Ultrasound Background/Terminology

Question 1

Ultrasound (definition)

Answer 1

Application of acoustic (sound wave) energy, inaudible of the human ear which causes a mechanical vibration.

Question 2

Produces non thermal effects of ultrasound

Answer 2

Pulsed duty cycle

Question 3

Pulsed ultrasound causes:

Answer 3

Acoustical streaming, micro-streaming, and cavitation which increases cellular metabolism.

Question 4

Increased cellular metabolism produced by ultrasound results in: (4)

Answer 4

1) Increased enzyme activity
2) Stimulates immune system
3) Increased O2 uptake
4) Increased cellular permeability

Question 5

Pulsed ultrasound facilitates and increases (2) specific things:

Answer 5

1) Facilitates tissue repair (increased phagocytic activity, fibroblast, & granulation tissue formation)
2) Increases pain threshold (decrease muscle spasm, increase conduction of peripheral nerves, serotonin release)

Question 6

Produces thermal effects of ultrasound

Answer 6

Continuous duty cycle

Question 7

In addition to non-termal effects, thermal ultrasound also produces the following (4) benefits:

Answer 7

1) Can produce deep heat (up to 5cm)
2) allows for soft tissue (collagen) extensibility
3) Increases blood flow
4) Increases cellular metabolism

Question 8

Three types/intensities of ultrasound

Answer 8

1) Low intensity: Diagnostic- Sonogram
2) Medium Intensity: Theraputic
3) High Intensity: Tissue destruction (tumors)

Question 9

Medical ultrasound is generally between what Mhz’s

Answer 9

.8Mhz to 3.0Mhz

Question 10

Ultrasound in the 1950’s

Answer 10

AMA recommends use of US as a modality for use of soft tissue healing and pain. Often used in MD offices by non-trained individuals.

Question 11

Ultrasound in the 1960’s

Answer 11

Regulations were tightened by states and US mainly perscribed for use by PT. OT began use of US in a widespread manner by 1980’s.

Question 12

Ultrasounds in the 1990’s

Answer 12

National push to demand OT’s competence. Driven mainly by APTA. Individual states established regulations. NY state regulations indicate OT’s must receive training in modalities that include a background in physics.

Question 13

This is the device that is held/aimed at the pts. skin (with gel or water as a medium)

Answer 13

Transducer: Also called the sound head

Question 14

Movement of the sound head on the surface should occur at how many cm per second:
Which two motions can be used:

Answer 14

4cm (1.5 inches) per second:

1) overlapping circles
2) back and forth, side to side with overlap

Question 15

This is housed in the transducer it is more recently made of ceramic or a synthetic material and is only about 1/6” thick

Answer 15

Crystal

Question 16

Characteristics (4) Of the crystal

Answer 16

1) Subject to breakage if sound head is dropped.
2) Damage can occur if not in contact with transmission medium/skin prior to turning on.
3) Check 1-2x per year to assure it is intact.
4) Informal integrity test: submerging in H20 and observe for bubble formation on surface indicating crystal is functioning.

Question 17

Reverse Piezoelectric effect

Answer 17

When alternating current is applied (to an electrical charge) to the crystal it responds by expanding and contracting. When the crystal expands and contracts it results in a mechanical response in the tissue in front of it.
The alternating compression - rarefaction is the ultrasound wave.

Question 18

Compression of crystal

Answer 18

Moves the tissue together

Question 19

Expanding of crystal

Answer 19

Causes rarefaction or pulling the tissue apart

Question 20

Degree to which the sound wave passes through the tissue w/o regard to absorption by the given tissue

Answer 20

Penetration

Question 21

5 types of transmission mediums (coupling agents)

Answer 21

1) Ultrasound gel (97% %= transmit ion or penetration of sound waves) Water based gel that is hypoallergenic (warmed gel is 10% less effective)
2) Ultrasound lotion (90%)
3) Hydrocortisone cream (0-10%) Used in the 80’s-Early 90’s.
4) Other medication infused gels (88%)
5) Water: submersion technique can be used for surfaces that are bony. Transducer is then placed 1/2” away from the skins surface.

Question 22

Application of ultrasound with a topical drug

Answer 22

Phonophoresis

Question 23

The process of energy loss

Answer 23

Attenuation

Question 24

4 ways attenuation occurs

Answer 24

1) Absorption is a main way energy is lost either into tissue or into the transmission medium .
2) Reflection- redirection away in the equal and opposite direction; generally occurs at skin surface if not enough transmission medium.
3) Sound waves decrease in intensity as they travel through the tissue.
4) Refraction- redirection of a sound wave generally due to a blockage by foreign tissue.

Question 25

The degree to which the sound wave is transferred into the tissue there by limiting penetration.

Answer 25

Absorption

Question 26

What tissues have a greater absorption of the sound wave

Answer 26

Denser tissues with more protein and collagen.

Question 27

Formation, growth, and pulsation of gas and vapor filled bubbles caused by the non-thermal mechanical effects of ultrasound.

Answer 27

Stable Cavitation

Question 28

The steady flow of cellular fluid induced by the mechanical effects of ultrasound

Answer 28

Acoustical Streaming

Question 29

This number reflects the intensity of the ultrasound output as it varies from the center of the sound head to the outer edges.

Answer 29

Beam Non-Uniformity (BNR)
BNR is greatest at the center.
Those with a ratio that is lower have a more desirable BNR and are generally 2:1.
The highest ratios are 5:1 or 6:1

Question 30

Why is the BNR important

Answer 30

Hot Spots.
The higher the ratio the ore important it is to you to have constant movement and slightly faster movement of the ultrasound head to prevent hot spots.

Question 31

The area on the transducer face where the ultrasound energy radiates.

Answer 31

Effective Radiating Area (ERA)
This area is smaller than the actual size of the face of the traducer as the crystal is smaller than the actual face size.