Ch 1 System Operation And Components Flashcards Preview

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Flashcards in Ch 1 System Operation And Components Deck (126):
1

Ct uses X-rays to image individuals at different

P 1

Cross sectional anatomy

2

Reconstructed image

Measurement of photons of xray beam in which each tissue has its own characteristic intensity

3

Overview of Ct system

Control panel
Computer
Scan controller
Digital analog converter
Gantry
High voltage
Generator
Info converted into tiny electrical signals
Pass through amplifier
Analog signal sampled
Then digitized by analog digital converter
Data stored temporarily in raw data file
Calculated image by array processor
Image transferred to host computer

4

Scan controller

Responsible for timing and operation of patient table , gantry , and high voltage generator

5

Digital analog converter (dac)

Electronic signal converted into analog or continuous waveform

6

Gantry

Contains X-ray tube and detectors

7

High voltage generator

Generates high voltage potential between cathode and anode

8

1st commercial scanner

1973

9

First gen scanner

Type beam?
What does?
Scan time?

Pencil beam
Single detector moved 180 degrees
Tube detector moved across patient then rotated 1 degree
Scan time : 5mins

10

2nd gen Ct


Type beam?
What does?
Scan time?

Fan beam
Multiple detectors in straight line
Tube detector moved across patient then rotated 5 degrees
Total scan time : 20 sec per image

11

3rd gen Ct

Type beam?
What does?
Major difference?
What does difference help with?
Scan time?

Fan beam geometry

Detector array rotates with tube in tube/detector assembly within gantry

Detector array curved arc

Arc arrangement improves reproducibility across array and minimize artifacts

Scan time: less 1 sec per image

12

Scanners today mostly based off?

3rd gen scanner

13

Scan

Collection of anatomical information during time X-ray beam is on

14

4th gen scanner

Similar to 3rd gen

Tube generates X-rays in fan beam geometry , rotates about gantry same as 3rd

Difference: detectors don't travel with tube in 4th. Circle around patient. Many more detectors

Same time: less 1 sec per image

15

Slip ring technology

Large rotating ring surrounds gantry aperture

Eliminates winding of high tension cables from high frequency generator

16

Electrical brushes

Conveys electrical power and data to components on rotating ring

17

Slip rings conveys scanning instructions from _______to gantry component in order preform scan

Conveys measure attenuation data from patient to computer and _______ in order facilitate and image

Host computer

Array processor

18

Sling ring transfers

Electrical signal
Scanning instructions
Detected signal between stationary components and rotating gantry components

19

Multi row detectors
From?
Scan time vs?
Type beam?
Aka?

Collect from multi slices

Faster scan without increase in slice thickness or varying pitch

Very thick X-ray beam and multiple detector arrays

Aka : mdct, msct, multi array scanners

Each parallel detector array composed hundreds scanners along arc

20

Single row detector

Detector array aligned in one row

21

Multi row detector scanner

Detectors/ why?

Equation

Multiple parallel detector arrays in order to vary the number of slices collected in single,rotation and to vary slice thickness

When thick X-ray beam is measured by multiple parallel detector array , thickness of beam \ total number detectors = desired slice thickness

22

Mdct beam is ____ shape?

Cone

23

___ detector scanners collect info from multiple anatomical slices in each rotation of the X-ray tube

Multirow detector scanner

24

Benefits of multi row detector scanner

Fast scans

Increased anatomical coverage

Scanner with thinner slices to improve resolution along slice direction

25

Electron beam Ct (ebct)

No X-ray tube

Very fast scan times: good for cardiac Ct and coronary artery imaging

Produce electron beam that streams from electron gun and which I electromechanical directed toward an army of tungsten anodes.

