ULTRASOUNDULTRASOUND

A Deep Thermal & Non-A Deep Thermal & Non-thermal Mechanical Modalitythermal Mechanical Modality

What is Ultrasound?What is Ultrasound?

• Located in the Acoustical SpectrumLocated in the Acoustical Spectrum

• May be used for diagnostic imaging, May be used for diagnostic imaging, therapeutic tissue healing, or tissue therapeutic tissue healing, or tissue destructiondestruction

• Thermal & Non-thermal effectsThermal & Non-thermal effects

• We use it for therapeutic effectsWe use it for therapeutic effects

• Can deliver medicine to subcutaneous Can deliver medicine to subcutaneous tissues (phonophoresis)tissues (phonophoresis)

UltrasoundUltrasound

• Sinusoidal waveformSinusoidal waveform– Therapeutic ultrasound waves range Therapeutic ultrasound waves range

from 750,000 to 3,000,000 Hz (0.75 to 3 from 750,000 to 3,000,000 Hz (0.75 to 3 MHz)MHz)

• Displays properties of Displays properties of – wavelength, wavelength, – frequency, frequency, – AmplitudeAmplitude

TransducerTransducer• A device that converts one form of energy to anotherA device that converts one form of energy to another• Piezoelectric crystal:Piezoelectric crystal: a crystal that produces (+) and a crystal that produces (+) and

(-) electrical charges when it contracts or expands(-) electrical charges when it contracts or expands– Crystal of quartz, barium titanate, lead zirconate, or titanate Crystal of quartz, barium titanate, lead zirconate, or titanate

housed within transducerhoused within transducer

• Reverse (indirect) piezoelectric effect:Reverse (indirect) piezoelectric effect: occurs when an occurs when an alternating current is passed through a crystal alternating current is passed through a crystal resulting in contraction & expansion of the crystalresulting in contraction & expansion of the crystal– US is produced through the reverse piezoelectric effectUS is produced through the reverse piezoelectric effect– Vibration of crystal results in high-frequency sound wavesVibration of crystal results in high-frequency sound waves

• Fresnal zoneFresnal zone (near field) – area of the ultrasound beam (near field) – area of the ultrasound beam on the transducer used for therapeutic purposeson the transducer used for therapeutic purposes

Types of CurrentTypes of Current

• Direct Current:Direct Current: the uninterrupted the uninterrupted unidirectional flow of electronsunidirectional flow of electrons

• Alternating Current:Alternating Current: the uninterrupted the uninterrupted bidirectional flow of electronsbidirectional flow of electrons– Ultrasound is produced by this type of current Ultrasound is produced by this type of current

flowing through a piezoelectric crystalflowing through a piezoelectric crystal

• Pulsed Current:Pulsed Current: the flow of electrons the flow of electrons interrupted by discrete periods of interrupted by discrete periods of noncurrent flownoncurrent flow

Longitudinal vs. Transverse Longitudinal vs. Transverse WavesWaves

• Longitudinal wavesLongitudinal waves – molecular – molecular displacement is along direction in which displacement is along direction in which waves travel (bungee cord)waves travel (bungee cord)– CompressionCompression – regions of high molecular – regions of high molecular

density (molecules in high pressure areas density (molecules in high pressure areas compress)compress)

– RarefractionRarefraction – regions of low molecular density – regions of low molecular density (molecules in low pressure areas expand)(molecules in low pressure areas expand)

• Transverse wavesTransverse waves – molecular – molecular displacement in direction perpendicular to displacement in direction perpendicular to wave (guitar string)wave (guitar string)

• Longitudinal wavesLongitudinal waves – travel in solids – travel in solids & liquids& liquids– Soft tissue – more like liquidsSoft tissue – more like liquids– US primarily travels as longitudinal waveUS primarily travels as longitudinal wave

• Transverse wavesTransverse waves – cannot pass – cannot pass through fluids; found in the body only through fluids; found in the body only when ultrasound strikes bonewhen ultrasound strikes bone

