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CT Scan With Field Exposure > Part II > Flashcards

Part II Flashcards

1
Q

1st Generation CT Scanner

A

Method: Rectilinear Pencil Beam Scanning
Acquisition Geometry: Parallel Pencil Beam Geometry
Principle: Translate-Rotate Principle
Rotation degree: 1 degree to next angular posi
Time: 4.5 - 5.5 min data acquisition
[EMI MARK I - made by Hounsfield]

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2
Q

1st Generation CT Scanner [disadv]

A

-CT techs manually move to rotate - tedious
-too long
-limited to head scanning
-not allowed for chest,abdomen
-motion artifact

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3
Q

2nd Generation CT Scanner

A

Method: Rectilinear Multiple Pencil Beam Scanning
Acquisition Geometry: Fan Beam Geometry
Principle: Translate-Rotate Principle
Rotation: 6 degrees increment
Time: 20 seconds
[utilized multiple beams]

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4
Q

2nd Generation CT Scanner [adv]

A

-over 1st gen: faster scanning time
-multiple pencil beam = more pt throughput = more slices

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5
Q

3rd Generation CT Scanner

A

Method: Continuously Rotating Fan Beam Scanning
Acquisition Geometry: Fan Beam Geometry
Principle: Continuous Principle
Rotation: Complete Rotation of Tube & Detectors
Time: 2 seconds per rotation; scan time 5 seconds or less
[utilize slip ring] [arc centric detector cells]

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6
Q

3rd Generation CT Scanner [adv/disadv]

A

-adv. fast
-disadv. cannot do cardiac CT scan bc of cardiac motion

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7
Q

4th Generation CT Scanner

A

Acquisition Geometry: a rotating fan beam within a stationary ring of detectors and a complete rotation of the x-ray tube
Principle: complete rotation - no translation
Rotation: multiple detectors - stationary and X-ray tube rotating

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8
Q

4th Generation CT Scanner [adv]

A

Adv.
-multiple detectors - stationary and x-ray tube rotating
-more utilized
-can do cardiac but not optimal

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9
Q

5th Generation CT Scanner

A

-high speed CT scanning
-based on special configurations intended to facilitate fast scanning
-does not rotate
-continuous principle

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10
Q

Two types of 5th Generation CT Scanner

A
  1. EBCT - External Beam CT
  2. DSR - Dynamic Spatial Reconstructor
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11
Q

EXPLAIN electron gun

A

ELECTRON GUN (like filament → DEFLECT electron to TARGET TUNGSTEN RING (when hit produce x-ray) → electron PROJECTED UP to patient → ABSORBED BY DETECTOR

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12
Q

6th Generation CT Scanner

A

Dual Scanner Source CT (DSCT) Scanner
-multiple x-ray rubes and detectors
-intended for moving structures like heart

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13
Q

6th Generation CT Scanner [adv]

A

-great recorded artifact with less motion artifact
-2 x-ray used for cardiac CT

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14
Q

7th Generation CT Scanner

A

Flat-Panel CT Scanners

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15
Q

DIFFERENTIATE the IMAGE QUALITY of CONVENTIONAL R and CT IMAGES

A

CONVENTIONAL R.
1. Spatial R
2. Contrast R
3. Noise

CT IMAGES
1. Spatial R.
2. Contrast R.
3. Noise
4. Linearity
5. Uniformity

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16
Q

Ability to image small objects that have a subject contrast
Degree of blur or ability to see difference b/w two objects that are close together

A

Spatial R.

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17
Q

Spatial R. Is expressed in: [..]

A

Line pairs/mm (lp/mm)

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18
Q

A high-contrast line that is separated by an interspace of equal width

A

Line pair

19
Q

SR for a CT image is limited to the [..]

A

Pixel size

20
Q

[..] and [..] powerful way to affect SR

A

Image reconstruction and post-processing

21
Q

Scan Parameters affecting SR [Sexy Dudes Measure Right Ds]

A
  1. Section/Slice Thickness
  2. Display FOV
  3. Matrix
  4. Reconstruction Slice Thickness
  5. Detector Aperture Width
22
Q

-mathematical expression for measuring resolution
-the ratio of the image to the object as a function of SF
-used to describe CT spatial res.

A

Modulation Transfer Function (MTF)

23
Q

-determine fidelity of images

A

Modulation Transfer Function (MTF)

24
Q

MTF value : faithfully represents the object

A

1

25
Q

MTF value : image in blank, no info

A

0

26
Q

MTF value : intermediate levels of fidelity

A

Intermediate

27
Q

Fidelity with which the anatomy is represented on the radiograph

A

Image quality

28
Q

Accuracy of actual object presented on a radiograph

A

Fidelity

29
Q

Accuracy of actual image presented in image (there will always be magnification but should be close)

A

Fidelity

30
Q

Collection of pixels (picture element)
Always square in CT

A

Matrix

31
Q

3d element

A

Voxel

32
Q

Pixel size formula

A

DFOV/matrix

33
Q

CT PROCESS

A

IMAGE AQUI → IMAGE RECONSTRUCTION →DISPLAY → ARCHIVING

34
Q

Ability to differentiate b/w small structures in different density within the image
Tissues with density differences of less than 0.5 % can be distinguished

A

CR

35
Q

Scan Parameters Affecting CR [She ReImagined X-ray Size DetectorS]

A
  1. SLICE THICKNESS
  2. RECONSTRUCTION ALGORITHM
  3. IMAGE DISPLAY (WINDOW WIDTH)
  4. X-RAY BEAM ENERGY
  5. SIZE OF PT
  6. DETECTOR SENSITIVITY
36
Q

[..] determine the slice thickness

A

Collimator

37
Q

Better CR needs [..] collimator; Wider can cause [..]

A

Smaller/narrow
Scatter radiation

38
Q

Removal of low energy by filter

A

Beam hardening [x-ray beam energy]

39
Q

-importance for cardiac imaging
-the ability of CT system to freeze any motion of a scanned object
-shortest amount of time needed to acquire a complete data set

A

Temporal R

40
Q

Factors that improve TR

A
  1. Multi detector - continuous absorb and erase
  2. Tube/gantry rotation time - faster aquisition
  3. Dual-Source CT - 6th generation
41
Q

Most common cause of noise in CT

A

Quantum noise

42
Q

Primarily affects CR

A

Noise

43
Q

Scan Parameters that influence noise

A
  1. Matrix size
  2. Slice thickness
  3. Reconstruction algorithms
  4. Scattered radiation and patient size

CT Scan With Field Exposure (5 decks)

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