| Term | Definition |
|---|
| Transducer | Sound Head |
| Pizoelectric | Ability to generate electricity from a mechanical force or change shape in response to an electrical current |
| MultiFrequency Transducers | Have one crystal; only optimal fro one frequency |
| Effective Radiation Area (ERA) | Area of the transducer radiating ultrasound energy, always smaller than the area of transducer |
| Power (W) | Amount of acoustic energy per unit time, measeured in Watts |
| Intensity (W/cm2) | Power/Unit area of sound Head |
| WHO | Limits therapeutic ultrasound to intensity 3.0 W/cm2 |
| Frequency | Number of compression-rarefraction cycles per unity of time. Cycles per second; Hz |
| Spatial Average Intensity | Average intensity over the area of the transducer. Not uniform over entire transducer; this is the average intensity |
| Spatial Peak Intensity | Peak intensity over the area of the transducer, usually occurs at the center of the beam. |
| Beam Nonuniformity Ration (BNR) | Ratio of spatial peak intensity to spatial average intensity. 5:1 or 6:1, must be specified on unit |
| Standing Wave | When the reflected wave and incident wave are superimposed on one another. Sound head not moving |
| Continuous Ultrasound | Continuous delivery of ultrasound, Thermal |
| Attenuation | Decrease in US intensity as the wave moves through the tissues due to: Absorption (50%), reflection, refraction |
| Tissue and frequency specific (attenuation) | Highest in tissues with high collagen content, Increase in proportion to the frequency |
| Reflection | Redirection of the beam away from the interface surface at an opposite angle. Most reflection 35% occurs in soft tissues and bone |
| Refraction | Redirection of a wave at the interface. Enters the tissue at one angle and alters the angle when hitting the interface |
| Pulsed Ultrasound | Delivered only part of the treatment, Non thermal |
| Duty Cycle | Proportion of treatment time the US is delivered |
| Spatial Average Temporal Peak (SATP) | Spatial average intensity during on time of pulse |
| Spatial Average Temporal Average (SATA) | Spatial average intensity averaged over the entire treatment time. Amount of energy delivered to the tissues. SATP=SATA with continuous US |
| Cavitation | Formation, growth and pulsation of gas or vapor filled bubbles. |
| Cavitation Bubbles | Expand during the rarefraction phase adn shrink during the compression phase. Stable-Non themal, NonStable- Not thought to occur |
| Microstreaming | Microcurrents forming around oscillating bubbles |
| Acoustic Streaming | Circular flow of cellular fluids during US, alters cell activity by transporting materials within the US field |
| Near/Far Field | Beam converges(Near), and diverges (Far) *Length of field is dependent on US frequency and ERA |
| Half Depth | Depth where US intensity is 1/2 it's initial intensity. Tells us why it's more effective superficially |
| Phonophoresis | use of a topical drug in conjunction with US to facilitate transdermal delivery of the drug. |
Combine with other sets
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