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32 Cards in this Set
- Front
- Back
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Master Synchronizer |
Communicates with all of the individual components of the ultrasound system. Organize their functions Preparing them to operate as a single integrated system. |
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Transducer |
Converts electrical into acoustic energy during transmission |
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Pulser and Beam Former |
The component that controls the electric signals sent to the transducer for sound pulse generation. Creates the firing pattern for phased array systems. This is called the beam former. |
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Receiver |
The electronics associated with processing the electronic signal produces by the transducer during reception and producing a picture on an appropriate display.
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Display |
The device associated with the presentation of processed data of interpretation. (TV, Audio speakers, and or paper record) |
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Storage |
Any number of devices and media that are used to permanently archive the US data.
(Video tape, paper film, transparent film and computer discs) |
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Pulser |
Receives timing signal from the synchronizer,
Creates an electrical signal that will execute the PZT crystal.
Pulser signals depend upon system and transducer
Do not use a tranducer with a crack in the housing because of the potential for an electrical shock to the patient.
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Pulser Modes |
Continous wave (2 PZT crystals) - Constant Electrical signal in the form of a sine wave, electrical frequency.
Pulsed wave (1 PZT crystal) - Short duration electrical "spike", one electrical spike per ultrasound pulse.
For phrased array systems, the pulser is also called the "beam former."
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What will change the brightness in the entire image? |
OUTPUT power + Overall gain |
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The signals entering form the transducers are extremely weak. The receiver boosts the strength of these signals processes them and prepares them for display. |
Receiver operations:
1. Amplification 2. Compensation 3. Compression 4. Demodulation 5. Reject |
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Amplification (Total Gain) |
Receiver gain/ Overall gain - alters brightness
Every signal is treated identically. High brightness
The faster it vibrates the brighter the image appears. |
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Compensation (TGC, selective Time Gain Compenstion) |
Used to create image of uniform brightness from top to bottom.
Compensation treats echoes differently, depending upon the depth at which they arise.
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Compression (Contrast e.g. grey scale which produces shades of grey a.k.a. Dynamic Range) |
Keeps signals within the operating range of the systems electronics and the grey scale within the range of the human eye can visualize.
Decrease the dynamic range of the signals |
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Demodulation |
Modifies the signal into a form more suitable to display
(Converts electrical into an image for computer or television screens.)
Smoothes the waveforms. |
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Rejection |
(Operating Filters) -
Affects all low level signals everywhere on the image but does not affect the bright echoes. |
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Dynamic Frequency Tuning |
Pulses contain a wide range of frequencies (wide bandwidth).
System selectively processes lower and higher frequencies as the echoes return from greater depths.
Lower frequency signals are used to image deeper structures, since the higher frequencies have attuenuated High frequency is on top of the sector and lowest frequency on the bottom of sector |
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ALARA |
The rule based on the bioeffects principle known as As Low As Reasonably Achievable states that when modifications to either output power or receiver gain can improve the images diagnostic quality, the first and best choice is the one that will maximize the patients ultrasound exposure. |
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Harmonics |
Twice the transmitted frequency |
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Bistable |
Images are composed are composed of only 2 shades, White or Black, High Contrast |
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Grey Scale |
Display represent multiple level of brightness (White, Light gray, Medium gray, etc.) Different colors can represent different signal strengths. |
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Controls |
Brightness - Determines the brilliance of the signals displayed
Contrast - Determines the Range of Brilliance that is displayed. Bistable images are high contrast |
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Analog |
(Real World) A varible attains a continuum of values. |
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Digital |
(Computer World) A variable attains only discrete values. |
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What translates the information from the spoke format into the video format? |
Scan converters |
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Analog Scan Converter |
Dielectric matrix or silicon wafer
Advantage - Excellent spatial Resolution, provides a 1000 x 1000 grid
Disadvantages - 1. Image Fade - charges on silicon wafer dissipate 2. Image Flicker - constant switching between read and write modes 3. Drift - Inconsistent pictures from day to day 4. Deterioration - Tube ages and images degrade |
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Digital Scan Converter |
uses computer technology to convert images into numbers, a process called digitizing.
1. Uniformity 2. Stability 3. Durability 4. Speed 5. Accuracy |
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Two digital scan converters |
1. Pixel
2. Bit |
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Number of picture elements per inch. Spatial resolution improves with higher pixel density and creates an image with greater detail. |
Pixel Density
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Groups of bits and or a series of zeroes and ones |
Bit (Binary Code)
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The greater the number of bits assigned to each pixel of a digital image |
creates more shades of gray |
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Byte |
a unit of digital information in computing and telecommunications that most commonly consists of eight bits |
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Word |
a fixed-sized group of digits (binary or decimal) that are handled as a unit by the instruction set or the hardware of the processor. The number of digits in a word (the word size, word width, or word length) is an important characteristic of any specific processor design or computer architecture. |
