
  • Gives excellent bony detail but very poor for soft tissue (unlike medical CT)
  • Several machines available with different field sizes
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3
Q

What are the indications for a Cone Beam CT? (7)

A
  • Implants
  • Cysts and tumours in the jaws
  • Trauma
  • TMJ
  • Sinuses
  • Orthodontics
  • 3rd molar – ID nerve relationship
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4
Q

What are contrast techniques? (2)

A
  • Contrast agents are radiopaque substances that when introduced into the body alter subject contrast artificially
  • Many contain iodine so allergic reactions are possible
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5
Q

What contrast techniques are used in the head and neck? (5)

A
  • Sialography
  • TMJ arthrography
  • Angiography
  • Investigation of fistulae
  • As an adjunct to CT or MRI
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6
Q

What is Sialography? (3)

A
  • This involves the introduction of contrast into the ductal system of the parotid or submandibular salivary glands
  • Indicated when there is a history suggestive of obstruction
  • Also used to investigate patients with suspected Sjögren’s syndrome
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7
Q

What are the contraindications for Sialography? (3)

A
  • Acute salivary gland infection
  • Allergy to iodine
  • Discrete salivary gland swelling … other techniques are more informative
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8
Q

What is TMJ arthrography? (3)

A
  • This involves the introduction of contrast into, usually, the inferior, joint space of the TMJ to determine disc position and detect disc perforations and adhesions
  • Still used in some centres to investigate longstanding TMJ “dysfunction”
  • In Sheffield MRI is used instead
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9
Q

What are the advantages of TMJ arthography? (2)

A
  • May reveal perforations of
    the disc
  • Can produce a truly dynamic study of joint movement
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10
Q

What are the disadvantages of TMJ arthography? (4)

A
  • Unpleasant … quite invasive
  • Technically demanding … few Radiologists are trained to do it
  • Involves ionizing radiation
  • Does not image the disc directly
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11
Q

What is Angiography? (2)

A
  • Involves the injection of contrast directly into blood vessels via a catheter, usually inserted into the femoral artery, followed by selective catheterization of carotid branches
  • Done under fluoroscopic control
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12
Q

What are the indications for Angiography? (2)

A
  • To show the vascular anatomy and feeder vessels associated with haemangiomas
  • Investigation of arteriovenous malformations and suspected intracranial bleeds
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13
Q

What does MRI stand for? (1)

A
  • Magnetic Resonance Imaging
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14
Q

What is MRI? (7)

A
  • Involves placing the patient in a very strong magnetic field
  • Radiowaves are pulsed into the patient
  • This induces resonance of hydrogen protons
  • A radiowave signal is emitted and then converted into a visual tomographic image
  • Ionizing radiation is not involved at all
  • In contrast to CT, with MRI, bone does not emit a signal and so appears dark
  • T1 weighted images show normal anatomy well whilst T2 weighted images are good for showing disease
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15
Q

What are the indications for an MRI? (3)

A
  • Excellent for tumour staging … provides good soft tissue detail … in any plane
  • Excellent for intracranial disease
  • Can be used to directly image the disc position within the TMJ
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16
Q

What are the disadvantages of MRI? (3)

A
  • Expensive and not widely available - yet
  • Claustrophobic, noisy and time-consuming
  • Contra-indicated in patients with ferro-magnetic surgical clips, pacemakers, cochlear implants and in first 3m of pregnancy
17
Q

What is Ultrasonography? (4)

A
  • Uses high frequency (1.5-10MHz) sound waves from a transducer against the skin
  • Sound reflected by tissue interfaces … echoes
  • Echoes detected by transducer and converted to an electrical signal … image
  • Non-invasive, safe and cheaper than CT/MRI
18
Q

What are the uses of Ultrasonography? (3)

A
  • Excellent for assessment of superficial swellings eg parotid, thyroid, cervical lymph nodes
  • In some centres it is possible to do a fine needle aspiration of swellings under US guidance
  • Doppler US may help in assessing vascularity of lesions
19
Q

