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ULTRASOUND Biophysical Effects • Both thermal and nonthermal effects occur in the body • Nonthermal Effects – Changes within the tissues resulting from the mechanical effect of ultrasonic energy • Thermal Effects – Changes within the tissues as a direct result of ultrasound’s elevation of the tissue temperature ULTRASOUND Biophysical Effects-Nonthermal • Nonthermal Effects – Used in acute injuries or when increasing the tissue temperature is unwanted – Two methods of doing this: • Using a pulsed output and normal intensities • Using 100% duty cycle with low intensities (0.3 w/cm2) ULTRASOUND Biophysical Effects-Nonthermal – Nonthermal US energy leads to two interrelated events: • Acoustical Streaming - one directional flow of tissue fluids caused by the sound wave – The flow of bubble in the acoustical streams cause changes in cell membrane permeability • Cavitation – result of the pressure changes caused by the sound waves which results in gas bubbles moving in a cyclical manner – Stable vs Unstable (Transient) Cavitation ULTRASOUND Biophysical Effects-Nonthermal • Physiological Effects – Stimulates phagocytosis – Increases cell membrane permeability • Increases the movement of minerals and proteins in and out of the cell • Glycosaminoglycan and hydroxyproline are increased following low dose US – Mild acceleration of the inflammatory stage helps the body reach proliferation sooner – See Table 7-4 ULTRASOUND Biophysical Effects-Thermal • Thermal Effects – Amount of temperature increase depends on: • Duty Cycle, Intensity, Frequency • Vascularity and type of tissues • Size of tx area, speed of soundhead – 1 MHz = up to 5 cm deep, retains heat longer – 3 MHz = 2-3 cm deep ULTRASOUND Biophysical Effects-Thermal – To achieve a therapeutic effect temp must be increased for a minimum of 3-5 min. • 3 MHz = heats 3-4 times faster – Lower treatment intensities require a greater duration – The friction between the molecules results in a temperature increase – Collagen rich tissues are preferentially heated, adipose tissue is transparent to US ULTRASOUND Effects on the Injury Response Cycle • Cell Response – Increased cell membrane permeability for both thermal and nonthermal US – Thermal • Increased cell metabolism and inflammation – Nonthermal • Increased histamine release, calcium and rate of protein synthesis ULTRASOUND Effects on the Injury Response Cycle • Inflammation – No thermal US acutely – Effects later in injury cycle: • • • • Early onset of proliferation Stimulation of fibroblast activity Positively influence macrophage activity Increases the collagen synthesis and increased tensile strength ULTRASOUND Effects on the Injury Response Cycle • Blood Flow – Continuous can increase blood flow for up to 45 minutes – Pulsed US may effect blood flow through it’s effect on the cell membrane – Application of cold first? ULTRASOUND Effects on the Injury Response Cycle • Pain Control – May have some direct effect to the nerves or as a result of other effects – Direct effects are through eliciting changes within the nerve fiber themselves – Indirect effects: • Increase blood flow = more oxygen = less chemical pain • Decreased muscle spasm ULTRASOUND Effects on the Injury Response Cycle • Muscle Spasm – Why? • Tissue Elasticity – Increased extensibility in collagen-rich tissues, including scar tissue – Must be increased 7.2°F (4°C) – Must be used with passive stretching, within 3 minutes – Repeated treatments is often necessary – May want to place tissue on stretch during the treatment ULTRASOUND Effects on the Injury Response Cycle • Wound Healing – Some wounds have responded well to US – 100% US at 1.5 w/cm2 for 5 min, for 1 week (1 MHz) – 100% at 0.5 w/cm2 for 2 weeks also appeared to help ULTRASOUND Phonophoresis • Application of US to assist in the diffusion of medication through the skin • Non-invasive method that does not effect the liver • Occurs due to the effect US has on the skin which allows the medication to diffuse through – Skin factors can affect diffusion of medication • Has been found to push meds up to 6 cm deep ULTRASOUND Phonophoresis • Thermal – Increase kinetic energy of the local cells and the medication, open entry points, increase circulation, increase capillary permeability • Nonthermal – Enhances diffusion across the membranes, increase cell membrane permeability ULTRASOUND Phonophoresis • Medications – Table 7-7 • Application – Direct Method – Invisible Method ULTRASOUND Phonophoresis • Does it work?? – Salicylate (Myoflex) – Hydrocortisone – Dexamethasone • Low frequency US units may assist in the transmission of medications ULTRASOUND Contraindications • • • • • Acute injuries (Thermal US) Areas of impaired circulation DVT or cancerous tumors Over the eyes, heart, skull and genitals Pelvic, abdominal area in menstruating or pregnant women • Over active fracture or stress fractures (exception) • Over growth plates in adolescents?? • Use with caution over vertebrae ULTRASOUND Controversies in Treatment • US must be used properly in order to have a good therapeutic effect on the patient • Read Article: – Ten Mistakes Commonly Made with Ultrasound Use: Current Research Sheds Light on Myths ULTRASOUND Application • Treatment Area: – 2-3 times the ERA of the sound head • Coupling Methods – Optimal agent is distilled water – US head should not leave the body • Why? • Irregular shape body parts? ULTRASOUND Coupling Agents and Methods • Direct Coupling – Use of US gel • • • • Use enough gel Body hair can limit US delivery Try not to have air bubbles Use slight pressure on sound head • Water Immersion • Good for irregular body parts • Sound head is 1” away from skin @ 90° angle ULTRASOUND Coupling Agents and Methods • Bladder Method – Water filled bag or plastic bag coated with US gel – Good for irregular areas such as AC joint – Can not have air pockets ULTRASOUND Output Parameters • Frequency – Depth and rate of heating – 1 MHz vs 3 MHz – Table 8-2 • Treatment Duration – Table 8-3 ULTRASOUND Output Parameters • Duty Cycle • Output Intensity – Figure 8-6 – For thermal ultrasounds the patient should feel warmth! ULTRASOUND Output Parameters • Dose-Oriented Treatments – Still an inexact method – Deals with treating the tissue area to a certain temperature – Some units you can program this way – Needs more research ULTRASOUND Ultrasound and Electrical Stimulation • Treatment of trigger points and superficial painful areas • Ultrasound head serves as as electrode • Try to fatigue the trigger points to a point they no longer will fire or spasm • Placing the tissue at stretch may be a benefit in decreasing trigger point spasms ULTRASOUND Application • Duration – 3 to 12 minutes • Frequency – Once/day for 10 to 14 days • Precautions, Indications, and Contraindications are in your text (Pg. 181)