Intro Quiz 2 System Components Flashcards
Knobology
basicas are interchangable between manufactureres
reduces scan time in a clinical setting
know your controls
Acoustic power/transmit power
varies energy transmitted to patient
should be used at lowest level
ALARA limit
higher power=brighter image
transmit power controls
operator controlled
determines electrical voltage to pulsar
low voltage=gentle PZT vibration
high voltage=forceful vibration
Pulsar
creates electrical signals that excite the PZT crystals
only functions during transmission
operator controlled
0-500 volts
important in Bioeffects
Pulsar voltage
0-500 volts
high =brighter image
also called output gain, accoustic power, energy output or transmitter output
Pulsar Standardization
Thermal Index
Mechanical Index
Noise
random and persistant degradation
unwanted low level echoes
Signal to Noise ratio
power increase raises ratio
quiality improves with increase
pulser repitition
determines time between voltage spikes
PRP Pulse repition Period
controlled by operator
Pulse Repitition Period
PRP
determines depth of scan
operator controlled
Pulser single pulse
continuous wave
vascular
Pulser numerous pulses
pulsed wave
imaging
Shallow imaging
shorter listening time
shorter PRP
higher PRF
Deeper imaging
longer listening time
longer PRP
lower PRF
Bean Former
recieves the electrical spike from pulser and distributes to the active elements in an array transducer
used advanced microprocessor tech to produce digital format
Beam Former Switch
proteects the electrical components in the reciever
Reciever
prepares information from returning echoes for display
5 functions
5 reciever functions
Amplification
Compensation
Compression
Demodulation
Reject
Amplification
first function
affects all signal quality
receiver gain
measured in dB
adjustable
Gain/Overall Gain knob
Gain Overall Gain
controls degree of echo amplification or brightness or image
too much can fill artifactual echoes into a fluid structure
too little can negate echo information
Compensation
creates and image of uniform brightness
known as TGC Time Gain Compensation
DGC Depth Gain COmpensation
sompensates for the sound wave as it weakens or attentuates
TGC
DGC
operator controlled
sliders on console
structures will be same brightness regardless of depth
Compression
3rd function
keeps image grayscale content with range of human eye (20 shades)
keeps electrical signal level within accuracy range
called log compression or dynamic range (DR) most common
dB
operator controlled
Decibels dB
relative term that compares on one signal to another
important in quantifying strenght of sound beams, electrical signal strenght and brightness of image
notatoin is logarithmic
Demodulation
4th function
two part process that changes electrical signals in reciever into a more suitable form for the CRt or monitor
rectifies and smooths electrical signal
NOT adjustable
no effect on image
Reject
5th function
controls whether low level signals will be displayed
low leve signasl can be diagnostic or noise
called threshhold or suppression
operator controlled
Amplification overview
Adjustable
all signals affected identically
entire image gets brighter or darker
Compensation Overview
Adjustable
signals treated differently bases on reflective depth
images will be uniformly bright from top to bottom
Compression Overview
Adjustable
Signals treated differently depending on strenght
changes grayscale mapping
Demodulatoin Overview
NOT adjustable
prepares electrical signals to be suitable for display
NO effect on image
Reject Overview
Adjustable
Only weak signbals affected
Strong signals remain unchanged
Weak echoes appear or are eliminated from image
CRT
Monitor
Displays the information from returning echoes
2 user controls
brightness
contrast
Output Power
vs
Reciever Gain
patient exposure to sound energy is affected by output power NOT by reciever amplification
Output Power SUmmary
changes brightness of image
alters signal to noise ratio
alters patient exposure
bioeffect concerns
decrease this first if image too bright
Reciever Gain Summary
Changes brightness of entire image
does not affect signal to noise ratio
does not change patient exposure
NO bioeffect concern
increase this first if image is too dark
Persistance
frame averaging that allows echo information to be accumulated over time
Persistence Increase
subtle texture differences will be enhanced
Persistence Decrease
allows user to evaluate moving structures more easily
Zoom/Magnification
allows image magnification by increasing the pixal size
2 types
Read
Write
Read Zoom
occurs after the image is stored
number of pixals or scan lines is the same as original image
Can appear blurry
Write Zoom
Occurs while active scanning
box is placed on screen and the area seen within can be expanded to fill screen
number of pixals and scan lines remain the same
image is not degraded
Calipers
Markers available to measure distance
linear
ellipsoid
trace
Annotation
allows the labeling of the image
may be keyboard or preprogrammed keys
may be voice activated
Dual image
allows the screen to be split in order to show 2 views of an image or compare anatomy of abnormal side to normal side
