Ultrasound 2


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Ultrasound 2

  1. 1. ULTRASOUND A Deep Thermal & Non-thermal Mechanical Modality
  2. 2. What is Ultrasound? <ul><li>Located in the Acoustical Spectrum </li></ul><ul><li>May be used for diagnostic imaging, therapeutic tissue healing, or tissue destruction </li></ul><ul><li>Thermal & Non-thermal effects </li></ul><ul><li>We use it for therapeutic effects </li></ul><ul><li>Can deliver medicine to subcutaneous tissues (phonophoresis) </li></ul>
  3. 3. Ultrasound <ul><li>Sinusoidal waveform </li></ul><ul><ul><li>Therapeutic ultrasound waves range from 750,000 to 3,000,000 Hz (0.75 to 3 MHz) </li></ul></ul><ul><li>Displays properties of </li></ul><ul><ul><li>wavelength, </li></ul></ul><ul><ul><li>frequency, </li></ul></ul><ul><ul><li>Amplitude </li></ul></ul>
  4. 4. Transducer <ul><li>A device that converts one form of energy to another </li></ul><ul><li>Piezoelectric crystal: a crystal that produces (+) and (-) electrical charges when it contracts or expands </li></ul><ul><ul><li>Crystal of quartz, barium titanate, lead zirconate, or titanate housed within transducer </li></ul></ul><ul><li>Reverse (indirect) piezoelectric effect: occurs when an alternating current is passed through a crystal resulting in contraction & expansion of the crystal </li></ul><ul><ul><li>US is produced through the reverse piezoelectric effect </li></ul></ul><ul><ul><li>Vibration of crystal results in high-frequency sound waves </li></ul></ul><ul><li>Fresnal zone (near field) – area of the ultrasound beam on the transducer used for therapeutic purposes </li></ul>
  5. 5. Types of Current <ul><li>Direct Current: the uninterrupted unidirectional flow of electrons </li></ul><ul><li>Alternating Current: the uninterrupted bidirectional flow of electrons </li></ul><ul><ul><li>Ultrasound is produced by this type of current flowing through a piezoelectric crystal </li></ul></ul><ul><li>Pulsed Current: the flow of electrons interrupted by discrete periods of noncurrent flow </li></ul>
  6. 6. Longitudinal vs. Transverse Waves <ul><li>Longitudinal waves – molecular displacement is along direction in which waves travel (bungee cord) </li></ul><ul><ul><li>Compression – regions of high molecular density (molecules in high pressure areas compress) </li></ul></ul><ul><ul><li>Rarefraction – regions of low molecular density (molecules in low pressure areas expand) </li></ul></ul><ul><li>Transverse waves – molecular displacement in direction perpendicular to wave (guitar string) </li></ul>
  7. 7. <ul><li>Longitudinal waves – travel in solids & liquids </li></ul><ul><ul><li>Soft tissue – more like liquids </li></ul></ul><ul><ul><li>US primarily travels as longitudinal wave </li></ul></ul><ul><li>Transverse waves – cannot pass through fluids; found in the body only when ultrasound strikes bone </li></ul>
  8. 8. Frequency <ul><li>Frequency: number of times an event occurs in 1 second; expressed in Hertz or pulses per second </li></ul><ul><ul><li>Hertz: cycles per second </li></ul></ul><ul><ul><li>Megahertz: 1,000,000 cycles per second </li></ul></ul><ul><ul><ul><li>In the U.S., we mainly use ultrasound frequencies of 1, 2 and 3 MHz </li></ul></ul></ul><ul><ul><ul><li>1 = low frequency; 3 = high frequency </li></ul></ul></ul><ul><li> frequency =  depth of penetration </li></ul><ul><li> frequency = sound waves are absorbed in more superficial tissues (3 MHz) </li></ul>
  9. 9. Velocity <ul><li>The speed of sound wave is directly related to the density (  velocity =  density) </li></ul><ul><li>Denser & more rigid materials have a higher velocity of transmission </li></ul><ul><li>At 1 MHz, sound travels through soft tissue @ 1540 m/sec and 4000 m/sec through compact bone </li></ul>
  10. 10. Influences on the Transmission of Energy <ul><li>Reflection – occurs when the wave can’t pass through the next density </li></ul><ul><li>Refraction – is the bending of waves as a result of a change in the speed of a wave as it enters a medium with a different density </li></ul><ul><li>Absorption – occurs by the tissue collecting the wave’s energy </li></ul>
