Dr. Zatrok's blog
Dr. Zatrok's blog

Dr. Zatrok's blog

Guide on ultrasound dosing during treatment

by Dr. Zsolt Zatrok

As with other procedures and medicines, ultrasound treatment, usually used for musculoskeletal conditions, is not “consumable” indefinitely. Ultrasound dosing requires attention. It can be overdosed in the same way as drugs. Although it fortunately does not cause poisoning, it can cause an increase in symptoms and pain. If you experience this, stop the treatment and see what “dose” you need. Reducing the frequency, duration and/or intensity of treatment is the solution in such cases.

Basics of ultrasound dosing

Ultrasound frequency

The depth to which ultrasound rays penetrate the body depends on the frequency. The lower the frequency, the deeper it penetrates. In ultrasound treatments, the frequencies used are mostly between 1 and 3 MHz. If the point to be treated is close to the surface, use a 3 MHz frequency treatment head, if it is in deeper tissue, use a 1 MHz head.

Pulse rate

The ultrasound beam can be continuous or pulsed. Use a continuous beam only for chronic complaints. For example, if you’ve been struggling with tennis elbow or Achilles tendonitis for six months, you can use the continuous mode.

For all other conditions, especially acute inflammation, pain and injuries, use the pulsed mode. However, don’t expect such a mode from devices costing a few tens of thousands of dollars, only the better devices provide it.

Pulsating ultrasound means that the device transmits for a certain period of time, followed by a pause. Different diseases and conditions require different beam-to-pause ratios. You can usually find out which one is right for a particular problem in the instructions that come with the device.

The pulse rate is the ratio of the duration of the pulse to the duration of the subsequent pause. For example, 1:3 means that a beam with a duration of 1 time unit is followed by a pause of 3 time units (no ultrasound radiation during this period).

The choice of the correct pulse rate depends crucially on the condition of the tissue to be treated. The more recent the injury, the more sensitive the tissue is to the energy. In fresh disease, the ultrasound pulse should be followed by a longer pause, i.e. a ratio of 1:3 to 1:4 is recommended.

The more recent the disease, the more sensitive the tissue is.

The older the injury, the more the tissues “like” the concentrated energy input. In chronic cases, you can therefore reduce the pulse rate to 1:2, 1:1 or even use continuous (uninterrupted) ultrasound radiation.

A general principle is to use 1:4 or 1:3 for acute complaints, 1:2 or 1:1 for a few days of SUBACUTE complaints, and 1:1 pulsed or continuous ultrasound for chronic lesions.

Treatment intensity

As with the determination of the pulse rate, the ultrasound intensity required for the target tissue depends on the condition of the tissue. The more intense the lesion, the milder the ultrasound beam is sufficient. The longer the condition has been present, the less sensitive it is and therefore the higher the intensity you can use to induce healing. Also, consider that you lose some ultrasound energy if you don’t use enough ultrasound gel.

You can determine the treatment intensity from the table below:

Tissue condition Required intensity
Acute 0.1 – 0.3 W/cm2
Subacute 0.2 – 0.5 W/cm2
Chronic 0.3 – 0.8 W/cm2

Depth of coverage

The ultrasound is absorbed by the tissue. Its extent varies depending on the thickness and condition of different tissues (e.g. skin, fat, muscle, etc.). It is now generally accepted that 3 MHz treatment can be used to treat superficial lesions closer than 2 cm to the skin surface. If the area to be treated is deeper than this, a 1 MHz treatment head is recommended.

Knowing the absorption is important because the intensity set on the device does not reach deep into the skin. If you want to treat a formula 6cm deep, you need to take absorption into account. In other words, the deeper you want to treat, the higher the intensity you need to set on the device. The table below will help you determine the intensity value to set on your device.

Example: you want to treat an acute lesion 5cm deep. The intensity requirement of the acute tissue is 0.3 W/cm2. In the table, follow the 5cm column until you get to the 0.3W/cm2 row. Here you can see that you need to set your device to an intensity of 0.68 W/cm2 to get an intensity of 0.3W at 5 cm.

Depth of lesion (cm)
Intensity required 0.5 1 2 3 4 5 6
1.0 W/cm2 1.20 1.40 1.80 1.75 2.00 2.25 2.50
0.9 W/cm2 1.08 1.26 1.62 1.58 1.80 2.03 2.25
0.8 W/cm2 0.96 1.12 1.44 1.40 1.60 1.80 2.00
0.7 W/cm2 0.84 0.98 1.26 1.23 1.40 1.58 1.75
0.6 W/cm2 0.72 0.84 1.08 1.05 1.20 1.35 1.50
0.5 W/cm2 0.60 0.70 0.90 0.88 1.00 1.13 1.25
0.4 W/cm2 0.48 0.56 0.72 0.70 0.80 0.90 1.00
0.3 W/cm2 0.36 0.42 0.54 0.53 0.60 0.68 0.75
0.2 W/cm2 0.24 0.28 0.36 0.35 0.40 0.45 0.50
0.1 W/cm2 0.12 0.14 0.18 0.18 0.20 0.23 0.2

Treatment time

Rule: 1-minute treatment per area corresponding to the size of the treatment head.

Measure the relationship between the ultrasound treatment head and the area to be treated. The larger the area to be treated is compared to the treatment head, the more times 1 minute of treatment is needed. That is, if the area of pain is 5 times the size of the head, treat for 5 minutes; if it is 10 times the size, treat for 10 minutes.

You may overdose on ultrasound treatment, as indicated by your complaints and an increase in pain. If you notice this, reduce the treatment time and intensity.

You may experience adverse effects if you treat an area at too high an intensity and for too long. The main effect of ultrasound comes from heating the tissue. Giving too much to an area at once hinders healing instead of aiding it. Think of it like sun exposure. If you sunbathe regularly for 15-20 minutes, you will slowly tan, but if you lay out for 3-4 hours, you will not tan, you will burn. Ultrasound helps if used properly and in regular doses.

If you’re unsure, consult your doctor or a physiotherapist experienced in ultrasound treatment to determine the right setting for your complaint.

Below you find a summary guide ultrasound dosing guide about the above-mentioned.

rules of dosing ultrasound for certain treatments and injuries

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