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DMS 110 Sys Ops

system operations ultrasound DMS 110 acoustic physics

QuestionAnswer
what are the 6 core functions an US system must perform transmit beams receive beams process returned data perform measurements display processed data store processed data
synonyms for transmit power (7) acoustic power transmit gain power gain acoustic gain output intensity transmit voltage output voltage
increasing transmit power results in two effects more intense beam, hence, stronger echoes risk of bioeffects
the maximum or minimum of any quantity dynamic range
the range of signal amplitudes a system can receive and process without causing harmonic distortion input dynamic range system default there are many dynamic ranges, have to specify which one
the amplitude level below which no signals are visible because of noise noise floor
amplitude of signal divided by amplitude of noise S/N ratio, or, SNR
increasing amplification usually _____ the signal and ____ the noise increases, increases
a mistaken observation related to the S/N ratio usually caused by low gain apparent SNR SNR is fine, gain is set low and operator things there's bad SNR more gain is required to drive the signal into visual range
types of noise (4) electronic noise electronic interference clutter haze
noise from larger signals obliterating smaller ones clutter
noise that can be cause by poor interface contact haze
noise that can show up as bright flashes of light electrical interference
noise that shows up as random speckles or random color pixels electrical noise
all receiver functions are pre/post processing pre
pre/post processing can be performed on saved and live data post
pre/post processing is usually performed by the scan converter post
which part of an US machine conditions the signals for conversion, measurement and display receiver
the ___ ____ is part of an US machine that converts streamed data into a format where it can be measured, stored and displayed scan converter
which component of an US machine performs these functions transmitter
produce pulses also changes amplitude and produces small time delays also called 'pulser' and 'transmit beam former'
increasing the ____ ____ control increases the amplitude of the voltage driving the transducer output power
two effects when increasing power bioeffects increased acoustic power resulting in greater penetration
what are the functions of the receiver (5) compression compensation amplification rejection demodulation Memory aid: All Cars Can Drag Race
this function of the receiver is necessary because the signals returning from tissue are too small to process amplification also called receiver gain
synonyms for amplification (2) gain, receiver gain
synonyms for TGC (3) DGC, depth gain compensation SGC, swept gain compensation pots, potentiometers
the application of extra amplification to adjust for the increasing attenuation with depth compensation (what TGC does)
this function of the receiver is necessary because the dynamic range of the returning echoes is much larger than the dynamic range of the display compression
it is possible to compress signal levels into brightness levels visible to the human eye (Y/N) N
can clinically significant signals be compressed out of visibility (Y/N) Y
the process by which modulations of the reflected wave are removed or detected demodulation often called 'signal detection'
the two things that demodulation does to the US signal rectification smoothing
the process that converts negative components of a signal into positive rectification
the process that essentially averages the signal taking out bumps smoothing also called envelope detection
this function of the receiver effectively sets a threshold below which signals will not be visible on the screen rejection
imaging modality affects power because what two things duty factor, scanned vs non-scanned modality
when duty factor increases, the transmit power must _____ decrease
what happens to the transmit power when image size decreases decrease
what happens to the transmit power when pulse length increases decrease
what happens to the transmit power with shallower focus decrease
what happens to the transmit power with a lower image depth decrease
reasons (2) why the system internally applies approximately 30dB of compensation before TGC make TGC more responsive so TGC is not too sensitive
TGC is operative under color (T/F) F, TGC control is entirely internal for color
since TGC is entirely internal, what can the sonographer do to mask incorrect TGC use gain
what's it called when the system uses an algorithm to make a 'best guess' at TGC settings pre-compensated TGC
how is the amplification in each TGC zone calculated overall gain + TGC
name the two functions of the beam former (front end process) creates sequencing and phase delays for transmit and receive apodization, limiting which elements are active
the data output format from the front end is _____ digital
all post processing in the system takes place on the data in ____ format digital
what are the two core functions of the scan converted (back end process) converting A-mode into B-mode lines organizing lines into formatted image
the precise definition of a pre-process function is any process that is performed before the ___ ___ and ___ ___ scan conversion, data storage
the precise definition of a post-process function is any process that can be performed on ___ ___ after ____ stored data, conversion
