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Ct Review Class > Ch 1 System Operation And Components > Flashcards

Ch 1 System Operation And Components Flashcards

1
Q

Ct uses X-rays to image individuals at different

P 1

A

Cross sectional anatomy

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2
Q

Reconstructed image

A

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

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3
Q

Overview of Ct system

A 
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
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4
Q

Scan controller

A

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

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5
Q

Digital analog converter (dac)

A

Electronic signal converted into analog or continuous waveform

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6
Q

Gantry

A

Contains X-ray tube and detectors

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7
Q

High voltage generator

A

Generates high voltage potential between cathode and anode

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8
Q

1st commercial scanner

A

1973

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9
Q

First gen scanner

Type beam?
What does?
Scan time?

A

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

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10
Q

2nd gen Ct

Type beam?
What does?
Scan time?

A

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

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11
Q

3rd gen Ct

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

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

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12
Q

Scanners today mostly based off?

A

3rd gen scanner

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13
Q

Scan

A

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

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14
Q

4th gen scanner

A

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

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15
Q

Slip ring technology

A

Large rotating ring surrounds gantry aperture

Eliminates winding of high tension cables from high frequency generator

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16
Q

Electrical brushes

A

Conveys electrical power and data to components on rotating ring

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17
Q

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

A

Host computer

Array processor

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18
Q

Sling ring transfers

A

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

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19
Q 
Multi row detectors
 From?
Scan time vs?
Type beam?
Aka?
A

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

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20
Q

Single row detector

A

Detector array aligned in one row

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21
Q

Multi row detector scanner

Detectors/ why?

Equation

A

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

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22
Q

Mdct beam is ____ shape?

A

Cone

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23
Q

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

A

Multirow detector scanner

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24
Q

Benefits of multi row detector scanner

A

Fast scans

Increased anatomical coverage

Scanner with thinner slices to improve resolution along slice direction

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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

Ct Review Class (7 decks)

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