Ultrasound and Phonophoresis

Question 1

Ultrasound: Transducer head size

Answer 1

• Range from 1-10 cm
• 5cm most common
• Should be relative to treatment area size:
  
  • wrist- 1cm,
  • shoulder/leg - 5cm

Question 2

Ultrasound: Spatial average intensity

Answer 2

• Total power (watts) divided by area (cm2) of transducer head
• Typically the measurement used in documenting US treatments (0.25 w/cm2 - 2.0 w/cm2) (measure of intensity)

Question 3

Ultrasound: Beam non-uniformity ratio

Answer 3

• Ratio of spatial peak intensity to average intensity
• Lower BNR = more uniform energy distribution and less risk of tissue damage
• Should be between 2:1 and 6:1
• Ideal 1:1 is not technically feasible

Question 4

Ultrasound: Duty cycle

Answer 4

• The fraction of time the US is on over one pulse period time on/time on+time off
• Duty cycle of 50% or less is considered pulsed

Question 5

Ultrasound: Structures with high attenuation

Answer 5

Hight protein and collagen content - muscles, tendons, ligaments, capsules

Question 6

Ultrasound: Depth of penetration

Answer 6

• 3-5 cm
• At 3 MHz - greater attenuation in superficial tissues (e.g. TMJ)
• At 1MHz - increased heat production in deep layers due to less superficial scatter

Question 7

Ultrasound: Thermal effects

Answer 7

• Produced by continuous US at 0.5-3 W/cm2 (intensity will vary depending on tissue type and pathology)
• Increased:
  
  • Tissue temp,
  • pain threshold,
  • collagen extensibility,
  • enzyme activity,
  • tissue perfusion,
  • temp at tissue interfaces.
  • Alteration of nerve conduction velocity.
• Excessively high temps may produce sudden, strong ache due to overheating periosteal tissue - reduce intensity or increase surface area.

Question 8

Ultrasound: Non-thermal effects:

Answer 8

• Generated by very low intensity or pulsed US.
• Typically duty cycles of 20-50%
• Cavitation and Acoustic Streaming Effects

Question 9

Ultrasound: Non-thermal effects: Cavitation

Answer 9

• Cavitation:
  
  • Alternating compression and expansion of small gas bubbles caused by mechanical pressure waves.
• Stable cavitation:
  
  • Bubbles resonate but no tissue damage.
  • May be responsible for diffusional changes in cell membranes.
• Unstable cavitation:
  
  • Severe collapse of gas bubbles - can result in local tissue destruction due to high temps.

Question 10

Ultrasound: Non-thermal effects: Acoustic Streaming

Answer 10

• Acoustic streaming:
  
  • Movement of fluids along the boundaries of cell membranes resulting from mechanical pressure wave.
• May produce:
  
  • Alterations in cell membrane activity,
• increase:
  
  • cell wall permeability,
  • intracellular calcium,
  • macrophage response,
  • protein synthesis.
• May be of some value in tissue healing.

Question 11

Ultrasound: Goals/indications

Answer 11

• Modulate pain -
• increase CT extensibility,
• reduce inflammation,
• accelerate healing rate,
• reduce joint restriction/muscle spasm.

Question 12

Ultrasound: Precautions

Answer 12

• Acute inflammation,
• breast implants,
• open epiphyses,
• healing fractures.

Question 13

Ultrasound: Contraindications

Answer 13

• Impaired circulation/cognition/sensation
• Thrombophlebitis,
• joint cement,
• plastic components,
• over vital areas (ear, brain, heart, eye, cervical ganglia, carotid sinuses, reproductive organs, SC, pacemakers, pregnant uterus)

Question 14

Ultrasound: Procedures - Direct content

Answer 14

• Apply generous amount of coupling medium
• Move head slowly in overlapping circles or long strokes
• Do not cover an area greater than 2-3x size of the ERA per five minutes of treatment
• While head is moving turn up intensity to desired level
  
  • lower intensities for acute conditions or thin tissue;
  • higher intensities for chronic conditions or thick tissue.
• Treatment time: 3-10 mins depending area, intensity, condition and frequency

Question 15

Ultrasound: Procedures - indirect contact (water immersion)

Answer 15

• Use with irregular bod parts
• Plastic container preferred to decrease reflection
• Place part in water
• Place sound head in water, 0.5-1” from skin surface at right angle to body part
• Move head slowly - if using stationary technique decrease intensity or use pulsed US
• Turn up intensity to desired level
• Periodically wipe off any air bubbles that form on sound head or body part during treatment

Question 16

Ultrasound: Procedures - indirect contact (fluid-filled bag)

Answer 16

• Thin-walled bag over irregular bony surface
• Not widely used
• Place sound head inside bag, apply coupling agent to skin and place bag over treatment area
• Move head slowly within the bag, do not slide bag on skin Increase intensity to desired level

Question 17

Ultrasound: Phonophoresis

Answer 17

• Use of US to drive medications through the skin into deeper tissues
• Local analgesics (lidocaine, salicylates)
• Antiflams (dexamethasone)
• Method is similar to direct contact except medicine is used as part of coupling agent
• Intensity: 1-3 W/cm2
• Treatment time: 5-10mins
• Low intensities and longer time is more effective to introduce drug to skin