Basic Instrumentation Flashcards by Kate Grimeau

the US system converts _____ sound waves from the patient and converts them into _______ information

mechanical
electrical

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basic instrumentation box graph

Tx <–> beam former –> signal processer –> image processor –> display

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pulser (beam former) (does what/determines)

sends the voltage pulse to the probe determining the intensity, the operating frequency, and the PRF

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in doppler ____ determines PRF
in 2D ____ determines PRF

scale
depth

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pulse delays (beam former)

applies the delays necessary to accomplish focusing, beam steering, and aperture size (also apodization)

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T/R (beam former)

transmit/receive switch

directs the pulse in the correct direction to protect sensitive components from large voltage pulses

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amplifiers (beam former)

the pulses that return from the patient are weak and need this to make the trip through the circuitry of the machine

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ADCs (beam former)

analog to digital conversion

the pulses pass through this and become digitized. this is necessary for storage in memory and for manipulation of the image later on

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analog = ____ and shows ___
digitial = ____ and shows ____

ramp
every change of motion (ex. 9:19:08, (9:19:09)
stairs
not every change (9:19, 9:20)

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echo delays (beam former)

remember that the echo pulses were delayed and must be reset to properly construct an image

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sum (beam former)

adds together the pulses from each element in the segment to form the resulting scan line

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what happens if you add together before delaying

waves not in phase with each other = destructive interferance

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digitization of the voltage is crucial to maintain the ___ of the data through the system

integrity

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digitization is a process that involves converting the _____ into a ______ which is more ____

voltage
binary number
stable

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when can digitization occur

before or after echo delay but preference is to stabilize it early on

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signal processing involves two steps

ADC
the receiver

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receivers function

to process the returned echoes as analog voltages in preparation for display

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5 steps of the receiver

amplification
compensation
compression
rejection
demodulation (rectification and smoothing)

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amplification

returning echoes are weak and need to be amplified to make it through he circuitry of the machine

gain

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compensation

the sound attenuates as it travels further and needs to be compensated for (similar signals from same reflector should have same brightness regardless of the depth)

TGC

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TGC can also be called

DGC
depth gain compensation

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what does TGC usually operate in

1 cm increments

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what can TGC correct

the main bang artifact
attenuation in the far field

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compression

AKA dynamic range
process of decreasing the difference between the smallest and largest amplitudes

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what is compression expressed in

decibels

what equation is used for compression

logarithmic equation

logarithmic amplification is defined as the ___ applied exponentially as a function of the _____ level and the result is the compression of the dynamic range

gain input signal

rejection AKA

threshold suppression

rejection

used to eliminate or supress low level echoes that may represent noise helps reduce signal to noise ratio

is rejection operator controlled

it may or may not be

what is the reject level (compression)

the smallest amplitudes

what is the saturation (compression)

the largest amplitudes

rejection AKA, what, improves/reduces

threshold or suppression eliminates or suppresses low level echoes that may represent noise improves: SNR (signal to noise ratio) reduces: dynamic range

is rejection operator controlled

it may or may not be

demodulation process converts the _____ into a _______ for _____

radio frequency (RF) signal video signal monitor display

what are the two steps of demodulation

rectification smoothing

rectification turns what into what

the negative portions of the signal into positive ones (sine wave with negative waves flipped up to postive)

smoothing does what

filters the signal to smooth out the bumps (waves become one flat line - one shade of gray)

a simple function of the scan converter is to write the _____ acquired ultrasound data _____ to the memory

vertically horizontally

scan converter AKA

memory

how is the analog scan converter similar to the CRT

it is the same except that the phosphor face is replaced with a wafer of silicon called dielectric matrix

analog scan converter: electrons emitted by the filament pass through the ______ and strike the _______ leaving a ____ charge proportional to the amplitude of the signal strengths

deflection plates silicon wafer negative

the electron beam moves across the dielectric matrix in what is called a _____ format

raster

what is pre-processing

any processing of the wave signal before it is transferred and stored in the memory

six pre-processing functions

receiver functions maps interpolation edge enhancement write zoom persistance

what are maps

curves applied to the shades of gray to accentuate different levels enhances certain aspects of image

interpolation function

averages pixel grayscale values to fill in the info where none exists between scan lines

interpolation improves the image but the trade off is _____

what is real as the average could miss something

edge enhancement

sharpen the boundaries to make them more distinguishable and help make measurements precise

what is applied to the pixels to achieve edge enhancement

a kernel adds to inside of image and takes away for edge to enhance the edge

write zoom aka

regional expansion

write zoom function

expands the image before storage in the memory

ROI

region of interest

advantage to ROI using write zoom (3)

additional scan lines added = increased spatial resolution, detail, and pixel ratio

persistance

takes data from several US frames and averages them before displaying the image to improve the signal-to-noise ratio (multiple frames taken and averages them)

disadvantage to persistance

sampling over time decreases temporal resolution over time so the rate of movement must be small otherwise blurring occurs

what is persistence not used in

echo and obstetrics

post procesing

anything that occurs after the info has been stored to memory

7 post processing

measuring annotations post-processing curves read zoom (magnification) colour doppler mapping angle correction b-colour (coloured 2 d) (red, blue pink, etc)

curves are a ____ controlled function and accomplished in the ___

operator DAC (display to analog conversion)

curves can be applies to a frozen image and is the assignment of display intensity (brightness) to a _____ value

digital

read zoom

post-processing that magnifies frozen image by reassign he pixel size=decrease in resolution

b colour

uses various colour schemes which may help improve the contrast resolution of the image

final step of image processing

DAC to reconvert the digital information into a voltage signal (video or analog)

digital to analog converts numbers back to

waves

A way of writing the horizontal lines on a cathode ray tube that starts with odd lines and then adds even lines

interlacing

A frame averaging technique that is used to improve the signal to noise ratio and reduce acoustic speckle

persistance

The part of an instrument that accomplishes electronic beam scanning, apodization, steering, focusing and aperture with arrays

beam former

Which of the following increases the scan line density and improves spatial resolution? A) Read Zoom B) Write Zoom C) Persistence D) Interpolation

Which of the following is responsible for receive focusing? A) The receiver B) The echo delay C) The demodulator D) The scan converter

What defines the number of shades of gray that a system can display? A) RAM B) ROM C) Bit Depth D) Number of pixels

What process is used to fill in the gaps between scan lines? A) Persistence B) Apodization C) Over writing D) Interpolation

What process uses logarithmic amplification to exponentially apply the gain as a function of the input level of the signal? A) Rejection B) Compression C) Demodulation D) Compensation

Calculate the resolution in mm/pixel using a matrix of 1024x1024 and a depth setting of 8cm. A) 128 B) 12.8 C) 0.08 D) 0.008

Which of the following is the binary representation of 67? A) 1000011 B) 0111111 C) 1000101 D) 1010101

What process involves converting the radio frequency signal into a video signal? A) DAC B) Enveloping C) Rectification D) Demodulation

What is the refresh rate for each field of data in a cathode ray tube? A) 1/30 B) 1/60 C) 1/75 D) 1/120

What are the three colours used In a colour television set? A) Red, blue and white B) Red, green and blue C) Red, blue and yellow D) Red, green and yellow