Ultrasound

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Ultrasound
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ULTRASOUND

• Based on principles discovered by Wood and Loomis
  in 1927.
• US is acoustic vibrations (sound waves) above the
  frequency audible to the human ear.
• Human ear can detect up to 20,000 cycles per
  second. Anything above that is considered
  ultrasonic.

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• Crystal is given electrical impulse from a
  transducer causing it to vibrate at a certain
  frequency(same as in your watch)
• Frequency of vibration is measured in MHz -
  usually 1 or 3 MHz
• 1 MHz penetrates more deeply,
• 3 MHz more superficial
• the 3 MHz produces more energy which is absorbed
  more readily, thus depth is reduced
• This vibration causes sound waves which are
  directed by US head

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Actions of Ultrasound

• Generation of Heat through friction
• heat is deep

• Mechanical actions attributed to high alternating
  pressure forces and accelerations

• Vibratory effect which penetrates deeply

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EQUIPMENT

• This causes a crystal transducer to vibrate and
  generate sound waves

• A generator produces electrical oscillations of a
  desired frequency

• The sonic energy is transmitted to human tissue
  by contact with the ultrasound head

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Intensity

• Varies between 0 to 3 W/CM2
• Most machines have Watts (W) or W/CM2
• 1-1.5 W/CM2 is typical intensity

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Types of patients treated

• Muscle injuries
• Tendon injuries
• Ligament injuries
• Other soft tissue injuries
• Inflammatory conditions such as CTS,
  Tenosynovitis, DeQuervains, Radial Tunnel Syndrome

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OTHER CONDITIONS

• Lateral epicondylitis
• Medial epicondylitis
• Muscle spasms
• Do not apply high intensity US (1.5 W/cm2 ) to
  acute inflammatory conditions since it tends to
  aggravate the condition

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Continuous Vs. Pulsed US

• Pulsed delivers the ultrasound waves
  intermittently
• Usually represented in of continuous
• also called duty cycle
• 50, 20
• May be used for tissue healing
• 20, .1 - .2 W/CM2 , 30-60 seconds for each area
  the size of transducer head
• treatment repeated qd or bid

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CONTRAINDICATIONS FOR US

• Pregnancy (always ask document)
• Cancer (always ask document)
• Diminished circulation
• Electrical internal or external implanted device
• Spinal cord stimulators
• Acute inflammatory conditions
• Tendon lacerations for 1st 6 weeks

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US TECHNIQUE

• Explain to patient how it will feel
• Protect clothing from gel
• Apply US gel to skin liberally
• Spread gel over area to be treated

• Turn intensity knob all the way down
• Set machine to pulsed of continuous
• Set desired treatment time
• Place transducer on skin at right angle to skin.

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WHAT TO TELL PATIENT ABOUT US

• Explain how it works
• Ask them to tell you immediately if they feel
  anything
• They may feel warmth. This is normal.
• It should not feel hot. If it does, turn down
  the intensity or discontinue the treatment.
• They may experience a deep aching. This is
  caused by periosteal vibration. Turn down
  intensity if this happens.

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APPLICATION CONTINUED

• Up to 2 W/cm2 in obese pt as long as no C/O heat.
• Use a circular motion.
• Treatment usually lasts 8-15 minutes
• the area that can be effectively treated is 2X
  the size of transducer
• Move head 1 inch per second
• dont apply if bone blocks pathway

• Switch control to W/cm2
• Begin moving transducer head constantly and
  slowly
• Slowly turn up intensity
• Intensity usually W/cm2
• Consider the fact that the deeper the tissue, the
  poorer the therapeutic dosage due to the
  dissipating effect of blood flow

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Wound Care

• low intensity US promotes healing
• .1-.5 W/cm2
• duty cycle 20
• intensities of .8 W/cm2 or higher have no effect
  or retard healing

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PHONOPHORESIS

• Technique is same as Ultrasound
• Cortisone cream used
• Ultrasonic energy may push cortisone under skin
  for anti-inflammatory effect
• Or, US may increase cell permeability
• 5-10 cortisone cream used

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NEVER !!!

• Lift the transducer off the pts skin with the
  intensity on
• Stop moving the transducer during a treatment
• Do US over bone
• Place transducer directly on the skin

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UNDERWATER TECHNIQUE

• Transducer must be waterproof
• Useful for irregular surfaces such as a finger,
  the hand or the ankle
• Place the body part to be treated under water

• Hold transducer 1/2 inch from skin
• Move transducer as you would normally
• Never place directly on skin
• Do not allow patient to touch any sources of
  electricity during treatment

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BE CAREFUL IF...

• Patient has decreased sensation
• Skin is not intact (avoid these areas)

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Cavitation

• Cavitation - behavior of a micron sized gas
  bubble in fluids when energized by US
• If intensity too high duration is long enough,
  bubbles become progressively larger
• They take in air during rarefaction phase than
  they loose in compression phase
• If bubbles reach critical size, they collapse
  under pressure sending shock waves through
  tissue.
• This is called unstable cavitation
• Air bubbles in water should be avoided

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• Energy is absorbed in proportion to density
• Periosteum is dense and heats quickly
• bone, ligament and tendon circulation is not as
  good as muscle and they retain heat longer

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NOW LETS PRACTICE