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CMI 360 > Test 2 > Flashcards

Test 2 Flashcards

1
Q

What is data acquisition

A

method of how patient is scanned to obtain data for image reconstruction

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2
Q

What factors affect data acquisition

A

beam geometry
components

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3
Q

size, shape, and motion of incident x-ray beam
A. Beam geometry
B. Components
C. Single slice

A

A. beam geometry

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4
Q

what is a component fact for CT scanning

A

physical devices that shape and define the beam, measure transmission through patient, converts into digital data

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5
Q

what are the types of CT image acquisition

A

single slice CT (conventional)
multi-slice CT (recent)
spiral scan CT (cutting edge)

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6
Q

scanner moves along x-ray tube in straight line across patient’s body
A. Multi-slice
B. Spiral scan
C. Single Slice

A

C. single slice

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7
Q

creates single 3D slice from x-ray tube getting multiple slices at a time
A. Multi-slice
B. Spiral scan
C. Single Slice

A

A. multi-slice

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8
Q

array of multiple detectors used to improve image resolution and reduce dose
A. Multi-slice
B. Spiral scan
C. Single Slice

A

B. spiral scan

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9
Q

Why do we use multislice detectors?

A

reduce number of elements needed for thicker slices
reduce dead space/gap between elements

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10
Q

what is pitch

A

table movement per rotation divided by slice thickness - determined by collimation
aka. how far apart helical spiral gaps are

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11
Q

pitch = 1
A. Overlapping spiral
B. Contiguous spiral
C. Extended spiral

A

B

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12
Q

pitch > 1
A. Overlapping spiral
B. Contiguous spiral
C. Extended spiral

A

C

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13
Q

pitch < 1
A. Overlapping spiral
B. Contiguous spiral
C. Extended spiral

A

A

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14
Q

if pitch increases = gap _____

A

increases

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15
Q

what has higher radiation dose
A. Overlapping spiral
B. Contiguous spiral
C. Extended spiral

A

A

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16
Q

pitch ratio equation

A

pitch ration = mm traveled during 1 revolution / slice thickness

17
Q

patient dose is _____ proportional to pitch

A

inversely

18
Q

if pitch increases = dose _____

A

decreases

19
Q

what is used to reconstruct missing data

A

interpolation

20
Q

what is interpolation

A

computation of unknown value using known values on either side

21
Q

how does interpolation work?

A
  • calculates planar data set from volume data set
  • reconstructs image similar to conventional CT
22
Q

Advantages of helical CT (10)

A
  1. complete organs scanned in short time
  2. short scan times
  3. gapless scanning since volume is scanned
  4. reduced motion artifact
  5. slices can be obtained for any position within volume
  6. no slice shifting due to respiration
  7. contrast given times are shorter and smaller amounts needed
  8. contrast enhancement more uniform, lesion detection enhanced
  9. greater multi-planar reconstruction accuracy
  10. multiplanar imaging in fluoroscopy, angiography, endoscopy
23
Q

Limitations of CT

A
  1. additional x-ray tube demands - tungsten expensive
  2. interpolation removes streak artifacts but blurry images more likely to appear in low contrast regions of soft tissue = partial volume imaging
24
Q

what is considered a complementary view

A

views 180 degrees across from each other - corkscrew

25
Q

pro vs cons of MSCT (multislice CT)

A

pro:
reduced scan time full body 30 sec
very good spatial resolution
easier to reconstruct 3D views
con:
powerful computing power needed
longer processing time
potential for increased patient dose

26
Q

what are the differences between CT scanner generations

A

scanning geometry
scanning motion
x-ray sources
detectors

27
Q

why was the fifth generation developed for?

A

cardiac tomographic imaging

28
Q

what type of scanner does a fifth generation CT use?

A

electron beam scanner

29
Q

why would an electron beam scanner be used?

A

produces fast frame rate CT movies of heart beating

30
Q

how is spiral-helical CT made possible?

A

disk and cylinder –> design

31
Q

what is interscan delay time (ISD)

A

time to scan, collect data, and index the table and patient to next scanning position

32
Q

Limitations of conventional CT scanning

A
  1. longer exam times for table indexing a inter-breath scanning
  2. inaccurate 3D image creation –> missed anatomy from inconsistent levels of respiration
  3. only a few slices can be scanned when max contrast enhancement technique is possible
33
Q

scanning time of patients
A. 5 mm/sec
B. 10 mm/sec
C. 15 mm/sec
D. 20 mm/sec

A

B

34
Q

Data acquisition problems with conventional CT

A
  1. data collect in nonplanar geometry = different regions of volume and not through particular plane
  2. no defined slice = localization of voxels within a planar slice is difficult
  3. increased effective slice thickness
35
Q
A

CMI 360 (2 decks)

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