X-ray beam generated when electron beam strikes anode

26

Pet/Ct scanner

Nuclear imaging modality that involved injection of slightly radioactive pharmaceutical

Malignant tissue characterized by rapid growth and high metabolism , agent accumulation in abnormal tissue

27

Fusion imaging

Comparison of two imaging modality yielding coregistered images

28

Value in pet image resulting Ct

Associate change in metabolism with a specific structure

29

Attenuation correction

S

30

Cone beam oncology

Verifies patient positioning before radiation therapy

High quality 3D image while patient positioning in linear accelerator

Clinicians can compare images for patients treatment plan and positioning adjustment that puts tumor in direct in X-ray beam path

31

Operator console

Key point of interaction between technologist and imaging system

Consists of: keyboard, monitor, and mouse

32

Keyboard

Alphanumeric keys to type

System command for post processing

Image manipulation/ archiving

33

Mouse/ trackball

Graphic input device purpose of planing a scan, selecting image parameters, displaying images, selecting post processing parameters

34

Monitor

Provides feedback on data entry and displaying images

35

Host computer

Primary link between tech and other components of imaging system. Also controls storage devices

36

Host computer storage devices

Hard discs and removable media

37

Gantry contains

Ct tube
Detectors
Slip ring
High voltage generator

38

Patient table fed through _____ of the gantry

Aperture

39

Rotating frame assembly location

Located central aspect of gantry

40

Rotated assembly frame gantry contains

Tube, detector array, data acquisition system

41

Gantry tilts

+ or - 30

42

Gantry tilt

Tilting rotational angle of detector array and Ct tube as it moves around patient
- result: generating attenuated projection along slice plane that is encircled by the tube as it evolves around patient

43

Patient table movement

Controlled by software according to instructions entered by tech

44

Patient coordinate system

Z axis
Y axis
X axis

45

Z axis

Long axis of patients body( along table)

46

X axis

Extends patients left and right

47

Y axis

Extends posteriorly to anteriorly of patient

48

Ct tube located

In rotating frame assembly of the gantry

49

Electrons of X-ray charge?

Negative

50

Most X-ray reaction in Ct?

Bremsstahlung

51

Bremsstahlung radiation

Breaking radiation in which electrons Lose energy of X-ray photons

52

Characteristic radiation % or Ct X-rays?

10-12%

53

Characteristic radiation

Electron Collides with inner electron shell of target atom ejected, outer shell electron shifts positions , then X-ray photon produced . X-rays produced when fast moving electrons collide with target material and lose energy

54

X-ray tube two electrodes

Anode and cathode

55

Electron beam flow?

Cathode to anode

56

Cathode contains

Filament heating wires

57

Filament is in cup shaped _____

Cathode

58

Cup shaped region part cathode

Focuses electron beam to anode target material

59

Filament temp controlled by?

Ma selected by tech

60

Ma

Tube current that determines number of X-ray photons produced

61

Kv

Tube voltage that controls photo energy level selected by tech

62

Ma=_____ ampere

1/1000

63

Ct voltage range

90-140

64

Space charger compensator

Applied to tube filament which cools filament slightly as tube voltage increases in order to prevent an unwanted elevation in tube current in response to higher kv levels

65

X-ray photons produced at?

Anode

66

Target material

Tungsten

67

Whyntungsten target material?

High atomic number #74

Withstand heat

Melting point 3400degree c

68

Target located

Rotating anode

69

Why anode rotates

Avoid excess heat and extends life tube

70

Cathode of Ct tube

Contains more than one filament

Small filament - smaller area covered- determines focal spot

71

Focal spot

Area of target from which useful X-rays emitted

72

Small focal spot

Thin slices, higher resolution

73

Interscan delay

Minimum amount of time frame that must transpire between one scan and initiation of next

Shorter the better

74

Window of tube

X-ray beam exits

Filter restricts low level X-ray photons

75

Beam hardening

Filter out low energy rays to lessen patient dose and improve image quality

76

Collimation

Restricts X-rays only to selected cross section region thereby minimizing patient dose and reducing scatter

77

Scatter radiation

X-rays that are deflected at many angles
- degrades image

78

Two types collimation

-

Pre patient

Post patient

79

Pre patient collimating

Restricts X-ray beam to thickness of the slice in single row detector
- made of thick metal plates attached to bottom tube housing

80

Multi row detector pre patient collimating

Select thickness of X-ray beam which spreads over multiple detectors
- reduces dose

