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CTOMO > HISTORY > Flashcards

HISTORY Flashcards

1
Q
  • Hounsfield build a who,e body ct scanner
A

1975

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2
Q

Hounsfield and Cormack were bith awarded with nibel prize in Physiology and Medicine; Two Popular Names of Computed Tomography

A

1979

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3
Q

Two Popular Names of Computed Tomography

A
  • Computer Axial Tomography (CAT)
  • Computerized Tomography (CT scan)
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4
Q

Electrical Musical Instrumentation (EMI) CT SCANNER

A

1979

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5
Q

Introduced by Sir Godfrey Hounsfield
* Exclusive for neurologic examinations only
* Worked by a process called translation or rotation
* Patient’s head was recessed via a rubber membrane into a water filled box

A

1971

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6
Q

Features: 1ST GEN

A
  1. Scanning Motion or Tube Detector
    Movements: Translate- Rotate
  2. Detectors: Single
  3. Xray source: Single
  4. Xray beam: narrow pencil shaped xray beam
  5. Duration of scan: 25-30 mins; 3-5 mins to scan one slice; 1.5 min to reconstruct
  6. Scan mode: step and shoot scanning
  7. Power supply: straighten twisted system cables
  8. Number of slice per rotation: 1
  9. Motion of gantry: linear and rotary
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7
Q

is made up of Sodium lodide (Nal): (1ST GEN)

A

Detector

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8
Q

180 translations with __rotation in linear motion (1ST GEN)

A

1 degree

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9
Q

Total Rotary motion encompassed a ___ (1ST GEN)

A

180 degrees semicircle

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10
Q

___ passed through the center of the patient’s head (1ST GEN)

A

Axis of rotation

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11
Q

X-ray beam is “__” throughout the linear movement and “__” during rotary movements

A

ON
OFF

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12
Q

ADVANTAGE
(1ST GEN)

A
  • Low scattered radiation
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13
Q

DISADVANTAGE (1ST GEN)

A
  • Time Consuming
  • Slow Reconstruction time
  • Low Anatomic in an image
  • Poor Spatial Resolution
  • Nal is hygroscopic (absorbs moisture from air)
  • Complicated Patient Positioning
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14
Q

was an improvement in efficiency from its predecessor, while still utilizing similar general concepts.

A

second-generation CT

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15
Q

The ____ is still used with an addition of multiple small fan beam to allow for a
more optimized and better coverage when compared to just one detector. (2ND GEN)

A

translate and rotate acquisition

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16
Q

second-generation CT was first introduced, developed, and installed by ___ at Georgetown University in February 1974.

A

Ledley et al.

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17
Q

machine utilizes 30 photomultiplier tubes as detectors and can complete a scan in only 9 translate/rotate cycle.

A

2ND GEN CT

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18
Q

The device introduced many features that are now standard in modern CT____

A

(table movement through the gantry, gantry angulation, and a laser indicator to position slices) as well as a Fourier-based reconstruction.

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19
Q

Second generation CT scanner

A

Narrow fan beam (10°)
Multiple detectors
Multiple angle acquisition at each position
Larger angle rotate Translate still required
Slow
- 20s per slice

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20
Q

Pros: (2ND GEN)

A
  • reducing scan time by 3-fold
  • The trunk could be imaged
  • By adding detectors angularly displaced , several projections could be obtained in a single translation
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21
Q

CONS:(2ND GEN)

A
  • Further speed improvements were hindered by the mechanical complexity of the rotate-translate geometry
  • Translations and rotations have to be performed quickly and precisely while moving heavy (lead-shielded) x-ray tubes and the associated gantries and electronics- all while minimizing vibrations, which would cause artifacts.
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22
Q

3 detectors each displaced by ___ (EARLY VERSION 2ND GEN)

A

1°

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23
Q

Since each detector viewed the x-ray tube at a different angle , a single translation produced ___ (2ND GEN, EARLY VERSION)

A

3 projections

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24
Q

The system could rotate 3° to the next projection rather than 1° (EARLY VERSION, 2ND GEN)

A

2ND GEN CT

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25
Q

– make only 60 translations instead of 180 to acquire a complete section (EARLY VERSION)

A

2ND GEN CT

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26
Q

Scan times were reduced X 3 (EARLY VERSION)

A

2ND GEN CT

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27
Q

up to 53 detectors

A

2ND GEN CT, LATER VERSION

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28
Q

– Fast enough (tens of seconds)to permit acquisition during a single breath hold – First designs to permit scans of the trunk
– Because rotating anode tubes could not

A

2ND GEN CT, LATER VERSION

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29
Q

an electrical engineer at EMI (Electric and Musical Industries Ltd).

A

Sir Godfrey Hounsfield

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30
Q

are first introduced in 1975, in this generation marked the breakthrough of modern ct scan making it one of the successful generations. Thus making it as a bedrock of contemporary era of diagnostic imaging .

