1. ESAT 3640 Therapeutic Modalities
Ultrasound
ESAT 3640
Therapeutic Modalities

2. Ultrasound in Sports Medicine
One of the most widely used therapeutic modalities
Overused?
Primary use is for stimulating the repair of soft tissue injuries and pain relief

3. Background Acoustic energy
Produces thermal or non-thermal physiological effects
Deep heat

4. Basic Physics of US Ultrasound unit construction Transducer
Sound head
Piezoelectric crystal
Piezoelectric effect

5. Transmission of Acoustical Energy in Biological Tissue
Acoustic energy requires molecular collision for transmission
“Stone in a pool of water”
US is a mechanical wave in which energy is transmitted by the vibrations of the molecules of the biological medium through which the wave is traveling

6. Transverse vs. Longitudinal Waves
Transverse wave
Compressions
Rarefactions

7. Frequency of Wave Transmission
US has frequency greater than 20 kHz
0.75 – 3 MHz
Audible sound (16 – 20 kHz)
The lower the frequency, the greater the depth of penetration

8. US Wave Attenuation
Decrease in energy intensity as the US wave is transmitted through various tissues due to scattering and dispersion
US penetrates tissues high in H2O content
Absorbed in dense tissues high in protein
Penetration and absorption are inversely related

9. Ultrasound Beam
Larger diameter and higher frequency = more focused beam
Smaller diameter and lower frequency = more divergent beam

10. Wave Reflection
Some of the wave may be reflected or refracted as it encounters various tissue
Acoustic impedance
Standing waves
Hot spots

11. Effective Radiating Area
Portion of the transducer that actually produces the sound wave
Dependant on the surface area of the crystal
Transducer is not indicative of the actual radiating surface

12. Frequency of US 3 MHz = superficial heat 1 MHz = deep heat
US and fracture detection?

13. Amplitude, Power, & Intensity
Amplitude – Magnitude of the vibration in a wave
Power – Total amount of US energy in the beam (Watts)
Intensity – Measure of the rate at which energy is being delivered per unit area (Watts/cm2)

14. Intensity Spatial average intensity Spatial peak intensity
Intensity of beam averaged over area of transducer
Spatial peak intensity
Highest value occurring w/in beam
Temporal peak intensity
Max intensity during on period w/ pulsed US

15. Intensity Continued Temporal averaged intensity
Average power during pulsed US during on and off periods
Spatial averaged temporal peak intensity
Spatial mean during a single pulse

16. Beam Non-uniformity Ratio
BNR
% to which intensity of beam varies
SPI/SAI

17. Pulsed vs. Continuous Wave US
Continuous wave – sound intensity remains constant
Thermal effect
Pulsed wave – intensity is periodically interrupted with no US energy being produced during the off period
Duty cycle
Nonthermal effect

18. Physiological Effects
US may cause clinically significant responses in cells, tissues, and organs through both thermal and nonthermal mechanisms

19. Thermal Effects Increase in the extensibility of collagen
Decrease in joint stiffness
Reduction of muscle spasm
Modulation of pain
Increased blood flow
Mild inflammatory response
May help in the resolution of chronic inflammation
Increased blood flow for healing and pain reduction through heating
Chronic inflammation

20. Thermal Effects
Tissue must be raised to a level of 40 to 45° C for 5 minutes.
Dyson, M. Physiotherapy, 73(3): , 1987
Temperature rise above base line is key factor
increases of 1° C increases metabolism and healing
Increases of 2 - 3° C decreases pain and muscle spasm
Increases of 4° C and greater increase extensibility of collagen and decrease joint stiffness
Lehmann et al

22. Nonthermal Effects
Cavitation – Formation of gas-filled bubbles that expand and compress due to ultrasonically induced pressure changes in tissue fluids
Acoustic streaming – Unidirectional movement of fluids along the boundaries of cell membranes resulting from the mechanical pressure in an ultrasonic field

23. Cavitation Stable vs. unstable
Results in increased flow in the fluid around the vibrating bubbles

24. Acoustic Streaming
Produces high viscous stresses that can alter cell membrane structure and function
Changes in cell permeability to sodium and calcium ions

25. Nonthermal Effects Increased cell membrane permeability
Altered rate of diffusion across cell membrane
Increased vascular permeability
Secretion of cytokines
Increased blood flow
Increased fibroblastic activity
Stimulation of phagocytosis
Production of healthy granulation tissue
Synthesis of protein
Synthesis of collagen
Reduction of edema
Diffusion of ions
Tissue regeneration
Formation of stronger, more deformable scar

26. Techniques of Application
Frequency of treatment
Acute vs. chronic
How many treatments should be given?
Duration of treatment
Dependent on treatment goal
Keep the transducer moving!!!

27. Coupling Methods Direct contact Immersion Bladder Technique
Watch for bubbles
Bladder Technique

28. Clinical Applications of US
Soft tissue healing and repair
Scar tissue and joint contracture
Stretching of connective tissue
Chronic inflammation
Bone healing
Pain reduction
Plantar warts
Placebo effects

29. Phonophoresis
The use of ultrasound to drive a topical application of a selected medication into the tissues
Safer than iontophoresis
Potentially deep penetration
What is effect on medication when mixed with coupling agent?
Not as point specific as iontophoresis
Wave attenuation

30. Contraindications Areas of decreased temperature sensation
Areas of decreased circulation
Vascular insufficiencies
Eyes
Reproductive organs
Pelvis immediately following menses
Pregnancy
Pacemaker
Epiphyseal areas in developing individuals
Total joint replacements
Infections
Over spinal column