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CT Scan > P1 > Flashcards

P1 Flashcards

1
Q

Is the process of creating a cross-sectional
tomographic plane of any part of the body.

A

CT-SCAN

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2
Q

The term “tomography” is derived from the Greek word “____”, meaning “____’’.

A

tomos, section

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3
Q
  • refers to the old scanners that is only capable of displaying Axial Scans
A

CAT scan

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4
Q
  • refers to the ability to define small objects.
A

Spatial Resolution

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5
Q
  • refers to the ability of the system to differentiate small objects with
    similar densities.
A

Low Contrast Resolution

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6
Q
  • refers to the speed on which the data can be acquired. Increase in temporal resolution can decrease/eliminate artifacts
A

Temporal Resolution

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7
Q

The mathematical principles of CT were first developed by ___ in ____.

A

Radon, 1917

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8
Q

CT-scan was first demonstrated by ___ on ___

A

Godfrey Houndsfield, 1970

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9
Q

developed the mathematics used to reconstruct images

A

Allan Cormak

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10
Q

Allan Cormak (developed the mathematics
used to reconstruct images) and Godfrey
Houndsfield received the nobel prize award
on ____

A

1982

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11
Q

•Beam: Pencil-like x-ray beam
•EMI labs
•Detectors: One
•Tube-detector movements: Translate-rotate
•Number of slices per rotation: One
•Scan duration: 5 minutes

A

1ST GENERATION CT scanners

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12
Q

▪ Were also translate and rotate type.
▪ Fan beam
▪ Mutiple detector array
▪ 30 seconds imaging time
▪ Uses the bow tie filter to equalize the radiation intensity reaching the
detector

A

2nd Generation CT-scan

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13
Q

a CT imaging system consists of a finely collimated x-ray beam and a single detector, both of which move synchronously in a translate and rotate fashion. Each sweep of the source detector assembly results in a projection, which represents the attenuation pattern of the patient profile

A

1ST GENERATION CT scanners

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14
Q

operated in the translate and rotate mode with a multiple detector array intercepting a fan-shaped x-ray beam.

A

Second-generation computed tomography
imaging systems

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15
Q

▪rotate-only units, third generation imaging systems can now produce an image in less than 100 ms.
▪uses a curvilinear detector array and a fan beam
▪The curvilinear detector array produces a constant source-to-detector path length
▪seconds scanning time.
▪Still widely used today.

A

3rd Generation CT-scan

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16
Q

operate in the rotate-only mode with a fan x-ray beam and a multiple detector array revolving concentrically around the patient

A

Third-generation computed tomography imaging systems

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17
Q

▪Incorporates a rotate and stationary configuration
▪Radiation detection is accomplished through a fixed circular array of detectors
▪May contain as many as 4000 individual detectors.
▪Fan shape beam
▪Free of ring artifact

A

4th Generation CT-scan

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18
Q

operate with a rotating x-ray source and stationary detectors

A

Fourth-generation computed tomography imaging systems

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19
Q

▪Also known as Electron-Beam CT (EBCT)
▪Was pioneered for cardiac imaging
▪No moving parts in the gantry

A

5th Generation CT-scan

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20
Q

▪ Also known as the “Helical CT scanner”
• Data collection: Data is collected without pausing
• Speed: Helical CT scanners are faster than other CT scans
• Cost: These scanners are less expensive to produce and purchase

A

6th Generation CT-scan

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21
Q

▪ Multi-spiral CT makes use of multiple detector arrays to make use of a wider portion of the x-ray fan beam d
▪ Section thickness in multi-slice CT is determined by detector width rather than by collimation thickness, using data
acquisition.
▪ This technology makes better use of the x-ray tube output and decreases heat loading for a given coverage range.
▪ Was introduced in 1998

A

7th Generation CT-scan

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22
Q

CT Scan Modes

A

Step And Shoot
HELICAL (SPIRAL SCANNING)
Multi Detector Row scanning

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23
Q

-the x-ray tube rotated 360° around the patient to acquire data for a single slice

-the motion of the x-ray tube was halted while the patient was advanced on the CT table to the location appropriate to collect
data for the next slice

A

Step And Shoot

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24
Q

▪ When the examination begins, the x-ray tube rotates continuously. While the x-ray tube is rotating, the couch moves the patient through the plane of the rotating x-ray beam. Continuous data acquisition.