FrequencyFrequency• Frequency:Frequency: number of times an event number of times an event

occurs in 1 second; expressed in occurs in 1 second; expressed in Hertz Hertz or pulses per secondor pulses per second– Hertz:Hertz: cycles per second cycles per second– Megahertz:Megahertz: 1,000,000 cycles per second 1,000,000 cycles per second

• In the U.S., we mainly use ultrasound In the U.S., we mainly use ultrasound frequencies of 1, 2 and 3 MHzfrequencies of 1, 2 and 3 MHz

•1 = low frequency; 3 = high frequency1 = low frequency; 3 = high frequency

frequency = frequency = depth of penetration depth of penetration frequency = sound waves are frequency = sound waves are

absorbed in more superficial tissues (3 absorbed in more superficial tissues (3 MHz)MHz)

VelocityVelocity

• The speed of sound wave is directly related The speed of sound wave is directly related to the density (to the density ( velocity = velocity = density) density)

• Denser & more rigid materials have a Denser & more rigid materials have a higher velocity of transmissionhigher velocity of transmission

• At 1 MHz, sound travels through soft tissue At 1 MHz, sound travels through soft tissue @ 1540 m/sec and 4000 m/sec through @ 1540 m/sec and 4000 m/sec through compact bone compact bone

Influences on the Transmission Influences on the Transmission of Energyof Energy

• ReflectionReflection – occurs when the wave can’t – occurs when the wave can’t pass through the next densitypass through the next density

• RefractionRefraction – is the bending of waves as a – is the bending of waves as a result of a change in the speed of a wave result of a change in the speed of a wave as it enters a medium with a different as it enters a medium with a different densitydensity

• AbsorptionAbsorption – occurs by the tissue – occurs by the tissue collecting the wave’s energycollecting the wave’s energy

AttenuationAttenuation• Decrease in a wave’s intensity resulting from Decrease in a wave’s intensity resulting from

absorption, reflection, & refractionabsorption, reflection, & refraction– as the frequency of US is as the frequency of US is because of molecular friction because of molecular friction

the waves must overcome in order to pass through tissuesthe waves must overcome in order to pass through tissues

• US penetrates through tissue high in water content US penetrates through tissue high in water content & is absorbed in dense tissues high in protein& is absorbed in dense tissues high in protein

Absorption = Absorption = Frequency (3 MHz) , and Frequency (3 MHz) , and Penetration = Penetration = Absorption (1 MHz) , so Absorption (1 MHz) , so Penetration = Penetration = Frequency + Frequency + Absorption (1 MHz) Absorption (1 MHz)

• Tissues Tissues water content = low absorption rate (fat) water content = low absorption rate (fat)• Tissues Tissues protein content = high absorption rate protein content = high absorption rate

(peripheral nerve, bone)(peripheral nerve, bone)– Muscle is in between bothMuscle is in between both

Attenuation: Acoustic Attenuation: Acoustic ImpedanceImpedance

• Determines amount of US energy reflected at tissue Determines amount of US energy reflected at tissue interfacesinterfaces– If acoustic impedance of the 2 materials forming the If acoustic impedance of the 2 materials forming the

interface is the same, all sound will be transmittedinterface is the same, all sound will be transmitted– The larger the difference, the more energy is reflected & The larger the difference, the more energy is reflected &

the less energy that can enter the 2the less energy that can enter the 2ndnd medium medium

• US passing through air = almost all reflected (99%)US passing through air = almost all reflected (99%)• US through fat = 1% reflected US through fat = 1% reflected • Both reflected/refracted @ m. interfaceBoth reflected/refracted @ m. interface• Soft-tissue: bone interfaced = much reflectedSoft-tissue: bone interfaced = much reflected

• As US energy is reflected @ tissue interfaces with As US energy is reflected @ tissue interfaces with different impedances, intensity is increased creating different impedances, intensity is increased creating a a Standing WaveStanding Wave (hot spot) (hot spot)

• Effective Radiating Area (ERA):Effective Radiating Area (ERA): area of the area of the sound head that produces ultrasonic waves; sound head that produces ultrasonic waves; expressed in expressed in square centimeters (cmsquare centimeters (cm22))– Represents the portion of the head’s surface area Represents the portion of the head’s surface area

that produces US wavesthat produces US waves– Measured 5 mm from face of sound head; Measured 5 mm from face of sound head;

represents all areas producing more than 5% of represents all areas producing more than 5% of max. power outputmax. power output

