Therapeutic Ultrasound Chapter 7. © 2005 – FA Davis Description Acoustical energy (sound waves) above the range of human hearing Acoustical energy (sound.

Therapeutic Therapeutic UltrasoundUltrasound

Chapter 7Chapter 7

© 2005 – FA Davis© 2005 – FA Davis

DescriptionDescription

Acoustical energy (sound waves) Acoustical energy (sound waves) above the range of human hearingabove the range of human hearing– Therapeutic range: 0.75 to 3.3 MHzTherapeutic range: 0.75 to 3.3 MHz

Effects:Effects:– ThermalThermal– Nonthermal (mechanical)Nonthermal (mechanical)


UsesUses

Calcific bursitisCalcific bursitis Inflammatory conditionsInflammatory conditions Joint contracturesJoint contractures PainPain Muscle spasmMuscle spasm Acute orthopedic injuries (low pulses, Acute orthopedic injuries (low pulses,

low intensity) low intensity)


Production of UltrasoundProduction of Ultrasound

An alternating current An alternating current is passed through a is passed through a crystalcrystal

The current causes the The current causes the crystal to vibratecrystal to vibrate– Electropiezo effectElectropiezo effect

Vibrating crystal Vibrating crystal produce high-produce high-frequency sound frequency sound waveswaves


Effective Radiating Area Effective Radiating Area (ERA)(ERA)

Area of the crystal that Area of the crystal that actually produces sound actually produces sound waveswaves– Produces more than 5% of Produces more than 5% of

the energy at 5 mm from the energy at 5 mm from the transducer facethe transducer face

ERA is always smaller than ERA is always smaller than the transducer facethe transducer face

Energy is concentrated Energy is concentrated near the centernear the center

ERA


Beam ProfileBeam Profile

Multiple waves emerge Multiple waves emerge from the headfrom the head

Energy diverges as it Energy diverges as it moves away from the moves away from the sourcesource

Energy is uniform close to Energy is uniform close to the headthe head– Near zone (Fresnel zone)Near zone (Fresnel zone)

Becomes less consistent Becomes less consistent farther away from the farther away from the headhead– Spatial peak intensitySpatial peak intensity Spatial Peak Intensity


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

Describes the amount of variation Describes the amount of variation in the beamin the beam

Ratio between:Ratio between:– Spatial peak intensity (SPI)Spatial peak intensity (SPI)– Average intensity (SAI - metered Average intensity (SAI - metered

output)output)– BNR = SPI/SAIBNR = SPI/SAI

Perfect beam would have a BNR Perfect beam would have a BNR of 1:1of 1:1

Minimally acceptable BNR is 8:1Minimally acceptable BNR is 8:1 The actual peak output is equal to The actual peak output is equal to

the SAI * the BNRthe SAI * the BNR– 10 W total output * 6:1 BNR10 W total output * 6:1 BNR– 60 watt SPI60 watt SPI

Spatial Peak Intensity

Spatial Average Intensity(Displayed on the unit)


Modes of ApplicationModes of Application

ContinuousContinuous Ultrasonic energy is constantly producedUltrasonic energy is constantly produced Can produce thermal effects based on:Can produce thermal effects based on:

– Output intensityOutput intensity– Treatment durationTreatment duration

PulsedPulsed Ultrasonic output is regularly interruptedUltrasonic output is regularly interrupted Produces nonthermal effectsProduces nonthermal effects


Pulsed OutputPulsed Output

Ultrasonic output is cycled Ultrasonic output is cycled “On” and “Off”“On” and “Off”– On = Pulse lengthOn = Pulse length– Off = Pulse intervalOff = Pulse interval

Expressed as a Expressed as a Duty Duty CycleCycle– ON/(ON+OFF) * 100ON/(ON+OFF) * 100– 20mSec/(20mSec+10mSec) 20mSec/(20mSec+10mSec)

* 100* 100– 20/30 * 10020/30 * 100– 67%67%

Continuous Output (100% Duty Cycle)

Pulsed Output (67% Duty Cycle)


