Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Physical Agents > Therapeutic Ultrasound > Flashcards

Therapeutic Ultrasound Flashcards

(40 cards)

Start Studying
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

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

Spatial peak intensity

Study These Flashcards
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

Study These Flashcards
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

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

duty cycle

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

Beam nonuniformity ratio (BNR)

Study These Flashcards
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)

Study These Flashcards
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

Study These Flashcards
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
Why does absorption increase as frequency increases?
* - 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
Absorption
* -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
Absorption coefficients
bone \> cartilage\> tendon\> skin\> muscle (perpendicular)\> muscle (parallel)\> nerve \> fat \> blood
28
Reflection
* 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
US rate of healing per minute
Ultrasound Rate of Heating Per Minute Intensity (W/cm2) 1 MHz 3MHz .5 .040C .30C 1. 0 .20C .60C 1. 5 .30C .90C 2. 0 .40C 1.40C
30
Refraction
- wave enters tissue at one angle and continues through at another angle
31
attenuation
* - 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
Attenuation constant
bone\>cartilage\>tendon\> skin\> blood vessels\> muscle \> nerve (no value) \> fat \> blood
33
standing waves
* -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
cavitation
* -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
Microstreaming
* -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
Characteristics of US waves
* -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
Couplant
* -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
Therapeutic US physiological effects
* -Thermal * - increases tissue temp * -Non-thermal * - alter cell membrane permeability
39
Physiological effects: thermal effects
* 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
Absorption coefficent
* 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.
© 2025 Bold Learning Solutions. Terms and Conditions