Ultrasound therapy is often used to treat pain such as knee, hip, elbow, finger, knuckle, TMJ, back pain and radiating sciatica pain but if the caregive or therapist is not careful the choice of the head size may defeat the treatment.
As previously discussed in our article on using ultrasound and also choosing which frequency it is equally important to choose the right head size for the ultrasound machine application. Ultrasound will not flow through air and if the head of the applicator is too large for the area being treated then the ultrasound machine will repeatedly turn itself off as a safety mechanism to prevent harm to the patient.
As an example if the head of the applicator is much larger than the area being treated and the area being treated is rounded then it's not uncommon for most of the surface area of the head to be literally touching air, rather than touching the skin surface to disperse the ultrasonic energy. Air is an insulator and the best ultrasound machines detect a "non contact" area and immediately turn off. This is done due to the air being a resistor and also safeguards the ultrasound machine from overheating.
The most common example of this happening is when a joint such as knuckle, elbow, ankle or knee is being treated and the ultrasound head is much larger than the knuckle or ankle joint. Rather than choosing a machine with a smaller head or changing the head or applicator the procedure is tried and the unit actually turns off during the initial start of the treatment. Without the warning bells and whistles the treatment continues although the ultrasound energy is off. This historically was not uncommon and oftern the patient and care giver assumed a treatment had been given when in actuality it had not.
The other issue with head size is making sure the size of the head area is actually emitting ultrasonic energy. In the past a crystal was placed under the head and it may have been only 1/4th the size of the applicator head that was visible. It was natural to assume the energy was coming from the entire visible head but again it was not since the crystal, from which the ultrasound comes from, was proportionally small compared to the head. What this meant was the area thought to have been treated had not been due to the assumption the head area was emitting in 100% of the surface area.
Today it's very important to deal with knowledgeable reputable people who understand the dynamics of ultrasound therapy.