– Always lesser area than actual size of sound headAlways lesser area than actual size of sound head– Large diameter heads – column beamLarge diameter heads – column beam– Small diameter heads – more divergent beamSmall diameter heads – more divergent beam– Low frequency (1 MHz) – diverge more than 3 Low frequency (1 MHz) – diverge more than 3

MHzMHz

• Treatment Duration:Treatment Duration: time for total treatment time for total treatment

Intensity Output & Power Intensity Output & Power • Power:Power: measured in watts (W); measured in watts (W);

– amount of energy being produced by the amount of energy being produced by the transducertransducer

• Intensity:Intensity: strength of sound waves @ a given strength of sound waves @ a given location within the tissues being treatedlocation within the tissues being treated

• Spatial Average Intensity (SAI):Spatial Average Intensity (SAI): amount of amount of US energy passing through the US head’s US energy passing through the US head’s ERA; ERA; – expressed in expressed in watts per square centimeter (W/cmwatts per square centimeter (W/cm22))

(power/ERA)(power/ERA)– Changing head size affects power density (larger Changing head size affects power density (larger

head results in lower density)head results in lower density)– Limited to 3.0 W/cmLimited to 3.0 W/cm2 2 of maximum outputof maximum output

Intensity Output & PowerIntensity Output & Power• Spatial Average Temporal Peak Intensity (SATP):Spatial Average Temporal Peak Intensity (SATP):

average intensity during the “on” time of the average intensity during the “on” time of the pulsepulse– Output meter displays the SATP intensityOutput meter displays the SATP intensity

• Spatial Peak Intensity (SPI):Spatial Peak Intensity (SPI): max. output (power) max. output (power) produced within an ultrasound beamproduced within an ultrasound beam

• Spatial Average Temporal Average Intensity Spatial Average Temporal Average Intensity (SATA) (SATA) oror Temporal (time) Average Intensity: Temporal (time) Average Intensity:– Power of US energy delivered to tissues over a given period of Power of US energy delivered to tissues over a given period of

timetime– Only meaningful for Pulsed US Only meaningful for Pulsed US

– SAI x Duty CyclesSAI x Duty Cycles

Beam Nonuniformity Ratio Beam Nonuniformity Ratio (BNR)(BNR)

• Ratio between the spatial peak Ratio between the spatial peak intensity (SPI) to the average output intensity (SPI) to the average output as reported on the unit’s meteras reported on the unit’s meter– The lower the BNR, the more uniform the The lower the BNR, the more uniform the

beam isbeam is– A BNR greater than 8:1 is unsafeA BNR greater than 8:1 is unsafe– Because of the existence of high-intensity Because of the existence of high-intensity

areas in the beam (hot spots), it is areas in the beam (hot spots), it is necessary to keep the US head movingnecessary to keep the US head moving

BNRBNR

SPI

Duty CycleDuty Cycle• Percentage of time that US is actually Percentage of time that US is actually

being emitted from the headbeing emitted from the head• Ratio between the US’s pulse length & Ratio between the US’s pulse length &

pulse interval when US is being delivered pulse interval when US is being delivered in the pulsed modein the pulsed mode– Pulse lengthPulse length = amount of time from the initial = amount of time from the initial

nonzero charge to the return to a zero chargenonzero charge to the return to a zero charge– Pulse intervalPulse interval – amount of time between – amount of time between

ultrasonic pulsesultrasonic pulses– Duty cycleDuty cycle = pulse length/(pulse length + = pulse length/(pulse length +

pulse interval) x 100pulse interval) x 100– 100% duty cycle indicates a constant US 100% duty cycle indicates a constant US

outputoutput– Low output produces nonthermal effects (20%)Low output produces nonthermal effects (20%)

