Ultrasound

• diagnostic
• surgical
• therapeutic

freq - 1-3 (.7-3.3)MHz

int - 0.1-2.5 (5) W/cm2

skin and subcutaneous


HP, paraffin, hydrotherapy, infrared, fluido, moist air cabinet

2-5

deeper subcutaneous tissues and superficial musculature

1

the high frequency alternating current (.75 to 3 MHz) travels thru the coaxial cable to the transducer

it is then converted into mechanical vibrations by a reversal of the piezoelectric effect

when the current passes thru the crystal head, it vibrates and molecules are compressed and released

• separation of collagen fibers (increases tissue extensibility)
• increased permeability of cell membranes

all those of non thermal, plus increased tissue temp and all those of heating

• can produce temp changes deep within tissue
• local-few generalized responses
• short application times

• difficult to monitor disage (pt feels little sensation)
• pressure on body part (tenderness)

• soft tissue shortening (joint contractures, scarring)
• subacute and chronic inflammation
• can treat acute conditions if using pulsed mode
• painful conditions-muscle guarding, neuroma, trigger areas
• warts
• phonophoresis (delivers meds locally to tissues)

• arterial circulation unable to meet increased metabolic demand
• if bleeding is present it will increase
• pregnant uterus-cavitation
• cancer
• spinal cord after laminectomy-cavitation
• infection
• carotid sinus or cervical ganglia
• possible increased destruction of articular cartilage in acute inflammatory joint pathologies
• some plastics used in implant joints
• DVT
• anesthetized areas

• maintain constant energy transfer-if not>BURNS...keep sound head moving, even contact, remove air bubbles, keep off bony prominences
• dont hold sound head in air
• avoid higher intensities than those therapeutic
• careful over anesthesized skin

the absorption and scattering of the US beam as it travels thru tissue

denser tissue - with more protein content

uptake of heat converted from acoustic (sound) energy by propagation of US through the tissues

protein content of the tissues sonated

• superficial bone
• joint capsules
• tendon
• scar tissue
• peripheral nerves
• myofasical interface
• cell membranes

perpendicular

scattering

reflection/refraction is worse and you lose energy

reflection

occurs when there is a mismatch of acoustic impedence between two tissue levels

the greater the acoustical impedance, the greater the reflection

interfaces are heated more (tendon/muscle, ligament/muscle, periosteum)

reflection of energy from a straight path when passing obliquely from one medium to another

increases as the transducer head becomes less perpendicular to the tx area

lead to concentration of US energy at the point of refraction (where tendon joins bone)

intensity

• total output of transducer and is expressed in watts
• measured on an US power meter

w/cm2 = total power output (W)/transducers ERA (cm2)

available - 0-5 w/cm2

most common - 0.5-2 w/cm2

yes...pulsed mode is nonthermal

• number of oscillations in one second
• expressed in megahertz (MHz)

• 1MHz - deep
• 3MHz - superficial

diverging (gradually gets bigger)

collimating (stays same size)

a coupling medium

US energy will not pass thru the air or skin without the presence of a coupling medium

aqueous gels

• high transmission and low absorption of US
• exclude air
• minimal air entrapment
• good impedance match with transducer/skin
• low drag coefficient
• good viscosity
• low salt content
• economical cost
• easy to use

3.3mm thick transparent polyscrylamide agar gel, containing 96% water

can be used as a coupling medium for US and then left on as a sterile wound dressing

sterile saline must be appiled below and on top of the dressing to eliminate air trapped between the dressing and underlying tissues and to improve the drag coefficient to transducer head

when tissue depth and surface topography is irregular or sensitive to pressure

hands, ankles

room temp degassed (get bubbles off side of tub) water in a plastic tank

helps decrease reflection

move transducer as close as possible while remaining perpendicular to area

water cushions - transparent, resealable, rigid, small

• 40-45C
• 104-112F

5 mins

mild sensation of warmth

• increased local metabolism and perspiration
• local vasodilation with hyperemia
• muscle relaxation
• sensory nerve endings sedated
• ..long tx times- increased body temp, resp, pulse, decreased BP

what fraction of time the sound is present over one pulse period

duty factor= duration of pulsed time on/total pulsed time

• 20% (1:4)
• 50% (1:1)
• 10% (1:9)

(1:4)=1 min on, 4 mins off

• acute- 5-15%
• subacute- 20-50%

• edema reduction
• pain and muscle spasms
• improved blood flow
• induction of non-union bone repair
• tissue regeneration and soft tissue repair

NOTHING at all..subsensory

• acoustic streaming
• cavitation
• micromassage

unidirectional flow of tissue components, which occurs at the cell membrane

• increased cell membrane and vascular wall permeability
• increased ion flexes and cellular activity
• increased capillary density and improved blood flow
• increased protein synthesis with increased wound healing

US vibrations cause compression and expansion of small gas bubbles in the blood and tissue fluids. the pulsation of the bubbles can cause changes in the cellular activity..sufficiently intense can cause tissue damage

stable cavitation - increased cellular activity, results in diffusional changes along cell membrane

unstable/transient cavitiation - violent collapse of bubbles with tissue damage (blood vessel damage)....sends a shock wave thru the tissues

oscillatory movement of tissue and cells

effects intercellular fluids thus reducing edema (milks out edema)

stimulation of mechanoreceptor and autonomic nervous system - stimulates sensory nerves, somewhat works with gate theory, relaxation

beam non-uniformity ratio

ratio of highest intensity (w/cm2) found in the near field to the average intensity (w/cm2)

smaller..more homeogenous

results in greater pt comfort, focused tx areas, slower head movement (will produce consistent therapeutic dose throughout target tissues)

less homeogenous the US beam...causes hot spots of increased wattage

effective radiating area

the area of the transducer head that is effective...always smaller than the actual head.

before...cooling/heating alters the patients perception of pain and warmth

stationary....casues selective heating and hot spots which can burn and damage tissue

• overlapping circles
• parallel stroking technique

*cover half of previous area

4 inches per second

by power and time

sonation can change the nerve conduction velocities

• low and high increases (0.5 or 3.0 w/cm2)
• moderate decreases (1 to 2 w/cm2)

1.5 is like perfect

• goal of treatment
• site of lesion
• acuteness

medicinal molecules that are driven across the skin into deeper muscle and nerves by US

no invasion of skin like injections

• subacute inflammatory conditions with antiinflammatory drugs
• use low intensity, long duration

10% hydrocortisone cream, cortisol, salicylates, dexamethasome in glycerol, cream, oil, or water

• 1. complete relief of signs/symptoms or restoration of function
• 2. find no beneficial effects after 3-4 treatments
• 3. after course of 12-15 treatments- no proof of further US benefits
• 4. modify tx is symptoms get worse