Basic Science

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Basic Science

• HHP 393 Therapeutic Modalities

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Basic Science

• Often there is confusion regarding the
  relationship of different modalities to the
  electromagnetic and acoustic spectra.
• Electromagnetic Radiations
• Electrical stimulation currents, shortwave and
  microwave diathermy, the infrared modalities,
  ultraviolet therapy and low powered lasers.
• Acoustic Spectrum
• Ultrasound

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Radiant Energy

• Radiation is the process by which energy in
  various forms travels through space.
• The sun is the best example
• Electromagnetic Spectrum
• If a ray of sunlight is passed through a prism
  what happens??

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Prism
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Electromagnetic Radiations

• Common characteristics
• They may be produced when sufficiently intense
  electrical or chemical forces are applied to any
  material
• They all travel readily through space at an equal
  velocity
• Their direction of travel through space is always
  in a straight line and will alter this straight
  line travel only when they come into contact with
  some other surface
• They may be reflected, refracted, absorbed, or
  transmitted, depending on the specific medium
  they strike

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Electromagnetic Radiations

• All forms travel at the same speed
• Difference between the rays is in the wavelengths
  and frequencies of the radiations
• Wavelength distance between the peak of one
  wave and the peak of the next wave
• Frequency number of wave oscillations or
  vibrations occurring in one second (Hz)

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Laws of Electromagnetic Radiations

• When electromagnetic rays come into contact with
  something they can either be reflected,
  transmitted through, refracted or absorbed.
• In general, those radiations with the longest
  wavelengths tend to have the greatest depths of
  penetration.

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Laws of Electromagnetic Radiations

• Arndt-Schultz Principle
• No reaction or changes can occur in the body
  tissues if the amount of energy absorbed is
  insufficient to stimulate the absorbing tissues
• Law of Grotthus-Draper
• If the therapeutic energy is not absorbed by the
  superficial tissues, it will penetrate to deeper
  tissues

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Laws of Electromagnetic Radiations

• Cosine Law
• The smaller the angle between the propagating ray
  and the right angle, the less radiation reflected
  and the greater the absorption
• Inverse Square Law
• The intensity of the radiation striking a
  particular surface is known to vary inversely
  with the square of the distance from the source

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Acoustic Spectrum

• Ultrasound is classified as an acoustic rather
  than electromagnetic energy
• Acoustic vibrations travel at a velocity
  significantly lower then electromagnetic
  radiations
• 300 million meters/sec vs. hundreds meters/sec
• Wavelengths are considerably shorter in acoustic
  energy

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Acoustic Spectrum

• Acoustic vibrations can not be transmitted
  through a vacuum and will travel faster when
  going through a more dense medium.
• Opposite to electromagnetic radiation
• Indication/Contraindication Table