| Term | Definition |
|---|
| ultrasound | alternate compression and rarefaction of soundwaves - frequency >20,000 cycles/sec |
| therapeutic ultra sound frequency | 0.7 to 3.3 MHz |
| Max. energy absorption in soft tissue | 2 to 5 cm |
| Intensity decreases as | waves penetrate deeper |
| thermal effects due to | absorption of sound waves |
| non-thermal effects from | cavitation, microstreaming, and acoustic streaming |
| transducer (sound head) | Pizoelectric crystal ( and housing) that converts electrical energy into sound waves |
| Effective Radiation Area (ERA) | area of transducer radiating energy |
| Power (W) | amount of acoustic energy per unit time - measured in watts |
| Intensity (W/cm2) | power/unit area of the sound head - limited by WHO to 3.0 W/cm2 |
| Frequency | number of compression - rarefraction cycles per unit of time -- cycles per second Hz |
| increased frequency | decreased penetration |
| Spatial Average Intensity | Avg. intensity over the area of the transducer |
| Spatial Peak Intensity | Peak intensity over the area of the transducer - usually in cneter of beam |
| Beam Nonuniformity Ratio (BNR) | Ratio of spatial peak intensity to spatial average intensity - usually 5:1 or 6:1 |
| Standing wave | When reflected eave and original wave are superimposed on one another - happens when sound head is not moving |
| Near field / far field | ultrsound beam first converges then diverges |
| length of near field | dependent on ultrasound frequency and ERA |
| Half depth | Depth where ultrasound intensity if 1/2 its original intensity |
| Phonophoresis | use of a topical drug in conjunction with US to facilitate transdermal delivery of the drug |
| Continuous Ultrasound | uninterrupted delivery of ultrasound - responsible for thermal effects |
| Absorbtion | converting mechanical energy of ultrasound into heat |
| Absorbtion coefficient | amt. of absorbtion that occurs in a tissue at a specific frequency - highest in tissue with high collagegn content - increases as frequency increases |
| Reflection | redirection of the beam away from the interfacxe surface at an opposite angle |
| 35% of reflection occurs at | the soft tissue bone interface (tendon) |
| 100% reflection occurs when | no medium is used |
| 0.1% reflection occurs when | a transmission medium is used |
| Refraction | redirection of a wave at interface |
| Attenuation | decrease in ultrasound intensity as the wave moves through tissue due to: Absorbtion, reflection, and refraction |
| 50% of attenuation due to | absorbtion |
| Pulsed ultrasound | US delivered only part of the treatment, responsible for non-thermal effects |
| Duty cycle | proportion of treatment time the ultrasound is delivered (on:total time) 20% duty cycle 1:5 duty cycle=on 20% and off 80% |
| Spatial Average Temporal Peak (SATP) | spatial average intensity during the on time of pulse |
| Spatial Average Temporal Average (SATA) | spatial average intensity averaged over the entire treatment time - SATP x duty cycle =SATA |
| Cavitation | formation, growth, and pulsation of gas or vapor filled bubbles |
| Microstreaming | microcurrents forming around oscillating bubbles |
| Acoustic streaming | circular flow of cellular fluids during US - alter cell activity by transporting materials within the US field |
Combine with other sets
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