Ultrasound sound waves vibrating at frequencies above all those that the human ear can hear, larger than 20,000cycles per 2nd (hertz, Hz).
Therapeutic ultrasound is that which is used for therapeutic (rather than diagnostic) uses and is typically developed at one million cycles for each next or 1 megacycle (MHz). Normally US frequency is involving .seven and three.3 MHz.
Ultrasound was first investigated in Europe and was introduced to the United States in the early 1950`s, considering the fact that this time, the use of ultrasound has grown, and it stays a incredibly popular modality now.
System of action
US is produced by a high-frequency alternating present currently being used to a crystal made of quartz or a synthetic (i.e. barium titanate or guide zirconate). The current will cause the crystal to bend, initial in a single way and then the other, as the latest alternates. This deformation of the crystal produces what is identified as piezoelectric energy. The vibration strength is transferred to a steel plate, ordinarily nickel-plated brass, and then the patient’s tissue. The crystal and metallic plate are housed in the transducer or sound head of the unit.
It is not transmitted by a vacuum
It is transmitted badly via gases
It is transmitted finest by way of gas-totally free liquids and large-density solids
Identical to a radio transmitter.
Has an oscillator that creates electromagnetic wave at superior frequencies.
Converts electromagnetic waves into audio waves.
Larger transducer surface is greater (7-13cm*), but small sufficient to manage skin get hold of.
Waves are emitted in a cylindrical beam perpendicular to traducer surface. For that reason maintain the transducer head parallel to tissue surface area.
In no way allow for the beam to shoot straight into the air with no gel or water as this may possibly injury the crystal.
To examination crystal: h2o on the head, change up the depth the drinking water should stream.
Air does not perform properly, ought to use a coupling medium. Use a commercial gels, not mineral oil and some gels will incorporate substances that can market therapeutic these types of as, vit E, aloe.
As US travels through human tissue, it slowly decreases in depth because of to attenuation. Attenuation is the outcome of absorption, reflection and refraction, with absorption accounting for about 50 percent of attenuation.
– Proteins are the major absorbers of US
– Maximize protein content boost absorption
– Tissues with high drinking water content material lessen absorption (waves go by)
– Homogenous tissues lower absorption (body fat)
– Heterogeneous tissues, fascia planes increase absorption
e.g. bone periosteum, excess fat muscle mass, diff muscle mass teams.
– Bone demonstrates waves, which fulfill incoming waves: resonance therefore heat manufacturing (periosteal burning)
– Steel artefacts reflects waves but take in warmth thus caution
Conversion of the mechanical energy of US into heat is expressed as an absorption coefficient and is dependent on tissue type and frequency. This coefficient is expressed in decibels/cm and is maximum for tissues with the optimum collagen articles and maximize in proportion to the US frequency.
Absorption coefficients in decibels/cm at one and 3 MHz
50 percent depth
The depth of tissue at which the US depth is 50 % its initial depth is frequency and tissue kind dependent
50 percent depths in mm at one and 3 MHz
Is the redirection of an incident beam absent from a reflecting floor at an angle equivalent and opposite to the angle of incidence. US waves are mirrored at tissue interfaces with most reflection developing in which there is the best big difference involving the acoustic impedance of adjacent tissues.
There is 100% reflection of US at an air-skin interface and only a .one% reflection at couple medium- pores and skin interface. In the human body most reflection approx 35% occurs at gentle tissue-bone interface.
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The redirection of a wave at an interface
When refraction happens, the US wave enters the tissue at a single angle and carries on through the tissue at a various angle.
The selection of compressions-rarefactions cycles per unit of time expressed as (hertz). Increasing the frequency decreases the depth of penetration.
Use 1 MHz for tissue up to five cm deep and three MHz for tissue 1 to two cm deep.
There is no sure way of precisely calculating how a lot electricity is absorbed in any individual tissue, the conclusion about dosage is a issue of judgement to some extent. This judgement should be based mostly on the acknowledged factors governing ultrasound absorption and is based on the subsequent:
Method of supply:
– Ongoing output
Continuous shipping and delivery of US throughout the cure period
Utilised sub acute and persistent stages
– Pulsed output
Sound on and off alternately (variable ratio)
I.e. twenty% or one:five duty cycle is on 20% of the time off 80% of the time: on for 2ms off for 8ms
When ultrasound is delivered in at pulse mode, with a 20% responsibility cycle or reduced the warmth produced through the time on is dispersed through the off time.
Utilised additional for acute and sub-acute stage in which heat is not fascinating. Also pulsed US has been proven to enhance cellular permeability more the frequent US (see beneath) in particular at 1:five at an depth of .5-.seventy five W/cm.
The sum of acoustic power for each device time (Watts)
The electric power per unit region of the transducer head expressed in Watts/cm and is restricted to 3W/cm
The intensity used really should be altered in accordance with the mother nature of the lesion (long-term greater than acute) tissue variety (see over) decrease intensities for increased absorbers.
When making use of US for non-thermal consequences guidelines of thumb, use .5 to 1. W/cm. For thermal results when using a frequency of 1 MHz use an intensity of concerning one.5 to two. W/cm, at a 3MHz frequency ordinarily an depth of .five W/cm is enough owing to the power remaining absorbed in a lesser much more superficial volume of tissue. When hunting to obtain thermal results you assume the affected individual to feel a mild warming following 2 to 3 minutes of treatment method, if this does not choose location enhance the intensity.
The amount of vitality applied to the tissues and that’s why the outcomes is dependent not only the depth but also the length of time utilized. In typical, cure duration ought to be increased when decreased intensities or reduce frequencies are made use of.
Least remedy situations are deemed to be 1-two min, optimum ten-15 min. It is also instructed that serious lesions advantage from extended treatment method instances.
Results of US on human tissue
The friction brought about by the vibration of the molecules in just the patient’s tissues will generate warmth. For that reason US can be utilized as a thermal agent to improve the temperature of deep tissues on common comfortable tissue temperature has been proven