Output FrequencyOutput Frequency

Measured in megahertz (MHz)Measured in megahertz (MHz)– 1 MHz = 1,000,000 waves per 1 MHz = 1,000,000 waves per

secondsecond Determines the depth of effectsDetermines the depth of effects 1 MHz Output1 MHz Output

– Penetrates 5 to 7 cmPenetrates 5 to 7 cm– Thermal effects last longerThermal effects last longer– More divergent beamMore divergent beam

3 MHz Output3 MHz Output– Penetrates 2 to 3 cmPenetrates 2 to 3 cm– Heats 3 times faster than 1 MHz Heats 3 times faster than 1 MHz

outputoutput– More collimated beamMore collimated beam

Power and IntensityPower and IntensitySpatial Average IntensitySpatial Average Intensity

Spatial Average Temporal Peak Spatial Average Temporal Peak IntensityIntensity

Spatial Average Temporal Average Spatial Average Temporal Average IntensityIntensity


Spatial Average Intensity Spatial Average Intensity (SAI)(SAI)

Describes the energy per unit of areaDescribes the energy per unit of area Total output (watts)/areaTotal output (watts)/area

– Watts/effective radiating area (cmWatts/effective radiating area (cm22))– W/cmW/cm22

15 watts being applied with a 10 cm15 watts being applied with a 10 cm22 ERA ERA – 15 Watts / 10 cm15 Watts / 10 cm22

– 1.5 W/cm1.5 W/cm22


Power Measures – Pulsed Power Measures – Pulsed OutputOutput

Spatial Average Temporal Spatial Average Temporal Peak Intensity (SATP)Peak Intensity (SATP)

The average energy The average energy delivered during the “On” delivered during the “On” time of the duty cycle.time of the duty cycle.

Spatial Average Temporal Spatial Average Temporal Average Intensity Average Intensity (SATA)(SATA)

Energy delivered over timeEnergy delivered over time– Spatial Average Intensity * Spatial Average Intensity *

Duty CycleDuty Cycle Meaningful only during Meaningful only during

pulsed outputpulsed output

Biophysical EffectsBiophysical Effects

ThermalThermal


Thermal EffectsThermal Effects Increased sensory nerve conduction velocityIncreased sensory nerve conduction velocity Increased motor nerve conduction velocityIncreased motor nerve conduction velocity Increased extensibility of collagen-rich Increased extensibility of collagen-rich Increased vascular permeability structuresIncreased vascular permeability structures Increased collagen depositionIncreased collagen deposition Increased blood flowIncreased blood flow Reduction of muscle spasmReduction of muscle spasm Increased macrophage activityIncreased macrophage activity Enhanced adhesion of leukocytes to damaged Enhanced adhesion of leukocytes to damaged

endothelial cellsendothelial cells


Heating ClassificationsHeating Classifications

IncreaseIncrease Used ForUsed For

MildMild 11°°CC Mild inflammationMild inflammationAccelerate metabolismAccelerate metabolism

ModerateModerate 22°° – 3 – 3°°CC Decreasing muscle Decreasing muscle spasmspasm

Decreasing painDecreasing painIncreasing blood flowIncreasing blood flowChronic inflammationChronic inflammation

VigorousVigorous 33°° – 4 – 4°°CC Tissue elongationTissue elongationScar tissue reductionScar tissue reduction


Heating RateHeating Rate

Heating rate and magnitude is based Heating rate and magnitude is based on:on:– Duty cycleDuty cycle– Output frequencyOutput frequency– IntensityIntensity– Target tissuesTarget tissues– Size of the treatment areaSize of the treatment area


Thermal EffectsThermal Effects Same as other heat modalitiesSame as other heat modalities

– Smaller volume of tissueSmaller volume of tissue– Shorter duration of effectsShorter duration of effects

Preheat the skin with a moist heat packPreheat the skin with a moist heat pack– Decreases the time to reach vigorous heatingDecreases the time to reach vigorous heating

