| nonthermal effects that make US theraputic are | effects form cavitiaion, microstreaming and acoustic streaming |
| Transducer (sound head) | Pizoelectric crystal (and casing housing it) converts electrical energy into sound waves. |
| What is Pizoelectric? | ability to generate electricity from a mechanical force or change shape in respinse to an electrical current. |
| What is Power(W)? | amount of acoustic energy per unit time, Measured in watts. |
| What is Intensity(W.cm2)? | power/unit area of the sound head, WHO limits thereputic ultrasound intensity to 3.0 W/cm2 |
| What is Spatial Average Intensity? | Average intensity over the area of the transducer , intensity is not uniform over the entire transducer, this is the average intensity. |
| What is Spatial Peak Intensity? | Peak intensity over the area of the transducer, usually this occurs at the center of the beam |
| What is Beam Nonuniformity Ratio(BNR)? | Ration of spatiial peak intensity to spatial average intensity, usually 5:1 or 6:1 |
| BNR 5:1, spatial average intensity 1 W/cm2= spatial peak intenstiy________ W/cm2 | 5 |
| BNR, spatial average intensity 2 W/cm2= spatial peak intensity __________W/cm2 | 12 |
| what is continuous US?(conversion of sound wave to heat) | Continuous delivery of US, responsible for thermal effects |
| What is pulsed US? | US dellivered only part of the treatment, responsible for non thermal effects (breaks up edema) |
| What is Duty cycle? | Proportion of treatment time the US is delivered, 20 % duty cycle=1.5 duty cycle=20% on and 80% off, continuous US=100% duty cycle |
| What is Spatial Average Temporal Peak (SATP) | Spatial average intensity during on time of pulse |
| What is Spatial Average Temporal Average (SATA)? | spatial average intensity averaged over the entire treatment time,the amount of energy delivered to the tissues, |
| what is effective Radiation Area(ERA)? | area of the transducer radiating US energy, the ERA is always smaller than the area of the transducer. |
| When the US beam converges it is called what? | near field |
| When the US beam diverges it is called what? | far field |
| Length of near field is dependant on US frequency and ERA | transducer radius/US wavelength |
| US intensity in the near field varies due to inerference of the beam this causes what? | less uniform distribution to the near field tissues. |
| the attenuation of 2-5 cm in most tissues fall into the___________ for most transducers? | near field |
| What is absorption? | converting mechanical energy of US into heat. |
| What is absorption coefficent? | the amount of absorption that occurs in a tissue type at a specific frequency, tissue and frequency specific, highest in tissues wih high collagen content, increases in proportion to the frequency. |
| What is reflection? | redirection of the beam away from the interface surface at an opposite angle.. |
| Most reflection (35%) occurs where? | at the soft tissue-bone interface (tendon) |
| In attenuation, tissue and frequency specific is an ______________ | in proportion to the frequency. |
| What is half depth? | depth where US intensity is 1/2 its initial intensity, this tells us why it is more effective superficially than deep. |
| What is Standing Wave ? | When the reflected wave and incident wave are superimposed on one another, occurs when the sound head is not waving. |
| What is Cavitiaiton? | happens beneath the skin, it is a formation, growth and pulsation of gas-or vapor filled bubbles. |
| In cavitation bubbles ____________ during the rarefaction phase and ___________during the compression phase. | expand, shrink |
| What is stable cavitaiton? | may be the mechanism for non-thermal effects of US. |
| What is unstable cavitiation? | which cause free radical formation when the bubble burst, is not thought to occur with therapeutic frequencies of US |
| What is Microstreaming? | microcurrents forming around oscillating bubbles |
| what is Acoustic streaming? | Circular flow of cellular fluids during US, alters cell avtivit by transporting materials within the US field. |
| What is Phonophoresis? | Use of a topical drug in conjunction with US to facilitate transdermal delivery of the drug. |
| thermal effects of US on Soft tissue extensibility | increase |
| Compared with superfical thermal, US reaches_______________________________ | deeper tissues and heats a smaller area |
| Heating rate is proportional to the absorption coefficent at the applied frequency | Higher temperature will be achieved in high collagen tissues and with higher frequency US |
| Total heat transferred at a givern setting is the same regardless of the absorption coefficent | if tissue has a higher coefficent greater temperature increase to a smaller area of more superficial tissues |
| To increase total heat transferred _______________________ of treatment must be increased. | duration and intensity |
| jWhat is 1MHz frequency and intensity? | heats tissues up to 5 cm deep, can be applied at higher intensities because of lower heat production |
| What is 3 MHz frequency and intensity? | heats tissues 1-2 cm deep, no more actual heat transfer than 1 MHz , its just more superficial, in order to protect the individual, 3 MHz US should be applied at intensities 3-4 times lower than 1 MHz US. |
| What is duration? | Longer treatments will ultimately transfer more heat, highest tissue temperature increases occur at sogt tissue-bone interfaces due to high reflection |
| burns and discomfort are avoided by? | moving the transducer head, because there are many factors influencing the heat transfer, start with clinically determined values and alter from there based on pt. report |
| Non-thermal effects are due to _____________________________? | cavitation, microstreaming, and acoustic streaming, a duty cycle of 20% will not allow heat, preventing thermal effects. |
