How does ultrasound therapy?
By Dave Cooper
Ultrasound, sound waves vibrating at frequencies higher than those that the human ear hears more than 20,000 cycles per second (hertz, Hz).
Therapeutic ultrasound is what is used in a therapeutic (not diagnostic) purposes and, usually performed on one million cycles per second or 1 megahertz (MHz). In general, the U.S. rate of 0.7 to 3.3 MHz.
Ultrasonography was the first time in Europe and was introduced to the U.S. in the early 1950s, since that time, the use of ultrasound has increased, and it remains a very popular method today.
The mechanism of action
U.S. is using high-frequency alternating current applied to the crystal of quartz or synthetic (for example, barium titanate and lead zirconate). At present, causes the crystal to bend, first in one direction, then another, as the current alternates. This deformation of the crystal creates a so-called piezoelectric energy. Vibration energy is transferred metal plate, usually made of nickel plated brass, and then the patient’s tissue. Crystal and a metal plate placed in the drive or sound department head.
It is not transmitted through a vacuum
It is transmitted through the bad gas
It is transmitted through better gas without the liquid and solid high-density
Like the radio.
Has a generator which produces electromagnetic waves at high frequencies.
Converts electromagnetic waves into sound waves.
The large surface of the converter is better (7-13cm *), but small enough to maintain contact with the skin.
The waves are emitted in a cylindrical beam is perpendicular to the surface of the accuser. Therefore, to carry out head-to-parallel converter surface of the fabric.
Never let a ray shoot straight in the air without gel or water, as this may damage the crystal.
To check the crystal water on the head, raise the intensity of the water should flow.
The air is not good to use communications environment. The use of commercial gels, rather than oil, and some gels contain substances that can promote healing such as vitamin E and aloe.
In the United States passes through human tissue, it gradually decreases in intensity due to absorption. Attenuation is the result of absorption, reflection and refraction, the absorption of about half of the decay.
– Proteins are the major sinks of the U.S.
– Increasing the protein content increased absorption
– Fabrics with a high content of reducing the absorption of water (waves pass through)
– Homogeneous tissue, reduced absorption (fat)
– Heterogeneous tissue, fascia planes to increase the absorption
such as bone \ periosteum, fat \ muscle, change a group of muscles.
– Bone reflects the waves, which correspond to incoming waves, so the response of heat (combustion periosteal)
– Metal objects reflect the waves, but absorb heat so be warned
Converting mechanical energy into thermal energy is expressed as U.S. absorption coefficient and depends on tissue type and frequency. This ratio is expressed in dB / cm and the highest for tissues with a high content of collagen and increases in proportion to the frequency of the USA.
The absorption coefficients in dB / cm at 1 and 3 MHz
Half the depth of
The depth of tissue in which the intensity of the U.S. half of its original intensity and the frequency dependence of the type of fabric
Half of the depth in mm for 1 and 3 MHz
This redirection of the incident beam from the reflecting surface at an angle equal and opposite angles of incidence. U.S. waves are reflected at the tissue interaction with the best reflection of the place where there is a big difference between the acoustic impedance of the surrounding tissues.
There is a 100% reflection of the U.S. air interface skins, and only 0.1% of the reflection of a couple of medium-skin interface. In a reflection of the body most about 35% were soft tissue, bone interface.
Redirects wave at the boundary
When there is a refraction of the wave enters into the fabric of the United States at the same angle and continues through the tissue from a different angle.
The number of compression-rarefaction cycles per unit time in the form (Hz). Increasing the frequency reduces the depth of penetration.
Use 1 MHz for the tissue to 5 cm in depth and 3 MHz for tissue from 1 to 2 cm in depth.
There is no definite way of calculating exactly how much energy is absorbed in a given tissue, the decision about the dosage is about the decision to some extent. This decision should be based on known factors determining the absorption of ultrasound and is based on the following:
Method of delivery:
– Continuous power
Continuous supply of the U.S. during the treatment period
Used for acute and chronic stage
– Pulse output
The sound on and off alternately (variable rate)
That is 20% or 1:5 duty cycle of 20% of free-time 80% of the time: within 2 ms to 8 ms
When ultrasound is delivered in a pulsed mode, with 20% duty cycle, or reducing the heat dissipated during the time after hours.
