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Radiographic Interpretation > Advanced Imaging Modalities > Flashcards

Advanced Imaging Modalities Flashcards

1
Q

what are the 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 other names for MDCT

A
  • multidetector helical CT
  • multislice CT
  • multirow CT
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4
Q

what does MDCT stand for

A

multi detector computed tomography

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5
Q

what are the older terms for MDCT

A
  • CAT
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6
Q

who developed CT imaging

A

Godfrey Hounsfield and Allan Cormack

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7
Q

what did Dr. Ledley do

A

developed patent for the first whole body CT scanner for larger patient openings

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8
Q

what does the MDCT image

A

greater hard tissue object sensitivity than conventional XR systems
- demonstrates soft tissues

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9
Q

MDCT technique uses a _____ beam

A

fan-shaped

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10
Q

how many detector arrays are in MDCT

A

4

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11
Q

describe the CT basis image capture and how many images are captures

A
  • two basis image capture sequences as the machine rotates counterclockwise
  • scans routinely capture in the range of 100-600 basis images per rotational scan
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12
Q

how does 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 for a given voxel
  • numerical value is assigned a gray scaled value for the part voxel
  • spatial and numerical information is used by imaging software to construct images
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13
Q

what planes of images does MDCT construct

A

coronal
- axial
- sagittal

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14
Q

human eye can discriminate up to _____ shades of gray

A

40

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15
Q

monitors show up to ____ shades of gray

A

256

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16
Q

most CT data have _____ shades of gray

A

4096

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17
Q

a 14 bit system has _____ shades of gray

A

17,024

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18
Q

what units are used for density in MDCT

A

hounsfield units

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19
Q

hounsfield units do not translate to CBCT because of variations in:

A
  • FOV
  • exposure
  • position in scanner
  • size of object
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20
Q

the narrower window width produced images with ____ contrast

A

high

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21
Q

a narrow window with varying window levels selectively windows:

A

hard and soft tissue

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22
Q

where is the window level number

A

at the center of the window

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23
Q

what are the disadvantages of CT

A
  • high dose of radiation
  • expensive and not as readily available as conventional imaging
  • sensitive to artifacts from metallic restorations and patient movement
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24
Q

what is the dose for head MDCT

A

960-1500

25
Q

one of the most important advantages MRI has is:

A

the ability to separate tissues with extracellular water from cellular tissues with intracellular water

26
Q

what are the components of MRI

A
  • magnets
  • resonant energy
  • imaging
27
Q

what are the MRI experiences for the patient

A
  • confined space
  • clanging noise
  • mild vibration and movement
28
Q

What does MRI target in cells

A
  • uses the resonance property found in some of the nuclei present in the human body
  • the hydrogen nucleus is of interest due to its large presence in water and body molecules
  • only atoms with an odd number of protons and/or neutrons in the nucleus have the mangetic properties required
29
Q

magnetic moments of MR active nuclei point in____ so they _____

A

random directions; produce no overall magnetic effect

30
Q

what is alignment in magnetic moments

A

magnetic moments line up with the magnetic field flux lines

31
Q

what is the contrast between soft tissues in MRI-

A
  • proton density
  • T1 relaxation time
  • T2 relaxation time
  • flow
32
Q

what are T1 weighted images

A
  • “fat images”
  • the surrounding fat produces the image contrast
33
Q

what are T2 weighted images

A

-“water images”
- normal or abnormal location of free water can be evaluated

34
Q

what are the advantages of the MRI

A
  • no ionizing radiation
  • best soft tissue imaging
35
Q

what are the disadvantages of MRI

A
  • sensitive to motion artifacts
  • expensive financial and temporal demands
  • claustrophobia
  • cost
  • availability
  • time to image
  • claustrophobic patients
36
Q

what are the absolute contraindications for MRI

A
  • imbedded ferrous metals
  • cardiac pacemakers- not always
  • cerebral aneurysm clips
  • cochlear implants
  • intra ocular metallic foreign bodies
37
Q

what is the best modality to study soft tissue disease

A

MRI

38
Q

what are the most common imaging sequences to evaluate change in soft tissue structures

A

T1 and T2

39
Q

what are the positive contrast examinations

A
  • arthrography
  • sialography
  • urography
  • pyelography
  • barium series
40
Q

what is arthrography used for

A

synovial spaces

41
Q

what is done in a sialogram

A

infusion of a radiopaque dye into a salivary glands ductal pattern to evaluate the fill pattern

42
Q

what is the sialogram used for in dentisry and why

A

evaluation of the parotid and submandibular glands because these glands have a primary duct amendable for gland infusion

43
Q

why cant you do a sialogram on the sunlingual gland

A

it lacks a primary duct, it has multiple ducts excreting into the floor of the mouth so its not suitable

44
Q

describe the nuclear medicine bone scan

A
  • 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
Q

what are the advantages of nuclear medicine bone scan

A

radioactive isotope concentrates in areas of rapid bone turnover and gives positive response with 10% increase in osteoblastic activity

46
Q

what are the disadvantages of nuclear medicine bone scan

A
  • expensive and invasive
  • morphologic changes not imaged
  • findings not specific to any disease process
47
Q

what does PET -CT

A

positron emission tomography - computer tomography

48
Q

combination of PET and CT is referred to:

A

as hybrid or fusion imaging

49
Q

PET CT is superior to:

A

plain nuclear medicine alone

50
Q

what is the PET CT useful for

A
  • location of a tumor
  • followup of chemotherapy or surgery
  • staging dementia, evaluate stroke
51
Q

describe PET-CT

A
  • fluorine-18 is a positron emitting radioactive isotope that is used with glucose analogue for quantitative imaging
  • CT is fused or co-registered with the PET scna to aid in interpretation
52
Q

Describe FDG uptake

A

increased FDG uptake is evident as increased brightness in left condyle laterally and superiorly. comparison of left and right condyles joints illustrates difference in FDG uptake

53
Q

what are the advantages and disadvantages of PET scan

A

-A: allows functional study of a metabolic process. provides a visual image that corresponds with patient anatomy
-D: higher dosimetry, high finances, slow imaging;not capable for time sequences greater than 30 seconds

54
Q

what does ultrasound use and is it associated with carcinogenesis

A

uses non ionizing sound waves and has not been associated with carcinogenesis

55
Q

ultrasound is _____ expensive to conduct than CT or MRI

A

less

56
Q

ultrasound imaging is useful for:

A

the evaluation of physiology as well as anatomy

57
Q

how does ultrasound work

A

sends ultrasound pulses into tissue and then receives echoes back with spatial and contrast information on a 2D grayscale image

58
Q
A

Radiographic Interpretation (13 decks)

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