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Description : Describes modalities and indications to use the modality

Tags : Ultrasound

Published on : Aug 24, 2020 | Views : 6659 | Downloads : 16

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Slide 1-

Therapeutic Ultrasound and Phonophoresis Chapman University, PT539 Summer 2019 Yvonne B. Brewer, DPT, MPT
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Principles of US Known as the “Reverse Piezoelectric Effect” Converts electrical current to mechanical energy as it passes through a piezoelectric crystal (e.g., quartz, barium titanate, and lead zirconate titanate) housed in the transducer head.
Slide 3-

Principles of US, cont… Voltage is applied across the face the crystal, causing it to expand and contract and/or vibrate molecules moving in longitudinal waves. Moving molecules and surrounding fluid is energy. This energy is transmitted into the deep tissues to produce temperature increases (thermal effects), and/or mechanical and chemical alterations (non-thermal effects).
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The effectiveness of US and the rate of tissue absorption depends on: Frequency of the US beam (Megahertz or MHz) Wavelength Intensity of the ultrasonic output (W/cm2)…in other words, how high you turn it up.
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Frequency of Ultrasound Waves Frequency of a sound wave = the number of oscillations a molecule undergoes per second. Therapeutic ultrasound uses: 1 million cycles/second = Megahertz (MHz) Before we choose which frequency or MHz to use, we must consider tissue attenuation…
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Attenuation Attenuation is rate at which the intensity of the US decreases as it penetrates through tissue. Areas of high attenuation means the ultrasound waves are LESS able to penetrate through the intended target area/tissue. It is the result of several factors: Energy absorption of tissue: The ability of the target tissue to actually absorb the sound wave based on its biological composition. Reflection and scattering: can occur in conjunction with each other. When the ultrasound strikes a reflective surface, it can scatter, resulting in less effect on the target tissue.
Slide 7-

Attenuation, Cont… It is the result of several factors: Energy absorption of tissue: The ability of the target tissue to actually absorb the sound wave based on its biological composition. Tissues with higher protein/collagen content and low water content will absorb US better (ie…ligaments, tendons, fascia, joint capsule, scar tissue). Reflection and scattering: can occur in conjunction with each other. When the ultrasound strikes a reflective surface, it can scatter, resulting in less effect on the target tissue.
Slide 8-

Attenuation of a 1 MHz Ultrasound Beam
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Clinical Question: how does knowing about attenuation help with clinical decision making?
Slide 10-

Frequency & Attenuation The higher the frequency, more rapidly the molecules are forced to move against internal friction within the tissue, causing more sound absorption and leaving LESS sound energy available to propagate further or deeper through the tissue. Therefore, frequency and penetration are inversely proportional. 1.0 MHz = deep 3.0 MHz = superficial
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Frequency and Depth of Treatment More energy is absorbed in the superficial tissues than in the deep tissues. In order for energy to have an effect it must be absorbed. So…. Use 1.0 MHz to treat deeper tissues… from 2.5 cm to 5 cm Ex: Deep muscle or thick tendon Use 3.0 MHz to treat more superficial tissues up to about 2.5 cm from skin surface Ex: palpable mm-tendon junction
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Principles of US: Wavelength The appropriate wavelength is determined by what effect you want to have on the tissue…i.e…what stage of healing is the body part in, what are you trying to accomplish, and are you following the US treatment with another treatment? Wavelength is calculated as the Duty Cycle and expressed as either pulsed or continuous
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Wavelength, cont. Duty cycle = duration of pulse = % pulse period pulse period = time on + time off duration of pulse = time on
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Wavelength, cont… A duty cycle of 100% is called a continuous ultrasound. (C-US) A duty cycle of anything less than 100% is called a pulsed ultrasound. (P-US) Typical therapeutic duty cycles are 20%, 50%, and 100%. When a duty cycle is pulsed, there is a negligible thermal effect on the tissue. So…if you want to heat up the tissue, you must use C-US!
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Principles of US: Intensity Intensity = strength of the sound waves at a given location within the tissue being treated or the rate at which energy is delivered per unit area. Intensity = W/cm2 W/cm2 takes into account the size of the soundhead, giving the spatial avg. intensity. Intensity is partly determined by the ERA (effective radiating area of a transducer). ERA is a measure of the actual cross-sectional area of the ultrasound beam as it exits the metal plate. Determined by the size and vibrational properties of the crystal. (cm2)
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Intensity, cont… Your treatment area should be a maximum of 2 x ERA. (essentially no more than 2x the size of the soundhead) What does this mean clinically? The following intensity ranges are appropriate for therapeutic applications of continuous US settings: 0.25 to 2.0 W/cm2 C-US higher than therapeutic ranges can slow growth of long bones, damage spinal cord tissue, and destroy tissues!
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Intensity, cont… Beam is not uniform and can generate “hot spots” = highest intensity anywhere on sound head “Hot spots” can damage tissue and irritate the patient (most notably when using C-US). To avoid hot spots: Always continuously move the applicator to prevent any build-up of energy in any one spot. Always keep the sound head in contact with the tissue without raised edges. DO NOT PICK UP AND MOVE SOUND HEAD OFF TISSUE!
Slide 18-

