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CT Theory > Notes From Week 4 > Flashcards

Notes From Week 4 Flashcards

1
Q

Couch aka table

A 
▪️movements
-vertical and horizontal
▪️carbon fiber properties
⬇️ absorption
⬆️strength
⬇️vibration
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2
Q

Mechanical injection systems include:

A
  • consistency
  • programming
  • precise flow rates and volumes
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3
Q

Gantry

A

Houses the imaging components of the scanner

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4
Q

Data acquisition system (DAS)

A

Measures the number of photons that strike the detector, converts the information to a digital signal, and sends the signal to the computer 💻

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5
Q

X-ray tube

A

▪️Considerations for heat dissipation

  • high anode rotation speeds
  • larger and thicker anodes
  • metal envelops
  • dual focal spots
  • power supplied by high frequency generator which enables ⬇️ heat loading
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6
Q

Detectors cooperate more consistently with a ____ beam

A

Homogenous

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7
Q

What does beam filtration do?

A
  • beam uniformity

- filters out lower energy photons

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8
Q

Added/inherent filtration

A
  • shape matches the beam divergence and the patient shape
  • bow tie
  • using a filter makes it easier for the detector to figure out what’s going on
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9
Q

True or false: scanners require beam filtration

A

True

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10
Q

What are the two types of source collimation?

A
  1. Pre

2. Post

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11
Q

What does collimation affect?

A

⬇️patient dose

⬇️scatter

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12
Q

What does collimation control?

A
  • slice thickness by shaping the x-ray beam

- voxel length

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13
Q

Detectors

A
  • measure exit radiation

- ultimately converts the measurements into an electrical signal proportional to the radiation intensity

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14
Q

True or false: detector spacing affects scatter radiation

A 
True!
-spacing bars: arc
-distance measurements: middle to middle
-size: spatial resolution 
▪️want small spacing bars
▪️want detectors to be as close as possible
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15
Q

want smaller sized detectors for better _____

A

Spatial resolution

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16
Q

Smaller detector = ⬆️ what?

A

Patient dose

-because it collects less data so need to ⬆️ dose

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17
Q

Detector characteristics

A
  1. high efficiency (QDE)- photons must be captured, absorbed, and converted
    - influenced by detector: size, spacing and material
    - material: want high atomic #, high density, and increased thickness, if thickness is increased it is more likely to absorb
  2. High stability- detector response to radiation must be consistent
    - determined by: calibration requirements
  3. Fast response time- no lag
  4. Wide dynamic range- the variety of signals that can be measured by the detector
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18
Q

QDE

A

Detector efficiency

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19
Q

The wider the detector surface area the ____ the efficiency

A

⬆️ efficiency

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20
Q

Spacing contributes ____ to the image, x-rays hit it and nothing happens, so want spacing ____

A

Nothing to the image, want spacing closer together

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21
Q

Types of detectors

A
  • ionization (xenon gas) ionization chamber

- solid state/scintillation

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22
Q

Ionization (xenon gas) ionization chamber

A

-not used in MDCT, MSCT
-1 step energy conversion
-converts directly to electrical energy
-used only in older models
Advantages:
-cheaper
-stable
-response time
Disadvantages:
-needs to be under pressure
-needs alot of space
-aluminum casing (causes a loss of photons)

23
Q

Solid state/scintillation

A

-used in MDCT/MSCT
-2 step energy conversion
-x-ray energy converts to light energy converts to electrical energy
Advantages:
-⬆️absorption efficiency (94-100%)
-⬆️response time
Disadvantages:
-afterglow
-temperature and moisture sensitive
-spectral matching

24
Q

Detector arrays

A

▪️Single detector row systems
-wide “Z” axis
-collimation controls slice thickness (largest allowable is less then the detector width)
-360 degree rotation = a single slice
▪️Multidetector row systems (better)
-collimation and number of detectors determine: number of slices and slice thickness, ⬇️slice thickness
-2 configurations

25
Q

MSCT detector configurations

A
  1. Matrix array
    - aka fixed array, or uniform array
    - isotopic (dimensions are the same)
    - goal is to improve spatial resolution
    - slice thickness is symmetrical
  2. Adaptive array
    - aka non-uniform array, or hybrid array
    - anisotropic (dimensions are not the same, different shapes and sizes)
    - slice thickness is variable
    • thinner in the center, wider at the periphery
26
Q

Multislice detector advantages

A
  • more slices are obtained in a single 360 degree rotation
  • increased volume coverage speed
    • decreased time for data collection
  • 4 -> 320 slices per rotation
  • ⬆️anatomical coverage (less chance of motion)
  • design enables slice thickness manipulation
    • partial volume effect
    • retrospective slice thickness
  • ⬇️ breath holds
27
Q

