06-14: Ultrasound

Question 0

Piezoelectric Effect

Answer 0

Piezoelectric transducer (head) converts electrical energy into sound

Question 1

Definition of ultrasound

Answer 1

• Deep heat transferred through conversion
• Uses vibration to produce thermal and no thermal effects
• Acoustic effects = friction = effects

Question 2

Depth of US

Answer 2

• Tissue temp increases up to depths of 5cm

- Requires coupling agent (gel)

Question 3

Reverse Piezoelectric Effect

Answer 3

• Electricity applied to crystal through AC at a specific frequency will produce movement in the crystal that creates US waves at that same frequency
• Therapeutic US uses those waves to create vibrations in the tissue that has thermal effects if continuous US and/or non-thermal effects for continuous or pulsed US

Question 4

Size of Transducer head

Answer 4

• Selected for body part treated

Question 5

Penetration

Answer 5

• US penetrates through tissue with high water content

- Ex: Fat

Question 6

Attenuation

Answer 6

• Loss of heat during transmission through the tissues
• Occurs when US absorbed into dense tissue with high protein (muscle, nerve, bone)
• Greatest heating occurs where absorption is greatest
• Penetration and absorption are inversely related

Question 7

Reflection

Answer 7

• US is reflected when It travels through air or through interface between two different types of tissue
• Causes hotspots (tissue in front of bony areas will get reflections that can burn - deep burn)
• Can burn tissue
• Reason for cooling gel - allows penetration into tissue

Question 8

Refraction

Answer 8

Waves change somewhat as they pass through tissue

Question 9

More reflection

Answer 9

• Holding transducer in air causes reflection and build up of heat that can damage crystal or burn patient when you make contact.
• Coupling medium must be used to transmit sound waves between sound head and pt without allowing air between
• US transmitted through fat and reflected and refracted at muscle interface.
• At bone-soft tissue interface, almost all vibration reflected. Reflected energy runs into new energy, can create hotspot and damage tissue
• Moving transducer using pulsed US. can he’ll avoid hotspots

Question 10

Depth of penetration

Answer 10

• Derermined by US frequency, not intensity (W/cm2)
• Higher frequency sounds absorbed by more superficial tissues
• Lower frequency sound waves have greater depth of perception

Question 11

Frequency

Answer 11

• 0.75-3MHz
• 1 MHz: Heating deeper tissue, up to 5cm DOP
• 3 MHz: higher temp, absorbed in more superficial tissues, heard faster, less than 2cm DOP

Question 12

Continuous mode

Answer 12

Thermal or non- thermal effects, elevates tissue temp

Question 13

Pulsed mode

Answer 13

Non-thermal effects

Question 14

Duty Cycle

Answer 14

• Amount of total treatment time during which ultrasound is generated
• Continuous: 100% duty cycle
• US waves continuously generated 100%
• Higher intensity of thermal effect; also has non-thermal
• Pulsed: 20% duty cycle
• US generated 20% of time
• Non-thermal

Question 15

Intensity

Answer 15

• Measure of the rate energy is being delivered per unit area
• W/cm2
• Range from .25-3.0 w/cm2
• Deteines rate heating occurs, but not DOP

Question 16

Thermal effects

Answer 16

• increased collagen extensibility
• decrease joint stiffness
• pain relief
• increased blood flow
• decrease muscle spasm
• May have mild inflammatory response to help chronic inflammation

Question 17

Non-thermal effects

Answer 17

• stimulation of tissue regeneration
• increase macrophage responsiveness
• pain relief
• soft tissue repair
• increase blood flow
• increase skin and cell membrane permeability

Question 18

Cavitation

Answer 18

• acoustic energy causes micro bubbles in tissue fluids to wxpand and contract

Question 19

Stable cavitation

Answer 19

Bubbles expand and contract in response to repeated pressure changed but do not burst

• small flow of fluid around bubbles (microstreaming)
• flies in a unidirectional movement along boundary of cell mnrancdz; can alter structure and function

Question 20

Transient cavitation

Answer 20

Micro bubbles burst and cause increase in temp and pressure - not a good thing

Question 21

Acoustic

Microstreaming

Answer 21

Consistent and unidirectional flow of cellular fluids that results from US

Question 22

Indications

Answer 22

Soft tissue repair
Decrease inflammatory response
Decrease pain
Contracture
Bone fracture
Trigger point
Dermal ulcer
Scar tissue
Muscle spas plantar wary

Question 23

Contraindications

Answer 23

Over eyes
Over pregnant uterus
Over cemented prosthetic joint
Impaired circulation
Thronbohlebotis
Impaired pain or temp sensory deficits
Over heart
Over tested
Over epiphyte all areas in childr
Infection
Malignancy

Question 24

Coupling agents

Answer 24

Get rid of air between transducer and pt so US can be transmitted
Us gel room temp or warmed
Gel packs, pads, hydrogel sheets - over wounds
Immersion for irregular body part
Water filled bladder
analgesic cremes
MedicTikns

Question 25

Treatment parameters

Answer 25

Coupling agent
Thermal or nonthermal
Duration: 5-10 min, 2-3x size of transducer requires 5 min
Frequency 1 or 3 MHz
Duty cycle applies to pulsed
Intensity - continuous: ,5-2 w/cm2
Pulsed .5 - ,75w/cm