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Advanced Imaging Modalities Flashcards

1
Q

What are the different types of advanced imaging modalities?

A
  • MDCT
  • CBCT
  • MRI
  • Positive Contrast Examinations
    — Arthrography
    — Sialography
  • Nuclear Medicine
    — PET-CT
  • Ultrasound
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2
Q

What are the advanced imaging modalities that use CT?

A
  • MDCT
  • CBCT
  • MRI
  • PET-CT
  • Ultrasound
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3
Q

What are the emerging imaging modalities that use CT for dentistry?

A

*CBCT
*MRI
*Ultrasound

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4
Q

What is an MDCT?

A

Multi-Detector Computed Tomography
- Greater hard tissue object sensitivity than conventional
x-ray imaging systems
- Demonstrates soft tissues

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5
Q

Dr. Ledley (DDS) developed patent for the first ____________ scanner for larger patient openings in 1976.

A

“whole body” CT

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6
Q

What are the parts of the MDCT?

A
  • gantry
  • couch
  • control console
  • helical CT
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7
Q

MDCT Technique
uses a ____-shaped beam

A

fan-shaped

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8
Q

How does the MDCT basis-image capture work?

A
  • Two basis-image capture sequences as the machine rotates counterclockwise from Position 1 to Position 2
  • scans routinely capture in the range of 100 to 600 basis images per rotational scan
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9
Q

The greater the # basis images, the better the…

A

reconstruction algorithm

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10
Q

How does the MDCT work?

A
  • Attenuated beam photon capture in the solid state cadmium tungstate detector affects energy, the degree of ionization and electrical charge
  • Electrical charge is assigned a numerical value (“digitized”) for a given voxel
  • Numerical value is assigned a gray scale value for the part of the object (voxel)
  • Spatial and numerical information is used by imaging software to construct images (visual analogs)
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11
Q

Images constructed in the anatomic planes of imaging are…

A
  1. Coronal (frontal)
  2. Axial (transverse)
  3. Sagittal
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12
Q

What allows for determining what level of dentisty (bone, soft tissue, etc.) you want to see?

A
  • windowing
  • Hounsfield (density) Units
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13
Q

What is windowing?

A

the window width can be narrowed around a selected window level

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14
Q

Why is windowing necessary?

A
  • Human eye discriminate up to 40 shades of gray
  • Monitors show up to 256 (8 bit) shades of gray (28)
  • Most CT data have 4096 (12 bit; 212) shades of gray i.e., from 0 – 4095 Hounsfield units
  • A 14-bit system (214) has 17,024 shades of gray
  • But… the human eye cannot discriminate all the shades of gray if displayed
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15
Q

______ contrast resolution yields details of hard and soft tissue densities

A

High

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16
Q

Hounsfield (density) units do not translate to CBCT units because of variations in…

A
  • FOV
  • Exposure
  • Position in scanner
  • Size of object
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17
Q

The narrower window width produces images with _____ contrast

A

high

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18
Q

A ________ window with varying window levels selectively windows hard and soft tissue

A

narrow

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19
Q

What are the disadvantages of CT?

A
  • High dose of ionizing radiation
  • Expensive and not as readily available as conventional imaging
  • Sensitive to artifacts from metallic restorations and patient movement
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20
Q

What is the effective dose for a common MDCT on the head, abdomen, and chest?

A

960-1500 uSv
5300 uSv
5800 uSv

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21
Q

What is an MRI (magnetic resonance imaging)?

A

One of the most important advantages MRI has is the ability to separate tissues with extracellular water from cellular tissues with intracellular water

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22
Q

What are the three main components of magnetic resonance imaging (MRI)?

A
  1. Magnets
  2. Resonant energy
  3. Imaging
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23
Q

What are the two parts of the MRI system?

A

Image Capture
Image Processing

24
Q

What is the average MRI experience for the patient?