A

3RD GEN CT

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31
Q

It uses fan beam shaped of 40 – 60 degrees which covers the entire patient (all anatomy) acquiring all the data within each view

A

3RD GEN CT

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32
Q

It uses a an acquisition mode of “rotate-rotate” both the x-ray source and x-ray detector are rotating together. Using a rigid ring the x-ray tube and detector can be mounted such that they rotate around the patient. Larger array of detectors (more than 800) were used. Scanning time was reduced to 2 seconds.

A

3RD GEN CT

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33
Q

it is capable of generating high quality contrast images while delivering lower doses of ionizing radiation than their predecessors.

A

3RD GEN CT

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34
Q

What is exactly “rotate-rotate “ acquisition mode?

A
  1. The x-ray beam hits a row of detectors wide enough to image the whole slice
  2. The two then rotate together to image a different angle
  3. This is repeated until a single slice is scanned then the array is moved to a different slice (axial scanning).
  4. Alternatively, the detector array is continually moved down the patient as it rotates (spiral scanning This is the most commonly used method today and takes about 0.3 seconds to image a single slice
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35
Q

It requires extremely high detector stability and matching of the detector response

A

3RD GEN CT

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36
Q

If one of the detectors is out of calibration on a third-generation (rotating x-ray tube and detector assembly) scanner, the detector will give a consistently erroneous reading at each angular position, resulting in a circular artifact.

A

RING ARTIFACTS

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37
Q

CT scan image of a water-filled phantom shows ring artifacts

A

3RD GEN CT

38
Q

A scanner with solid-state detectors, where all the detectors are seperate gas detectors, in which more susceptible to ring artifacts than a scanner with gas detectors, in which the detector array consits of a single xenon- filled chamber subdivided by electrodes

A

3RD GEN

39
Q

were inherently stable and well matched because factor affecting detector response were either uniform for the entire array or constant over chamber.

A

XENON

40
Q

Xenon were eventually replaced by solid state detectors

A

3RD GEN CT

41
Q

Detectors:3RD GEN CT

A

multiple, originally 288; newer ones use over 1000 arranged in an arc

42
Q

Type of beam::3RD GEN CT

A

fan-shaped x-ray beam

43
Q

Helical (“spiral”) image acquisition due to Slip-ring technology. Dual energy CT scanning

A

3RD GEN CT

44
Q

Number of slice per rotation:3RD GEN CT

A

multiple due the parallel detectors array configuration, include x-ray detectors large enough to cover an entire organ in a single rotation.

45
Q

Duration of scan (average):3RD GEN CT

A

approximately 5 sec

46
Q

In 1976, 1 second scans were achieved with a design incorporating a large stationary ring of detectors, with the x-ray tube alone rotating around the patient.

A

4TH GENERATION CT SCAN

47
Q

In 4th Generation CT Scan, the X-ray tube has to move inside this detector. Since it is rotated continuously, very fast scan time is possible. It has inter scan delay times, since the X-ray tube had to return to its starting position

A

Rotary X-ray Source

48
Q

4th Generation Stationary array of detectors encircles the patient. These systems had fewer moving parts and needed not pass signal data across the moving gantry. It has a stationary ring of about 4,800 detectors

A

.Stationary Detector Ring

49
Q

INNOVATIONS (4TH GEN CT)

A
  1. SHORTER SCANNING TIME
    Only the x-ray generator and tube rotate at 360, thus shortening the scanning time even more
  2. REDUCE MOTION
    Since the procedure takes up for a short amount of time only, motion is reduced which resulted in reduction of complexity.
  3. ELIMINATE RING ARTIFACTS
    The primary purpose of the fourth-generation scanner is that it overcomes a specific third- generation artifact. A ring or arc artifact in a CT is a hardware related artifact that occurs due to a defective or miscalibrated detectors.
50
Q

LIMITATIONS(4TH GEN CT)

A
  1. HIGH COST
    The design principle, however, has currently been abandoned because of high system costs as a consequence of the large number of detector elements and other problems.
  2. LESS EFFICIENT
    In 4th generation CT scanners only small portion (about 30% to 40%) of a large array of detectors are exposed at any one time in operation.
  3. INEFFECTIVE SCATTER REJECTION
    Anti-scatter grids attached to stationary detectors would not remain focused to a moving X-ray source in operation, focused anti- scatter grids have not been used in fourth generation scanners
  4. HIGHER PATIENT DOSE
    The x-ray tube is closer to the patient, resulting
    in higher skin dose.
51
Q

Make images without rings

A

4th Gen 1976

52
Q

All Anatomy Rotate-Stationary 1 sec
Expensive, not good for scatter

A

4th Gen 1976

53
Q

Both the x-ray source material and the detector are stationary. In this sense this is a stationary-stationary design.

