Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
20 Cards in this Set
- Front
- Back
Reverse peizoelectric effect |
generating mechanical strain from the applicationof an electrical signal to piezoelectric material |
|
Direct Peizoelectric effect |
generating electrical signal from the application of a mechanical strain (sound wave) applied to a peizoelectric material |
|
Peizoelectric materials |
Ceramic and crystalline materials with the capacity to generate electrical charge in response to applied mechanical stress |
|
Relationship between frequency and: - Wavelength - Penetration - Resolution |
Higher frequency has: - Shorter wavelength - Greater penetration - Greater axial resolution |
|
Acoustic impedance |
resistance to propagation of sound waves throughtissues fixed property of tissues determined by mass density and propagation speedof sound in a specific tissue |
|
Attenuation |
Loss of energy as sound waves are transmitted through a medium Due to: - Absorption - Deflection - Divergence |
|
Absorption |
Loss of energy from the ultrasound beam transferred to the tissues in the form of heat |
|
Deflection |
Reflection, refraction, and scattering of energy within tissue |
|
Divergence |
Loss of the energy as the ultrasound beam widens and the same power is spread over a greater area |
|
Doppler effect |
Shift in frequency of sound wave due to relative motion between source and observer - If source moving towards observer then higher frequency shift - If source moving away from observer then lower frequency shift |
|
Spectral doppler |
Display of doppler velocities (y-axis) over time (x-axis) |
|
Pulsed wave doppler |
Emission of sound waves in pulses that allows measurement of doppler shifts at a specific area/depth |
|
Pulse repetition frequency (PRF) |
Cycle frequency pulsed wave doppler |
|
Aliasing |
Phenomenon with color doppler and pulsed wave spectral doppler whereby the direction/velocity of flow cannot be accurately determined |
|
Nyquist limit |
The doppler velocity at which aliasing occurs = PRF/2 |
|
Continous wave doppler |
Measures doppler velocities along the entire length of the ultrasound beam |
|
Color flow doppler |
Displays doppler shifts over a superimposed 2-d image Pulse wave doppler from multiple small areas |
|
Power flow doppler |
Shows only information on velocity of flow but not direction Useful for low flow states |
|
Thermal index |
Measure of U/S's thermal bio effects Ratio of attenuated acoustic power at depth of interest to estimated power needed to raise tissue by 1 degree celcius |
|
Mechanical index |
Measure of potential for cavitation/micro mechanical damage |