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OSI Ignacio > Chapter 9: Other Imaging Modalities > Flashcards

Chapter 9: Other Imaging Modalities Flashcards

1
Q

The other imaging modalities include:

A

6:
1. Conventional tomography
2. Computed tomographic scanning (CT scan)
3. Cone beam conventional tomography (CBCT)
4. Magnetic resonance imaging (MRI)
5. Ultrasonography
6. Sialography

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2
Q

Conventional tomography:

A

Radiographic technique designed to image a slice or plane of tissue

  • it’s accomplished by blurring the images of structures lying outside the plane of interest through the process of motion
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3
Q

Focal plane tomography:

A
  • in conventional tomography
  • same as focal trough
  • tomography by simultaneously moving the xray generator and xray detector so as to keep a consistent exposure of only the plane of interest during image acquisition
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4
Q

Conventional tomography: what are the two objects involved

A

X-ray tube and radiographic film

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5
Q

The fixed axis in the conventional tomography is

A

Fulcrum

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6
Q

Principle of conventional tomography:

A

Moves in opposite directions simultaneously

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7
Q

Where is the X-ray tube and film positioned in conventional tomography?

A

On opposite sides of the fulcrum (located within the body’s plane of interest)

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8
Q

The images of objects outside the focal plane are?

A

Blurred

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9
Q

Tomographic layer is the zone of?

A

Sharp

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10
Q

Blurring in conventional tomography depends on?

A
  • structures lie far from FP
  • FP lies far from the film
  • distance of the tube
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11
Q

Indications of conventional tomography?

A
  • frontal plane: maxillary sinus, ethmoid bone, conchae
  • sagittal plane: TMJ
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12
Q

Computed tomographic scanning (CT):

A

X-ray tube that emits a finely collimated FAN shape xray beam directed through a patient to a series of scintillation detectors or ionisation chambers

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13
Q

What do the detectors in CT scan do?

A

Measure the number of photons that exit the patient

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14
Q

CT scan produces what kind of image?

A

Cross sectional

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15
Q

What are the two objects involved in CT scanning?

A
  • X-ray tubes and detectors
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16
Q

X-ray tubes in CT scans:

A
  • tubes with rotating anodes
  • high heat capacity
  • 120 kVp/ 200-800 mA
  • beam collimated to a thin FAN beam
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17
Q

Detectors of CT scans:

A
  • array of solid detectors
  • ceramic or crystal
  • photodiode
  • the signal from the detector is amplified, digitised, and sent to a computer for analysis
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18
Q

Image reconstruction of CT scan:

A
  • photons recorded by receptors
  • cross sectional images constructed by computer algorithms
  • CT image is recorded as individual VOXELS
  • 512 x 512 pixels or 1024 x 1024 pixels
19
Q

Advantages of CT scans:

A
  • eliminates superimposition
  • high contrast resolution
  • multi planar reformatted image: from a single CT can see axial, coronal , and sagital planes
  • 3D images
20
Q

Disadvantages of CT scans:

A
  • expensive, maintenance
  • metallic restorations
  • patient motionless during examination
21
Q

Applications of CT scans:

A
  • infections
  • osteomyelitis
  • cysts
  • tumours
  • maxillofacial trauma
  • implantology
    -maxillary sinuses
  • salivary glands
  • TMJ
  • cleft palate
22
Q

Cone beam computed tomography (CBCT):

A
  • performed using a rotating platform
  • divergent cone shape or pyramidal source of radiation is directed through the region of interest and the residual attentuated radiation beam is projected onto a detector on the opposite side
  • the xray source and detector rotate around a rotation center
23
Q

Difference between cone (CBCT) and fan shaped (CT)

A
  • cone: reduces range, narrow xray beam by reducing ET, more accurate images
24
Q

ET is up to ___% less than scanning time

A

50

25
Q

The dimensions of the filed of view depend on the ?

A

Detector size and shape, projection geometry and collimation

26
Q

CBCT takes ____ seconds and ____ individual projections frames

A

20, 600

27
Q

Patient selection criteria for CBCT

A

Radiation doses higher than other dental Radiographic procedures

28
Q

Specific applications of CBCTs:

A
  • implant site assessments
  • endodontics, orthodontics + 3D cephalometry
  • impacted teeth
  • TMJ
  • maxilofacial pathoses
  • treatment planning and virtual simulations
29
Q

Strengths of CBCTs:

A
  • size and cost: available for dental office
  • fast acquisition: 30 seconds
  • submilimeter resolution
  • relatively low radiation doses
  • interactive analysis
30
Q

Limitations of CBCTs:

A

Image noise
Poor soft tissue contrast

31
Q

Magnetic resonance imaging (MRI)

A

Patient is placed inside a large magnet, this magnetic field causes the nuclei of many atoms in the body to align with the magnetic field
Scanner directs a radio frequency pulse into the patient, causing hydrogen nuclei to absorb energy, the stored energy is then released and detected as a signal in the coil in the scanner, the signal is then used to construct an image

32
Q

Is MRI an ionising technique?

A

No

33
Q

Which of the imaging modalities is used in TMJ in dentistry ?

A

MRI

34
Q

Advantages of MRI?

A

Soft tissue best contrast resolution
No ionising radiation is involved
Multi planar imaging without reorienting the patient

35
Q

Disadvantages of MRI

A

Long imaging times
Expensive
Patients with ferromagnetic metals (cardiac pacemakers, cerebral aneurysm clips)

36
Q

Applications of MRI:

A
  • soft tissue conditions
  • disk in TMJ
  • tumours
  • lymph nodes
  • mandibular nerve
37
Q

Ultrasonography:

A
  • no radiation
  • based on sound waves that acquire images in real time without ionising radiation
  • scanners generate electrical impulses that are then converted into ultra high frequency sound waves by a transducer (electrical energy into sonic energy)
  • sonic waves reflect toward the transducer
38
Q

Anechoic tissues:

A

Free from echo
Don’t produce signals
Appear black
Fluid filled cyst

39
Q

Hypo echoic tissues:

A

Produce a weak signal

40
Q

Hyper echoic tissues:

A

Produce intense signals , ligaments , skin, needles, or catheters, appear bright

41
Q

Which of the 6techniques are non ionising

A

MRI
Ultrasonography

42
Q

Sialography:

A
  • Radiographic examination of the salivary glands, involves injecting contrast medium into the salivary duct of a single gland
43
Q

Indications of sialography:

A
  • functional integrity of the salivary glands
  • obstructions
  • ductal patterns
  • Intra glandular neoplasms
44
Q

Sialography procedure :

A
  • duct is dilated using lacrimal probes
  • a cannula is inserted into the duct
  • radio opaque fluid (iodine) is injected
  • a series of radiographs are taken to determine the flow of the fluid, identify obstructions, and the rate of fluid excretion from the gland

OSI Ignacio (10 decks)

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