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OSI Ignacio > Chapter 9: Other Imaging Modalities > Flashcards

Chapter 9: Other Imaging Modalities Flashcards

(44 cards)

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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:

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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:

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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:

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

Applications of CT scans:

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

Cone beam computed tomography (CBCT):

Study These Flashcards
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)

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

ET is up to ___% less than scanning time

25
The dimensions of the filed of view depend on the ?
Detector size and shape, projection geometry and collimation
26
CBCT takes ____ seconds and ____ individual projections frames
20, 600
27
Patient selection criteria for CBCT
Radiation doses higher than other dental Radiographic procedures
28
Specific applications of CBCTs:
- implant site assessments - endodontics, orthodontics + 3D cephalometry - impacted teeth - TMJ - maxilofacial pathoses - treatment planning and virtual simulations
29
Strengths of CBCTs:
- size and cost: available for dental office - fast acquisition: 30 seconds - submilimeter resolution - relatively low radiation doses - interactive analysis
30
Limitations of CBCTs:
Image noise Poor soft tissue contrast
31
Magnetic resonance imaging (MRI)
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
Is MRI an ionising technique?
No
33
Which of the imaging modalities is used in TMJ in dentistry ?
MRI
34
Advantages of MRI?
Soft tissue best contrast resolution No ionising radiation is involved Multi planar imaging without reorienting the patient
35
Disadvantages of MRI
Long imaging times Expensive Patients with ferromagnetic metals (cardiac pacemakers, cerebral aneurysm clips)
36
Applications of MRI:
- soft tissue conditions - disk in TMJ - tumours - lymph nodes - mandibular nerve
37
Ultrasonography:
- 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
Anechoic tissues:
Free from echo Don’t produce signals Appear black Fluid filled cyst
39
Hypo echoic tissues:
Produce a weak signal
40
Hyper echoic tissues:
Produce intense signals , ligaments , skin, needles, or catheters, appear bright
41
Which of the 6techniques are non ionising
MRI Ultrasonography
42
Sialography:
- Radiographic examination of the salivary glands, involves injecting contrast medium into the salivary duct of a single gland
43
Indications of sialography:
- functional integrity of the salivary glands - obstructions - ductal patterns - Intra glandular neoplasms
44
Sialography procedure :
- 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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