Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physical Agents > Therapeutic Ultrasound > Flashcards

Therapeutic Ultrasound Flashcards

1
Q

What is therapeutic ultrasound? (TUS)

A

-Sound wave > acoustic energy (mechanical pressure wave) due to alternately compressing and rarefying material -energy proprogation -frequency greater than 20,000 Hz (cycles/sec) -inaudible to human ear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How is TUS generated?

A

The generator - high frequency electrical generator - oscillator circuit: produces electrical current of specific frequency -Crystal: frequency causes this to vibrate which then sets off sound wave -Control panel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The Crystal

A
  • -Synthetic ceramic (2-3mm thick) - produces uniform beam
  • -Transducer
    • * converts electrical energy to mechanical acoustic energy
    • * reverse piezoelectric effect
    • * creates vibration at frequency of electrical oscillation of generator
    • * vibrating crystal causes soundhead to vibrate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Reverse Piezoelectric effect

A

The mechanical deformation of certain crystals or ceramics when exposed to an electric field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Piezoelectric effect

A

the generation of an electric charge by subjecting certain crystals or ceramics to mechanical strain (ex hitting material with hammer will produce electric charge)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

The sound head

A
  • -Transfers acoustic energy to tissues
  • -ceramic, aluminum, or stain-less steel plate attached to crystal
    • generally matches frequency of crystal thus not interchangable
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Applicator

A
  • -housing for crystal and soundhead
  • -held by PT to apply ultrasonic wave to pt - made of hard insulated plastic
  • -should be ergonomically designed for therapist comfort
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Electromagnetic wave

A

Photon moves along the wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Mechanical wave

A

Molecules bump into their neighbor resulting in propagation of energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Wave types

A
  • -Longitudinal waves
  • -Transverse waves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Longitudinal waves

A
    • movement of molecules is along the direction the wave travels
      • * seen in liquids and gases
    • molecular flow occurs parallel to direction of wave prorogation and is known as MICROSTREAMING
    • near field (fresnel zone)
    • area of US beam closest to transducer
      • * sound wave transmitted in straight line -Far field (Fraunhofer zone) area of US beam where wave begins to diverge
      • * sound wave begins to diverge or scatter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Power

A
  • -The amount of acoustic energy per unit of time
  • -measured in watts (W) - 1 W= 1 Joule/sec
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

1 Joule is equal to…

A
  • a unit of work equivalent to the energy expended in one second by an electric current of one ampere in a resistance of one ohm.
    • one joule is = to 0.738 foot pounds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Effective radiating area (ERA)

A
    • the size of the area of the transducer that radiates the US beam
  • -Dependent upon surface area of the crystal -generally less than the size of the tranducer cover -measured in cm^2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Spatial intensity

A

-Relates to size of transducer ERA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Temporal intensity

A

Relates to time transducer is “on”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Spatial average intensity

A
  • -Acoustic power (W) divided by the effective radiating area (ERA) of the transducer
  • -measured in W/cm^2
18
Q

Spatial peak intensity

A

-Peak intensity of the US beam over the area of the transducer -generally greatest at the center

19
Q

Spatial average temporal peak (SATP) intensity

A
    • the spatial average intensity of the US during the on time of the pulse
  • -generally displayed on US generator as W/cm^2
20
Q

Spatial average temporal average (SATA) intensity

A
  • -SATP x duty cycle=SATA
    • measures amount of energy delivered to tissue
21
Q

duty cycle

A
  • -The percentage the US beam is on -Continuous= 100%
    • pulsed= generally expressed as 10%, 20%, 50%
22
Q

Beam nonuniformity ratio (BNR)

A
  • -Ratio of spatial peak intensity to spatial average intensity
  • -ratio of the intensity of the highest peak to that of the average intensity of all the peaks
    • the lower the BNR the lower the intensity of the highest peak - the lower the BNR the lower the probability of the pt feeling undesirable hot spots
23
Q

Range for beam nonuniformity ratio (BNR)

A
  • Recommended to be between 2:1 and 8:1
    • ex: with transducer with BNR of 5:1 * if SATA is 1 W/cm^2 then SATP could be as high as 5 W/cm^2
24
Q

Frequency

A
  • The number of compression-rarefraction cycles per unit of time -expressed in cycles per sec (Hz)
      • TUS frequency range: 0.75 to 3.3 MHz (3.3 million cycles/sec)
    • -effects of depth penetration
      • * 1 MHz- penetrates 5 cm * 3 MHz- penetrates 1-2 cm
25
Q

Why does absorption increase as frequency increases?

