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US Flashcards

1
Q

US

A
  • —Sound with frequency greater than 20,000 cycles per second that when applied to the body produces thermal and non-thermal effects
  • —Measure in Hz & MHz
    • —1 Hz = 1 cycle / second
    • —1 MHz = 1 million cycles / second
  • —Audible sound 16 – 20,000 Hz
  • —Ultrasound is above 20,000 Hz
  • —Therapeutic ultrasound – 0.7-3.3 MHz
    • —Maximizes energy absorption at a depth of 2-5 cm
  • —Travels faster through denser material
    • —More quickly dissipated
    • —Heats tissues with high collagen content such as tendons, ligaments, or fascia
  • —Sinusoidal pattern
  • Diverge from source
  • —If higher frequency, then less divergence
  • —Wave length = distance between 2 successive peaks
  • —Frequency is inversely related to wave length
  • —Velocity = frequency x wavelength
  • —In all tissues except compact bone, waves travel longitudinally
  • —Compact bone waves travel longitudinally & transversely
  • —Increases danger of burning at level of bone
  • —Delivers acoustic vibrations via a transducer that utilizes a quartz crystal to convert electrical energy to ultrasonic waves (acoustic energy)
  • —The US waves transmit energy by alternately compressing and rarefying material.
  • —Collagen in the tissue absorbs this energy
    • —Muscle, tendon, ligaments
  • —Produces thermal and non-thermal effects
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2
Q

Conversion

Energy Transfer

A
  • —Conversion: The process of changing energy from one form to another
    • —US: Electrical energy converted to acoustic energy
    • —Energy absorbed by tissues with high collagen content such as tendons, ligaments, or fascia
    • —Produces thermal and mechanical (non-thermal) energy
  • —Travel by deforming & vibrating molecules
    • —They bump next molecule & transfer energy
    • —Chain reaction until energy is dissipated
  • —Coupling Agent
    • —Must go through a medium
    • —Decreases impedance of air
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3
Q

Frequencies

A
  • —1 MHz-low- MORE likely to use this. penetrates DEEPER
  • —Increase intensity watts
  • —Penetrates to about 5 cm
  • —3 MHz –high- PIP/ snuff box not as deep
  • —Decrease intensity watts
  • —Penetrates 1-2 cm
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4
Q

Intensity

A
  • —Determined by strength of energy produced
  • —Measured in W/cm2 (watts per centimeter squared)
  • —Higher intensity leads to higher temps
  • —Crystal of US head vibrates unevenly
  • —Intensity varies
  • —Highest intensity occurs where crystal vibrates most: spatial peak average intensity
  • —Average power delivered: spatial average intensity
  • —Effective Radiating area (ERA)
  • —treatment area should not be more than 2-3 times the ERA
  • —Beam nonuniformity ratio- want lower ratio ideally 3:1
  • —Ratio of spatial peak intensity & spatial average intensity
  • —< 6:1 are acceptable
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5
Q

Duration

A
  • —Duration: The amount of time the US treatment is applied
    • — 5-10 minutes most typical
      • —Increase duration for the following:
        • —When lower frequencies/intensities are used
        • — When treating larger areas
        • —When the goal is to further increase the tissue temp.
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6
Q

Attenuation

A

—Attenuation: as sound waves travel through tissue it gradually decreases in intensity

—Waves are attenuated by reflection/refraction and absorption

—Reflection: redirection of a beam away from a surface at an angle equal and opposite to the angle of incidence

—Refraction: redirection of a wave at an interface at a different angle in which it entered the tissue

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7
Q

Absorption

A
  • —Absorption is greatest in tissues with a high collagen content
  • —Absorption of energy per cm
    • —Blood 3%
    • —Fat 13%
    • —Muscle 24%
    • —Blood vessel 32%
    • —Skin 39%
    • —Tendon 59%
    • —Cartilage 68%
    • —Bone 96%
  • —Impedance: resistance to transmission (absorption)
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8
Q

Terms

A
  • —Intensity__: The power per unit area of the sound head, expressed in watts per cm squared (W/CM²)
  • —World Health Organization limits therapeutic US to 3 W/cm²)
  • —Frequency__: The number of compression-rarefaction cycles per unit of time. Expressed in cycles per second or Hertz.
  • —Therapeutic frequency range: 1-3 MHz
  • —Increases in frequency decreases the depth of penetration in superficial tissues
  • —1 MHz : penetrates up to 5 cm
  • —3MHz: penetrates 1-2 cm
  • —Duty Cycle: The proportion of the total treatment time that the US is on.
  • —Expressed as a % or ratio ie 20% or 1:5 duty cycle (US is on 20% of the time and off 80%)
  • —100% = continuous ultrasound
  • —Duration: The amount of time the US treatment is applied
  • — For most non-thermal , thermal treatments 5-10 min
  • —If goal is to increase tissue temp., duration should be adjusted according to frequency and intensity
  • —Mode: Know the difference between Continuous and Pulsed US
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9
Q

Terms

A
  • —Spatial average temporal peak intensity (SATP): Highest intensity occurs where crystal vibrates the most
  • —Spatial average temporal avererage (SATA): Average power delivered
  • —Effective Radiating area (ERA): the total area of the surface to the transducer that actually produces sound wave
  • —Beam nonuniformity ratio (BNR): the ratio of the spatial peak intensity to the spatial peak average intensity. Usually between 5:1 and 6:1
  • —Cavitation: the formation, growth, and pulsation of gas-filled bubbles caused by US.
  • —Microstreaming: unidirectional movement of fluids along cell membranes via mechanical pressure changes with the US field
  • —Attenuation: decrease in US intenstiy as it travels through tissue
  • —Absorbtion: conversion of mechanical energy into heat
  • —Reflection: redirection of a beam away from a surface at an angle equal and opposite to the angle of incidence
  • —Refraction: redirection of a wave at an interface at a different angle in which it entered the tissue
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10
Q