A

5th generation CT

54
Q
  • Three rings
  • Each ring makes connectivity to the X-ray generator, detector, and control signals.
A

SLIP-RING

55
Q

SLIP-RING

A

6TH GEN CT

56
Q

The X-ray tube can rotate faster (5 s/rot) and move more than 360 degrees.

A

6TH GEN CT

57
Q
  • Reconstruction is possible at any desired z-axis position.
A

6TH GEN CT

58
Q
  • Eliminatedinterscandelay.
A

6TH GEN CT

59
Q
  • Made helical CT possible.
A

6TH GEN CT

60
Q

ADVANTAGES: 6TH GEN CT

A

Shorter total scan time
Requires less contrast media Improve image resolution Decreased patient risk to contrast media reactions Eliminates overlap & missed areas
Pitch settings can be set to oversample sections of interest Improved diagnostic accuracy
Beneficial to patient comfort.
Large volume of tissue in a single breath hold.
Beneficial to department productivity
Superior MPR & 3D reformation

61
Q

DISADVANTAGES: 6TH GEN CT

A

Full 360° projection data is not acquired for each section. Characteristics
Sections are reconstructed to represent approximate acquisition of planar data.

62
Q

Applications 6TH GEN CT

A
  • CT Angiography
  • Radiation Therapy treatment planning
  • Imaging uncooperative patient
63
Q
  • Multislice CT
  • Multidetector Array (MDA)
  • Produces multiple slices in a single rotation.
  • The number of X-ray detected is 4 times higher.
A

7TH GENERATION

64
Q
  • Increases slice thickness
  • Reduced spatial resolution
A

Single Array

65
Q

Single Array

A

7TH GENERATION

66
Q
  • Slice thickness is determined by detector size not by the collimator.
A

Multiple Detector Array

67
Q

Multiple Detector Array

A

7TH GENERATION

68
Q

High - Speed CTScanner

A

5TH GEN

69
Q

Electron - Beam Scanner (EBC Use for cardiac only and
Has a dynamic spatial reconstruction ability.

A

5TH GEN

70
Q
  • HIGH SPECIALIZED AND HIGH SPEED
  • HIGH SPECIALIZED AND HIGH SPEED SCANNER
  • REOUIRE SCAN DATE IN MILLISECOND
A

5TH GEN

71
Q

was dedicated cardiac scanning.

A

The niche of 5th generation CT

72
Q

This method allows for very fast acquisitions and is ideal for cardiac scanning (with a temporal resolution of a given slice as low as 17ms).

A

5th generation CT

73
Q

these scanners did not have full volumetric coverage and the flux that could be delivered was more limited.

A

5th generation CT

74
Q

Both the x-ray source material and the detector are stationary.

A

5th generation CT

75
Q

The x-tube in this design is a scanning x-ray tube, where the electrons are steered magnetically (like in old TVs) rather than physically moving the x-ray tube.

A

5th generation CT

76
Q
  • Helical or Spiral CT
  • Volumetric Scanners
  • Continuous data acquisition scanning
  • Uninterrupted table movement
A

6TH GEN

77
Q
  • Willi Kalender
    German medical physicist
  • Kazuhiro Katada
    Professor, Department of radiology, Faculty of Medicine, Fujita Health University
A

6TH GEN

78
Q

is an electromechanical device that conducts electricity through rings & brushes across a rotating surface onto a fixed surface.

A

Slip-ring Technology

79
Q

Helical CT Scanners

A

6TH GEN

80
Q

Perform a scan in which the patient moves slowly through the gantry.

A

Slip-ring Scanners (6TH GEN)

81
Q

Patient is simultaneously transported at a constant speed through the gantry.
One breath-hold & obtain a volume of x-rayed tissue. Data are continuously acquired without pausing.

A

6TH

82
Q

Scans with CT technique recquired 15 to 30 minutes. but Helical CT scanner is faster.

A

6TH

83
Q

The x-ray beam from the CT traces a helical path.

A

6TH

84
Q
  • The tube is energized continuously.
A

SLIP-RING TECHNOLOGY

85
Q
  • 8 Slice (7TH)
A

2000

86
Q
  • 64 Slices (7TH)
A

MODERN

87
Q

Multislice CT * 4 slice (7TH)

A

1998

88
Q
  • 16 Slice (7TH)
A

2001

89
Q
  • 256 Slices (7TH)
A

Future Advanced

90
Q

ADVANTAGES(7TH)

A

Provides longer & faster z axis coverage Increased volume coverage/ unit time Reduces total examination time
Allows post-acquisition reconstruction Increases image resolution

91
Q
  • Artificial Intelligence (AI) * Detect acute neurologic occurrences within 1.2 seconds * Using 37,000 head CT exams * The process is 150 times faster.
A

THE FUTURE OF CT SCAN

CTOMO (2 decks)

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