A
    • Less available for transmission to deeper tissues (more absorbed superficially)
    • absorption occurs in 1/3 the time for 3 Hz vs 1 MHz US
26
Q

Absorption

A
  • -Conversion of mechanical energy of US wave into kinetic or heat energy
  • -Expressed by absorption coefficient
    • * tissue and frequency dependent
    • * highest in tissue with high collagen content (tendon, ligament, bone)
    • * increase in proportion to intensity
27
Q

Absorption coefficients

A

bone > cartilage> tendon> skin> muscle (perpendicular)> muscle (parallel)> nerve > fat > blood

28
Q

Reflection

A
  • Redirection of the US beam away from the surface -US reflected at tissue interfaces
    • * 35% @ soft tissue bone interfaces
      • * 100% at skin air interface
    • * .1% at couplant skin interface
    • ***cosine law
29
Q

US rate of healing per minute

A

Ultrasound Rate of Heating Per Minute

Intensity (W/cm2) 1 MHz 3MHz

.5 .040C .30C

  1. 0 .20C .60C
  2. 5 .30C .90C
  3. 0 .40C 1.40C
30
Q

Refraction

A
  • wave enters tissue at one angle and continues through at another angle
31
Q

attenuation

A
    • measures the decrease in US intensity as the wave travels through tissues
  • -Due to either absorption of US wave due to reflection and refraction
  • -penetrates easily through tissues high in water content and is absorbed best in dense tissues of high protein content -expressed as attenuation constant
    • * higher for tissues with higher collagen content (protein)
    • penetration & absorption are inversely related
  • -absorption increases as frequency increases thus less energy is available for transmission to deeper tissues
32
Q

Attenuation constant

A

bone>cartilage>tendon> skin> blood vessels> muscle > nerve (no value) > fat > blood

33
Q

standing waves

A
  • -Reflected wave interacts with wave moving in opposite direction
    • if both are in phase energy will stimulate and be more intense
    • must keep soundhead moving to minimize standing waves
34
Q

cavitation

A
  • -Formation, growth, pulsation of bubbles exposed to US beam
    • compression phase- bubbles compress
  • -rarefraction phase- bubbles expand
    • may be stable or unstable
      • * stable=bubbles intact
      • * unstable= too much energy put in and bubbles burst
    • stable cavitation is thought to produce non thermal US effects
    • true unstable cavitation does not occur at therapeutic levels
35
Q

Microstreaming

A
  • -Minute unidirectional flow of fluid in the vicinity of pulsating bubbles
  • -results from pressure of sound wave that moves ions or small molcules
  • -produces stresses that can effect change cell membrane structure and function
36
Q

Characteristics of US waves

A
  • -Velocity of sound wave is dependent upon the physical properties of the medium through which it travels -changes as densities of tissue changes
    • * 3360 m/sec-bone
    • * 1500 m/sec- water
    • * 330 m/sec- air
37
Q

Couplant

A
  • -Any agent that allows for smooth transmission of US from sound head to tissue (skin)
    • mediums that transmit US well
      • * water- 100%
      • * mineral oil- 97%
      • * US gel (ultraphonic)- 96%
      • * US lotion ( polysonic)- 90%
38
Q

Therapeutic US physiological effects

A
  • -Thermal
    • increases tissue temp
  • -Non-thermal
    • alter cell membrane permeability
39
Q

Physiological effects: thermal effects

A
  • occurs when using any mode US
  • causes molecules to vibrate
  • higher intensities and more continuous beam produces more vigorous vibration
  • increased extensibility of collagen fibers
  • reduced viscosity of fluid elements in tissues
  • decreased jt stiffness
  • reduced muscle spasm
  • diminished pain preception
  • increased metabolism
  • increased blood flow
40
Q

Absorption coefficent

A
  • the amount of absorption of US energy that occurs in a tissue type at specific frequency
  • higher for tissues with higher collagen content
  • increase proportionally with US frequency

Physical Agents (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions