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
7
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