Other technical applications of CT

A 
All about the heart rate
▪️cardiac imaging
-beta blockers: used to help reduce heart rate
-ECG: monitors heart rate
-Patients not allowed to have caffeine prior to exams because heart would be moving too much
▪️CT fluoro 
-drainages and biopsies
▪️CT angiography
-contrast: PE's and stroke
▪️screening
-virtual colonoscopies 
▪️CT simulation vs conventional CT scanners
28
Q

5th generation

A
  • fan beam geometry
  • stationary-stationary
  • millisecond scan time
  • used for cardiac imaging in the 1980s
  • ⬇️ spatial resolution
29
Q

6th generation (where CT scanners are heading to or becoming)

A
  • dual source CT
  • two tubes, detectors and DAS
  • fan beam geometry
  • short scan times designed for cardiac imaging
  • ⬆️ spatial resolution
  • can use two kVp techniques
30
Q

1st generation

A

▪️Motion of system: translate-rotate (180 degree rotation)
-(translate means move in a straight line)
▪️Shape or geometry of the beam: narrow pencil beam
▪️Path of tube travel: 180 degree rotation
▪️Detectors: no array (1-2 max)
▪️Scan time: 4.5-5.5 min total

31
Q

2nd generation

A

▪️Motion of system: translate-rotate
▪️Shape or geometry of the beam: narrow fan beam (multiple pencil beam scanning)
▪️Path of tube travel: 180 degree rotation
▪️Detectors: linear detector array (max 30)
▪️Scan time: 20s-3.5 min total

32
Q

3rd generation

A

▪️Motion of system: continuously rotating fan beam (rotate-rotate)
▪️shape or geometry of fan beam: wide fan beam geometry
▪️Path of tube travel: 360 degree rotation (cables eliminated now using slip rings)
▪️Detectors: curved detector array (30-40 degree arc)
Scan time: a few seconds total

33
Q

4th generation

A

▪️Motion of system: continuously rotating fan beam (rotate-fixed)
▪️Shape or geometry of the beam: wide fan beam geometry
▪️Path of tube travel: 360 degree rotation (tube rotates but detectors are fixed)
▪️Detectors: circular single row detector array (4800 detectors, ⬆️ scatter)
▪️Scan time: very short

34
Q

What does HIS stand for?

A

Hospital information system

35
Q

What does CIS stand for?

A

Clinical information system

36
Q

Which of the following is not part of the HIS/CIS?
A) patient demographics
B) financial data
C) patient locations within the hospital or clinic
D) storing reports

A

D) storing reports!!

37
Q 
What is a primary categorization for this type of information? (Storing reports)
A) radiological
D) diagnostic
C) administrative 
D) technical
A

C) administrative

38
Q

The radiology information system is also known as?

A

RIS

39
Q

What should the radiology information system have?
A) two way communication with the HIS/CIS
B) small data sets
C) only soft copy media documentation
D) patient demographic data conversion

A

A) two way communication with the HIS/CIS

40
Q 
What is fundamental to the success of a PACS?
A) image display
B) image storage
C) the network
D) workstation
A

C) the network

41
Q

Why is the network so important?
A) regulates the movement of data and directly affects all users
B) it operates independently from the PACS
C) digitizes information for easier access and distribution
D) converts information into a lossy data format

A

A) regulates the movement of data and directly affects all users

42
Q 
Which of the following is not a geometric arrangement of a computer system?
A) bus
B) star
C) diamond
D) ring
A

C) diamond

43
Q

What is DICOM?
A) a lossless imaging scheme from compression
B) a redundancy minimizing system failure
C) requires less bandwidth increasing transmission efficiency
D) a recognized standard for electronic images across vendors

A

D) a recognized standard for electronic images across vendors

44
Q

What is HL7?

A

Universal standards for clinical and administrative data

45
Q

Which type of image compression does not compromise diagnostic quality?
A) lossy
B) lossless

A

B) lossless

46
Q

A direct digital DICOM capture allows:
A) full spatial resolution and windowing capabilities
B) frame grabbing
C) a protocol that defines a common set of signals
D) decreased network bandwidth

A

A) full spatial resolution and windowing capabilities

47
Q 
Which of the following is a disadvantage to LCD and plasma display technologies?
A) lifespan
B) space
C) cost
D) luminance
A

C) cost

48
Q 
What is a vital function of any PACS?
A) encrypting sensitive data
B) increased image spatial resolution 
C) accurate and fast image distribution
D) increased bandwidth
A

C) accurate and fast image distribution

49
Q

The process of saving image data from the originating modality to an electronic medium is called?

A

Archiving

50
Q

Which type of data is stored due to bandwidth limitations?

A

Image data

51
Q

What is designed to work together and appear to the computer as a single storage device?

A

RAID

52
Q

Blue-ray discs, DVD’s, and CD’s are examples of what type of storage?

A

Optical

53
Q

What is the purpose of a virtual private network?

A

Provides secure transmission of information

54
Q

The degree to which a table can move horizontally is called _____. And it will determine the extent a patient can be scanned without repositioning

A

Scannable range

CT Theory (11 decks)

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