Movement of the Movement of the TransducerTransducer• 4 cm4 cm22/sec/sec• Remaining stationary can cause problemsRemaining stationary can cause problems• Moving too rapidly decreases the total Moving too rapidly decreases the total

amount of energy absorbed per unit areaamount of energy absorbed per unit area– May cause clinician to treat larger area and the May cause clinician to treat larger area and the

desired temps. May not be attaineddesired temps. May not be attained

• Slower strokes can be easier maintainedSlower strokes can be easier maintained• If patient complains of pain or excessive If patient complains of pain or excessive

heat, then heat, then decrease intensitydecrease intensity but increase but increase timetime

• Apply constant pressure – not too much & Apply constant pressure – not too much & not too littlenot too little

Coupling AgentsCoupling Agents

• Optimal agent – distilled HOptimal agent – distilled H220 0 (.2% reflection)(.2% reflection)

• Modern units have a shut down Modern units have a shut down mechanism if sound head becomes too hot mechanism if sound head becomes too hot (Dynatron beeps; red lights on (Dynatron beeps; red lights on Chattanoogas)Chattanoogas)– Improperly coupled head causes Improperly coupled head causes temp. temp.

• Types of agents:Types of agents:– DirectDirect

– HH220 immersion0 immersion

– BladderBladder

• Reduce amount of air bubblesReduce amount of air bubbles

Direct CouplingDirect Coupling

• Effectiveness is Effectiveness is if body part is hair, if body part is hair, irregular shaped, or uncleanirregular shaped, or unclean

• Must maintain firm, constant Must maintain firm, constant pressurepressure

• Various gels utilized Various gels utilized

Water ImmersionWater Immersion• Used for odd shaped partsUsed for odd shaped parts• Place head approx. 1” away from partPlace head approx. 1” away from part• Operator’s hand should not be Operator’s hand should not be

immersed No metal on part or immersed No metal on part or operator’s handoperator’s hand

• Ceramic tub is recommendedCeramic tub is recommended• If nondistilled HIf nondistilled H220 is used, intensity can 0 is used, intensity can

be be .5 w/cm .5 w/cm22 because of air & minerals because of air & minerals • Don’t touch skin except to briefly sweep Don’t touch skin except to briefly sweep

skin when bubbles formskin when bubbles form

Bladder Bladder

• HH220 filled balloon or plastic bag coated 0 filled balloon or plastic bag coated with coupling gelwith coupling gel

• Use on irregular shape partUse on irregular shape part

• Place gel on skin, then place the Place gel on skin, then place the bladder on the part, and then place bladder on the part, and then place gel on bladdergel on bladder

• Make sure all air pockets are removed Make sure all air pockets are removed from bladderfrom bladder

IndicationsIndications• Soft tissue healing & repairSoft tissue healing & repair• Joint contractures & scar tissueJoint contractures & scar tissue• Muscle spasmMuscle spasm• NeuromaNeuroma• Trigger areasTrigger areas• WartsWarts• Sympathetic nervous system disordersSympathetic nervous system disorders• Postacute reduction of myositis ossificansPostacute reduction of myositis ossificans• Acute inflammatory conditions (pulsed)Acute inflammatory conditions (pulsed)• Has been shown to be ok to use following Has been shown to be ok to use following

the stopping of bleeding with an acute the stopping of bleeding with an acute injury (pulsed)injury (pulsed)

ContraindicationsContraindications• Acute conditions (continous output)Acute conditions (continous output)• Ischemic areas or impaired circulation areasIschemic areas or impaired circulation areas• Tendency to hemorrhageTendency to hemorrhage• Around eyes, heart, skull, or genitalsAround eyes, heart, skull, or genitals• Over pelvic or lumbar areas in pregnant or Over pelvic or lumbar areas in pregnant or

menstruating femalesmenstruating females• Cancerous tumorsCancerous tumors• Spinal cord or large nerve plexus in high dosesSpinal cord or large nerve plexus in high doses• Anesthetic areasAnesthetic areas• Stress fracture sites or over fracture site Stress fracture sites or over fracture site

before healing is complete (continuous); before healing is complete (continuous); epiphysisepiphysis