Intensity and BNR…(some technical stuff!) BNR = beam nonuniformity ratio (labeled on machine by manufacturer) BNR is the max point intensity on the transducer to the avg. intensity value across the transducer surface BNR should be low as possible, between 2:1 and 6:1. This is typically labelled on the machine. The lower the BNR, the more even the distribution of energy from transducer  less risk of tissue damage and the slower you can move the ultrasound head to the recommended 4 cm/sec. The higher the BNR, typically the less comfortable the treatment is (older machines).
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Thermal Ultrasound: C-US Based on the ability of the sound waves to penetrate through a target tissue, one can elicit a thermal effect…ie…the tissue will warm up. The indications for heating a tissue can be as follow. Change tendon extensibility: high collagen content and fewer blood vessels in connective tissue allows for tendons and ligaments to heat faster than muscles. Able to make a change in tendon extensibility. Reduce joint stiffness and pain Increase blood flow (subacute or chronic soft tissue inflammation): studies support increased flow at 1MHz and at treatment sizes no larger than 2x’s the ERA. Time should be chosen to ensure mm heating of a least 1ºC (1.8ºF). Alter motor nerve conduction velocity (MNCV): Varies studies show that C-US can decrease or increase MCNV. The clinical applicability is not definitive.
Slide 20-

Effects of Temperature Change:Based on Incremental Degrees A 1°C increase, considered mild heating, accelerates metabolic rate in tissues. An increase of 2-3°C, or moderate heating, can reduce muscle spasms and pain, increase blood flow, and reduce chronic inflammation. To have an effect on the viscoelastic properties of collagen, the ideal temperature increase at the target tissue is approximately is 4.0°C.
Slide 21-

C-US rate of heating per minute*Draper et al, European Journal of Physical and Rehabilitation Medicine 2014:50:209-16
Slide 22-

Thermal Effects Deep Superficial
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Thermal Effects: How long will it take to influence tissue extensibility? The minimum effective time to heat up a deeper tissue (>2.5 cm),at the MAXIMUM intensity (2.0 W/cm2) to 4.0°C is about 8 minutes. The minimum effective time to heat up a superficial tissue (<2.5 cm) at the MAXIMUM intensity (2.0 W/cm2) to 4.0°C is about 2.5 minutes. Clinical question: What should happen if your patient cannot tolerate an intensity at 2.0 W/cm2?
Slide 24-

Thermal Effects: How long will it the heat last? Approximately 3.5 minutes! Clinical Question: What does that mean for PT? Why do you think the heat dissipates so fast? T-3.5 min
Slide 25-

Factors to Consider with C-US Tissue attenuation. Consider if your patient has a lot of adipose tissue in the region. If using at a tendon, remember that tendons have a high collagen content, and will be able to absorb a large amount of the US beam. If using at a tissue/bone interface, the tissue can be heated almost 2x’s greater than normal due to US beam bouncing off the bone due to attenuation…so….the patient may complain of increased heat at the region!
Slide 26-

US Thermal Effects vs. Others At a depth of 3 cm for 10 min treatment: 1. Hot pack = ↑ temp 0.8º C 2. Warm whirlpool = ↑ temp 0.8º C 3. C-US, 1MHz = ↑ temp 4.0º C *Draper et al, 2014:50:209-16
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Non-Thermal US Pulsed or non-thermal US does not elevate tissue temperature significantly. The effects of P-US are due to a combination of Cavitation and Acoustic Streaming. Effects are most beneficial once active bleeding of region has stopped.
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Non-Thermal US: Acoustic Streaming P-US at low intensities causes acoustic streaming, which is a unidirectional flow of tissue components exposed to the ultrasound field primarily at the cell membrane interface. Acoustic streaming is thought to transport materials around ultrasound field  altering cellular activities and flow of ions. During acute inflammation, can accelerate process and lead to rapid onset of the proliferative phase of wound healing. WHY? Acoustic streaming influences cellular diffusion rates, and membrane permeability; it can accelerate synthesis of collagen.
Slide 30-

Non-Thermal US: Cavitation Cavitation is the formation and growth of gas bubbles from the accumulation of dissolved gases in blood or tissue fluids. Stable cavitation: occurs at therapeutic doses, and enhances the effects of acoustic streaming. Unstable cavitation: if the intensity of the P-US is too high, or above therapeutic dosages, the gas bubbles form; but then rapidly collapse, releasing a large amount of energy which is detrimental to tissue viability. It can cause damage to tissues or blood vessels. ***The result of the combined effects of stable cavitation and acoustic streaming is that the cell membrane becomes ‘excited, thus increasing the activity levels of the whole cell.
Slide 31-

Non-Thermal US: Broad Indications ↓ Inflammation ↑ tissue regeneration Improve wound healing Improve cell membrane permeability Attraction of immune cells to injured area ↑ Vascular regeneration ↑ Endochondral bone growth ↑ fibroblast activity ↑ histamine release Calcium ion influx ↑ phagocytic activity of macrophages
Slide 32-

