Ultrasound

Ultrasound is sound with a frequenzy gre

Human ear can hear sound in this frequency range

16-20,000 Hz

Generation of US occurs by applying a high frequency AC to a __________

piezoelectric crystal

Ultrasound enters the body and is attenuated in the tissue by ____, _____, and _____

absorption, reflection and refraction

Critical angle of US

15*

True/False: US intensity increases as the wave travels through tissue

False; decreases

US attenuation is greatest in tissues with ____________

with high collagen content

Fresnel Zone vs Fraunhofer Zone

Fresnel Zone	Fraunhofer Zone
Near Field	Far field
Maxima and minima area close to each other	Ideal: near part of the far field
Length of near field depends on: Diameter of the treatment head Frequency	Practical Application: Underwater Technique

True/False: US generally heats smaller, deeper areas compared to superficial heating agents

True

High absorption coefficient = __________

more heating received; tissue with high collagen content

Low absorption coefficients are usually found in tissue with ________

high water content

US is well suited to heating these types of tissue

tendons, ligaments, joint capsules, and fascia

True/False: US is well suited to heating tendons, ligaments, joint capsules and fascia without heating overlying fat

True

True/False: US is not ideal for muscle heating

True

US is effective for heating small areas of ________ in muscle

Scar tissue (due to increased collagen)

True/False: The speed with which the ultrasound transducer is moved affects the increase in tissue temperature

False; does not affect the increase in tissue temperature

True/False: Changing the absorption coefficient alters the total amount of energy and the heat distribution

False; alters heat distribution but NOT the total amount of energy

Causes of nonuniformity of intensity and temperature increase of US

1. Variety of tissue types

2. Different absorption coefficients

3. Reflection at tissue boundaries

If the ultrasound intensity is too high, the patient will complain of a deep ache from overheating the ________

perioosteum

3MHz vs 1MHz US

3 MHz	1MHz
Lower depth of tissue penetration (1-2cm deep)	Deeper tissue penetration (up to 5cm deep)
For superficial structures	For deep structures
Higher max temperature	Lower max temp

Mechanical Applications of US

1. Cavitation

2. Microstreaming

3. Acoustic streaming

Non thermal effects can be delivered in ____ mode or _____ duty cycle

pulsed mode and 20% duty cycle

Effects of Low Average Intensity US

1. Increase intracellular calcium levels

2. Increase cell membrane permeability

3. Mast cell degranulation

4. Release of chemotactic factor and histamine

5. Promotes macrophage responsiveness

6. Increase rate of protein synthesis by fibroblasts and tendon cells

7. Stimulates proteoglycan synthesis by chondrocytes

Acoustic Streaming

• The steady, circular flow of cellular fluids induced by US

• Reason why US is being used in phonophoresis

Cavitation

The formation, growth, and pulsation of gas-filled bubbles by US

Micromassage

microscopic movement or oscillations of body fluids and tissues induced by US

Thermal vs Non-Thermal Effects

the use of ultrasound to increase the percutaneous absorption of a drug, usually an anti-inflammatory or anesthetic agent

Phonophoresis

Indications for Thermal US

1. Before stretching shortened soft tissues

2. Reduction of pain

Non-thermal / Pulsed Indications for US

1. To accelerate tissue healing

   • Dermal ulcers

   • Surgical skin incisions

   • Tendon injuries

   • Bone fractures

2. Phonophoresis / Sonophoresis

   • Transdermal drug delivery

   • More localized

US intensity for Soft tissue lengthening

1 MHz for 5-10 minutes

US intensity for pain control

1.5 W/cm² for 3 weeks

US intensity for Skin incision healing

 PULSED US x 0.75 or 3 MHZ x 0.5w/cm2 x 20% cycle for 5 minutes daily

US intensity for acute phase of tendon inflammation

pulsed mode at low intensity (0.5 - 1W / cm²)

US intensity for non union fractures

1.5 MHz frequency, 0.15 W/cm2 intensity, 20% duty cycle for 20 minutes

Clinical Application Guidelines

Depth of penetration of 3Mhz

1-2 cm

Depth of penetration of 1MHz

up to 5 cm

The ratio of spatial peak intensity to the spatial average intensity

Beam non-uniformity ration

Application guidelines for shortened soft tissues

Application guidelines for painful areas

0.5 - 3.0 W/cm² x 1 or 3 MHz x 3-10 minutes

Application guidelines for wound healing

0.5 - 1.0 W/cm² x 3MHz x 3-10 mins x 20% duty cycle

Application guidelines for carpal tunnel syndrome

0.15-1.0 W/cm² x 1 MHz x 5-15 mins

Application guidelines for phonophoresis

0.15 - 1.0 W/cm² x 3 MHz x 5-10 mins x 20% duty cycle

US duration is usually _____ for each treatment that is 2x the Effective Radiating Area

5-10 mins; 20 cm² area = ERA of 10cm² = 5-10 mins

Direct method of application

• Moving the US transducer head help keep hot spots from forming

• The speed of moving the US head, between 2 & 8 cm/sec, does not alter the effects

• Strokes overlapping half of ERA is recommended

• Fastest rate of heating occurs with slightly warm conduction gel

  Properties:

  • Non-staining

  • Not irritating to skin

  • Ease of application

  • Cost

Glove or balloon technique is AKA

Bladder technique

Underwater treatment ideally uses _________

degassed water

Contraindications of US

1. Malignant tumor

2. Pregnancy

3. CNS tissue

4. Joint cement or plastic components of arthroplasty

5. Pacemaker

6. Thrombophlebitis

7. Eyes

8. Reproductive Organs

Precautions

1. Acute inflammation (used pulsed mode)

2. Epiphyseal plates

3. Fractures

4. Breast implants

Documentation of US

1. Duty cycle

2. Frequency

3. Intensity

4. Duration

5. Area of the body to be treated

6. Patient position

7. Method of application

8. Goal or rationale of treatment