A

HELICAL (SPIRAL SCANNING)

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25
Q

▪ This technology was expanded on in 1992 when scanners were introduced that contained two rows of detectors, capturing data for two slices per gantry rotation. Multiple slices per rotation

A

Multi detector row scaning

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26
Q
  • refers to the thickness of a cross sectional slice
A

Z axis

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27
Q
  • Rows and colums of pixels that makes up the whole image.
    -512 x 512 is the most common
A

Matrix

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28
Q
  • the degree to which a beam’s energy is reduced.
A

Beam Attenuation

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29
Q
  • the amount of xray photons absorbed/scattered per unit thickness
A

Linear Attenuation Coefficient

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30
Q

quantifies the degree that a structure
attenuates an x-ray beam

A

Density

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31
Q

CT numbers or Density Value

A

Houndsfield Units

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32
Q
  • is an artifact that occurs when multiple tissues with different densities occupy the same voxel
A

Volume Averaging

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33
Q

-composed of low and high intensity beams
-causes artifacts due to scattered radiation
-filtering with a substance such as Teflon or
aluminum eliminates the photons with weaker energies, thus reducing patient dose and improves image quality

A

Polychromatic X-rays

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34
Q

-all the thousands of bits of data acquired with each scan.
-These are the data that is waiting to be
processed in order to create the “Image Data”

A

RAW data

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35
Q

-the process of converting Raw data to Image Data

A

Reconstruction

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36
Q

-processed Raw Data

A

Image Data

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37
Q

-then ring shape part of the CT-scan that houses components necessary to produce and detect Xrays.

A

The Gantry

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38
Q

-permits the gantry frame to rotate continuously making helical scanning possible

A

Slip Rings

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39
Q

-located within the gantry
-prevents fluctuating temperatures within the gantry.

A

Cooling System

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40
Q

-CT-tubes made of tungsten anode, has a higher intensity beam. Higher heat capacity.

A

Xray Source

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41
Q

-improves image quality and reduces patient dose

A

Filtration

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42
Q

-restricts the x-ray beam to a specific area
-decreases scattered radiation, improves image quality and reduces patient dose

A

Collimator

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43
Q

2 types of collimators

A

Source Collimator
Pre detector Collimator

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44
Q

-affects the patients dose and determines how the dose is distributed across the slice thickness.

A

Source Collimator

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45
Q

-ensures the beam coming from the patient is the exact width and prevents scatter radiation reading.

A

Pre Detector Collimator

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46
Q

-collects the information regarding the degree to which each anatomic structure is attenuated by the beam

A

Detectors

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47
Q

-absorption rate of 60% to 87%
-less expensive
-still being manufactured but has become
obsolete
-due to its design prevents them for MDCT

A

Xenon Gas Detectors

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48
Q

-uses crystals that fluoreces when struck with and xray photon

A

Solid State Crystal Detectors/Scintillation Detectors

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49
Q
  • transforms light to energy
A

Photo iodide

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50
Q

-measures the number of photons that strikes the detector, converts the analog signal to digital (ADS - Analog to Digital Converter) and then sends it to the computer

A

DAS (Data Acquisition System)

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51
Q
  • is a finite set of unambiguous steps performed in a sequence to solve a problem
  • they are a precise set of steps to be performed in a specific to solve a problem..
A

Algorithm

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52
Q
  • a mathematical tool that allows for the efficient reconstruction
A

Fourier Transform

53
Q
  • Fourier Transform is developed by the 17th century mathematician ____
A

Baron Jean- Baptiste-Joseph Fourier.

