Ultrasonoterapia en fisioterapia
20/05/2024 19:28:12

Machine translation from Spanish

Dosage in ultrasonotherapy

Applying ultrasonotherapy does not consist of moving the head for a while on the patient's skin.

Ultrasonotherapy, or the application of US in physiotherapy, is the most complex electrotherapy technique (provided that it is intended to dose correctly).

It is understood that it is not the same:

Suggestions on how to apply US we find several in the literature: some recommend that it always be pulsed, others that it always be continuous, others with a fixed head, others always in motion, some that always 5 minutes, others 10 minutes, etc, etc.

So much suggestion means that it is not known how to do it correctly, or that interestedly, for some "convenient" reason, a certain methodology is proposed "to save time."

The best and most classic proposal from the origins of the technique is the one that proposes:

This proposal is very interesting because it contemplates all the parameters, but it is the account of "the grandmother" that only counted on the fingers. Well, the moment we modify any parameter it affects the others and we are already lost.

Above he asks, how do we combine all this? Well, knowing each parameter well, what it means and what it implies in the session. Let's see:

  1. 1 Mhz penetrates more and admits more power in W / cm2 than 3 Mhz. With 3 Mhz we could reduce it by 1/3 of the power that would be applied with 1 Mhz.
  2. The continuous power is the one named, the pulsed power is the one referred to continuously reduced to the percentage or fraction in which we adjust the pulse, that is, the power decreases to the effective one.
  3. The power is not the dose, the power is the work that the machine does just in 1 s; and the session lasts more than 1 s. NEVER CALL THE POWER INTENSITY.
  4. We can operate with the power of the entire head or with the power emitted by each cm2 of the head. It is better to use the latter because this is how we contemplate the real emission surface (ERA) in the head.
  5. Power is the speed with which energy is applied. With a lot of power (the supply is very accelerated) it does not give the body time to absorb it. With little power (very slow energy supply) it does not accumulate and there is no therapeutic effect. Too much power causes a prick in the patient during the session.
  6. What is the proper wattage? the one that the patient tolerates and just before feeling pain. It usually manifests as well-perceived heat. Less potency is a cause of low therapeutic efficacy. Finding the right power requires two or three trial runs.The head can be used fixed or mobile. NEVER MIX THE TWO SHAPES IN THE SAME SESSION. The treated area is well defined, delimited and the scan of the head is distributed homogeneously over the decided surface. In small areas little power and in large areas more power. How much? View electrotherapy notes a work in PDF and look for the epigraph on US doses, the tables of potencies according to surface and those of doses in some diseases. View PDF of dosage in US.
  7. The treated surfaces should not exceed 90 or 100 cm2.
  8. What is the dosage? It is the amount of energy that is deposited on the patient at the end of the session, but distributed among the cm2 of the treated area. However, that amount that you will receive when the session ends, we have to decide before starting the treatment or the session.
  9. The dose or amount of energy that we "WANT", that we "PRETEND" to apply: is the product of multiplying the power of the device by the time of the session and dividing it between the surface of the treated area. That result is J/cm2. How do we solve this problem? Physics and mathematics give us the formula.

The typical problem would be - If we intend to deposit 40 J/cm2; about 60 cm2; with continuous US; at 1 Mhz; adjusted to 1.5 W/cm2; with a 5 cm2 head; How long will the session last ?:

Physics gives us the solution (and let's stop with "other nonsense"). We develop:

Power in W/cm2 * ERA *% * time in seconds

Surface treated in cm2

The factor of [% or fraction] refers to whether we work continuously, or in what percentage of pulse.

Dosage formula

All are previously set parameters (except ONE) in the previous formula, we adjust them before starting the session and they are not modifiable, the variable that can act as an unknown will be time and we can isolate it in the first term. So the resulting formula will be:

Dose per area in cm2
40 J/cm2 x 60 cm2

time =
= 320 seconds (3.3 minutes)

W/cm2 x ERA x 100% (continuous)
1.5 W/cm2 x 5 x 100%

Other suggestions may be considered for a specific pathology or for profitability interests, but if we intend to boast of "scientism", this is the correct formula.

Logically it implies that if we apply pulsed, the effectiveness of the power is lost, so, in some way, we must compensate it.

In the following calculation template for dosing ultrasound, we can enter and modify the values in the double-lined boxes to find the correct time values.

By default, values are proposed to work continuously; but if we want to do it in the pulse, in the FRACTION OF THE RIGHT we put the values of the fraction corresponding to the pulse that we would use. The blue buttons select the most common values.

Continuing with pressing, in the FRACTION OF THE LEFT we introduce the inverse values to those of the fraction on the right or REDUCING FACTOR OF THE PULSE. This is so because we should raise the adjusted power to higher values than the continuous positions. How much? at the levels indicated by the COMPENSATED POWER box, and that the equipment allows.

Dosing calculators

Formula to dose ultrasonotherapy
Ultrasound therapy dosage


Sp. in cm2


|  W/cm2
|  W/cm2



Value of power to compensate, in case of using pulsed,
to keep the same session time.

J. Totals


W effective

% / 60

Click on the sign [=] to see results

Element to present it well on computer screens over 500 pixels wide

At the bottom of the template you can see another formula to use at will, in case you want to compensate for a certain increase in time in order to eliminate, as far as possible, deficiencies in the application of the technique. A PERCENTAGE BETWEEN 5% AND 20% IS USUALLY INCLUDED.

If the pulsed power is compensated, we will observe that there appear values in the already compensated power, which are not practical, because the equipment does not allow them, but we can observe, learn and analyze the variability that occurs.

Note to manufacturers

It is time for manufacturers to modernize the design of their ultrasound equipment, including the parameter of J / cm2 that they intend to apply to patients, along with the other parameters that affect the technique so that the session time is calculated automatically.


Self built meter for US power.

formulas de dosis

Equipment containing the formulas to dose correctly.

Ultrasound videos

Ultrasound application video

Ultrasonotherapy Dosing Video

Multiple head

This last type of application in ultrasonotherapy is not very suitable, and if the dosage is not specified well, they tend to generate "US burns". The causes of these burns are in the bad balance of some of the emitters, in concentrating a lot of power and leaving them excessive time, for that reason; "... we no longer have to be bored shaking the head and we can leave it a little longer...."

View PDF on US dosage
View PDF on electrotherapy notes (in this work look for the ultrasound therapy section).

Translated January 2021

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Nota al público general

Las técnicas de electroterapia no consisten en aplicarse un aparato “que alivia o elimina los dolores” y aplicárselo sin más. O usar un potenciador muscular que publicita “menganito de tal” y . . . ¡a ponerse fuertes!. Estas técnicas requieren de una base de conocimientos que el profesional conoce para ajustar los parámetros, situar los electrodos, dosificar correctamente e indicar la metodología de tratamiento.

20/05/2024 19:28:12

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José Mª Rodríguez Martín

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