Poorly vascularized, collagen-rich tissues Poorly vascularized, collagen-rich tissues are preferentially heatedare preferentially heated– Fascia, tendon, scar tissueFascia, tendon, scar tissue

Tissues containing an increased proportion Tissues containing an increased proportion of fluid do not heat as wellof fluid do not heat as well– Adipose tissue, articular fluidAdipose tissue, articular fluid

Biophysical EffectsBiophysical Effects

NonthermalNonthermal


Nonthermal EffectsNonthermal Effects Increased cell membrane Increased cell membrane

permeabilitypermeability Altered rates of diffusion Altered rates of diffusion

across the cell membraneacross the cell membrane

Increased vascular Increased vascular permeabilitypermeability

Secretion of cytokines Secretion of cytokines

Increased blood flowIncreased blood flow Increased fibroblastic Increased fibroblastic

activity activity Stimulation of Stimulation of

phagocytosis phagocytosis

Granulation tissue Granulation tissue productionproduction

Synthesis of proteinSynthesis of protein Synthesis of Synthesis of

collagencollagen Reduction of edemaReduction of edema Diffusion of ionsDiffusion of ions Tissue regenerationTissue regeneration Formation of Formation of

stronger deformable stronger deformable connective tissue connective tissue


Nonthermal ApplicationNonthermal Application

Pulsed outputPulsed output– 20 to 25% duty cycle20 to 25% duty cycle– Nonthermal output intensityNonthermal output intensity

Continuous outputContinuous output– 100% duty cycle100% duty cycle– Output intensity of less than 0.3 W/cmOutput intensity of less than 0.3 W/cm22


Acoustical StreamingAcoustical Streaming

Ultrasound causes interstitial Ultrasound causes interstitial fluids to flowfluids to flow

Fluids strike cell membranesFluids strike cell membranes Produce Produce eddy currentseddy currents Eddy currents displace ions Eddy currents displace ions

and moleculesand molecules Alter:Alter:

– Cell membrane permeabilityCell membrane permeability– Cellular functionCellular function

Effect on Injury Effect on Injury ResponseResponse


Cellular ResponseCellular Response

Acoustical streaming:Acoustical streaming:– Increases cell membrane permeabilityIncreases cell membrane permeability– Alters cell membrane diffusion rateAlters cell membrane diffusion rate– Increased histamine releaseIncreased histamine release– Mast cell degranulationMast cell degranulation– Increased rate of protein synthesisIncreased rate of protein synthesis

Thermal effects:Thermal effects:– Increased cell metabolismIncreased cell metabolism– Increased rate of inflammationIncreased rate of inflammation


InflammationInflammation

May lead to an earlier onset of May lead to an earlier onset of proliferationproliferation– Increased fibroblast proliferationIncreased fibroblast proliferation– Release of growth factors and plateletsRelease of growth factors and platelets

Increased macrophage activityIncreased macrophage activity Leukocytes bind to damaged Leukocytes bind to damaged

endothelial cellsendothelial cells Cell division is increasedCell division is increased


InflammationInflammation

Frequency SpecificityFrequency Specificity 1 MHz Output1 MHz Output

– Release of preformed fibroblastsRelease of preformed fibroblasts 3 MHz Output3 MHz Output

– Increased synthesis and secretion of Increased synthesis and secretion of fibroblast precursorsfibroblast precursors Increased in areas of high collagen Increased in areas of high collagen

concentrationconcentration


Blood and Fluid DynamicsBlood and Fluid Dynamics

May increase blood flow for 45 May increase blood flow for 45 minutesminutes– Thermal effectsThermal effects– Decreased vascular toneDecreased vascular tone– Histamine releaseHistamine release

Causes vasodilationCauses vasodilation

Moist heat application prior to Moist heat application prior to treatment decreases net increase in treatment decreases net increase in blood flowblood flow


Pain ControlPain Control

Direct Pain ReductionDirect Pain Reduction Increased nerve cell sodium permeabilityIncreased nerve cell sodium permeability Alters nerve functionAlters nerve function Increases pain thresholdIncreases pain thresholdIndirect Pain ReductionIndirect Pain Reduction Increased blood flowIncreased blood flow Increased capillary permeabilityIncreased capillary permeability Increased oxygen deliveryIncreased oxygen delivery Decreased muscle spasmDecreased muscle spasm


