Term
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Definition
| property of certain crystals to emit energy by expanding and contracting when pressure from a returning sound beam is applied |
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Term
| reverse piezoelectric effect |
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Definition
| property of certain crystals to expand and contract when an electrical current is applied, creating a mechanical sound wave |
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Definition
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Term
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Definition
| temperature at which piezoelectric crystals lose magnetic properties (300-400 degrees Celsius) |
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Term
| What happens to a crystal if heated above Curie point? |
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Definition
| loses piezoelectric properties |
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Term
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Definition
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Term
| How to calculate transducer frequency (MHz) |
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Definition
| crystal propagation speed (mm/us) / 2x crystal thickness (mm) |
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Term
| thickness of typical pulsed elements |
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Definition
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Term
| propagation speeds of typical pulsed elements |
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Definition
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Term
| How is frequency determined in PW US? |
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Definition
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Term
| How is frequency determined in CW US? |
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Definition
| by electrical voltage applied to the element |
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Term
| What does damping material do? |
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Definition
| reduces # cycles in pulse, pulse duration, SPL and improves axial resolution |
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Term
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Definition
| electronic suppressing of ringing by applying a voltage of opposite polarity to the crystal after the pulse |
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Term
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Definition
| difference between highest & lowest frequency found in a pulse; measured in MHz |
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Term
| How to increase bandwidth |
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Definition
| limit amount of ringing in the crystal (damping material) |
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Term
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Definition
| describes homogeneity of beam frequency |
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Term
| How is Q-Factor related to bandwidth and axial resolution? |
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Definition
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Term
| How q-factor is related to frequency |
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Definition
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Term
| How to calculate q-factor |
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Definition
| operating frequency / bandwidth |
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Term
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Definition
| decreases the impedance difference between the crystal and the skin |
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Term
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Definition
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Term
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Definition
| all points on a wave are a source for the production of spherical secondary wavelets (determines direction of the sound beam) |
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Term
| constructive interference |
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Definition
| Wave amplitudes reinforce each other, building a wave of even greater amplitude |
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Term
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Definition
Waves intersect “out-of-phase.” The peak of one wave lines up with the trough of the other
Results in a decreased amplitude or a canceling out of the wave altogether |
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Term
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Definition
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Term
| How is focal length related to frequency and crystal diameter? |
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Definition
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Term
| How is the amount of widening in the far zone related to frequency and crystal diameter? |
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Definition
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Term
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Definition
| ability to distinguish close objects |
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Term
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Definition
| temporal, contrast, detail |
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Term
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Definition
| ability to distinguish closely spaced events in time |
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Term
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Definition
| ability of the equipment’s gray scale display to distinguish between echoes of slightly different intensities |
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Term
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Definition
| ability to distinguish 2 adjacent objects as 2 distinct objects |
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Term
| 3 types of detail resolution |
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Definition
| axial, lateral, elevational |
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Term
| other names for axial resolution |
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Definition
| LARD - longitudinal, axial, range, depth |
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Term
| other names for lateral resolution |
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Definition
| LATA - lateral, angular, transverse, azimuthal |
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Term
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Definition
| ability to distinguish 2 structures laying one on top of the other, parallel to the path of sound travel |
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Term
| How to calculate axial resolution |
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Definition
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Term
| How to improve axial resolution |
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Definition
| higher frequency and less ringing (damping) |
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Term
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Definition
| resolution perpendicular to the beam path; minimum distance of 2 structures lying next to each producing 2 echoes |
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Term
| What determines lateral resolution? |
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Definition
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Term
| How to improve lateral resolution |
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Definition
| focusing and higher frequency |
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Term
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Definition
| thickness of the tissue perpendicular to the scan plane |
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Term
| Other names for elevational resolution |
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Definition
| section thickness, Z-axis, elevational axis, or out-of-plane focusing |
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Term
| Increased slice thickness: |
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Definition
Decreases spatial resolution (ability to detect & display adjacent entities)
Causes slice thickness artifacts
Reduces ability to detect small low-contrast lesions |
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Term
| 2 types of electronic focusing |
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Definition
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Term
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Definition
| uses interference phenomena by delaying (phasing) the electrical pulses to each crystal to cause the wavefronts to converge at variable focal points |
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Term
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Definition
| crystal elements are timed to be sensitive to listening at a particular depth (using the range equation) |
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Term
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Definition
| time delays at reception to process returning echoes and optimize image quality |
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Term
| sequential electronic beam focusing |
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Definition
| applied to individual beams to improve lateral & slice thickness resolution |
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Term
| phasing electronic transmission focusing |
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Definition
| Delays the pulse to the crystals so they are pulsed in an outer to inner method |
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Term
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Definition
| Delaying the electronic pulse to each crystal causes the wave fronts to be steered at various angles by the wave interference phenomenon |
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Term
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Definition
Transmit/receive technique using different pulses across aperture of linear array to reduce the intensity of grating/side lobes
Maximum voltages are at the center & lower voltages toward boundary |
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Term
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Definition
| Crystal element divided into many smaller sub-elements wired together to form original size element - reduces grating lobes |
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Term
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Definition
| aperture increases to maintain a constant focal width during echo reception |
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Term
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Definition
| Transducer surface size producing beam |
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Term
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Definition
| fixed focus crystal mechanically steered to produce a sector image; crystal is physically rocked or rotated through an arc sweeping the beam back & forth over the region being scanned |
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Term
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Definition
| weaker beams of sound traveling out from a single element in directions different than that the main beam |
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Term
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Definition
| Concentric rings of crystals on a motor assembly that rotated back & forth that created a curved top/blunted sector image |
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Term
| Transducer that provides the thinnest beam of all probes |
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Definition
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Term
| advantages of annular array |
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Definition
superior image quality
small footprint (tight windows)
narrowest beam thickness |
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Term
| disadvantages of annular array |
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Definition
mechanical parts wear out
mechanical system provide limited Doppler capability
vibrations from probe can be annoying to the user & the patient |
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Term
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Definition
no moving parts to wear out
better lateral resolution
faster frame rates |
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Term
| disadvantages to linear array |
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Definition
| larger footprint creates loss of body contact & cannot be used in small windows |
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Term
| advantages to curved linear array |
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Definition
no moving parts to wear out
better lateral resolution
faster frame rates
larger field of view |
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Term
| disadvantages to curved linear array |
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Definition
| hard to use in small windows due to larger footprint |
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Term
| advantaged to phased arrays |
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Definition
no moving parts to wear out
better lateral resolution
faster frame rates
larger field of view
small footprint |
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Term
| disadvantages to phased linear arrays |
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Definition
expensive
limited near field of view
grating lobe artifacts |
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Term
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Definition
| Combine linear & phased technologies to produce a trapezoidal-shaped image |
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