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DMS 110 Sys Ops
system operations ultrasound DMS 110 acoustic physics
| Question | Answer |
|---|---|
| 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 |
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