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
2
Q
what are the advanced imaging modalities that use CT
A
- MDCT
- CBCT
- MRI
- PET-CT
- ultrasound
3
Q
what are the other names for MDCT
A
- multidetector helical CT
- multislice CT
- multirow CT
4
Q
what does MDCT stand for
A
multi detector computed tomography
5
Q
what are the older terms for MDCT
A
- CAT
6
Q
who developed CT imaging
A
Godfrey Hounsfield and Allan Cormack
7
Q
what did Dr. Ledley do
A
developed patent for the first whole body CT scanner for larger patient openings
8
Q
what does the MDCT image
A
greater hard tissue object sensitivity than conventional XR systems
- demonstrates soft tissues
9
Q
MDCT technique uses a _____ beam
A
fan-shaped
10
Q
how many detector arrays are in MDCT
A
4
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
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
13
Q
what planes of images does MDCT construct
A
coronal
- axial
- sagittal
14
Q
human eye can discriminate up to _____ shades of gray
A
40
15
Q
monitors show up to ____ shades of gray
A
256
16
Q
most CT data have _____ shades of gray
A
4096
17
Q
a 14 bit system has _____ shades of gray
A
17,024
18
Q
what units are used for density in MDCT
A
hounsfield units
19
Q
hounsfield units do not translate to CBCT because of variations in:
A
- FOV
- exposure
- position in scanner
- size of object
20
Q
the narrower window width produced images with ____ contrast
A
high
21
Q
a narrow window with varying window levels selectively windows:
A
hard and soft tissue
22
Q
where is the window level number
A
at the center of the window
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
24
Q
what is the dose for head MDCT
A
960-1500
25
one of the most important advantages MRI has is:
the ability to separate tissues with extracellular water from cellular tissues with intracellular water
26
what are the components of MRI
- magnets
- resonant energy
- imaging
27
what are the MRI experiences for the patient
- confined space
- clanging noise
- mild vibration and movement
28
What does MRI target in cells
- 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
magnetic moments of MR active nuclei point in____ so they _____
random directions; produce no overall magnetic effect
30
what is alignment in magnetic moments
magnetic moments line up with the magnetic field flux lines
31
what is the contrast between soft tissues in MRI-
- proton density
- T1 relaxation time
- T2 relaxation time
- flow
32
what are T1 weighted images
- "fat images"
- the surrounding fat produces the image contrast
33
what are T2 weighted images
-"water images"
- normal or abnormal location of free water can be evaluated
34
what are the advantages of the MRI
- no ionizing radiation
- best soft tissue imaging
35
what are the disadvantages of MRI
- sensitive to motion artifacts
- expensive financial and temporal demands
- claustrophobia
- cost
- availability
- time to image
- claustrophobic patients
36
what are the absolute contraindications for MRI
- imbedded ferrous metals
- cardiac pacemakers- not always
- cerebral aneurysm clips
- cochlear implants
- intra ocular metallic foreign bodies
37
what is the best modality to study soft tissue disease
MRI
38
what are the most common imaging sequences to evaluate change in soft tissue structures
T1 and T2
39
what are the positive contrast examinations
- arthrography
- sialography
- urography
- pyelography
- barium series
40
what is arthrography used for
synovial spaces
41
what is done in a sialogram
infusion of a radiopaque dye into a salivary glands ductal pattern to evaluate the fill pattern
42
what is the sialogram used for in dentisry and why
evaluation of the parotid and submandibular glands because these glands have a primary duct amendable for gland infusion
43
why cant you do a sialogram on the sunlingual gland
it lacks a primary duct, it has multiple ducts excreting into the floor of the mouth so its not suitable
44
describe the 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 nuclear medicine bone scan
radioactive isotope concentrates in areas of rapid bone turnover and gives positive response with 10% increase in osteoblastic activity
46
what are the disadvantages of nuclear medicine bone scan
- expensive and invasive
- morphologic changes not imaged
- findings not specific to any disease process
47
what does PET -CT
positron emission tomography - computer tomography
48
combination of PET and CT is referred to:
as hybrid or fusion imaging
49
PET CT is superior to:
plain nuclear medicine alone
50
what is the PET CT useful for
- location of a tumor
- followup of chemotherapy or surgery
- staging dementia, evaluate stroke
51
describe PET-CT
- 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
Describe FDG uptake
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
what are the advantages and disadvantages of PET scan
-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
what does ultrasound use and is it associated with carcinogenesis
uses non ionizing sound waves and has not been associated with carcinogenesis
55
ultrasound is _____ expensive to conduct than CT or MRI
less
56
ultrasound imaging is useful for:
the evaluation of physiology as well as anatomy
57
how does ultrasound work
sends ultrasound pulses into tissue and then receives echoes back with spatial and contrast information on a 2D grayscale image
58