54
Q

-is a mathematical method of creating missing data

A

Interpolation

55
Q
  • portion of the computer that can be physically touched.
A

Hardware

56
Q
  • is the instructions that tell the computer what to do to do it.
A

Software

57
Q
  • essential component of the CT system. Determines the number of images the CT system can store.
A

Hard Disk

58
Q
  • interprets computer program instructions and sequences task
  • Brain of the CT system.
A

CPU (central processing unit)

59
Q
  • imprinted in the factory. Used to store frequently used instructions. Required to start up the system.
A

ROM (read only memory)

60
Q
  • includes instructions that are frequently changed. Data that are used to reconstruct images.
A

RAM (random access memory)

61
Q

type of data storage device that reads date sequentially

A

SAM (sequential access memory)

62
Q
  • a computer storage device that can be written once, but read many timed (CD-R, DVD-r, DVD+R, rewritable disk)
A

WORM (write once read many)

63
Q
  • includes all measurements obtained from the detector array. Requires larger computer storage space than image data.
A

RAW DATA (Scan Data)

64
Q

-are those which result once the computer has processed the raw data. One Houndsfield unit is assigned in every pixel

A

IMAGE DATA

65
Q
  • compiles the information from all of the attenuation profiles to create an image
A

Back Projection

66
Q
  • helps reduce the appearance of artifacts.
A

Filter Functions

67
Q
  • determines the area, within the gantry, from which the raw data are required.
    -determines the number of detector cells collecting data.
A

SFOV (Scan Field of View)

68
Q
  • also called zoom or target. Determines how much of the raw data
    is to be used to create and image. Affects the image quality by changing
    the pixel size
A

DFOV (Display Field of View)

69
Q

-used in mammography
⚬ uses an area x-ray beam to produce
multiple digital images.
⚬ form a three-dimensional data set from
which any anatomical plane can be
reconstructed.
⚬ even better image contrast

A

Digital Radiographic Tomosynthesis.

70
Q

-also called axial tomography
-plane of the image is parallel to the long axis of the body
-results in sagittal and coronal images

A

Conventional tomography

71
Q

-Trans-axial or transverse image
-perpendicular to the long axis
-Coronal and sagittal images can be reconstructed from the transverse image data set

A

Computed Tomography

72
Q

In CT, the most common matrix
size is

A

512

73
Q

This speed is particularly important to
reduce or eliminate artifacts that result
from object motion, such as those
commonly seen when imaging the heart

A

Temporal Resolution

74
Q

The degree to which an X-ray beam is reduced by an object is referred to as

A

attenuation

75
Q

If an x-ray passed into an object and is less attenuated, the shade will be _____.

A

black

76
Q

If an x-ray will pass into a structure and there is more attenuation them the shade will be ____.

A

white

77
Q

the quantity of matter per unit volume, specified in units of kilograms per cubic meter

A

Mass density

78
Q

The amount of x-ray beam that is scattered
or absorbed per unit thickness of the
absorber is expressed by the ______, represented by the Greek letter μ

A

linear attenuation coefficient

79
Q

In general, the attenuation coefficient
_____ with increasing photon energy and ____ with increasing atomic number and density

A

decreases, increases

80
Q

These units are also referred to as CT numbers or density values

A

Hounsfield Unit

81
Q

The purpose of the ____ is to identify if there is something wrong with a particular organ

A

Hounsfield unit

82
Q

Using the system of _____, a measurement of an unknown structure that appears on an image is taken and compared with measurements of known structures

A

Hounsfield units

83
Q

CT can be broken down into three segments

A

Data acquisition
Image reconstruction
Image display

84
Q

It houses many of the components necessary to produce and detect x-rays

A

Gantry

85
Q

The range of aperture size of gantry is typically

A

70 to 90 cm

86
Q

The degree of tilt varies among systems of gantry but _____ is usual

A

15 to 30 degree

87
Q

Current systems use electromechanical devices called

A

Slip rings

88
Q

___ use a brushlike apparatus to provide continous electrical power and electronic communication across a rotating surface

