ULTRASOUND Biophysical Effects

1
ULTRASOUND Biophysical Effects

• Both thermal and nonthermal effects occur in the
  body
• Nonthermal Effects
• Changes within the tissues resulting from the
  mechanical effect of ultrasonic energy
• Thermal Effects
• Changes within the tissues as a direct result of
  ultrasounds elevation of the tissue temperature

2
ULTRASOUND Biophysical Effects-Nonthermal

• Nonthermal Effects
• Used in acute injuries or when increasing the
  tissue temperature is unwanted
• Two methods of doing this
• Using a pulsed output and normal intensities
• Using 100 duty cycle with low intensities (0.3
  w/cm2)

3
ULTRASOUND Biophysical Effects-Nonthermal

• Nonthermal US energy leads to two interrelated
  events
• Acoustical Streaming - one directional flow of
  tissue fluids caused by the sound wave
• The flow of bubble in the acoustical streams
  cause changes in cell membrane permeability
• Cavitation result of the pressure changes
  caused by the sound waves which results in gas
  bubbles moving in a cyclical manner
• Stable vs Unstable (Transient) Cavitation

4
ULTRASOUND Biophysical Effects-Nonthermal

• Physiological Effects
• Stimulates phagocytosis
• Increases cell membrane permeability
• Increases the movement of minerals and proteins
  in and out of the cell
• Glycosaminoglycan and hydroxyproline are
  increased following low dose US
• Mild acceleration of the inflammatory stage helps
  the body reach proliferation sooner
• See Table 7-4

5
ULTRASOUND Biophysical Effects-Thermal

• Thermal Effects
• Amount of temperature increase depends on
• Duty Cycle, Intensity, Frequency
• Vascularity and type of tissues
• Size of tx area, speed of soundhead
• 1 MHz up to 5 cm deep, retains heat longer
• 3 MHz 2-3 cm deep

6
ULTRASOUND Biophysical Effects-Thermal

• To achieve a therapeutic effect temp must be
  increased for a minimum of 3-5 min.
• 3 MHz heats 3-4 times faster
• Lower treatment intensities require a greater
  duration
• The friction between the molecules results in a
  temperature increase
• Collagen rich tissues are preferentially heated,
  adipose tissue is transparent to US

7
ULTRASOUND Effects on the Injury Response Cycle

• Cell Response
• Increased cell membrane permeability for both
  thermal and nonthermal US
• Thermal
• Increased cell metabolism and inflammation
• Nonthermal
• Increased histamine release, calcium and rate of
  protein synthesis

8
ULTRASOUND Effects on the Injury Response Cycle

• Inflammation
• No thermal US acutely
• Effects later in injury cycle
• Early onset of proliferation
• Stimulation of fibroblast activity
• Positively influence macrophage activity
• Increases the collagen synthesis and increased
  tensile strength

9
ULTRASOUND Effects on the Injury Response Cycle

• Blood Flow
• Continuous can increase blood flow for up to 45
  minutes
• Pulsed US may effect blood flow through its
  effect on the cell membrane
• Application of cold first?

10
ULTRASOUND Effects on the Injury Response Cycle

• Pain Control
• May have some direct effect to the nerves or as a
  result of other effects
• Direct effects are through eliciting changes
  within the nerve fiber themselves
• Indirect effects
• Increase blood flow more oxygen less chemical
  pain
• Decreased muscle spasm

11
ULTRASOUND Effects on the Injury Response Cycle

• Muscle Spasm Why?
• Tissue Elasticity
• Increased extensibility in collagen-rich tissues,
  including scar tissue
• Must be increased 7.2F (4C)
• Must be used with passive stretching, within 3
  minutes
• Repeated treatments is often necessary
• May want to place tissue on stretch during the
  treatment

12
ULTRASOUND Effects on the Injury Response Cycle

• Wound Healing
• Some wounds have responded well to US
• 100 US at 1.5 w/cm2 for 5 min, for 1 week (1
  MHz)
• 100 at 0.5 w/cm2 for 2 weeks also appeared to
  help

13
ULTRASOUND Phonophoresis

• Application of US to assist in the diffusion of
  medication through the skin
• Non-invasive method that does not effect the
  liver
• Occurs due to the effect US has on the skin which
  allows the medication to diffuse through
• Skin factors can affect diffusion of medication
• Has been found to push meds up to 6 cm deep

14
ULTRASOUND Phonophoresis

• Thermal
• Increase kinetic energy of the local cells and
  the medication, open entry points, increase
  circulation, increase capillary permeability
• Nonthermal
• Enhances diffusion across the membranes, increase
  cell membrane permeability

15
ULTRASOUND Phonophoresis

• Medications
• Table 7-7
• Application
• Direct Method
• Invisible Method

16
ULTRASOUND Phonophoresis

• Does it work??
• Salicylate (Myoflex)
• Hydrocortisone
• Dexamethasone
• Low frequency US units may assist in the
  transmission of medications

17
ULTRASOUND Contraindications

• Acute injuries (Thermal US)
• Areas of impaired circulation
• DVT or cancerous tumors
• Over the eyes, heart, skull and genitals
• Pelvic, abdominal area in menstruating or
  pregnant women
• Over active fracture or stress fractures
  (exception)
• Over growth plates in adolescents??
• Use with caution over vertebrae

18
ULTRASOUND Controversies in Treatment

• US must be used properly in order to have a good
  therapeutic effect on the patient
• Read Article
• Ten Mistakes Commonly Made with Ultrasound Use
  Current Research Sheds Light on Myths

19
ULTRASOUND Application

• Treatment Area
• 2-3 times the ERA of the sound head
• Coupling Methods
• Optimal agent is distilled water
• US head should not leave the body
• Why?
• Irregular shape body parts?

20
ULTRASOUND Coupling Agents and Methods

• Direct Coupling
• Use of US gel
• Use enough gel
• Body hair can limit US delivery
• Try not to have air bubbles
• Use slight pressure on sound head
• Water Immersion
• Good for irregular body parts
• Sound head is 1 away from skin _at_ 90 angle

21
ULTRASOUND Coupling Agents and Methods

• Bladder Method
• Water filled bag or plastic bag coated with US
  gel
• Good for irregular areas such as AC joint
• Can not have air pockets

22
ULTRASOUND Output Parameters

• Frequency
• Depth and rate of heating
• 1 MHz vs 3 MHz
• Table 8-2
• Treatment Duration
• Table 8-3

23
ULTRASOUND Output Parameters

• Duty Cycle
• Output Intensity
• Figure 8-6
• For thermal ultrasounds the patient should feel
  warmth!

24
ULTRASOUND Output Parameters

• Dose-Oriented Treatments
• Still an inexact method
• Deals with treating the tissue area to a certain
  temperature
• Some units you can program this way
• Needs more research

25
ULTRASOUND Ultrasound and Electrical Stimulation

• Treatment of trigger points and superficial
  painful areas
• Ultrasound head serves as as electrode
• Try to fatigue the trigger points to a point they
  no longer will fire or spasm
• Placing the tissue at stretch may be a benefit in
  decreasing trigger point spasms

26
ULTRASOUND Application

• Duration
• 3 to 12 minutes
• Frequency
• Once/day for 10 to 14 days

• Precautions, Indications, and Contraindications
  are in your text (Pg. 181)