Intro Quiz 2 System Components Flashcards by William Kerns

Knobology

basicas are interchangable between manufactureres

reduces scan time in a clinical setting

know your controls

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Acoustic power/transmit power

varies energy transmitted to patient

should be used at lowest level

ALARA limit

higher power=brighter image

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transmit power controls

operator controlled

determines electrical voltage to pulsar

low voltage=gentle PZT vibration

high voltage=forceful vibration

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Pulsar

creates electrical signals that excite the PZT crystals

only functions during transmission

operator controlled

0-500 volts

important in Bioeffects

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Pulsar voltage

0-500 volts

high =brighter image

also called output gain, accoustic power, energy output or transmitter output

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Pulsar Standardization

Thermal Index

Mechanical Index

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Noise

random and persistant degradation

unwanted low level echoes

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Signal to Noise ratio

power increase raises ratio

quiality improves with increase

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pulser repitition

determines time between voltage spikes

PRP Pulse repition Period

controlled by operator

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Pulse Repitition Period

PRP

determines depth of scan

operator controlled

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Pulser single pulse

continuous wave

vascular

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Pulser numerous pulses

pulsed wave

imaging

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Shallow imaging

shorter listening time

shorter PRP

higher PRF

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Deeper imaging

longer listening time

longer PRP

lower PRF

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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

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Beam Former Switch

proteects the electrical components in the reciever

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Reciever

prepares information from returning echoes for display

5 functions

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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

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