Mode: Continuous vs. pulsed US

A
  • —Continuous produces sound wave 100% Thermal effect
  • —Pulsed US has on / off cycles Nonthermal effect
    • —Duty cycle = time on / cycle time
    • —20% duty cycle most common
    • —During off time heat can dissipate
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11
Q

Thermal and non-thermal effects

A
  • —Thermal Effects
  • —Continuous US
  • —Amount of heat depends on
  • —Intensity
  • —Duration
  • —Size of treatment area
  • —Properties of tissues
  • —All effects of heat
  • —1 degree C increases metabolism
  • —2-3 degree C reduces muscle spasm, pain
  • —> 4 degree C increases tissue extensibility
    • —Can reach superficial and deep tissues

—Mechanical Effects (Non-Thermal)

  • Pulsed US
  • —Most common: 20% duty cycle
  • —Ions in fluids move—called microstreaming
    • —Increase cell membrane permeability and cellular activity
  • —Gas bubbles expand & contract—called cavitation
    • —Contribute to changes in cell membrane
    • —Unstable cavitation = bursting of bubble
      • Can lead to tissue destruction
      • Unlikely with therapeutic US
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12
Q

Muscular effects of US

A
  • US has been found to be effective at heating tissues
  • Hemodynamic Effects
    • —Increase blood flow due to heat & changes in cell permeability
    • —Chose parameters to increase muscle temp. at least 1C
    • —Max. results occur after 5 minutes
    • —Longer treatments maintain blood flow
    • —Return to baseline after 1 minute
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13
Q

Connective Tissue Effects

A
  • —Temperature changes occur faster than in muscle
  • —Need increase of > 4C temperature to increase extensibility
  • —Temperature at this level only maintained 4 minutes post treatment
  • —Stretch during/immediately after US and maintain stretch for at least 4 minutes after US
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14
Q

Neurological Effects

A
  • —Motor NCV mixed depending on parameters
  • —Sensory NCV increases with thermal US
  • —Pain threshold raised at 0.8 MHz at 1.5 W/cm2
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15
Q

Pain/ Edema reduction

A

—Pain

—May need to apply w/in 48 hours post injury for best effects

—US plus exercise improves pain relief

—Continuous US may be effective for reducing pain. Settings @ 1 or 3 MHz, 0.5 to 3.0 W/cm intensity & 3-10 minutes duration.

—Edema

—Mixed results in studies

—In general, studies support US initially supports inflammatory process, but then speeds edema reduction

—Generally low intensity pulsed US

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16
Q

US application

A
  • —Coupling agent decreases the impedance at the air skin juncture
  • —For optimal effects, the transducer of the sound head should be parellel to tx surface
  • —Move sound head 4-6 cm/sec—keep sound head moving
  • —Alternate Exposure Techniques
    • —Direct contact: not frequently used, surface must be larger than transducer
    • —Immersion Technique
      • —Used when treatment area is smaller than transducer or when treating an irregular surface
      • —Tap water and plastic/rubber basin
      • —Move transducer parallel to surface: .5-1cm away, increase intensity 50%
17
Q

Phonophoresis

A
  • —Use of US to deliver medication through the skin
    • —Medication added to the US gel
    • —Theory is that US drives the medication through the skin at the hair cells, sweat glands
    • —Evidence for effectiveness, other than for dexamethasone, is weakPhonophoresis
18
Q

Recap

A
  • —Frequency determines the depth of penetration
  • —3MHz increases tissue temperature 3 times more than 1 MHz
  • —Keep US head moving : 4-6 cm/sec
  • —Effective tissue area treatment= 2 times the ERA
  • —4 C increase from baseline= optimum heat for tissue extensibility
  • —Collagen rich tissue=higher absorbtion of ultrasound
  • —Window of optimum time for stretching 3-5 minutes
19
Q

Contra/ Precautions

A

Precautions

  • For co—ntinuous, same as with other heat modalities
  • —Unhealed fracture site
  • —Primary ligament or tendon repair
    • —First 2 weeks
  • —Osteoporosis
  • —Metal implants
  • —Decreased sensation
  • —Patients unable to communicate

Contraindications

  • —Pacemaker in area
  • —Pregnancy
  • —Malignant Tumor
  • —Thromboplebitis
  • —Infection
  • —Irradiated area
  • —Epiphysis of growing bone
  • —Fluid-filled areas
  • —Exposed or superficial nerve tissue
  • —Over joint cement or plastic components
  • —Eyes
  • —Reproductive organs
20
Q

Uses

A

—Heat tissues

—Increase blood flow

—Increase tissue extensibility

—Increase fracture healing

—Wound healing

—Decrease pain

—Decrease edema

—Phonophoresis

—Medical Imaging

21
Q

Document

A
  • —Record specific parameters in order to reproduce or change treatments
  • —Include: Frequency, Intensity, Pulsed/continuous, Duration i.e. 1MHz at 1.5w/cm^2 at 20%duty for 8 min
  • —Pt. response to modality

Modalities (4 decks)

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