1. Therapeutic Ultrasound (Part two)By
Prof.Dr.Gehan Mosaad

2. At the end of this lecture the student should be able to
Discuss therapeutic effects of US
Identify physiological effects of US
Understand indications and contraindications of US
Know the precautions and adverse effects of US
Understand the different techniques of US application

3. Therapeutic Effects of US
Ultrasound has a variety of biophysical effects:
A-Thermal effects
B- Nonthermal effects
The most effect of continuous US is on tissue temperature; however, nonthermal effects can also occur with the use of continuous ultrasound.
Pulsed US has mainly nonthermal effect, but it also produces a minimal sustained changes in tissues temperature, it probably does have a small brief heating effect during the on time of a pulse

4. Thermal Effects of US
As the energy within the sound waves is passed and absorbed by the tissues, it will cause oscillation of the molecules of that tissues about their mean position, clearly any increase in the molecular vibration will result in heat generation.
The thermal effects of ultrasound are the same as
those obtained with other heating modalities including:
acceleration of metabolic rate
reduction or control of pain and muscle spasm
alteration of nerve conduction velocity
increased circulation
increased soft tissue extensibility

5. Thermal Effects of US (cont.)
The structures heated by US are different from other heating modalities
US reaches more deeply and heats smaller areas than most superficial heating agents.
US also heats tissues with high US absorption coefficients more than those with low absorption coefficients tissues
Tissue with high absorption coefficients are generally those with a high collagen content while tissues with low absorption coefficients generally have a high water content such as muscles.
Thus
US is particularly well-suited to heat such as tendons, ligaments joint capsules and fascia
US is generally not the ideal physical agent for heating muscle tissue because muscle has a relatively low absorption coefficient also, most muscles are much larger than the available ultrasound transducers.

6. Factors affecting amount of temperature increase
The increase in tissue temperature produced by the absorption of ultrasound varies according to:
Type of tissue (absorption coefficient)
Frequency
Intensity
Duration of the ultrasound.
Blood circulating through the tissue
Reflection US waves in regions of soft tissue-bone interfaces
Thus, higher temperatures are achieved
in tissue with high collagen content
with high frequency
with high intensity
with long duration

7. Non-Thermal Effects of US
When ultrasound is delivered in a pulsed mode, with a 20% duty cycle, the heat generated during the on time of the cycle is dissipated during the off time, resulting in no measurable net increase in temperature.
Thus, pulsed US is used to produce nonthermal effects that including the following:
increase intracellular calcium,
increase skin and cell membrane permeability
increase mast cell degranulation,
increase histamine release
increase macrophage responsiveness,
increase the rate of protein synthesis by fibroblast

8. Non-Thermal Effects of US (cont.)
Nonthermal effects of US are the result of the mechanical events produced by US, including, cavitations, acoustic streaming and micro – massage.
1- Cavitation
The formation of gas filled bubbles within the tissues & body fluids during the phase of relaxation or rarefaction of US waves
There are 2 types of cavitation
Stable and non stables which have very different effects.

9. Non-Thermal Effects of US (cont.)
Stable cavitation
It occurs at therapeutic doses of US. This is the formation & growth of gas bubbles by accumulation of dissolved gas in the medium. The cavity acts to enhance the acoustic streaming phenomena & as such would appear to be beneficial.
Unstable (transient) cavitation
It is the formation of bubbles at the low pressure part of the US cycle. These bubbles then collapse very quickly releasing a large amount of energy which is detrimental to tissue viability.
This phenomenon occurs at higher US intensities with stationary head.
Pulsing also reduces the risk of damage due to cavitation.

10. Non-Thermal Effects of US (cont.)
2- Acoustic streaming
It is a small scale eddying of fluids near a vibrating structure such as cell membranes & the surface of stable cavitation gas bubble. Or, it is the steady, circular flow of cellular fluid induced by US.
3- Micro-massage (Microstreaming).
It is a mechanical effect in which the sound wave traveling through medium will cause molecules to vibrate, possibly enhancing tissue fluid interchange.
The result of combined effects of stable cavitation and acoustic streaming is the alteration of cell membrane permeability and increased cellular activity which in turn responsible for the therapeutic effect of US.

11. Physiological Effects of Ultrasound
1- Effect on blood flow
2- Pain control
3- Effect on adhesion and scar tissue
4- Effect on wound healing
5- Effect on fracture healing

12. Physiological Effects of Ultrasound (cont.)
1-Effect on blood flow
Continuous US can increase the blood flow up to 45 minutes after treatment because of:
Thermal effect
Alteration of cell permeability
Histamine release

13. Physiological Effects of Ultrasound (cont.)
2- Pain control
Direct effect:
Increase pain threshold
Decrease transmission of pain impulse along nerve fibers
produce counterirritant effect (gate theory for pain inhibition)
Indirect effect:
It results from the other effect of US which could lead to removing the source of pain such as:
removing waste products and edema reduction,
improving tissues healing
decrease muscle spasm
breaking down adhesion.

