Ultrasound in the field of medical physiotherapy

1. What is ultrasound?

Ultrasound refers to mechanical vibration waves with a frequency of more than 20,000 Hz that cannot cause normal human auditory response. The method of applying ultrasound to the human body to achieve the purpose of treatment is called ultrasound therapy.



2. Unit of ultrasound intensity

Sound intensity is the intensity of sound energy per unit time, that is, the sound energy that passes vertically through each square centimeter of area per second. The commonly used measurement unit is watt/cm2 (W/cm2). For example, the clinical treatment dose is 0.1-3W/cm2.

3. Characteristics of ultrasound propagation

Sound waves are a form of material propagation energy, so their propagation must rely on a medium, and they cannot propagate in a vacuum, which is different from light waves and electromagnetic waves. Therefore, in ultrasound therapy, the ultrasound treatment head cannot act directly on the skin, but requires a medium-coupling agent. I believe that people who have done ultrasound therapy or ultrasound examination will not be unfamiliar with it. It is the sticky and cool jelly-like thing.



4. Depth of ultrasound action

First, understand a concept-semi-absorption layer, which refers to the thickness when ultrasound waves attenuate to half of their original energy in a certain medium. For ultrasound treatment, the half absorption layer value of muscle is 3.6 cm, that of fat is 6.8 cm, and that of muscle plus fat is 4.9 cm. The same tissue absorbs ultrasound waves of different frequencies differently. The higher the ultrasound frequency, the more it absorbs and the shallower the penetration. For example, 1MHz ultrasound penetrates about 5 cm, while 4MHz ultrasound can only penetrate 1 cm. Therefore, when we use ultrasound treatment, we must choose the ultrasound mode reasonably according to the depth of the lesion.



5. The effect of ultrasound treatment on the human body system

(1).The effect on the nervous system

Small doses of ultrasound can reduce nerve excitability and slow down the conduction speed, thus having a significant analgesic effect on peripheral nerve diseases such as neuritis and neuralgia. However, large doses of ultrasound acting on peripheral nerves can cause vascular paralysis, tissue cell hypoxia, and then necrosis. The central nervous system shows a high sensitivity to ultrasound waves. Some people point out that even if the intensity of 0.1W/cm2 is directly applied to brain tissue, it can cause irreversible damage. Therefore, some foreign data point out that "ultrasound is prohibited for use in the brain."



(2). Effects on the circulatory system

(3). Effects on the skeletal system

Low doses of ultrasound can promote bone growth and callus formation; medium doses can be used for bone and joint trauma; high doses of ultrasound acting on unossified bones can cause bone dysplasia, so ultrasound is prohibited for the epiphyses of young children.

(4). Effects on connective tissue

Ultrasound stimulates the growth of connective tissue in wounds with tissue damage; when connective tissue grows excessively, ultrasound has a softening and dissipating effect, especially for concentrated fibrous tissue. Therefore, it can also be seen clinically that ultrasound has a more obvious softening and dispersing effect on scars.

(5). Effects on the reproductive system

Female reproductive organs are more sensitive to ultrasound. Although the therapeutic dose of ultrasound is not enough to cause morphological changes in the reproductive organs, it can cause miscarriage in animal experiments, so it is prohibited for pregnant women's lower abdomen. Male testicular tissue is very sensitive to ultrasound, and high-intensity effects can cause substantial damage and infertility. Experiments have also shown that appropriate amounts of ultrasound can reduce sperm production in humans and animals.

6. Choice of ultrasound mode - continuous or pulse?

Continuous ultrasound: During the entire treatment process, the sound head continuously radiates sound energy to the body. It acts evenly and has a greater heat generation effect.

Pulsed ultrasound: During the treatment process, sound energy is intermittently radiated to the body, and its heat effect is smaller. Generally speaking, acute injuries are mainly treated in pulse mode, while chronic injuries or old injuries are mostly treated in continuous mode. However, the choice of treatment mode varies from person to person and should be used under the guidance of professionals according to the period of injury and individual sensations.



7. Indications and contraindications

Indications:

Traumatic sports diseases such as low back pain, myalgia, contusion, sprain, periarthritis of shoulder, proliferative spondylitis, temporomandibular arthritis, tenosynovitis, etc.; scars, adhesions, post-injection induration, scleroderma, and hematoma organization; neuritis and neuralgia can be treated when acting on local and corresponding nerve segments.

Contraindications:

Malignant tumors, active pulmonary tuberculosis, heart area and stellate ganglion of severe heart disease, bleeding tendency, venous thrombosis are all contraindicated; other treatments are best used for the abdomen of pregnant women (early stage) and the bones of children. The dosage should be strictly controlled when treating the head, eyes, heart, and genitals.