  11. 11. Attenuation <ul><li>Decrease in a wave’s intensity resulting from absorption, reflection, & refraction </li></ul><ul><ul><li> as the frequency of US is  because of molecular friction the waves must overcome in order to pass through tissues </li></ul></ul><ul><li>US penetrates through tissue high in water content & is absorbed in dense tissues high in protein </li></ul><ul><li> Absorption =  Frequency (3 MHz) , and </li></ul><ul><li> Penetration =  Absorption (1 MHz) , so </li></ul><ul><li> Penetration =  Frequency +  Absorption (1 MHz) </li></ul><ul><li>Tissues  water content = low absorption rate (fat) </li></ul><ul><li>Tissues  protein content = high absorption rate (peripheral nerve, bone) </li></ul><ul><ul><li>Muscle is in between both </li></ul></ul>
  12. 12. Attenuation: Acoustic Impedance <ul><li>Determines amount of US energy reflected at tissue interfaces </li></ul><ul><ul><li>If acoustic impedance of the 2 materials forming the interface is the same, all sound will be transmitted </li></ul></ul><ul><ul><li>The larger the difference, the more energy is reflected & the less energy that can enter the 2 nd medium </li></ul></ul><ul><li>US passing through air = almost all reflected (99%) </li></ul><ul><li>US through fat = 1% reflected </li></ul><ul><li>Both reflected/refracted @ m. interface </li></ul><ul><li>Soft-tissue: bone interfaced = much reflected </li></ul><ul><li>As US energy is reflected @ tissue interfaces with different impedances, intensity is increased creating a Standing Wave (hot spot) </li></ul>
  13. 13. <ul><li>Effective Radiating Area (ERA): area of the sound head that produces ultrasonic waves; expressed in square centimeters (cm 2 ) </li></ul><ul><ul><li>Represents the portion of the head’s surface area that produces US waves </li></ul></ul><ul><ul><li>Measured 5 mm from face of sound head; represents all areas producing more than 5% of max. power output </li></ul></ul><ul><ul><li>Always lesser area than actual size of sound head </li></ul></ul><ul><ul><li>Large diameter heads – column beam </li></ul></ul><ul><ul><li>Small diameter heads – more divergent beam </li></ul></ul><ul><ul><li>Low frequency (1 MHz) – diverge more than 3 MHz </li></ul></ul><ul><li>Treatment Duration: time for total treatment </li></ul>
  14. 14. Intensity Output & Power <ul><li>Power: measured in watts (W); </li></ul><ul><ul><li>amount of energy being produced by the transducer </li></ul></ul><ul><li>Intensity: strength of sound waves @ a given location within the tissues being treated </li></ul><ul><li>Spatial Average Intensity (SAI): amount of US energy passing through the US head’s ERA; </li></ul><ul><ul><li>expressed in watts per square centimeter (W/cm 2 ) (power/ERA) </li></ul></ul><ul><ul><li>Changing head size affects power density (larger head results in lower density) </li></ul></ul><ul><ul><li>Limited to 3.0 W/cm 2 of maximum output </li></ul></ul>
  15. 15. Intensity Output & Power <ul><li>Spatial Average Temporal Peak Intensity (SATP): average intensity during the “on” time of the pulse </li></ul><ul><ul><li>Output meter displays the SATP intensity </li></ul></ul><ul><li>Spatial Peak Intensity (SPI): max. output (power) produced within an ultrasound beam </li></ul><ul><li>Spatial Average Temporal Average Intensity (SATA) or Temporal (time) Average Intensity: </li></ul><ul><ul><li>Power of US energy delivered to tissues over a given period of time </li></ul></ul><ul><ul><li>Only meaningful for Pulsed US </li></ul></ul><ul><ul><li>SAI x Duty Cycles </li></ul></ul>
  16. 16. Beam Nonuniformity Ratio (BNR) <ul><li>Ratio between the spatial peak intensity (SPI) to the average output as reported on the unit’s meter </li></ul><ul><ul><li>The lower the BNR, the more uniform the beam is </li></ul></ul><ul><ul><li>A BNR greater than 8:1 is unsafe </li></ul></ul><ul><ul><li>Because of the existence of high-intensity areas in the beam (hot spots), it is necessary to keep the US head moving </li></ul></ul>
  17. 17. BNR SPI
  18. 18. Duty Cycle <ul><li>Percentage of time that US is actually being emitted from the head </li></ul><ul><li>Ratio between the US’s pulse length & pulse interval when US is being delivered in the pulsed mode </li></ul><ul><ul><li>Pulse length = amount of time from the initial nonzero charge to the return to a zero charge </li></ul></ul><ul><ul><li>Pulse interval – amount of time between ultrasonic pulses </li></ul></ul><ul><ul><li>Duty cycle = pulse length/(pulse length + pulse interval) x 100 </li></ul></ul><ul><ul><li>100% duty cycle indicates a constant US output </li></ul></ul><ul><ul><li>Low output produces nonthermal effects (20%) </li></ul></ul>
