THERAPEUTIC ULTRASOUND

THERAPEUTIC ULTRASOUNDArlene Y. Aranzaso, PTRP

Objectives:To present the physical principles and biophysical effects of Ultrasound

Discuss the clinical conditions for which ultrasound is effective

Discuss the clinical procedures for the application of ultrasound

Present guidelines for the safe use of ultrasound, including a discussion of the contraindications and precautions for treatment with this agent

UltrasoundIs used in medicine for diagnosis ( imaging of internal structures)

Physical therapy (functional restoration and healing of soft tissue ailments)

Tissue destruction

A deep heating agentEmployed in medicine for over 50 yearsWood and loomis in 1927-biologic effect in tissue to US1930 germany application of US1940 Unuted statesLowest intensity use for diagnosticHigh intensity use for tissue destruction3

Physical Principles Nature of Sound

Sound is a non-ionizing radiation, it is propagation of the vibratory motion.

Ionizing radiation cause cancer production and chromosome breakageAcoustic radiation= US4

Frequency Number of oscillations a molecule undergoes in 1 secondHzHuman ear 16 Hz and 20, 000 HzGreater than 20,000 Hz is UltrasoundUltrasound beams is collimated85 KHz and 3 MHz

1 Hz = 1 cycle/sec.1 kHz = 1000 cycles/sec1 MHz = 1 million cycles/sec.Collimated beam that oscillating crystal produces sound waves with little dispersion of energy5

Attenuation reduction of acoustical energy as it passes through soft tissue.

Scattering

Absorption - attenuation frequency

1.0 MHz most use for deep penetration3.0 MHZ widely used for superficial Absorption highest muscle, tendons, ligaments and capsuleScattering reflection and refraction6

Sound Velocity

Is the speed at which the vibratory motion is propagated through a material

1540 m/s soft tissue4000 m/s compact bone

The more rigid the material= the greater the velocity of sound passing through it

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WavelengthDistance between 2 successive peaks in the pressure wave

Phase shift time delay

Condensations the concentration of molecules increase in the regions

Rarefactions decrease in alternating regions

Wavelength is inversely related to frequencyV= FxW8

Types of WavesLongitudinal waves

Transverse waves

LW- the direction of motion of the molecules is parallel to the direction of wave propagationTW-is perpendicularNo TW in gases and liquidsSolids= LW & TW- is found in bone

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Continuous wave

Pulsed wave

CW- sound intensity is constant use to achieve thermal effects chronic conditionsPW intermittently interrupted used when non thermal effects are desired acute soft tissue injuriesDuty cycle- fractions of time in pulsed wave11

Duty cycle = duration of pulse (time on) pulse period (time on + time off)

< 50% is Pulsed US

Pulsed mode -0.05 (5%) to 0.5 (50%)20% is most commonly used 2msec. On time and 8 msec.off time51%-99%- it produces less acoustic energy and less heatPulsed mode duty cycle is important12

Intensity It determined the strength of an US beamIt is the rate at which energy is delivered per unit Watts/square centimeterW/cmThe greater intensity result greater Temperature elevationPT 0.25 to 2.0 W/cm (therapeutic application)- 1 to 3 W/cm (Sullivan&Siegelman)

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Spatial Average Intensity Total Power Output (watts) area (cm)

Spatial Peak Intensity the greatest intensity anywhere within the beam.

Continuous US spatial characteristic is predominantSPI hot spot using moving technique and pulsed lower the SPI14

BNR (beam non-uniformity ratio)- defines the maximum point intensity on the transducer to the average intensity value across the transducer surface.

2:1 and 6:1

Low BNR more even energy distribution and less risk of tissue damage

Temporal peak intensity or pulse average intensity- maximum intensity in pulsedTemporal average intensity US power average over 1 pulsed periodTgemporal average intensity- on period+off periodPulsed minimize heating needed- like stasis ulcers and acute coft tissue injuriesHot spots =can cause damage to the insonated tissueMoving applicator technique17

Example:CW

3.0 MHz/0.5 W/cm/CW/5min

PW

3.0 MHz/0.5 W/cm/p 20%/5min

SAI 0.25 to 2.0 W/cm used therapeutic application10.0 W/cm used to destroy tissue surgically0.1 W/cm used for diagnostic purposesParasitic radiation therapist result acute pain in hand fingers18

Generation of Ultrasound

The Piezoelectric Effect2 forms

Direct Piezoelectric effect

Reverse Piezoelectric effect (indirect)

Direct Piezoelectric EffectIs the generation of an electric voltage across a crystal when the crystal is compressed.