14. Physiological Effects of Ultrasound (cont.)
3-Effect on Adhesion and scar tissues
Collagen has high US absorption coefficient
The thermal effect of US lead to increasing extensibility of collagen rich tissues
Thus US could be used prior to range of motion exercises and stretching exercises.
Also, US is used to help improving the quality of the scar, resulting in a slightly stronger & more elastic scar.

15. Physiological Effects of Ultrasound (cont.)
Effect on wound healing
Pulsed ultrasound at low intensities (0.8 W/cm²) enhance healing of wound by
stimulating collagen production by fibroblasts,
increases the intracellular calcium ion levels
improve the local blood supply
encourage the growth of new capillaries
stimulates the MYOFIBROBLASTS to contract, giving rapid initial wound strength.

16. Physiological Effects of Ultrasound (cont.)
Fracture healing
The use of ultrasound accelerate the rate of fracture repair when US delivered at low intensity (0.03 W/cm²) at 1.5MHz pulsed at a ratio of 1:4. for 20 minutes.
Using higher ultrasound doses(1 – 2 W/cm²) could have an adverse effect on the fracture healing process

17. Indications of Ultrasound
Muscle spasm
Trigger areas
Neuroma
Scar tissue
Joint capsule shortening
Acute and chronic soft tissues injuries.
Acute and chronic inflammation
Wound and ulcers healing.
Fracture healing.
Neurogenic pain

18. Contraindications of Ultrasound
Pregnancy when used over the pelvic or lumbar area.
Over areas of acute infection
Areas of severely impaired circulation
Over malignant tumors
Over growing epiphyseal plates
Areas around the eyes, heart, and genitals
Tissues at risk of haemorrhage
Venous thrombosis

19. Precautions and adverse effects of US applications
It is recommended to avoid using high doses of US or sufficient intensity in the following cases:
Acute inflammation
Epiphyseal plates
Fractures
Breast implants
The most common adverse effect is a burn, which may occur in the following conditions:
high-intensity, continuous ultrasound is applied.
if a stationary application technique is used.
in areas with impaired circulation or sensation
with superficial bone

20. Techniques of ultrasound applications
a. Direct contact
b. Water immersion
c. Water bag
d. Solid sterile gel as coupling

21. a-Direct contact
In this technique, the transducer head is applied directly to the skin with a gel as a conducting coupling media.
Firm constant pressure should be used to hold the sound head in contact with the skin.
It is important to move the US head continuously in a small circular strokes.

22. a-Direct contact

23. b. Water immersion application
This technique is used in treating an irregular shapes as extremities.
A water bath may be used. The part to be treated immersed in distilled water which is used as a medium for transmission of US.
The head is placed in the water and moved parallel to the surface of the part which is being treated and as close to the skin as possible.

24. a-Direct contact

25. a-Direct contact

26. Water immersion

27. c. Water bag application
In this technique, a plastic or rubber bag filled with water and coated with a coupling gel to form a water cushion between US head and the skin is used.
This method is used in treatment of irregular surfaces which cannot be placed in a water bath.
Couplant is used onto the surface of bag, skin and the treatment head.
The bag is held in place over the area to be treated. The US head is moved firmly over the bag.

28. d. Solid sterile gel as coupling
Ultrasound can't be used over open wounds or injured skin because there is a risk of transmission of infection or moving the treatment head may cause further damage.
So in treatment of such cases, a sterile gel sheet is used as
a couplant instead of regular US gel.
Its benefits:
This is a material in sterile packs used for wound dressings and over skin graft.
It is 96% water but impermeable to bacteria.
It is better to put a sterile saline with it to ensure that there is no air bubbles between the sheet and surface of the body.
Also the slightly wetted outside surface of the gel sheet will allow US head to move smoothly over it.

29. Sterile gel sheet

30. Ultrasound in conjunction with other physical therapy agents

31. Phonophoresis
It is the application of ultrasound with a topical drug in order to facilitate transdermal drug delivery up to 6 cm.
In the application of phonophoresis, the medication is in form of gel or cream.
Preheating the area to increase the absorption of the medication
Use only approved ultrasound transmission media.
The direct coupling method is recommended
Ensure that the skin is well moistened; avoid areas of dry skin.
Lower frequency and Pulsed US lead to deeper penetration.
High intensity is recommended.
The duration depends on the size of the area to be treated.

32. Case study
Case 1
JG is an 80-year-old female with 10 cm² infected pressure ulcer over her left greater trochanter. She is bedridden and completely dependent onto others for feeding and bed mobility as the result of three strokes over the past 5 years.
Case 2
TR is a 60-year-old male,3 months post-open reduction
and internal fixation of a right hip fracture, with placement of a plate and screws. He complains dull pain in the right anteromedial hip and shortening of right anteromedial hip capsule, resulting in limited ambulation and inability to work.

33. Gate control theory of pain
Assignment
Gate control theory of pain

34. Thank you