A

Slip rings

89
Q

They permit the gantry frame to rotate continuously

A

Slip rings

90
Q

Generator that are currently used in in CT

A

High frequency generators

91
Q

The power capacity of generator is listed in

A

Kilowatts

92
Q

_____ produce the xray photons that create the Xray image

A

X ray tubes

93
Q

Are used to shape the xray beam

A

Compensating filters

94
Q

Used to describe the entire collection of detectors included in a CT system

A

detector array

95
Q

The space between the grid

A

Interspace material

96
Q

refers to the ability with which the detector obtains photons that have passed through the patient

A

Capture Efficiency

97
Q

•refers to the number of photons absorbed by the detector and is dependent on the physical properties of the detector face (e.g., thickness, material).

A

Absorption Efficiency

98
Q

•Is the time required for the signal from the detector to return to zero after stimulation of the detector by x-ray radiation so that it is ready to detect another x-ray event

A

Response Time

99
Q

•Is the ratio of the maximum signal measured to the minimum signal the detectors can measure.

A

Dynamic Range

100
Q

is used because of its ability to remain stable under pressure.

A

Xenon gas

101
Q

A xenon detector channel consists of ____
tungsten plates

A

three tungsten plates

102
Q

The process of moving the table by a specified measure us most commonly called

A

incrementation

103
Q

The degree to which a table can move horizontally is called the

A

Scannable range

104
Q

is a method to study waves
of many different sorts and also to solve several kinds of linear differential equations.

A

Fourier transform

105
Q

is a mathematical method of
estimating the value of an unknown function using the known value on either side of the function

A

interpolation

106
Q

is a mathematical method of
creating missing data

A

Interpolation

107
Q

• is the simplest type and is frequently used in mathematics and science

A

Linear interpolation

108
Q

• assumes that an unknown
point falls along a straight line between two
known points

A

Linear interpolation

109
Q

are ancillary pieces of computer hardware
designed to feed data into the computer or accept processed data from the computer.

A

Input and output devices

110
Q

include monitor, laser camera, printer, and archiving equipment such as optical disks or magnetic tape

A

Output devices

111
Q

The ___ is the component that interprets
computer program instructions and sequences tasks.

A

CPU

112
Q

It contains the microprocessor, the control
unit, and the primary memory

A

CPU

113
Q

In the past the CPU design frequently used for CT image reconstruction was the ____ also called as

A

array processor, vector processor

114
Q

, this design was able to run mathematical operations on multiple data elements simultaneously

A

vector processor

115
Q

refers to the computers internal memory

A

Primary storage

116
Q

-is used to store data that are likely to be in active use.
-is typically very fast

A

Primary memory

117
Q

is very fast, but is also volatile, losing
the stored data in the case of a power loss

A

RAM

118
Q

The opposite of RAM is ____, which stores data that can only be accessed sequentially (like a cassette tape)

A

serial access memory (SAM)

119
Q

• The reconstruction that is automatically
produced during scanning

A

Prospective Reconstruction

120
Q

• The same raw data may be used later to
generate a new image

A

Retrospective Reconstruction

121
Q
  • displayed in the monitor
A

Pixel

122
Q
  • contains value acquired by the
    algorithm and it will be averaged to have one value to place it in front
    as a HU and this is the pixel
A

Voxel

123
Q

The path that the x-ray beam takes from the tube to the detector is referred to as a ___.

A

ray

124
Q

: the detector senses each
arriving ray and measures how much
of the beam has been attenuated.

A

Ray Sum

125
Q

: a complete set of ray sums

A

View

126
Q

: the system accounts for the attenuation
properties of each ray sum and correlates it to the position of the ray.

A

Attenuation Profile

127
Q

The process of applying a filter function
to an attenuation profile is called

A

convolution

128
Q

⚬ common type of image reconstruction in CT scan

A

Filtered back-projection

129
Q

is also called calibration field of view.

A

Scan Field of view

CT Scan (1 decks)

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