Ultrasound audio waves vibrating at frequencies earlier mentioned these that the human ear can hear, larger than 20,000cycles for each second (hertz, Hz).
Therapeutic ultrasound is that which is applied for therapeutic (relatively than diagnostic) reasons and is generally developed at 1 million cycles for every second or one megacycle (MHz). Typically US frequency is amongst .7 and three.three MHz.
Ultrasound was initially investigated in Europe and was introduced to the United States in the early 1950`s, considering that this time, the use of ultrasound has developed, and it remains a very well-known modality today.
System of motion
US is manufactured by a substantial-frequency alternating present-day becoming applied to a crystal manufactured of quartz or a artificial (i.e. barium titanate or guide zirconate). The recent results in the crystal to bend, to start with in one direction and then the other, as the present-day alternates. This deformation of the crystal results in what is termed piezoelectric energy. The vibration electricity is transferred to a metal plate, commonly nickel-plated brass, and then the patient’s tissue. The crystal and steel plate are housed in the transducer or sound head of the unit.
Actual physical homes
It is not transmitted via a vacuum
It is transmitted improperly by way of gases
It is transmitted ideal by means of fuel-free of charge liquids and superior-density solids
Related to a radio transmitter.
Has an oscillator that produces electromagnetic wave at superior frequencies.
Converts electromagnetic waves into seem waves.
More substantial transducer surface area is improved (7-13cm*), but modest more than enough to preserve skin make contact with.
Waves are emitted in a cylindrical beam perpendicular to traducer area. Therefore maintain the transducer head parallel to tissue floor.
Never allow for the beam to shoot straight into the air without gel or h2o as this may perhaps destruction the crystal.
To exam crystal: drinking water on the head, convert up the intensity the drinking water need to stream.
Air does not conduct properly, will have to use a coupling medium. Use a professional gels, not mineral oil and some gels will have substances that can advertise therapeutic these kinds of as, vit E, aloe.
As US travels as a result of human tissue, it step by step decreases in intensity owing to attenuation. Attenuation is the result of absorption, reflection and refraction, with absorption accounting for about fifty percent of attenuation.
– Proteins are the important absorbers of US
– Increase protein content increase absorption
– Tissues with high h2o content decrease absorption (waves go through)
– Homogenous tissues lower absorption (excess fat)
– Heterogeneous tissues, fascia planes enhance absorption
e.g. bone periosteum, fats muscle mass, diff muscle mass groups.
– Bone reflects waves, which satisfy incoming waves: resonance as a result heat manufacturing (periosteal burning)
– Steel artefacts reflects waves but take up warmth consequently caution
Conversion of the mechanical power of US into heat is expressed as an absorption coefficient and is dependent on tissue variety and frequency. This coefficient is expressed in decibels/cm and is maximum for tissues with the greatest collagen material and improve in proportion to the US frequency.
Absorption coefficients in decibels/cm at 1 and three MHz
50 % depth
The depth of tissue at which the US intensity is 50 % its original intensity is frequency and tissue kind dependent
50 percent depths in mm at one and 3 MHz
Is the redirection of an incident beam away from a reflecting surface at an angle equal and reverse to the angle of incidence. US waves are reflected at tissue interfaces with most reflection transpiring where there is the finest change between the acoustic impedance of adjacent tissues.
There is a hundred% reflection of US at an air-skin interface and only a .1% reflection at couple medium- pores and skin interface. In the body most reflection approx 35% occurs at tender tissue-bone interface.
The redirection of a wave at an interface
When refraction happens, the US wave enters the tissue at one particular angle and proceeds via the tissue at a diverse angle.
The variety of compressions-rarefactions cycles for each unit of time expressed as (hertz). Expanding the frequency decreases the depth of penetration.
Use one MHz for tissue up to 5 cm deep and three MHz for tissue one to 2 cm deep.
There is no particular way of accurately calculating how considerably energy is absorbed in any specific tissue, the choice about dosage is a subject of judgement to some extent.
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This judgement have to be primarily based on the known variables governing ultrasound absorption and is dependent on the pursuing:
Method of supply:
– Ongoing output
Ongoing supply of US all through the treatment method period of time
Used sub acute and continual stages
– Pulsed output
Audio on and off alternately (variable ratio)
I.e. 20% or one:5 obligation cycle is on twenty% of the time off 80% of the time: on for 2ms off for 8ms
When ultrasound is delivered in at pulse manner, with a 20% responsibility cycle or decrease the heat produced in the course of the time on is dispersed for the duration of the off time.
Used far more for acute and sub-acute phase exactly where warmth is not fascinating. Also pulsed US has been revealed to boost mobile permeability far more the continuous US (see under) specifically at one:5 at an intensity of .five-.75 W/cm.
The amount of money of acoustic energy per unit time (Watts)
The electric power for every unit spot of the transducer head expressed in Watts/cm and is confined to 3W/cm
The depth used ought to be altered in accordance with the character of the lesion (chronic better than acute) tissue style (see higher than) decrease intensities for higher absorbers.
When making use of US for non-thermal outcomes guidelines of thumb, use .5 to 1. W/cm. For thermal outcomes when utilizing a frequency of 1 MHz use an depth of among one.5 to 2. W/cm, at a 3MHz frequency generally an intensity of .five W/cm is ample because of to the strength getting absorbed in a lesser much more superficial volume of tissue. When looking to achieve thermal outcomes you count on the affected person to truly feel a gentle warming soon after two to three minutes of therapy, if this does not acquire position raise the depth.
The amount of strength utilized to the tissues and as a result the results is dependent not only the depth but also the size of time applied. In general, treatment method period ought to be elevated when reduced intensities or lessen frequencies are used.
Bare minimum treatment occasions are thought of to be one-two min, most ten-fifteen min. It is also instructed that continual lesions gain from for a longer period procedure situations.
Effects of US on human tissue
The friction triggered by the vibration of the molecules within the patient’s tissues will generate heat. For that reason US can be used as a thermal agent to improve the temperature of deep tissues on regular gentle tissue temperature has been revealed