A
  • Confined space
  • “Clanging” noise
  • Mild vibration and movement
25
How does an MRI machine work?
- makes use of the resonance property found in some of the nuclei present in the human body - the hydrogen nucleus (proton) is of interest due to its large presence in water and body molcules - only atoms with an odd number of protons and/or neutrons in the nucleus have the magnetic properties required
26
Magnetic moments of MR active nuclei point in random directions thus they produce...
no overall magnetic effect
27
When magnetic moments line up with the magnetic field flux lines this is called...
alignment
28
What allows contrast between soft tissues?
* Proton density * T1 relaxation time * T2 relaxation time * flow
29
What are T1 weighted images?
“fat images” (the surrounding fat produces the image contrast)
30
What are T2 weighted images?
“water images” (normal or abnormal location of free water can be evaluated)
31
What are the properties of a T1 image (MRI)?
* Lower contrast * More gray shades gives better discrimination of water in the different soft tissues (i.e. fat, muscle, neural tissue, blood, etc.)
32
What are the properties of a T2 image (MRI)?
* CSF has brighter signal * Better differentiation of tissue with high extracellular or “free” water content
33
What are the advantages of MRI?
1) No ionizing radiation 2) Best soft tissue imaging
34
What are the disadvantages of MRI?
1) Sensitive to motion artifacts 2) Sensitive to metal artifact 3) Expensive financial 4) Long scan times 5) Claustrophobia 6) Availability
35
What are absolute contraindications for MRIs?
* Imbedded ferrous metals * Cardiac pacemakers (not always, if special precautions followed) * Cerebral aneurysm clips * Cochlear implants * Intra-ocular metallic foreign bodies
36
What is the best modality to study soft tissue disease?
MRI
37
__________ most common imaging sequences to evaluate change in soft tissue structures
T1 and T2
38
What is an example of an MRI platform dedicated for dental?
Magnetom Free.Max Dental Edition
39
What are the uses for positive contrast examinations?
● arthrography ● sialography ● urography ● pyelography ● barium series
40
What is an arthrography?
- google says... a medical imaging procedure that uses contrast material injected into a joint to provide a detailed view of the joint's structure and soft tissues - used for TMJ synovial spaces
41
What is a sialogram?
Infusion of a radiopaque dye into a salivary gland’s ductal pattern and evaluating the fill pattern with radiographic imaging
42
What is a sialogram used for?
evaluation of the parotid and submandibular glands as these glands have a primary duct amenable for gland infusion
43
Why is the sublingual gland not good for a sialogram?
Sublingual gland lacks a primary duct; it has multiple ducts excreting into the floor of the mouth therefore it is not suitable for sialographic examination
44
What is a nuclear medicine bone scan?
* Imaging technique where bone binds a radioisotope Tc99 * Gamma camera takes images of where the radioisotope has collected * Metabolic activity determines degree of radioisotope binding
45
What are the advantages of a nuclear medicine scan?
Radioactive isotope concentrates in areas of rapid bone turnover and gives positive response with 10% increase of osteoblastic activity
46
What are the disadvantages of a nuclear medicine scan?
1) Expensive and invasive 2) Morphologic changes not imaged 3) Findings not specific to any disease process
47
What is a PET-CT?
Positron Emission Tomography – Computed Tomography - a type of nuclear medicine
48
What are the features of PET-CT?
* Combination of PET and CT is referred to as hybrid or fusion imaging * Superior to plain nuclear medicine alone
49
Why is a PET-CT useful?
* location of a tumor * followup of chemotherapy or surgery * staging dementia, evaluate stroke
50
How does a PET-CT work?
» Fluorine-18 (18F) is a positron emitting radioactive isotope that is used with a glucose analogue for quantitative imaging » Computed tomography (CT) is fused or co-registered with the PET scan to aid in interpretation
51
What do you look for in a bilateral pet scan comparison of the condyles?
Increased FDG uptake is evident as increased brightness in left condyle laterally and superiorly. Comparison of left and right condyles illustrates difference in FDG uptake.
52
What are the advantages of a PET Scan?
* Allows functional study of a metabolic process * Provides a visual image that corresponds with patient anatomy
53
What are the disadvantages of a PET Scan?
* Higher dosimetry * High finances * Slow imaging; not capable for time sequences > 30 seconds
54
What are the other names of ultrasonography?
– Real-time echography – Real-time tomography
55
How does an ultrasound work?
- Ultrasound transducer sends ultrasound pulses into tissue and then receives echoes back with spatial and contrast information on a 2D grayscale image - ultrasound uses non-ionizing sound waves (mechanical) and has not been associated with carcinogenesis
56
What is less expensive ultrasound or CT or MRI?
ultrasound examination is less expensive to conduct than CT or MRI
57
ultrasound imaging is useful for the evaluation of...
physiology as well as anatomy

Radiographic Interpretation (23 decks)

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