the disparity between the 80dB dynamic range of the returning signal and the 36dB dynamic range of the eye is the reason why ___ ____ is required logarithmic compression
the primary clinical concern of compression techniques could loose important clinical data
compression takes place in the __ __ and the ___ ___ front end, back end
compression that takes place in the front end is under user control (Y/N) N
compression that takes place in the back end is under user control (Y/N) Y
what's the primary purpose of using tissue colorization using color hues extends the dynamic range of the eye
monitor formats standards (3) NTSC, United States, 525 lines, 29.97 fps color PAL, Europe, 625 lines, 25fps SECAM, France, 819 lines, 25 fps
interlaced monitors are divided into ___ and ___ groupings even, odd
interlaced monitors display __ frames per second 30
non-interlaced monitors display ___ frames per second 60
no motivation exists to improve the line frequency of monitors > 60 fps because 60 fps is the limit the eye can perceive
what's the smallest division of a monitor pixel
the human eye can only see __ shades of gray 64
the number of shades of gray is calculated by taking 2 to the power of the ___ __ ____ number of bits
since the eye can only see 64 shades of gray, only ___ bits are required for gray scale 6, 26 = 64
most systems store gray scale to at least 8 or 10 bits even though only 6 is needed. The reason for this is because of ___ ____ ambient light
what's one of the benefits of using cine loop the acoustic frame rate is higher than the monitor frame rate allowing more 'real' time frames to be examined
data from cine loop is stored in ___ memory
synonyms for zooming res, magnification
what are the two techniques used for zooming acoustic and non-acoustic
what zooming technique essentially 'stretches' the area of interest non-acoustic zooming
what's the zooming technique called where the system changes the beam profile to improve resolution acoustic zooming
another name for non-acoustic zoom read zoom, implies reading it from memory, like digital zoom on cameras
another name for acoustic zoom write zoom, implies new data is written to memory post-conversion, like optical zoom on cameras
what's a technique to improve lateral focus for a longer depth multiple transmit foci
what's the drawback of using multiple transmit foci degraded temporal resolution
a change in the maximum transmit power during multiple transmit foci causes what kind of artifact banding
the system is allowed to change parameters during receive time. This ability is used as an alternative to B-mode for _____ dynamic (continuous) receive focus
dynamic (continuous) receive focus uses the technique of _____ which changes the focus and delay profile apodization
parallel processing, which improves temporal resolution, works by sending a ___ transmit beam and processing ___ receive beams large, smaller
averaging techniques rely on the fact that the desired image remains _____ over time and noise is ____ constant, random
SNR equation sqrt(n), where n is the number lines averaged
compound (spatial) imaging besides benefiting from averaging has the advantage of reducing _____ ____ specular reflection
the compound image technique that has these two features angle is not changed between frames a weighted average is applied to each frame making newer frames count for more image persistence
image improvements made by making the center pixel the average of its neighbors spatial averaging
short name for constant depth mode C-mode, listening for echoes at a specific depth
an imaging mode where a single acoustic line is repeatedly transmitted, results plotted against time M-Mode
what are the three categories of resolution detail contrast temporal
this type of resolution is highly dependent on the transducer characteristics. It’s the combination of axial, lateral and elevation detail resolution
this type of resolution is the ability to distinguish structures based on variations of brightness contrast resolution
this type of resolution is the ability to distinguish dynamics or changes over time temporal resolution any factor that lowers frame rate lowers temporal resolution
name two averaging techniques commonly used that degrade temporal resolution persistence, compound imaging
what are the three components of resolution detail, contrast, temporal
elevation beam dimension affects which component of resolution? detail
SPL/2 affects which component of resolution? detail
lateral beam dimension affects which component of resolution? detail
the scan converter affects which component of resolution? contrast
the #bits/pixel affects which component of resolution? contrast
post processing curves affects which component of resolution? contrast
the monitor settings (contrast/brightness) affects which component of resolution? contrast
ambient light affects which component of resolution? contrast
acoustic impedance mismatch affects which component of resolution? contrast
depth affects which component of resolution? temporal
packet size (color) affects which component of resolution? temporal
image size affects which component of resolution? temporal
line density affects which component of resolution? temporal
parallel processing affects which component of resolution? temporal
# foci/line affects which component of resolution? temporal
persistence affects which component of resolution? temporal
compound imaging affects which component of resolution? temporal
Created by: gr8vibes on 2014-02-20



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