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MRI > Part III > Flashcards

Part III Flashcards

1
Q

3 Parts of MRI Suites

A

Gantry
Control Console
Computer Network/System

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2
Q

Operating console is composed of :

A

-imaging acquisition
-image processing

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3
Q

Operating console [added]

A

Start-up
Image acquisition
Prescan Calibrators
Image Scanning
Image Processing/Display/Manipulation

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4
Q

MRI computers is composed of:

A

Multitasking operating system
Control Computer
Acquisition Control System
Image Reconstruction
Processing Computer

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5
Q

MRI system electronics

A

Frequency Synthesizer
RF Amplifier
Gradient Coil Power Supply
Sequencing System
Digital Signal Acquisition System
Digital Image Processing System

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6
Q

Ancillary Equipment

A

Power Injectors
Infusion Pumps
Pads and Pillows
Cryogenic Filling Equipment

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7
Q

CM used in MRI

A

Gd DPTA -contrast (paramagnetic)
Diethylenetriamine Penta-acetic acid

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8
Q

[ancillary equip.] Facilitate introduction of CM, Nonmagnetic

A

Power injectors

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9
Q

[ancillary equip.] Used for introduction of saline/fluid, automatic set rate/amount

A

Infusion Pumps

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10
Q

[ancillary equip.] used for pt comfort, headphones, pillows, blankets

A

Pads and pillows

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11
Q

[ancillary equip.] cooling system used to ensure magnetic property

A

Cryogenic filling equipment

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12
Q

[operating console-start- up] energizes the system

A

Power On/Off

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13
Q

[operating console-start- up] should be used if the pt is in danger (in case of adverse fx, claustrophobic)

A

Emergency Off

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14
Q

[operating console-start- up] installed with TV system for communication

A

Intercom - speaker and Tv monitor to ensure pt is not moving

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15
Q

[operating console-start- up] selection of pulse sequence, pulse delay timings, other parameters

A

Scan Control Module

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16
Q

[operating console-start- up] SLICES (no of gaps); scout images

A

Image-Guided Graphical Prescription

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17
Q

[operating console-start- up] review the image (display windowing), parametric imaging processing

A

Image Display System

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18
Q

[operating console] involves stimulation of H and receiving of signal

A

Image Acquisition

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19
Q

[operating console-image acquisition] often automatic, accommodate the body part/FOV

A

Tuning Control

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20
Q

[operating console-image acquisition] RT can modify, 90-90deg..90-180deg/..

A

Pulse Sequence Selection

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21
Q

[operating console-image acquisition] selection of repetion time [TR] and echo time [TE]

A

Timing selection

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22
Q

[operating console-image acquisition] optimize image contrast and SNR (reduce artifacts)
X and y axis to get FID

A

RF pulse flip angle selection

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23
Q

[operating console-image acquisition] Matrix Size

A

256x256; larger matrix size = better image, longer imaging time

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24
Q

[operating console-image acquisition] FOV

A

reduced FOV = better spatial resolution (requires more signal acquisition)

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25
Q

[operating console-image acquisition] amount of FID needed

A

Number of Signal Acquisitions (NSA)
Number of Excitations (NEX)
Number of Averages (NA)

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26
Q

[operating console-image acquisition] Slice Thickness

A

Reduced slice thickness improves spatial resolution
Thicker slice = < detail

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27
Q

[operating console-image acquisition] affects the SNR and chemical shift artifact
Range of frequency/signals

A

Receiver Bandwidth (BW)

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28
Q

[operating console-image acquisition] pre saturation pulses to eliminate signals from certain samples (fats and water)

A

Magnetization Preparation Schemes

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29
Q

[operating console-image acquisition] 2D and 3D images, usually for advanced imaging system - possible in MRI arteriogram

A

Reconstruction Strategies

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30
Q

[operating console-image acquisition] number. Of slices, gaps b/w slices, orientations - sagittal , coronal, axial

A

Slice Positioning and Orientation

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31
Q

[operating console] role of computer system

A

Prescan Calibrators

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32
Q

[operating console-prescan calibrators] accommodate the patient’s size - adjust RF coil to match patient habitus

A

Transmit/Receive Coil Tuning

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33
Q

[operating console-prescan calibrators] establishes the slice position and resonance frequency of fats and water photons (automatic)

A

Center Frequency Tuning

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34
Q

[operating console-prescan calibrators] sets the duration that radio frequency is on and the amount of power to generate the radio frequency (if short-blurry)

A

Pulse Amplitude Calibration

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35
Q

[operating console-prescan calibrators] ensures that signal is not too low (noisy image) or too high (image distortion)

A

Receiver Gain Control

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36
Q

[operating console-prescan calibrators] makes the MF homogenous

A

Autoshimming

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37
Q

Importance of Magnetic Shimming

A

-maintain homogenousfield
-minimize fringe field-stray field that can interfere with electronic devices

38
Q

Magnet ensure safety within [..]