Muscle SpasmMuscle Spasm

Reduced secondary to:Reduced secondary to:– Decreased painDecreased pain– Altered nerve conduction velocityAltered nerve conduction velocity– Increased temperature (counterirritant Increased temperature (counterirritant

effect)effect)– Muscle relaxationMuscle relaxation


Tissue ElasticityTissue Elasticity

Ultrasound preferentially heats collagen-Ultrasound preferentially heats collagen-rich tissues (tendon, fascia, scar tissue)rich tissues (tendon, fascia, scar tissue)

Temperature must be increased 7.2Temperature must be increased 7.2°°FF Stretching window lasts approximately 3 Stretching window lasts approximately 3

minutes following the treatmentminutes following the treatment– Place tissues on stretch during applicationPlace tissues on stretch during application– Perform stretching/mobilization immediately Perform stretching/mobilization immediately

following the treatmentfollowing the treatment Multiple treatments are required to gain Multiple treatments are required to gain

lengthlength


Wound HealingWound Healing

Tendon HealingTendon Healing Continuous US application Continuous US application

may:may:– Increase tensile strengthIncrease tensile strength– Increase collagen depositionIncrease collagen deposition

Skin UlcersSkin Ulcers 3 MHz, low-intensity 3 MHz, low-intensity

pulsed output may assist pulsed output may assist the healing processthe healing process

Cover the wound with an Cover the wound with an occlusive dressingocclusive dressing


Fracture HealingFracture Healing Low-intensity pulsed Low-intensity pulsed

outputoutput Accelerates rate of fracture Accelerates rate of fracture

healing for:healing for:– Acute fracturesAcute fractures– Nonunion fracturesNonunion fractures– Stress fracturesStress fractures

Requires specialized unitRequires specialized unit Biophysical Effects:Biophysical Effects:

– Mechanical (sound) energy Mechanical (sound) energy strikes bonestrikes bone

– Microvibration of bone Microvibration of bone triggers growth triggers growth (osteogenesis)(osteogenesis)

PARAMETERSPARAMETERSFrequencyFrequency 1.5 MHz1.5 MHzERAERA 3.88 cm3.88 cm22

IntensityIntensity 30 mW/cm30 mW/cm22

Treatment DurationTreatment Duration 20 minutes20 minutesDailyDaily


ContraindicationsContraindications Acute conditions (thermal Acute conditions (thermal

mode)mode) Ischemic areasIschemic areas Areas of impaired Areas of impaired

circulationcirculation Over areas of deep vein Over areas of deep vein

thrombosisthrombosis Anesthetic areasAnesthetic areas Over cancerous tumors Over cancerous tumors Sites of active infection or Sites of active infection or

sepsissepsis Over the spinal cord or Over the spinal cord or

large nerve plexus in high large nerve plexus in high dosesdoses

Exposed penetrating metal Exposed penetrating metal (eg, external fixation (eg, external fixation devices) devices)

Around the eyes, heart, Around the eyes, heart, skull, or genitalsskull, or genitals

Over the thorax in the Over the thorax in the presence of an implanted presence of an implanted pacemakerpacemaker

Pregnancy when used over Pregnancy when used over the pelvic or lumbar areasthe pelvic or lumbar areas

Over a fracture site before Over a fracture site before healing is completehealing is complete

Stress fracture sites or Stress fracture sites or sites of osteoporosissites of osteoporosis

Over the pelvic or lumbar Over the pelvic or lumbar area in menstruating area in menstruating female patients female patients

Therapeutic Ultrasound Chapter 7. © 2005 – FA Davis Description Acoustical energy (sound waves) above the range of human hearing Acoustical energy (sound.

Documents

average energy

pulsed output slide

fa davis output frequency

continuous output

low intensity slide

time spatial average

head energy

actual peak output