• Acute infectionAcute infection

Thermal EffectsThermal Effects blood flowblood flow sensory & motor nerve conduction sensory & motor nerve conduction

velocityvelocity extensibility of structures (collagen); extensibility of structures (collagen);

joint stiffnessjoint stiffness collagen depositioncollagen deposition macrophage activitymacrophage activity• Mild inflammatory response which may Mild inflammatory response which may

enhance adhesion of leukocytes to enhance adhesion of leukocytes to damaged endothelial cellsdamaged endothelial cells

muscle spasmmuscle spasm painpain• + all Nonthermal effects+ all Nonthermal effects

Nonthermal EffectsNonthermal Effects cell membrane permeabilitycell membrane permeability vascular permeabilityvascular permeability blood flowblood flow fibroblastic activityfibroblastic activity• Altered rates of diffusion across cell membraneAltered rates of diffusion across cell membrane• Secretion of chemotacticsSecretion of chemotactics• Stimulation of phagocytosisStimulation of phagocytosis• Production of granulation tissueProduction of granulation tissue• Synthesis of proteinSynthesis of protein edemaedema• Diffusion of ionsDiffusion of ions• Tissue regenerationTissue regeneration• Formation of stronger CTFormation of stronger CT

Pulsed UltrasoundPulsed Ultrasound• Stimulates phagocytosis Stimulates phagocytosis (assists w/ (assists w/ of chronic of chronic

inflammation)inflammation) & increases # of free radicals & increases # of free radicals (( ionic conductance on cell membrane)ionic conductance on cell membrane)

• Cavitation:Cavitation: formation of gas bubbles that formation of gas bubbles that expand & compress due to pressure changes expand & compress due to pressure changes in tissue fluidsin tissue fluids– StableStable – occurs when bubbles compress during the – occurs when bubbles compress during the

-press. peaks followed expansion of bubbles during -press. peaks followed expansion of bubbles during -press. troughs-press. troughs

– Unstable (transient)Unstable (transient) – compression of bubbles – compression of bubbles during during -press. Peaks, but is followed by total -press. Peaks, but is followed by total collapse during trough (BAD!)collapse during trough (BAD!)

Pulsed UltrasoundPulsed Ultrasound• Acoustical Streaming:Acoustical Streaming: stable cavitation leads stable cavitation leads

this; one-directional flow of tissue fluids, & is this; one-directional flow of tissue fluids, & is most marked around cell membranes most marked around cell membranes – Facilitates passage of calcium potassium & other Facilitates passage of calcium potassium & other

ions, etc. in/out of cells ions, etc. in/out of cells – Collagen synthesis, chemotactics secretion, Collagen synthesis, chemotactics secretion,

update of calcium in fibroblasts, update of calcium in fibroblasts, fibroblastic fibroblastic activityactivity

• Eddies (Eddy) – circular current of fluid often Eddies (Eddy) – circular current of fluid often moving against the main flowmoving against the main flow– Flows around the cell membranes & its organellesFlows around the cell membranes & its organelles– Flow of bubbles in stream cause change in cell Flow of bubbles in stream cause change in cell

membrane permeabilitymembrane permeability

Clinical Applications – Soft Clinical Applications – Soft TissueTissue• Stimulates release of histamine from Stimulates release of histamine from

mast cellsmast cells– May be due to cavitation & streaming May be due to cavitation & streaming – transport of calcium ions across transport of calcium ions across

membrane that stimulates histamine membrane that stimulates histamine releaserelease

– Histamine attracts leukocytes, that clean Histamine attracts leukocytes, that clean up debris, & monocytes that release up debris, & monocytes that release chemotactic agens & growth factors that chemotactic agens & growth factors that stimulate fibroblasts & endothelial cells to stimulate fibroblasts & endothelial cells to form a collagen-rich, well-vascularized form a collagen-rich, well-vascularized tissuetissue

Clinical Applications – Soft Clinical Applications – Soft Tissue & Plantar WartsTissue & Plantar Warts

• Pitting edema - Pitting edema - temp. makes thick temp. makes thick edema liquefy thus promoting edema liquefy thus promoting lymphatic drainagelymphatic drainage

fibroblasts = stimulation of collagen fibroblasts = stimulation of collagen production = gives CT more strength production = gives CT more strength

• Plantar Warts - 0.6 W/cmPlantar Warts - 0.6 W/cm22 for 7-15 for 7-15 min.min.

