Chapter 7- Therapeutic Ultrasound

Question 1

Ultrasound

Answer 1

a deep-penetrating agent that produces changes in tissue through thermal and non-thermal (mechanical) mechanisms

Question 2

Ultrasound Production

Answer 2

Ultrasound is produced by an alternating current flowing through a piezoelectric crystal housed in a transducer
The reverse piezoelectric effect is used to produce therapeutic US
-AC current is passed through a piezoelectric crystal resulting in contraction & expansion

Question 3

Transmission of US Waves

Answer 3

sinusoidal waveform has the following properties:
-wavelength
-frequency
-amplitude
-velocity
Requires a coupling medium for energy to pass from the transducer to the tissues

Question 4

Longitudinal Waves

Answer 4

Molecule displacement in longitudinal waves occurs parallel to the direction of the sound

Question 5

Transverse (Shear) Waves

Answer 5

Molecules in transverse waves are displaced perpendicular to the direction of the energy

Question 6

Effective Radiating Area (ERA)

Answer 6

Proportion of the transducer’s surface area that produces ultrasonic energy
Expressed in terms of square centimeter
Large ERAs produce a collimated, focused beam
-treat a localized area, use collimated beam
Small ERAs yield a more divergent beam
-when treating a larger area

Question 7

Frequency

Answer 7

Measured in MHz
Low-frequency (1 MHz) penetrates approx. 5 cm; treats deep structures
High-frequency (3 MHz) penetrates 2.5-3 cm; treats superficial structures

Question 8

Power and Intensity

Answer 8

Power is measured in watts (W)
Intensity describes the strength of the sound waves at a given location within the tissues being treated
Spatial Average Intensity (SAI)-amount of energy passing through the sound head’s ERA (W/cm2)

Question 9

Beam Nonuniformity Ration

Answer 9

the variation between the peaks, the spatial peak intensity, and valleys

Question 10

Duty Cycle

Answer 10

Continuous Output (100% DC)
-causes primarily thermal effects
Pulsed Output
- causes primarily non thermal effects

Question 11

Contraindications

Answer 11

Impaired circulation
Ischemic areas
Areas having sensory deficit
Deep vein thrombosis or thrombophlebitis 
Cancerous tumors
Over-fluid-filled cavities
Over implanted pacemaker
Pregnancy/Menstruating women
Active fx or stress fxs
Metal or bony implants
Joint replacement
Caution over the vertebral column, nerve roots, or large nerve plexus

Question 12

Indications

Answer 12

Acute & post-acute conditions (non-thermal)
Soft tissue healing & repair
Joint contractures/ scar tissue
Chronic inflammation
Reduce muscle spasm
Pain modulation
Increase protein synthesis
Bone Healing
Neuroma
Trigger Points
Warts
Spasticity