Ultrasound
Terms
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- Thermal effects of US on Metabolic rate?
- increase
- thermal effects of US on Pain
- decrease
- what is effective Radiation Area(ERA)?
- area of the transducer radiating US energy, the ERA is always smaller than the area of the transducer.
- Transducer (sound head)
- Pizoelectric crystal (and casing housing it) converts electrical energy into sound waves.
- 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)
- 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
- To increase total heat transferred _______________________ of treatment must be increased.
- duration and intensity
- What is frequency?
- number of compression-rarefaction cycles per unit of time, cycles per second;MHz,
- 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
- 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 Microstreaming?
- microcurrents forming around oscillating bubbles
- What is Pizoelectric?
- ability to generate electricity from a mechanical force or change shape in respinse to an electrical current.
- jWhat is 1MHz frequency and intensity?
- heats tissues up to 5 cm deep, can be applied at higher intensities because of lower heat production
- Theraputic ultrasound frequency is usuallly___________
- 0.7 to 3,3 MHz
- thermal effects of US on Nerve conduction velocity
- increase
- what is Acoustic streaming?
- Circular flow of cellular fluids during US, alters cell avtivit by transporting materials within the US field.
- Reflection at the air-skin interface (no medium)=
- 10%
- When the US beam converges it is called what?
- near field
- Around the eyes or reproductive organs
- contraindication
- What is Phonophoresis?
- Use of a topical drug in conjunction with US to facilitate transdermal delivery of the drug.
- Compared with superfical thermal, US reaches_______________________________
- deeper tissues and heats a smaller area
- nonthermal effects that make US theraputic are
- effects form cavitiaion, microstreaming and acoustic streaming
- 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 Standing Wave ?
- When the reflected wave and incident wave are superimposed on one another, occurs when the sound head is not waving.
- What is unstable cavitiation?
- which cause free radical formation when the bubble burst, is not thought to occur with therapeutic frequencies of US
- thermal effects of US on Circulation
- increase
- Joint cement, metal or plastic components
- contraindication
- What is Cavitiaiton?
- happens beneath the skin, it is a formation, growth and pulsation of gas-or vapor filled bubbles.
- Fractures
- precaution
- Non-thermal effects are due to _____________________________?
- cavitation, microstreaming, and acoustic streaming, a duty cycle of 20% will not allow heat, preventing thermal effects.
- 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 Beam Nonuniformity Ratio(BNR)?
- Ration of spatiial peak intensity to spatial average intensity, usually 5:1 or 6:1
- Thrombophlebitis
- contraindication
- SATA=SATP with
- continuous US.
- US intensity in the near field varies due to inerference of the beam this causes what?
- less uniform distribution to the near field tissues.
- What is Spatial Peak Intensity?
- Peak intensity over the area of the transducer, usually this occurs at the center of the beam
- What is Intensity(W.cm2)?
- power/unit area of the sound head, WHO limits thereputic ultrasound intensity to 3.0 W/cm2
- Pacemaker
- contraindication
- Central Nervous System tissue
- contraindication
- What is stable cavitaiton?
- may be the mechanism for non-thermal effects of US.
- Malignant tumor
- contraindication
- thermal effects of US on Soft tissue extensibility
- increase
- 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 reflection?
- redirection of the beam away from the interface surface at an opposite angle..
- Epiphyseal plates
- precaution
- SATP x duty cycle=
- SATA
- In attenuation, tissue and frequency specific is highest in tissues with ___________________.
- high collagen
- 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
- What is pulsed US?
- US dellivered only part of the treatment, responsible for non thermal effects (breaks up edema)
- Maximum energy absorption in soft tissue at a depth____________
- 2 to 5 cm
- Imparied Sensation
- contraindication
- What is US?
- the alternate compression and rarfaction of sound waves with a frequency of > 20,000 cycles/sec.
- Reflection when a transmission medium is sued=
- 0.1%
- what is continuous US?(conversion of sound wave to heat)
- Continuous delivery of US, responsible for thermal effects
- Increased frequency=
- decreased penetration
- thermal effects that make US theraputic are______________
- effects likely due to absorption and the ability to generate heat during this process
- What is Spatial Average Temporal Peak (SATP)
- Spatial average intensity during on time of pulse
- When the US beam diverges it is called what?
- far field
- Most reflection (35%) occurs where?
- at the soft tissue-bone interface (tendon)
- thermal effects of US on Muscle Spasms
- decrease
- In attenuation, tissue and frequency specific is an ______________
- in proportion to the frequency.
- BNR, spatial average intensity 2 W/cm2= spatial peak intensity __________W/cm2
- 12
- What is duration?
- Longer treatments will ultimately transfer more heat, highest tissue temperature increases occur at sogt tissue-bone interfaces due to high reflection
- 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 Power(W)?
- amount of acoustic energy per unit time, Measured in watts.
- Length of near field is dependant on US frequency and ERA
- transducer radius/US wavelength
- the attenuation of 2-5 cm in most tissues fall into the___________ for most transducers?
- near field
- Pregnancy
- contraindication
- 3 W/cm2 SATP with 20% duty cycle=
- 3 x 0.2=0.6W/cm2 SATA
- In cavitation bubbles ____________ during the rarefaction phase and ___________during the compression phase.
- expand, shrink
- 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
- Acute inflammation
- precaution
- Breast Implants
- precaution
- BNR 5:1, spatial average intensity 1 W/cm2= spatial peak intenstiy________ W/cm2
- 5
- What is Spatial Average Temporal Average (SATA)?
- spatial average intensity averaged over the entire treatment time,the amount of energy delivered to the tissues,
- 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
- Intensity __________ as the waves penetrate deeper due to attenuation
- decrease