Term
| The diameter plays a major role in determining the beamwidth. True or False |
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Definition
|
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Term
| The thickness plays a role in determining the operating frequency for piezoelectric transducer. T or F? |
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Definition
|
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Term
| Beamwidth is also called: |
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Definition
| Lateral Resolution, Side-by-side dimension, angular, azimuthal, transverse. |
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Term
| The depth of natural focus is affected by which 2 principles? |
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Definition
- operating frequency
- diameter of the crystal |
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Term
| what is the distance between the surface of transducer and the natural focus called? |
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Definition
"focal depth"
or near zone length "NZL" |
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Term
| What is Near Zone Length Equation? |
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Definition
|
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Term
| Small diameter crystals are good for |
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Definition
|
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Term
| Large diameter crystals are good for |
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Definition
|
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Term
| What is relation of NZL and operation frequency |
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Definition
|
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Term
| A natural focus occurs when the operating frequency is ____ or/and when the crystal diameter is ____ |
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Definition
|
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Term
| where does the highest intensity occur? |
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Definition
| at the focus (shallower than the focus in reality) |
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Term
|
Definition
| thin layer, with impedance lower than that of piezoelectric crystal, but higher than that of tissue |
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Term
| an ideal diameter of matching layer |
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Definition
|
|
Term
| limitations of simple crystal |
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Definition
| high acoustic impedance, fixed focal depth, long SPL, no ability to steer |
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Term
| what does matching layer do? |
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Definition
| reduces acoustic mismatch between crystal (high) and tissue (low), thus improving transmission efficiency |
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Term
|
Definition
| ability to separate 2 structures in the axial (longitudinal, radial, depth, range) dimension |
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Term
|
Definition
| ability to separate 2 structures in the lateral (side by side, angular, transverse, azimuthal) dimension |
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Term
| axial resolution is determined by |
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Definition
|
|
Term
| lateral resolution is determined by |
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Definition
|
|
Term
| why increasing the frequency to achieve better AR is often not a solution? |
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Definition
| because of the required imaging depth (the size of patient), higher frequency leads to lower penetration |
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Term
| What is the best possible way to obtain the best AR in diagnostics? |
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Definition
| using backing material (shortening SPL by lowering number of cycles) |
|
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Term
| 5 ways of changing the focus |
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Definition
- mirror (not popularly employed)
- lenses
- curved elements
- electronic focusing (requires multiple beams)
- retrospective gating (requires multiple beams) |
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Term
| multiple transducer elements are called |
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Definition
|
|
Term
| disadvantages of lens in focusing |
|
Definition
- acoustic impedance mismatch
- potential heating surface of transducer |
|
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Term
| curved surfaces, a newly employed technique of focusing, requires the use of |
|
Definition
| composite material other than crystal |
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Term
| what are the 2 most useful techniques among the 5 techniques of focusing |
|
Definition
- electronic focusing
- retrospective gating
these are variable-focusing which allows user control |
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|
Term
| elevation resolution is determined by the |
|
Definition
| beamwidth in the elevation plane |
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Term
|
Definition
| convert voltage (electropotential) into sound waves and vice versa |
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Term
|
Definition
| shortens SPL, improving longitudinal resolution |
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Term
| backing material is also called |
|
Definition
|
|
Term
|
Definition
| minimize acoustic impedance mismatch between crystal and tissues |
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Term
|
Definition
| varying voltage which creates the transmit and is processed to create image with receive mode |
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Term
|
Definition
transmit- delivers voltage to signal
receive- delivers echo voltage to system receiver |
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Term
|
Definition
| helps to focus beam (2D arrays in elevation plane) |
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Term
|
Definition
- Doppler only transducer, Blind,
Pencil Beam transducer |
|
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Term
|
Definition
- inexpensive
- good sensitivity of Doppler
- small footprint, allowing insonation in smaller areas |
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Term
|
Definition
- no ability to produce an image
- fixed focus |
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Term
| With Hanafy lens, the crystal is ___ along crystal edges, and ____ in the middle |
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Definition
|
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Term
| The consequence of varying thickness in Hanafy lens is |
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Definition
| there are different resonance across crystal surface: higher frequency in the middle, lower frequency in the outer, thicker aspect -> resulting in a broader field of view in the elevation plane |
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Term
| 2D arrays can steer and focus in both ____ and _____ planes |
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Definition
|
|
Term
| Another name for near field |
|
Definition
|
|
Term
| Another name for far field |
|
Definition
|
|
Term
|
Definition
| the area between transducer to beam focus |
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|
Term
|
Definition
|
|
Term
|
Definition
| where the beam reaches minimum diameter |
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Term
| Focal region is the region over which the beam is most tightly focused and also called |
|
Definition
|
|
Term
|
Definition
| ability to distinguish between 2 objects in any of the three dimensions: axial, lateral, elevation |
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|
Term
| operating frequency is also known as |
|
Definition
|
|
Term
|
Definition
| the center frequency of the transmit bandwidth |
|
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Term
| f0 (operating frequency) in CW is determined by |
|
Definition
| frequency of the drive (transmit) voltage |
|
|
Term
| f0 (operating frequency) in PW is determined by |
|
Definition
| crystal thickness and speed of sound in crystal material.[image] |
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Term
| Electrical capacitance is defined as |
|
Definition
| stored electrical charge when a potential difference (voltage) is applied between electrical conductors |
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Term
|
Definition
| Capacitive Micromachined Ultrasound Transducer |
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|
Term
| CMUT technology is based on the concept of creating and detecting sound through _____ |
|
Definition
|
|
Term
|
Definition
|
|
Term
| Acoustic window in CMUT is |
|
Definition
| a material put over the cells as a barrier between patient and CMUT cells |
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Term
| CMUT doesn't require backing material but requires matching layer. T or F? |
|
Definition
| False. CMUT requires backing material, but doesn't require matching layer as it has acoustic window |
|
|
Term
| what are electrodes in CMUT used for? |
|
Definition
| Electrodes are basic components of capacitor, which hold electrical charge to create electric field |
|
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Term
|
Definition
| used to increase capacitance and keep electrodes from shorting in collapse mode |
|
|
Term
| when an electric voltage is applied to the faces of either type, the thickness of the element increases or decreases depending on |
|
Definition
|
|
Term
| other names of transducers |
|
Definition
| probe, scanhead, transducer assembly |
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