Basic Instrumentation Flashcards
the US system converts _____ sound waves from the patient and converts them into _______ information
mechanical
electrical
basic instrumentation box graph
Tx <–> beam former –> signal processer –> image processor –> display
pulser (beam former) (does what/determines)
sends the voltage pulse to the probe determining the intensity, the operating frequency, and the PRF
in doppler ____ determines PRF
in 2D ____ determines PRF
scale
depth
pulse delays (beam former)
applies the delays necessary to accomplish focusing, beam steering, and aperture size (also apodization)
T/R (beam former)
transmit/receive switch
directs the pulse in the correct direction to protect sensitive components from large voltage pulses
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
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
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)
echo delays (beam former)
remember that the echo pulses were delayed and must be reset to properly construct an image
sum (beam former)
adds together the pulses from each element in the segment to form the resulting scan line
what happens if you add together before delaying
waves not in phase with each other = destructive interferance
digitization of the voltage is crucial to maintain the ___ of the data through the system
integrity
digitization is a process that involves converting the _____ into a ______ which is more ____
voltage
binary number
stable
when can digitization occur
before or after echo delay but preference is to stabilize it early on
signal processing involves two steps
ADC
the receiver
receivers function
to process the returned echoes as analog voltages in preparation for display
5 steps of the receiver
amplification
compensation
compression
rejection
demodulation (rectification and smoothing)
amplification
returning echoes are weak and need to be amplified to make it through he circuitry of the machine
gain
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
TGC can also be called
DGC
depth gain compensation
what does TGC usually operate in
1 cm increments
what can TGC correct
the main bang artifact
attenuation in the far field
compression
AKA dynamic range
process of decreasing the difference between the smallest and largest amplitudes
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
b
Which of the following is responsible for receive focusing?
A) The receiver
B) The echo delay
C) The demodulator
D) The scan converter
b
What defines the number of shades of gray that a system can display?
A) RAM
B) ROM
C) Bit Depth
D) Number of pixels
c
What process is used to fill in the gaps between scan lines?
A) Persistence
B) Apodization
C) Over writing
D) Interpolation
d
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
b
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
c
Which of the following is the binary representation of 67?
A) 1000011
B) 0111111
C) 1000101
D) 1010101
a
What process involves converting the radio frequency signal into a video signal?
A) DAC
B) Enveloping
C) Rectification
D) Demodulation
d
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
b
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
b
