Ultrasound audio waves vibrating at frequencies earlier mentioned those that the human ear can hear, increased than 20,000cycles for each second (hertz, Hz).
Therapeutic ultrasound is that which is utilised for therapeutic (fairly than diagnostic) reasons and is usually made at one million cycles per 2nd or 1 megacycle (MHz). Frequently US frequency is concerning .7 and 3.3 MHz.
Ultrasound was initial researched in Europe and was launched to the United States in the early 1950`s, since this time, the use of ultrasound has grown, and it continues to be a very well-known modality these days.
Mechanism of motion
US is created by a large-frequency alternating existing staying utilized to a crystal manufactured of quartz or a synthetic (i.e. barium titanate or direct zirconate). The existing results in the crystal to bend, first in a person path and then the other, as the latest alternates. This deformation of the crystal generates what is known as piezoelectric electrical power. The vibration power is transferred to a metal plate, generally nickel-plated brass, and then the patient’s tissue. The crystal and metallic plate are housed in the transducer or audio head of the unit.
It is not transmitted by a vacuum
It is transmitted poorly via gases
It is transmitted most effective by means of fuel-absolutely free liquids and large-density solids
Similar to a radio transmitter.
Has an oscillator that makes electromagnetic wave at significant frequencies.
Converts electromagnetic waves into audio waves.
Much larger transducer surface area is far better (seven-13cm*), but tiny adequate to manage skin call.
Waves are emitted in a cylindrical beam perpendicular to traducer floor. Hence maintain the transducer head parallel to tissue area.
Never make it possible for the beam to shoot straight into the air without the need of gel or water as this may perhaps damage the crystal.
To exam crystal: drinking water on the head, convert up the depth the drinking water really should stream.
Air does not perform effectively, should use a coupling medium. Use a industrial gels, not mineral oil and some gels will have substances that can encourage healing this sort of as, vit E, aloe.
As US travels through human tissue, it step by step decreases in depth owing to attenuation. Attenuation is the outcome of absorption, reflection and refraction, with absorption accounting for about 50 % of attenuation.
– Proteins are the major absorbers of US
– Improve protein content material raise absorption
– Tissues with large h2o content reduce absorption (waves go by way of)
– Homogenous tissues lessen absorption (fat)
– Heterogeneous tissues, fascia planes raise absorption
e.g. bone periosteum, fats muscle mass, diff muscle mass teams.
– Bone reflects waves, which fulfill incoming waves: resonance therefore heat manufacturing (periosteal burning)
– Metallic artefacts demonstrates waves but absorb warmth hence caution
Conversion of the mechanical strength of US into warmth is expressed as an absorption coefficient and is dependent on tissue style and frequency. This coefficient is expressed in decibels/cm and is highest for tissues with the optimum collagen content and maximize in proportion to the US frequency.
Absorption coefficients in decibels/cm at 1 and three MHz
Fifty percent depth
The depth of tissue at which the US depth is fifty percent its original depth is frequency and tissue style dependent
Fifty percent depths in mm at one and 3 MHz
Is the redirection of an incident beam away from a reflecting surface area at an angle equivalent and opposite to the angle of incidence. US waves are mirrored at tissue interfaces with most reflection happening wherever there is the greatest difference among the acoustic impedance of adjacent tissues.
There is one hundred% reflection of US at an air-pores and skin interface and only a .1% reflection at couple medium- pores and skin interface. In the entire body most reflection approx 35% occurs at gentle tissue-bone interface.
The redirection of a wave at an interface
When refraction occurs, the US wave enters the tissue at one particular angle and proceeds by way of the tissue at a unique angle.
The number of compressions-rarefactions cycles per unit of time expressed as (hertz). Raising the frequency decreases the depth of penetration.
Use 1 MHz for tissue up to five cm deep and 3 MHz for tissue one to two cm deep.
There is no particular way of accurately calculating how much energy is absorbed in any particular tissue, the determination about dosage is a matter of judgement to some extent. This judgement will have to be centered on the recognised factors governing ultrasound absorption and is primarily based on the pursuing:
Manner of shipping and delivery:
– Steady output
Continuous shipping of US in the course of the remedy period of time
Employed sub acute and persistent phases
– Pulsed output
Seem on and off alternately (variable ratio)
I.e. 20% or one:five responsibility cycle is on twenty% of the time off eighty% of the time: on for 2ms off for 8ms
When ultrasound is sent in at pulse method, with a twenty% duty cycle or decreased the warmth produced in the course of the time on is dispersed in the course of the off time.
Utilised more for acute and sub-acute stage the place heat is not fascinating. Also pulsed US has been demonstrated to raise cellular permeability much more the continuous US (see beneath) particularly at one:five at an intensity of .five-.seventy five W/cm.
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The sum of acoustic vitality for every unit time (Watts)
The energy per device spot of the transducer head expressed in Watts/cm and is restricted to 3W/cm
The depth utilized should really be altered in accordance with the nature of the lesion (continual greater than acute) tissue type (see earlier mentioned) lower intensities for increased absorbers.
When implementing US for non-thermal results principles of thumb, use .five to one. W/cm. For thermal effects when applying a frequency of one MHz use an intensity of among 1.five to 2. W/cm, at a 3MHz frequency generally an intensity of .5 W/cm is ample because of to the vitality currently being absorbed in a smaller sized far more superficial quantity of tissue. When searching to accomplish thermal results you expect the patient to experience a moderate warming right after two to three minutes of therapy, if this does not consider location boost the intensity.