| Term | Definition |
|---|
| What is US? | the alternate compression and rarfaction of sound waves with a frequency of > 20,000 cycles/sec. |
| Theraputic ultrasound frequency is usuallly___________ | 0.7 to 3,3 MHz |
| Maximum energy absorption in soft tissue at a depth____________ | 2 to 5 cm |
| Intensity __________ as the waves penetrate deeper due to attenuation | decrease |
| thermal effects that make US theraputic are______________ | effects likely due to absorption and the ability to generate heat during this process |
| 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, |
| SATP x duty cycle= | SATA |
| 3 W/cm2 SATP with 20% duty cycle= | 3 x 0.2=0.6W/cm2 SATA |
| SATA=SATP with | continuous US. |
| What is frequency? | number of compression-rarefaction cycles per unit of time, cycles per second;MHz, |
| Increased frequency= | decreased penetration |
| 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) |
| Reflection at the air-skin interface (no medium)= | 10% |
| Reflection when a transmission medium is sued= | 0.1% |
| What is refraction? | redirection of a wave at the interface, enters the tissue at one angle and alters the angle when hitting the inerface. |
| What is attenuation? | decrease in US intensity as the wave moves through the tissues due to absorption , reflection and refraction (50% is due to absorption) |
| In attenuation, tissue and frequency specific is highest in tissues with ___________________. | high collagen |
| 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 Metabolic rate? | increase |
| thermal effects of US on Pain | decrease |
| thermal effects of US on Muscle Spasms | decrease |
| thermal effects of US on Nerve conduction velocity | increase |
| thermal effects of US on Circulation | increase |
| 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. |
| Results form non thermal application enchance the healing process by increasing_____________________________________________. | intracellular calium, skin and cell degranulation, chemotactic factor and histamine release, macrophages responsiveness, and rate of fibroblast protein synthesis |
| Malignant tumor | contraindication |
| Pregnancy | contraindication |
| Central Nervous System tissue | contraindication |
| Joint cement, metal or plastic components | contraindication |
| Pacemaker | contraindication |
| Thrombophlebitis | contraindication |
| Around the eyes or reproductive organs | contraindication |
| Imparied Sensation | contraindication |
| Acute inflammation | precaution |
| Epiphyseal plates | precaution |
| Fractures | precaution |
| Breast Implants | precaution |
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