Reverse Piezoelectric Effect

Is the contraction or expansion of a crystal in response to a voltage applied across it face.

The Transducer

Is any device that converts one form of energy into anotherPiezoelectric crystal is a transducer that converts electrical energy into sound energy, and vice versa.1 cm to 10 cm5 cm most commonly usedERA (effective radiating area) the area of the faceplate (crystal size), which is smaller than the sound head.

Is any device that converts one form of energy into anotherPiezoelectric crystal is a transducer that converts electrical energy into sound energy, and vice versa.Has a variety of sizes24

Biophysical EffectsThermal Those effects produced by the ability of ultrasound to elevate tissue temperature.

Non- Thermal Those effects that must be attributed to mechanism other than an increase in tissue temperature.

Conversion mechanical energy produces by sound waves26

Thermal EffectsIncrease collagen tissue extensibilityAlterations in blood flowChanges in nerve conduction velocityIncreased pain thresholdIncrease enzymatic activityChanges in contractile activity of skeletal muscle

Increase temp-5 cm or moreHigh dose = retard long bone growth, damage spinal cord tissue, destroy other tissueThermal using Continuous modeTissue with high collagen absorb a large amt.of US beam27

3 MHz most of the energy is absorbed within a depth of 1 to 2 cm

1 MHz absorption in deeper tissue - deeper than 2 cm from the skin surface

Tissue Attenuation (%/cm) Blood Fat Muscle Blood vessel Skin Tendon Cartilage Bone 313243239596896

Attenuation of a 1 MHz Ultrasound Beam

Attenuation of a 1 MHz Ultrasound BeamUS as deep heating elevate temp 40 C to 45 C 29

Non-Thermal effectsCavitation

Mechanical alterations

Chemical alterations

Using pulsed mode30

Cavitation

is the vibrational effect on gas bubbles by an US beam.Stable cavitation result diffusional changes along cell membrane and alter cell function.Unstable or transient cavitation the violent collapse of bubbles within the sound field result tissue destruction.

Rarefactions- small bubbles expandCondensations- bubbles compressedSC resonate without tissue damageUSC- high temp.31

Mechanical

Acoustical streaming refer to the movement of fluids along the boundaries of cell membranesIncrease fibroblastic activityIncrease calcium fluxesAlteration of cell membrane activityIncreased cell wall permeabilityIncreased protein synthesis

Result mechanical pressure waveIon fluxes- streamingProtein systhesis34

Clinical Application of Ultrasound at Therapeutic Intensities

Joint contracture and scar tissueReduction of pain and muscle spasmBursitis and tendinitisCalcium depositsPhonophoresisWound healingChronic wounds

Heat and stretch 45 degrees C- elevate tissue temp

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Therapeutic Ultrasound Units

Basic components

Power supplyOscillator circuitTransformerCoaxial cableUltrasound applicator

Ratio of the acoustic power to the intensity is constant ERA effective radiating areaQuality control calibrated and electrically safe38

Guidelines for Clinical AdministrationCoupling Techniques

Coupling medium to transmit US energy from transducer to irradiated surfaceWater soluble gelEliminates the air to minimize the amt of sound entering the bodyImmersion technique -0.5 to 3.0 cm from the body39

Moving vs. Stationary Applicator

Stationary

Moving slowly ~ 4 cm/s- longitudinal stroking or circular movements can be used- total area covered 2-3x the size of the irradiating crystal for every 5 minutes exposure.

Direct contactUsed stationary if the area is too small with low intensityHot spots= tissue damageRapid- decreased the amt.of enrgy the tissue absorbDistribute the energy even 40

Exposure Factors

5 minutes increase tissue extensibilityGeneral use it should be:an appropriate frequency for the depth of the tissue to be treatedA continuous wave or pulsed wave according to treatment aimsThe lowest intensity and duration that achieved desired result

Heat inadequate coupling mediumNot movingChoice of transducerTx.time 3-10 mins41

Indirect contact

Water immersion

Using thin walled bag

Irregular body partsPlastic container-less reflection1 cm from skin surface ryt angleWipe off bubblesNor widely used but can used as alternative for immersion42

Technique of Phonophoresis

Medication is rubbed directly onto the surface of the skin

Coupling gel spread over the medication

Then sonation is initiated

Then the part placed in water bath80%Anti inflammatory drugs cortisol, dexamethasone, salicylates, lidocainePulsed mode 20%0.5 -0.75 W/cm43

Patient Positioning and Field Selection

3 different examples of shoulder dysfunctionCapsular shortening or contracture

Supraspinatus tendinitis

Muscle-guarding spasm and pain 2to degenerative joint dse.

