Chapter 6: System Operations

the front end

what end has the transducer, pulser and receiver?

back end

what end has the scan converter-memory and display?

pulser, receiver, memory, display

what are the four basic system parts?

the pulser

what do the beam former and master synchronizer make up?

master synchronizer

what controls all the timing sequences for the subsystems in the unit and calculates round trip time?

digital beam former

what is considered part of the pulser on most scanners and determines the firing delay patterns for array systems?

increases

as voltage amplitude in the pulser increases, ultrasound amplitude _______

100 V

what is the upper level voltage?

100

0 dB= ____% of the default OP intensity

50

-3 dB=_____% of the default OP intensity

10

-10 dB=_____% of the default OP intensity

double

+3 dB=_____ the default OP intensity

10 times

+10 dB=_____ the default OP intensity

true

true or false: receiver gain is not the same thing as output intensity

beam former

what is referred to as the band director and controls timing and voltage crystals?

master synchronizer

what is known as the soccer mom and coordinates with other parts of the machine and round trip time?

doesn’t

increasing gain does or doesn’t increase likelihood of bio effects?

does

increasing output intensity does or doesn’t increase likelihood of bio effects?

signal to noise ratio, gain

increasing transmit output improves ________. ______ does not

pre-amplification

__________ occurs in the transducer

dynamic range

what is the range of voltage amplitudes that the receiver can detect and process?

amplification, compensation, compression, demodulation, rejection

what are the receiver functions? (Always Call Cindy During Recess)

amplification

what is the conversion of small voltages received from the transducer into larger ones suitable for processing and storage?

gain (2D)

amplification is controlled by what control?

gain

what is the ratio of output to input electric power expressed in decibels?

output power/input power

what is the equation for power ratio?

output voltage/input voltage

what is the equation for voltage amplitude ratio?

(VR)²

what is equal to PR?

10log(power ratio)

what is the log equation you use to calculate dB when given power or intensities?

20log(voltage ratio)

what is the log equation you use to calculate dB when given amplitude or voltages?

transmit output

deep penetration and improved signal to noise ratio are advantages of _____ ______

SNR

improved _____ means that the diagnostic signal is amplified but the noise levels are not.

minimize, maximize

rule of thumb in imaging: ______ transmit output and ______ receiver gain.

true

true or false: gain increases the amplitude of all returned echo voltages by the same amount (including noise)

signal to noise ratio

what is a measure of how strong a signal is relative to the background noise?

high

high or low SNR makes the signal data more reliable?

quantitative, qualitative

true SNR is ________ and apparent SNR is _______

signal amplitude/noise amplitude

what is the SNR equation?

transmit output power

true SNR is controlled by the ________

gain

apparent SNR is affected by receiver _____

increase, decrease

to improve SNR we must ______ signal strength and ______ noise levels

compensation

what is the process of adjusting amplitude of the echos by depth to create a uniform image?

TGC

what controls compensation?

shoulder

what is the term for where compensation begins?

knee

what is the term for the depth at which the system no longer has the capacity to further amplify the signal? (MID)

decreases

as frequency increases, slope _______ and the MID is reached more quickly

frequency

high attenuation=high ______ slope

frequency

low attenuation=low _______ slope

compression

what is the process of decreasing the difference between the largest and smallest amplitudes or voltages?

dynamic range

what is the control for compression?

dynamic range

the ratio of the largest to the smallest amplitudes or power that a system can handle or process

compressed

signals must be ________ before being sent to memory, and again before being sent to the display monitor.

20

monitors have a DR of ____dB

60,120

most amplifiers have a DR of _____ to _____dB

compression

_______ determines the amount of voltage difference there has to be between two echoes for them to be assigned a separate shade of gray.

dynamic range, log compression, grayscale

what are the three names for compression control?

true

true or false: excessive compression (high contrast or low dynamic range) can lead to missing subtle echogenicity changes in an organ

high

low dynamic range=_____compression

low

high dynamic range=_____ compression

soft-tissue

high dynamic range is needed when scanning _________ organs

blood-vessels

low dynamic range is required when examining _________

demodulation

the process of converting the voltages delivered to the receiver from one form into another. analog into digital

rectification and smoothing

demodulation is composed of….

modualted

signals that we send out are smooth but the signals we get back are ______

rectification

flips or eliminates all half cycles from below the baseline

smoothing

places an envelope around the signal by averaging peak amplitudes and creating new peaks

rejection

eliminates the smaller amplitude voltage pulses produced by weaker echos or electronic noise

bit

the smallest division of the analog to digital converter output is called a ____

dynamic range

the more bit, the higher the output _____ _____

scan converter

what converts a-mode into b-mode?

scan converter

the primary purposes of what thing are to have data conversion, image processing, and coordinate conversion?

digital scan converter

what uses multiple overlapping matrices or grids to organize data?

digital scan converter

what stores signals as binary numbers (0’s and 1’s) rather than as electrons or voltages

non-acoustic read

what feature is post processing and enlarges existing pixels, performed on frozen images, and prone to pixelization?

acoustic write

what feature is pre-processing(during real-time scanning), cannot be performed on frozen images, and has better spatial resolution?

scanning depth/grid length

what is the equation for SR?

decreases

as number of pixels increases, SR______

dynamic range/# of gray shades

what is the equation for contrast resolution?

grid area x bits of memory

what is the equation for total memory elements?

harmonic imaging

what transmits a low frequency but only processes the higher harmonic frequency echos generated by the tissue? it decreases image noise.

parallel processing

what is it called when you send out a fat beam and receive multiple narrower ones?

depth, amplitude

what is the x axis and y axis on a-mode?

time, depth

what is the x and y axis of m-mode?

temporal resolution

what is the term for the ability to accurately display changes occurring over a short period

high

good temporal resolution=____ frame rate

depthxPRF > 77,000

what is the equation for range ambiguity?