Clinical Applications – Scar Clinical Applications – Scar Tissue, Joint Contracture, & Tissue, Joint Contracture, & Pain ReductionPain Reduction mobility of mature scar mobility of mature scar tissue extensibilitytissue extensibility

• Softens scar tissueSoftens scar tissue

pain thresholdpain threshold

• Stimulates large-diameter myelinated n. Stimulates large-diameter myelinated n. fibersfibers

n. conduction velocityn. conduction velocity

Clinical Applications Clinical Applications • Chronic InflammationChronic Inflammation - Pulsed US has - Pulsed US has

been shown to be effective with been shown to be effective with pain & pain & ROM ROM – 1.0 to 2.0 W/cm1.0 to 2.0 W/cm22 at 20% duty cycle at 20% duty cycle

• Bone HealingBone Healing – Pulsed US has been – Pulsed US has been shown to accelerate fracture repair shown to accelerate fracture repair – 0.5 W/cm0.5 W/cm22 at 20% duty cycle for 5 min., at 20% duty cycle for 5 min.,

4x/wk4x/wk– Caution over epiphysis – may cause Caution over epiphysis – may cause

premature closurepremature closure

Treatment Duration & AreaTreatment Duration & Area• Length of time depends on theLength of time depends on the

– Size of areaSize of area– Output intensityOutput intensity– Goals of treatmentGoals of treatment– FrequencyFrequency

• Area should be no larger than 2-3 times the Area should be no larger than 2-3 times the surface area of the sound head ERAsurface area of the sound head ERA

• If the area is large, it can divided into smaller If the area is large, it can divided into smaller treatment zonestreatment zones

• When vigorous heating is desired, duration When vigorous heating is desired, duration should be 10-12 min. for 1 MHz & 3-4 min. should be 10-12 min. for 1 MHz & 3-4 min. for 3 MHzfor 3 MHz

• Generally a 10-14 day treatment periodGenerally a 10-14 day treatment period

Thermal Thermal ApplicatioApplicationsns

Treatment Goal & DurationTreatment Goal & Duration• Adjust the intensity & time according Adjust the intensity & time according

to specific outcometo specific outcome• Desired temp. Desired temp. /min. = treatment /min. = treatment

min.min.– Ex. For 1.5 W/cmEx. For 1.5 W/cm22: 2°C : 2°C .3°C = 6.67 min. .3°C = 6.67 min.

PhonophoresisPhonophoresis• US is used to deliver a medication via a safe, US is used to deliver a medication via a safe,

painless, noninvasive techniquepainless, noninvasive technique

• Opens pathways to drive molecules into the Opens pathways to drive molecules into the tissuestissues

• Not likely to damage or burn skin as with Not likely to damage or burn skin as with iontophoresisiontophoresis

• Usually introduces an anti-inflammatory drugUsually introduces an anti-inflammatory drug

• Preheating the area may enhance delivery of Preheating the area may enhance delivery of medicationmedication– Encourages vascular absorption & distribution of Encourages vascular absorption & distribution of

meds.meds.

• Some medications are poor conductorsSome medications are poor conductors

PhonophoresisPhonophoresis• Factors affecting rate of medication diffusionFactors affecting rate of medication diffusion

– Hydration – higher water content = skin more Hydration – higher water content = skin more penetrablepenetrable

– Age – better with younger agesAge – better with younger ages– Composition – better near hair follicles, Composition – better near hair follicles,

sebaceous glands & sweat ductssebaceous glands & sweat ducts– Vasularity – higher vascular areas are betterVasularity – higher vascular areas are better– Thickness – thinner skin is betterThickness – thinner skin is better

• Types of medicationsTypes of medications– Corticosteroids – hydrocortisone, dexamethasoneCorticosteroids – hydrocortisone, dexamethasone– Salicylates - Salicylates - – Anesthetics - lidocaineAnesthetics - lidocaine