1- glenohumeral jt-affected abduction and ER-position of the pt.shpoulder2- supraspinatus insertion abducted and ER acromion process3- comfortable and relaxed position46

Treatment PrecautionsShould not be applied over the eyeIrradiation over the heart should be avoidedOver pregnant uterusOver testesOver malignant tissueImpaired sensationImpaired circulationImpaired cognitive functionOver thrombophlebitisOver epiphyseal area in childrenOver exposed or unprotected spinal cord

Can produce cataractRetinas destruction2- study ECG changes happened Cardiac pacemaker3- abnormality sich as low birth wt., brain size reduction, orthopedic abnormalities (study)10 days after the onset of menses ok4- temporary sterility5- metatasis- increase tumor growthNot over healing fracture

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Clinical Decision MakingStage of inflammation and repair

Site of pathology

Total amount of tissue to be heated

Presence or absence of orthopedic implants

Factors need to be considered2- depth , location

Adjunct with HMPBut cold should not be given prior to US9-12 US should be given then discontinued for 2 weeks48

CASE STUDY

Joint Contracture and Scar TissueA 28 year old man sustained partial lacerations to the extensor tendons to the ring and small fingers over the metacarpophalangeal joints when he cut his fingers on a knife in dish water. The tendons were surgically repaired and immobilized for 2 weeks 2 to wound infection. You are now seeing the patient 4 wks.postop.

Problems: decreased gliding of the tendonWound infection and slow healingLimited functional activities

Assessment ROM, wound/scar eval, functional daily activitiesGoals Increase tendon gliding, ROM, FA50

US

3 MHz/0.5 W/cm/CW/5 min.

Small head

SuperficialSubacuteMeasure ROM after tx. HP= AROMScar- fiction massage and ROM51

Reduction of Pain and Muscle Spasm

The patient, a 45 year old woman, has had pain in the right cervical and interscapular area for ~ 2 wks. The onset of pain was caused by repetitive activity during spring cleaning.

Problems: pain, limited ROMAssessment: pain quality, quantity, locationFunctional activityCervical ROMGoals:Reduce pain, Increase FA, ROM52

US

1.0 MHz/0.5 W/cm/p 20%/5 min. Lying in prone or

Seated with UE well supported

Deep tissueSubacutePulse mode- pain relief53

Bursitis and TendinitisA 26 year old male patient has a patellar tendinitis. The insidious onset of pain occurred ~ 3 wks. ago. The patient was told to place ice on the area, rest, and do range of motion exercises.

Problem: persistent pain, limited FAAssessment: Pain, FAGoals: reduce pain, increase FA54

US

3.0 MHz/0.8 W/cm/p 50%/5 min.

DeepSubacutePulse- healing, pain

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Phonophoresis The patient, a 38 year old man, has a lateral epicondylitis. His symptoms, which first began after prolonged hammering, have continued for ~ 6 weeks. He was instructed to use ice on the affected area and to rest. In addition, anti-inflammatory medication was prescribed.

Problem: temporary relief, aggravation with activity, limited FAAssessment: pain, FAGials: reduce pain, incA use of involved side56

Phonophoresis

3.0 MHz/1.0 W/cm/CW/3 min.

In order to induce dexamethasone3MHz- less than 2cm deepSubacute to chronicThermal effect to increase diffusion of the drugs57

Chronic Wounds

A 40 year old male factory worker sustained a sprain of the lateral ankle. This occurred when he overturned his foot 1 day ago. Rest, ice, compression, and elevation were recommended to the patient by the company nurse.

Problems: swelling, bruising of the ankle, pain, decrease ROM, limited FAAssessment: volumetrics of ankle, pain, ROM, FA, gaitGoals: decrease swelling,reduce pain, increase ROM foot and ankle, strength, improve gait, FA58

US

Days 1-5 = 3.0 MHz/0.5 W/cm/p 20%/5 min

Days 6-14 = 3.0 MHz/1.0 W/cm/p 20%/5 min

Low dose US to reduce edema and increase mast cell degranulationSuperficialhealing59

References :Thermal Agents in Rehabilitation by Susan L. Michlovitz 3rd edition

Physical Agents in Rehabilitation From Research to Practice by Michelle H. Cameron 2nd edition

NPTE Review & Study Guide by O Sullivan & Siegelman