Non-Thermal US: Indications During Healing Phases Inflammatory Phase: Helps promote the acute stage by increasing the efficiency of the cell processes, thus helping it progress to next phase. Does not necessary decrease acute inflammation, but act as an “inflammatory optimizer” in soft tissue injuries (non-bleeding). If no repair is expected, than normal resolution of inflammatory phase is assisted with P-US. Proliferative Phase: Maximizes efficiency of cells (fibroblasts, endothelial and myofibroblasts) for optimal scar production.
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P-US Therapeutic Setting: other options Ebenbichler et. al. (2017) were able to reduce pain and some evidence of calcific tendinitis at the RCT with the following parameters: P-US, 1:4 (25%), sound head size 5cm2, 2.5 W/cm2 x 15 min; daily for 15 days, then 3x/week x 3 weeks Evidence at 6 months showed improvement or partial resolution of calcium deposits vs. sham, but no difference at 9 months. Mechanism of resolution was unclear. Watson (2008)
Slide 35-

US: Contraindications Directly over any metal implants Near cardiac pacemaker Over eyes (can damage vitrious fluid) During pregnancy: over pelvis, abdomen, or lumbar spine In the region of a deep vein thrombosis or thrombophlebitis Over the heart, stellate of cervical ganglia (stimulation of vagus nerve can slow HR) In the region of a tumor/malignancy In the region of active bleeding or infection Over epiphyseal plates of growing bones Over areas of healing fractures (need special unit for bone healing). Over reproductive organs (can damage gametes)
Slide 36-

THERMAL ULTRASOUNDPRECAUTIONS Over joint replacements (consider the type of joint replacement and how deep it lies in relation to area you are treating. With patient who has decreased sensation Over bony prominences With patients who have PVD (must be capable of increasing blood supply to region; not able in advance stage of disease). On a pt who cannot communicate/provide feedback. Why?
Slide 37-

CLINICAL APPLICATION Ultrasound treatment is only as effective as the parameters you choose! Determine and CHART the following: Frequency Duration Intensity Duty Cycle Clinical Decision Making: consider stage of inflammation, site of pathology (depth and anatomic location, total amount of tissue to be heated and presence of metal implants).
Slide 38-

US: Application Guidelines Treatment area to be only about 2 times the size of the sound head Coupling gel must be used Check, double check for contraindications/precautions Explain procedure to pt: what he/she will feel, purpose, mild warmth? If doing a C-US, tell pt he/she will feel warmth and it should not be hot. Strokes can be circular or longitudinal, but not overlap more than ½ the ERA to allow for systemic movement The sound head should be constantly moving in continuous US to avoid production of a standing wave & peaks of energy. However, too fast of a motion does not allow for even distribution of sound waves to the chosen area. Standing waves from not moving the sound head properly and overlapping too closely (<1/2 ERA) can cause periosteal pain and burns.
Slide 39-

US: Basic Dosage Guidelines *5-10 minutes for 1.5 to 2 times the ERA. (consider Draper study). Speed of application: approximately 4 cm/second Inflammation: Pulsed 20%, up to 1.0 W/cm2 Proliferation: Pulsed 20 to 50%, up to 1.0 W/cm2 Remodeling: Continuous up to 2.0 W/cm2 High intensities (> 3.5 W/cm2) cause unstable cavitation and tissue necrosis.
Slide 40-

US Application: Indirect Water-immersion method Used if unable to use small or appropriate sound head Submerge body part, usually hand or foot, in plastic basin. Avoid metal due to reflection. Move sound head around body part 1-2 cm away Watch and wipe off water bubbles on transducer or body part during Rx. Efficacy vs. direct contact method is questionable at same intensities. Watch electrical outlets. SAFETY!!!!
Slide 41-

PHONOPHORESIS The use of ultrasound to deliver medication through the skin. Medication is pre-mixed in ultrasound gel Most commonly used to treat inflammation Can contain steroidal MEDS such as hydrocortisone, dexamethasone, and NSAIDs such as methyl salicylate
Slide 42-

PHONOPHORESIS Use of ultrasound thought to help move medication past the stratum corneum PROBLEM: some medication thought to inhibit the US waves from actually transmitting through tissue Use of hydrocortisone adds air when mixed with gel…ultrasound can’t pass through air. Cameron and Monroe found 10% hydrocortisone in coupling gel blocked 93% of transmitted ultrasound! Some studies show better results with TheraGesic cream (menthol and methyl salicylate) and betamethasone. More promising results for dexamethasone
Slide 43-

PHONOPHORESIS Must have a Rx for patient that states drug and concentration. Do not mix Rx with regular US coupling gel. It must done at pharmacy. Limit use to superficial to the submuscular or subtendinous levels, as diffusion deep is unlikely. Clean/dry skin. Explain to pt. Get Consent. Apply MEDS. Can rub to attempt to reduce air bubbles. Set parameters to lower intensities. (1.0 -1.5 w/cm2) Use continuous mode. Move sound head and press “Start” Can wrap body in cellophane post treatment to get longer lasting results. Post exercise is not recommended as local MEDS may disburse.