Used by more acute and subacute stage, when the heat is not desirable. In addition, pulsed U.S. has been shown that an increase in cell permeability constant over the U.S. (see below), especially at 1:05 in the intensity of 0.5-0.75 W / cm
Amount of acoustic energy per unit time (W)
Power per unit area of the transducer head is expressed in W / cm and is limited 3W/cm
The intensity of the applied needs to be changed in accordance with the nature of the lesion (chronic higher than acute) tissue type (see above) below the highest intensity of sinks.
When applied to the U.S. non-thermal effects of rules of thumb, use 0.5 to 1.0 W / cm for thermal effects by using the frequency of 1 MHz using an intensity of 1.5 to 2.0 W / cm at a frequency of 3 MHz is usually the intensity of 0, 5 W / cm is sufficient due to the energy absorbed in a smaller volume of more superficial tissues. When looking to achieve a thermal effect you expect the patient to feel soft, warming after 2 to 3 minutes of treatment, if it does not increase the intensity.
The amount of energy used in the tissue and, therefore, the effect depends not only on the intensity and time of application. In general, the duration of treatment should be increased at lower intensities and lower frequencies.
Minimum processing time is 1-2 minutes, 10-15 minutes max. He also suggested that chronic lesions benefit from longer treatment.
The impact of the U.S. human tissue
The friction caused by the vibration of the molecules in the tissues of the patient will produce heat. So the U.S. can be used as a thermal agent to raise the temperature of deep tissues in the average temperature of the soft tissue has been shown
increase by 0.02C per minute at 1 W / cm at 1 MHz. Thermal effects are similar to thermotherapy (heat therapy, see notes), but the U.S. can heat deeper structures and can be applied more accurately, the surface heating agents. The U.S. also will selectively heat the tissue with a high absorption coefficient (bones, tendons, ligaments, joint capsules, fascia) than with low coefficients (fat, muscle).
To increase the heat delivered to the duration and / or intensity can be increased. The frequency will affect the penetration of 3 MHz to heat the tissue up to 1 up to 2 cm in depth, while the 1 MHz to heat the tissue up to 5 cm
Note that the 3-MHz maximum temperature is higher, but the depth of penetration below.
Non Thermal effects
Cavitation is the formation of tiny gas or vapor bubbles lodged in the tissues as a result of ultrasound. During the compression phase and the bubbles are compressed in a phase of depression, they are expanding.
Stable cavitation: occurs when the bubbles oscillate in the range of ultrasonic waves the size of the pressure, but remain unchanged, and when connected with a pair of speakers, it is believed that the therapeutic value. See below
Transient cavitation: occurs when the bladder volume is changing very rapidly, and what causes the decay of high pressure and temperature, resulting in gross tissue damage and free radical release. This occurs when high-intensity
As a result of cavitation is localized, unidirectional movement of fluid around the vibrating bubble. They are very small movement of fluid around the cells, called micro-flows, and is believed to play an important role in the therapeutic effect of the U.S. by changing the permeability of cell membranes in such a way to increase the rate of diffusion of ions through the membrane, for example, Ca which serve as second messenger, can stimulate the recovery process. Na, which alters the electrical activity of nerves, and therefore may be involved in pain. In addition, associated with an increase in mast cell degranulation, increased chemotactic factors, histamine release increased macrophage response and increase the rate of protein synthesis by fibroblasts. All of this is believed to improve healing.
This constant flow of blood through the radiation torque, and is believed to alter cellular activity due to transport from one part of the battle field of the United States to another.
Compression and rarefaction waves, can lead to a form of micro-massage which can reduce swelling and destroy the clutch at high intensity.
Is the application of the United States in connection with the current product as a pair of medium, an increase of pulsation in the U.S. through the skin, chemicals, ie
Counter irritants, vitamins, salicylate, etc.
United States is believed to control the pain by changing his shift, or perception, or by altering the underlying disease.
Stimulation of cutaneous thermal receptors
Changes in nerve conduction changes in thermal or thermal effects
Modulation of inflammation