39
Q

Protect the magnet from outside things that can affect the homogenous MF

40
Q

Protect public and environment

A

Fringe field

41
Q

Two types of magnetic shielding

A

Passive - walls of MRI gantry (s), MRI suite (f)
Active - magnet in gantry

42
Q

[operating console-Imaging Scanning] Patient Positioning

A

Uses: surface coils/phased array coils
Laser positioning system

43
Q

Surface coil purpose:

A

Added on POI, receive only
Shorten distance -enhance contrast

44
Q

[operating console-Imaging Scanning] Patient Monitoring

A

Uses TV and intercom

45
Q

[operating console-Imaging Scanning]inspect date for quality and positioning of data

A

Image Quality Inspection

46
Q

[operating console] Imaging Scanning

A

Pt Positioning
Pt Monitoring
Image Quality Inspection

47
Q

[operating console-Image Processing/Display/Manipulation] set the contrast and shades of gray. Wider range in MRI

A

Window Width Level

48
Q

[operating console-Imaging processing/ display/ manipulation] pointer

A

Cursor On/Off

49
Q

[operating console-Imaging Processing] calculation of area of measure and average and standard deviation of pixel values

A

Region of Interest (ROI)

50
Q

[operating console-Imaging processing] magnify the image. Some may produce fixed magnification. Reconstructive [..] is not possible in MRI

51
Q

[operating console-Image Processing] selects pixel values within a given range for special attention

52
Q

[operating console-Imaging Scanning] simultaneous display of multiple images or portions of an image on one wide screen

A

Display Matrix Format

53
Q

[operating console-image processing/display manipulation] plotting of pixel values along the identified axis in a line graph

A

Profile/ Histogram

54
Q

[operating console-image processing/display manipulation] selects pixel values within a given range for special attention

55
Q

[operating console-image processing/display manipulation] simultaneous display of multiple images or portions of an image on one wide screen

A

Display Matrix Format

56
Q

types of computer system

A

-control computer
-acquisition control computers

-image processing computer

57
Q

control computer provides an interface with the operator for:

A

control and display functions
data archiving
and network communications

58
Q

[computer system] computer that control the gantry, receive instructions from control computers
-converts instructions to specific pulses, timing delays and amplifier gain

A

acquisition control computers

59
Q

location of acquisition control computer

A

equipment room

60
Q

[computer system] for image reconstruction

A

image processing computer

61
Q

[computer system] should have high capacity to store data for manipulation; fast to handle the high rate of data acquisition; can accommodate enormous no. of calculations

A

image processing computer

62
Q

image processing time: [..]

A

1 sec - to entertain more frames

63
Q

additional subsystems to assist in the functioning of computers

A

MRI System Electronics

64
Q

[MRI System Electronics] produce RF pulse, generates the fundamental resonance frequency used to excite the magnetic nuclear spins

A

Frequency Synthesizer

65
Q

[MRI System Electronics] produces low-level sinusoidal wave signal from a fixed time base oscillator
[high intensity = low RF frequencu

A

Frequency Synthesizer

66
Q

types of RF Synthesizer

A

direct digital synthesizer (DDS)
dividing time

67
Q

[RF Synthesizer] creates arbitrary waveforms using frequency and pulse-tunable output signals

A

direct digital synthesizer (DDS)

68
Q

[RF Synthesizer] fixed frequency precision clock source referenced to DDS

A

MRI System Clock

69
Q

[MRI System Electronics] the DDS scales the frequency clock using a programmable binary tuning word that is typically […] long

A

Dividing Time

24-48 bits

70
Q

[MRI System Electronics] increase signal out put from the frequency synthesizer; should be immune to load changes

A

Radiofrequency Amplifier

71
Q

RF energy is [..] to RF frequncy

A

directly proportional

72
Q

T/F MRI amplifiers must have an increasing power ratings when used with higher field magnets

73
Q

RF AMPLIFIER : 1.5 T maximum outputs

A

18 kW -25 kW

74
Q

RF AMPLIFIER : 3 T maximum outputs

A

30 kW - 40 kW

75
Q

[MRI System Electronics] operates in a current-driven mode; installed with cooling system to ensure stability of temperature

A

Gradient Coil Power Supply

76
Q

Gradient Coil Power Supply : peak output current can range up to [..] and peak voltages up to [..]

77
Q

high powered GPS for the whole body categories

A

-Linear GPS
- Switching GPS System and Resonant System
-Pre-emphasis circuitry module

78
Q

[GPS] deliver power directly to the coils

A

linear GPS

79
Q

[GPS] uses energy storage strategies to reduce power dissipation [backup power]

A

Switching GPS System and Resonant System

80
Q

[GPS] modifies the gradient pulse waveform to minimize EDDY CURRENT

A

Pre-emphasis circuitry module

81
Q

result of current opposing the cause that produced them, produced in any conducting material subjected to changing MFs

A

EDDY CURRENT

82
Q

[MRI System Electronics] inorder to accept current, magnetic coils must have resistance

A

Magnetic Power Supply

83
Q

[MPS]

A

persistent switch
magnetic power supply
stabilized Bo Field

84
Q

[MPS} superconducting heat switch may be used - help in giving current

A

Persistent Switch

85
Q

programmed to slowly inject current until the specific MF had been attained

A

Magnet power supply

86
Q

[MPS] the current to the switch is turned off

A

Stabilized Bo field

87
Q

[MRI System Electronics] traffic cop of MRI Scanner that takes instruction from the computer and setting up proper parameters; controls the RF transmitter and gradient amplifiers to cause an MR image

A

Sequence System (Pulse Programmer)

88
Q

[MRI System Electronics] sets parameters such as bandwidth for the subsystem receiver

A

Sequence System (Pulse Programmer)

89
Q

[MRI System Electronics] signals (from H atoms) -receiver - preamplifiers

A

Digital Signal Acquisition System

90
Q

increase the amplitude of MRI signal from tens to hundreds of mV to several Volts

A

Pre Amplifiers

91
Q

[MRI System Electronics] Digital Image Processing System includes:

A

GENERAL PURPOSE MICROPROCESSOR FIELD PROGRAMMABLE GATE ARRAYS (FDGAS)

Digital Signal Controllers
Stream Processor

MRI (7 decks)

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