6- Ultrasound

Ultrasound

• A sound with a frequency greater than 20,000 cycles, that when applied to the body, has both thermal and nonthermal effects

• A crystal expands contracts creating an ultrasound wave

Thermal effects of US

• Accelerates metabolic rate

• Reduce pain

• Reduce muscle spasm

• Alteration of nerve conduction velocity

• Increased circulation

• Increased soft tissue extensibility (ligaments, tendons, joint capsules, etc.)

• Heat smaller areas of deeper tissue

Examples of diagnosis to use thermal US for

• Contracted soft tissue

• Chronic tendonitis (with tissue shortening)

Non-thermal effects of US

• Increased cell permeability

• Promotes tissue healing

• Facilitate transdermal drug penetration

• Modify inflammation

• Low-intensity pulsed US is used to facilitate tissue healing, modify inflammation and enhance transdermal drug delivery

• Used in a pulsed mode with 20% or lower duty cycle

• Uses cavitation - the formation, growth, and pulsation of gas-filled air bubbles caused by US

• Ex. acute tendonitis

Examples of diagnosis to use non-thermal US for

• Acute tendonitis

US intensity

The power per unit area of the sound head, expressed in W/cm²

Effective radiating area (ERA)

The area of the transducer from which the ultrasound energy radiates

Duty cycle

• The proportion of the total treatment time that the US is on

• Continuous = 100% of the time

• Pulsed = 20% of the time

What type of duty cycle does thermal US use?

100% continuous

What type of duty cycle does non-thermal US use?

20% (or less) pulsed

Reflection

The redirection of the incident beam away from a surface at an angle equal and opposite to the angle of incidence

Frequency

• The number of compression-rarefaction cycles per unit of time, expressed in cycle per second (Hz), frequency is typically 1-3 MHz for therapeutic US

Frequency used on superficial tissue (1-2 cm deep)

3 MHz

Frequency used on deep tissue (up to 5 cm deep)

1 MHz

Phonophoresis

• The use of US in combination with topical medication (US enhances the effects of transdermal drugs)

• Used with anti-inflammatory medications (hydrocortisone, dexamethasone, salicylates, lidocaine)

How does US effect pain?

• Altering transmission of perception

• Modifying the underlying condition

What frequency and intensity of pulsed US is used for surgical skin incisions?

1 or 3 MHz, 0.5-0.8 W/cm2

What frequency and intensity of pulsed US is used for tendon and ligament injuries?

Frequency varies, but 0.5-1 W/cm2

What frequency and intensity of US is used for bone fxs?

1.5 MHz, .15W/cm2

What is the duty cycle and intensity used with thermal US?

• Continuous

• 1MHz → 1 - 2.0 w/cm²

• 3MHz → 0.5 -2.0 w/cm²

What is the duty cycle and intensity used with non-thermal US?

• Pulsed

• 0.5 - 1.0 w/cm²

Contraindications for use of US

• Malignant tumor

• Pregnancy

• CNS tissue

• Joint cement

• Plastic components

• Pacemaker

• Thrombophlebitis

• Eyes

• Reproductive organs

• METAL IS NOT A PROBLEM FOR US

Ultrasound cannot be used over metal.

False, US can be used over areas with metal implants, such as screws, plates, or all-metal joint replacements

Precautions for US

• Acute inflammation

• Epiphyseal plates

• Fractures

• Breast implants

Adverse effects

• Usually occur when US is contraindicated or not applied correctly

• Burns

• Cross-contamination/infection

How long is the typical US application?

• Dependent on size of area being treated

• Larger areas = more time

What to include for US documentation

• Area to be treated

• Frequency

• Intensity

• Duty Cycle

• Duration

• Patient response

• US to the left lateral knee, 0.5 w\cm2, pulsed 20%, 3 MHz, 8 mins

How fast should you move the ultrasound head?

2-8 cm/sec

Which of the following is NOT one of the main clinical uses of ultrasound that is administered with a duty cycle of 20% or less?

increase collagen extensibility

Which modality would be MORE effective for heating the gluteus minimus tendon?

continuous ultrasound

What would be the ideal ultrasound parameters for heating tissues that is 4 cm deep?

1 MHz, 100% duty cycle

If a patient who is receiving ultrasound complains of a deep ache, what is most likely the cause of the pain?

Overheating of the periosteum

When trying to heat the origin of the latissimus dorsi muscle, what would be the most appropriate modality to select?

moist hot pack

What parameters would be the MOST appropriate for the use of ultrasound to heal bone fractures?

1.5 MHz, 0.15 w\cm2, 20% duty cycle for 15-20 mins daily

Do drugs that are delivered by phonophoresis become systemic?

Yes

Is continuous ultrasound to the knee of a pregnant woman contraindicated?

No

Is pulsed ultrasound contraindicated in the area where a thrombus may be present?

Yes