Term
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Definition
Cycles per second
Measured in Hertz |
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Term
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Definition
Time for one cycle
Wavelength is inversely proportional to frequency |
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Term
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Definition
| Creates sound energy to pass through tissues and receives the energy reflected back |
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Term
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Definition
| Electricity passes through piezoelectric crystal to create a sound beam and vice versa |
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Term
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Definition
1-20 MHz
Velocity is 1540 msec/cm |
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Term
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Definition
High frequency tranducer most commonly used
Most structures are 4 cm in depth |
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Term
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Definition
High frequency
Distance between waves is constant which gives good near field resolution
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Term
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Definition
Low frequency, require large surface area
Space between waves increases with depth and reduces image quality
Requires more pressure to contact skin, may occlude small blood vessels |
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Term
| High Frequency Transducers |
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Definition
Better resolution at shallower depths
> 10 MHz, best for up to 3 cm of depth
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Term
| Mid-Range Frequency Transducers |
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Definition
5-10 MHz
Best for 3-6 cm depth from skin |
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Term
| Low Frequency Transducers |
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Definition
Better for deep tissue but poor image quality
< 5 MHz |
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Term
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Definition
| Large smooth surfaces which reflect waves in one direction |
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Term
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Definition
| Uneven surface which reflects waves in various directions |
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Term
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Definition
Sound wave strikes boundary of 2 tissues
Depends on angle of strike of sound wave, difference of propagation velocities |
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Term
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Definition
Size of sound wave is greater than size of object it encounters which creates uniform scattered amplitude in all directions
No wave reflects back to transducer
Anechoic on screen |
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Term
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Definition
Sound wave energy lost as wave travels through tissues
Due to absorption, reflection, and scattering at tissue interfaces |
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Term
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Definition
| high frequency= high attenuation= limited tissue penetration |
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Term
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Definition
| Low frequency= low attenuation= deep tissue penetration |
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Term
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Definition
Compensates for attenuation by amplifying the signal intensity of returning echo
Amplifies noise too |
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Term
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Definition
Strong reflection of wave to probe, appears white on screen
Bone and Fascia
Higher impedence=higher reflection= hyperechoic |
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Term
|
Definition
Weak reflection of wave to probe, appear grey on screen
Adipose, deep structures
Lower impedence= waves move through= hypoechoic |
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Term
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Definition
No reflection of wave to probe, appears black on screen
Blood vessels, air
ateries, veins, cysts- rayleigh scattering |
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Term
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Definition
anechoic
easiliy compressible |
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Term
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Definition
anechoic
pulsatile
difficult to compress |
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Term
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Definition
hypoechoic
Irregular hyperechoic lines |
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Term
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Definition
| Heterogenous, hyperechoic lines with hypoechoic background tissue |
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Term
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Definition
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Term
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Definition
| Hyperechoic with shadow effect (hypoechoic) |
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Term
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Definition
Hyper and hypoechoic depending on location
above diaphragm- grapes dark
below diaphragm- white dots with small dots in it |
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Term
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Definition
Amplitude (A)
Brightness (B)- always in this mode
Motion (M)
Frame rates 30/sec |
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Term
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Definition
Sliding
Tilting
Compression
Rocking
Rotation |
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Term
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Definition
| Identical reflective properties in all directions |
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Term
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Definition
Reflection is directionally dependent on angle
Steep needle angle in plane does not allow for good reflection
Probe parallel to needle offers best reflection and image quality |
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Term
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Definition
Blue away
Red Towards
Blood floow directly perpendicular to tranducer will be black |
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Term
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Definition
| poor contact of probe to skin |
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Term
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Definition
| Created when wave contacts tissue with high attenuation coefficient (bone) |
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Term
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Definition
Sound wave contacts a strong reflector
Part of wave moves through the needle and bounces back |
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Term
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Definition
| Sound wave passes through structure of litte acoustic impedence into a structure with much higher impedance |
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