81

Slice thickness in mdct

Determined by image reconstruction

82

Post patient collimating

Further refines the path of X-ray photons after they pass through the patient and before they enter detectors


83

Two main purposes of post collimtion

Conjunction with pre patient collimator assembly to provide better definition of slice thickness ( single slice Ct)

Reduce scatter radiation to detectors

84

Detectors

First component of data acquisition system (das)

Measures in coming X-rays

85

In order X-ray photon to generate a signal

X-ray must be able to enter the chamber of the detector and be captured

X-ray collides with atom in detector material

Collision of X-ray photon and detector material must produce a measurable event( electricity or light)

86

Two categories :

Gas and solid state

87

Gas detector

Large detector array with hundreds of chambers with the array ( gas detectors)

88

Gas used in gas detector

Xenon

89

Pressure to compress gas?

Decrease vacant space and increase probability X-ray photons collide with xenon atom

90

Collision of X-rays gas detector

Xenon atom splits into xenon ion and an electron which migrates to detector electrode plates which detects event

91

Gas detector located

In stationary ring around the gantry in 4th gen

92

Gas chambers and collimating

Provides own post collimation

93

Must prevalent type detector

Solid state detector

94

Solid state detectors

Scitilation detectors

95

Solid state detector material

Solid crystalline

96

Solid state detector photon collision

Photon and detector atom occurs closer to surface then gas detector

97

Solid state detector arrangement

Multiple detector arrays , uses flash of light which is sensed by photodiode

98

Photodiode

Photon strikes the solid state material emits flash of light which converted into electrical pulse by

- attached to bottom of solid state material on detector

99

Single row detector arrays

Have single row array of detectors arranged along curved arc- opposite X-ray tube

100

On single row detector scanner _____ of X-ray determines final slice thickness

Collimation

101

Multiple parallel rows detector elements arranged along

Curved arc opposite X-ray tube

102

Mdct X-ray beam collimated

Thickly

103

Acquired slice thickness formula

Thickness of beam
_______________________
Total number of slices acquired in single rotation

104

How many adjacent multi row detectors in mdct

64

105

Thinner slices

Attenuation info for one slice can be measured by detectors in single detector array

106

Thicker slices

Measured by detectors in several adjacent detector arrays

107

Types detector arrays

Symmetric and asymmetric

108

Symmetric detector array

Size each detector is identical

109

Assymetric detector array

Detector size varies

110

Mdct several channels of measured attenuation info can be added together to generate

Slice thickness

111

Array processor

Primary location for all complex mathematical calculations involved in generation of Ct

Reconstruction of projected attenuation raw data into Ct images

Site to generate retrospective reconstruction and sometimes post process image data

112

Picture archiving and communication system( PACS)

Connects operator console to storage system and distribution images
- also patient list for console

113

Dicom- digital imaging and communications in medicine

Goal is to achieve compatibility and workflow efficiency between imaging systems in healthcare environments worldwide

114

Specified protocol for dicom

Tcp/ip

115

Network

A number of interconnected digital devices that need to share information

Devices operators consoles of digital imaging modalities , image workstations , image viewing stations, image storage devices, printers and personal computers

116

A network comprised of:

Server and client

117

Server

Archive device that stores image

118

Client

Image workstation which needs to access the images that are stored on a server

119

Hub

Receives incoming packets of data , amplifies electrical signal and then it broadcasts these packets out to all devices on the network

Includes one that originally sent packet

120

Network switch

Connects multiple clients to a server but individual traffic elements and selectively forwarding data to the one device that actually needs it

121

Bandwidth

Rate of transfer which in bits per second

122

File sizes denoted

MB( megabytes)

123

Bandwidth denoted in

Mb ( megabits)

124

Virtual private networks (vpn)

Allows remote authorized individuals to connect in secure fashion to server located in a location , using the routing infrastructure provided by public network

125

Electronic health network (ehr)

Contains and shares information from all providers involved in patient care

126

Electronic medical record ( emr)

Contains standard medical data gathered from a patient in a single provider office
- electronic medical records