Foundations of Therapeutic Modalities: Therapeutic Ultrasound

What is an ultrasound?

Mechanical (not electrical) energy is transmitted as sound waves. These high-frequency waves create compressions and rarefactions in tissue.

What are the indications for ultrasound?

• Shortened tissue / ROM

• Pain

• Dermal ulcers

• Carpal tunnel syndrome

• Surgical incisions

• Tendon and ligament injuries

• Bone healing

What are the contraindications for ultrasound?

• Cancer

• Pregnancy

• Directly over CNS tissue

• Total joint replacement near plastic components and bone cement

• Pacemakers

• Thrombophlebitis

• Eyes

• Reproductive organs

Why is it a contraindication to use US on cancer patients?

US may accelerate or increase tumor growth

Why is it a contraindication to use US on pregnant patients?

Do not apply over the pelvis, abdomen, or lower back region in patients who are pregnant or think they may be pregnant

Why is it a contraindication to use US on patients with pacemakers?

Avoid the region of the pacemaker & keep the coaxial cable that connects the US head to the machine off the patient's chest

Why is it a contraindication to use US on patients with thrombophlebitis?

Risk due to blood clots

What is US absorption?

soaking in the US energy for a therapeutic benefit

What does absorption depend on?

Tissue type; more collagen = more absorption

What is the relative US absorption rate of blood?

very low

What is the relative US absorption rate of fat?

Low

What is the relative US absorption rate of muscle?

Moderate

What is the relative US absorption rate of tendon?

High

What is the relative US absorption rate of ligament?

High

What is the relative US absorption rate of cartilage?

Very high

What is the relative US absorption rate of bone?

Extremely high

Increasing ________ content gives ____________ absorption?

protein; increasing

What is US attenuation?

The gradual reduction in US energy as it travels through tissue, draining power, and bouncing or breaking waves up

What is included in attenuation?

absorption, reflection, and refraction

When does attenuation increase?

With higher frequencies and longer distances

What does attenuation affect?

how deeply the US can penetrate

What are the adverse effects of US?

- burns

- standing waves

- cross contamination/infection

What are the mechanical (non-thermal) effects of US?

Enhance cellular processes to improve healing with acoustic streaming and cavitation.

What is acoustic streaming?

altering cell membrane permeability and cellular activity,

positively affects diffusion rates

What is cavitation?

Pulsation of gas bubbles that

may contribute to diffusion across cell

membranes, improving cell function

What are the clinical applications of the non-thermal effects of the US?

- Soft tissue injury repair

- Pain management

- Scar tissue breakdown

What are the thermal effects of the US?

Temperature elevation happens from production of

frictional heat

1 degree Celsius (1.8F) does what?

increases metabolic rate

2 to 3 degrees C (3.6 F- 5.4 F) does what?

reduce muscle spasm and pain; increase blood flow

Greater temperature increases ~4 degrees C (~7.2F) does what?

increase collagen extensibility and inhibit sympathetic activity

What does the frequency of the US do?

Target tissue depth

1 MHz US reaches tissue up to

5 cm deep

3 MHz US reaches tissue up to

1-2 cm deep

What would you use 1 MHz for?

deeper targets like quads

What would you use 3 MHz for?

superficial areas like wrist/finger extensors

What does the intensity of the US do?

It's for tissue depth and effect

What is intensity?

watts per square centimeter

What is the most common range for intensity on the US?

0.5-2.0 W/cm^2

When would you use higher intensities?

Chronic conditions

What is a Pulsed 20% duty cycle?

Non-thermal stimulation for acute injuries

What is a Pulsed 50% duty cycle?

Mild heating for subacute healing

What is a continuous duty cycle?

Thermal effect for chronic tightness and extensibility

How big should a treatment area be for the US?

2x the effective radiating area

What is the treatment time for the thermal effects of the US?

5-10 mins for each treatment area

What is the treatment time for the non-thermal effects of the US?

4 min/treatment area

What desired US effect do we want with soft tissue shortening?

Thermal

What duty cycle would you use for thermal effect?

100% continuous

If the depth of the target is 1-2 cm, what frequency do you use?

3 MHz

If the depth of the target is 3-5 cm, what frequency do you use?

1 MHz

For thermal effect using 100% continuous duty cycle, targeting 1-2 cm depth with 3 MHz, what intensity would you need?

0.5 W/cm^2

For thermal effect using 100% continuous duty cycle, targeting 3-5 cm depth with 1 MHz, what intensity would you need?

1.5-2 W/cm^2

What desired US effect do we want on delayed tissue healing/prolonged inflammation?

Non-thermal

What duty cycle would you use for the non-thermal effect?

20% pulsed

For non-thermal effect using 20% pulsed duty cycle, targeting 1-2 or 3-5 cm depth with 3 or 1 MHz, what intensity would you need?

05-1 W/cm^2

What US setting would you use for an acute phase that we want to reduce inflammation and protect?

Pulsed @ 20%, low intensity

What US setting would you use for a subacute phase that we want to support regeneration?

Pulsed @ 50% or low continuous

What US setting would you use for a chronic phase that we want to remodel and relieve tightness?

Continuous, 1-2 W/cm^2