What is Digital Imaging? (1+2, 1)

A
  • Uses conventional x-ray machine but traditional x-ray film is replaced by either:
    (1) a charge coupled device (CCD) or
    (2) a photostimulable phosphor plate
  • In both cases the image receptors convert received information into digital data
20
Q

How is Digital Imaging stored and used/assessed? (5)

A
  • The digital data is stored on a computer
  • Converted to a grey-scale visual image
  • Image displayed on a monitor
  • Possible to alter contrast and resolution
  • A hard copy can be produced
21
Q

What is Direct Digital Imaging? (4)

A
  • Uses the CCD image receptor
  • Produces instant images
  • With some systems the sensor is quite bulky making it awkward to position in the mouth
  • Examples include: Trophy’s Radiovisiography and Schick’s CDR
22
Q

What is Indirect Digital Imaging? (5)

A
  • Uses the photostimulable phosphor plate
  • After exposure the plate has to be placed in a “reader”
  • Digital info. then stored and manipulated
  • The plate can be cleared and reused
  • Example is the Soredex Digora system
23
Q

What are the advantages of Digital Imaging? (5)

A
  • Lower radiation dose
  • No need for conventional film processing
  • Possible to alter contrast and resolution and enhance images
  • Possible to transfer images between departments in a hospital or between hospitals
  • Storage of patient info - no lost x-ray films!
24
Q

What are the disadvantages of Digital Imaging? (4)

A
  • Expensive
  • Need large disc space for storage
  • Some loss of image definition and resolution compared with film
  • Image manipulation can be misleading and could be misused. Hard copy images may fade with time
25
Q

What is Radionuclide Imaging? (5)

A
  • Involves injection of radioactive agent which emits gamma rays … detected by gamma camera
  • The agents used have an affinity for the target tissue
  • Provides info. regarding function and/or structure of target tissue
  • Technetium 99m commonly used
  • Possible to attach this to other substances that are concentrated in different organs eg MDP (methylene diphosphonate) …bone
26
Q

What are the indications for Radionuclide Imaging? (6)

A
  • Detection of bony metastases
  • Detection of bony invasion by tumours
  • Investigation of salivary gland function
  • Condyle hyperplasia - assessment of continued growth
  • Evaluation of bone grafts
  • Thyroid investigations
27
Q

What are the disadvantages of Radionuclide Imaging? (5)

A
  • Limited image resolution
  • Images not usually disease specific
  • Radiation dose can be high
  • Difficult to localize exact anatomical site of source of emissions
  • Can be time consuming
28
Q

What are the further developments in Radionuclide Imaging? (3)

A
  • Single photon emission computed tomography (SPECT) … produces a cross-sectional image … good for localisation
  • Positron emission tomography (PET) also produces cross-sectional images … well localised. Can investigate disease at a molecular level and possible to superimpose the PET scan on a CT scan
  • See BJOMFS Feb 2005 page 1-6
29
Q

What sort of Imaging would you use for a Dental implant assessment? (1)

A
  • Cone Beam CT
30
Q

What sort of Imaging would you use for a Complex bony detail with soft tissue? (1)

A
  • CT
31
Q

What sort of Imaging would you use for a Salivary gland obstruction / Sjögren’s? (1)

A
  • Sialography
32
Q

What sort of Imaging would you use for a Complex soft tissue detail? (1)

A
  • MRI
33
Q

What sort of Imaging would you use for a Haemangioma/AVM? (1)

A
  • Angiography
34
Q

What sort of Imaging would you use for a Superficial soft tissue swelling? (1)

A
  • Ultrasound
35
Q

What sort of Imaging would you use for Condyle hyperplasia? (1)

A
  • Radionuclide Scan
36
Q

What sort of Imaging would you use to Search for bony metastases? (1)

A
  • Radionuclide Scan

Dental Radiology (9 decks)

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