  19. 19. Movement of the Transducer <ul><li>4 cm 2 /sec </li></ul><ul><li>Remaining stationary can cause problems </li></ul><ul><li>Moving too rapidly decreases the total amount of energy absorbed per unit area </li></ul><ul><ul><li>May cause clinician to treat larger area and the desired temps. May not be attained </li></ul></ul><ul><li>Slower strokes can be easier maintained </li></ul><ul><li>If patient complains of pain or excessive heat, then decrease intensity but increase time </li></ul><ul><li>Apply constant pressure – not too much & not too little </li></ul>
  20. 20. Coupling Agents <ul><li>Optimal agent – distilled H 2 0 (.2% reflection) </li></ul><ul><li>Modern units have a shut down mechanism if sound head becomes too hot (Dynatron beeps; red lights on Chattanoogas) </li></ul><ul><ul><li>Improperly coupled head causes  temp. </li></ul></ul><ul><li>Types of agents: </li></ul><ul><ul><li>Direct </li></ul></ul><ul><ul><li>H 2 0 immersion </li></ul></ul><ul><ul><li>Bladder </li></ul></ul><ul><li>Reduce amount of air bubbles </li></ul>
  21. 21. Direct Coupling <ul><li>Effectiveness is  if body part is hair, irregular shaped, or unclean </li></ul><ul><li>Must maintain firm, constant pressure </li></ul><ul><li>Various gels utilized </li></ul>
  22. 22. Water Immersion <ul><li>Used for odd shaped parts </li></ul><ul><li>Place head approx. 1” away from part </li></ul><ul><li>Operator’s hand should not be immersed No metal on part or operator’s hand </li></ul><ul><li>Ceramic tub is recommended </li></ul><ul><li>If nondistilled H 2 0 is used, intensity can be  .5 w/cm 2 because of air & minerals </li></ul><ul><li>Don’t touch skin except to briefly sweep skin when bubbles form </li></ul>
  23. 23. Bladder <ul><li>H 2 0 filled balloon or plastic bag coated with coupling gel </li></ul><ul><li>Use on irregular shape part </li></ul><ul><li>Place gel on skin, then place the bladder on the part, and then place gel on bladder </li></ul><ul><li>Make sure all air pockets are removed from bladder </li></ul>
  24. 24. Indications <ul><li>Soft tissue healing & repair </li></ul><ul><li>Joint contractures & scar tissue </li></ul><ul><li>Muscle spasm </li></ul><ul><li>Neuroma </li></ul><ul><li>Trigger areas </li></ul><ul><li>Warts </li></ul><ul><li>Sympathetic nervous system disorders </li></ul><ul><li>Postacute reduction of myositis ossificans </li></ul><ul><li>Acute inflammatory conditions (pulsed) </li></ul><ul><li>Has been shown to be ok to use following the stopping of bleeding with an acute injury (pulsed) </li></ul>
  25. 25. Contraindications <ul><li>Acute conditions (continous output) </li></ul><ul><li>Ischemic areas or impaired circulation areas </li></ul><ul><li>Tendency to hemorrhage </li></ul><ul><li>Around eyes, heart, skull, or genitals </li></ul><ul><li>Over pelvic or lumbar areas in pregnant or menstruating females </li></ul><ul><li>Cancerous tumors </li></ul><ul><li>Spinal cord or large nerve plexus in high doses </li></ul><ul><li>Anesthetic areas </li></ul><ul><li>Stress fracture sites or over fracture site before healing is complete (continuous); epiphysis </li></ul><ul><li>Acute infection </li></ul>
  26. 26. Thermal Effects <ul><li> blood flow </li></ul><ul><li> sensory & motor nerve conduction velocity </li></ul><ul><li> extensibility of structures (collagen);  joint stiffness </li></ul><ul><li> collagen deposition </li></ul><ul><li> macrophage activity </li></ul><ul><li>Mild inflammatory response which may enhance adhesion of leukocytes to damaged endothelial cells </li></ul><ul><li> muscle spasm </li></ul><ul><li> pain </li></ul><ul><li>+ all Nonthermal effects </li></ul>
  27. 27. Nonthermal Effects <ul><li> cell membrane permeability </li></ul><ul><li> vascular permeability </li></ul><ul><li> blood flow </li></ul><ul><li> fibroblastic activity </li></ul><ul><li>Altered rates of diffusion across cell membrane </li></ul><ul><li>Secretion of chemotactics </li></ul><ul><li>Stimulation of phagocytosis </li></ul><ul><li>Production of granulation tissue </li></ul><ul><li>Synthesis of protein </li></ul><ul><li> edema </li></ul><ul><li>Diffusion of ions </li></ul><ul><li>Tissue regeneration </li></ul><ul><li>Formation of stronger CT </li></ul>
  28. 28. Pulsed Ultrasound <ul><li>Stimulates phagocytosis (assists w/  of chronic inflammation) & increases # of free radicals (  ionic conductance on cell membrane) </li></ul><ul><li>Cavitation: formation of gas bubbles that expand & compress due to pressure changes in tissue fluids </li></ul><ul><ul><li>Stable – occurs when bubbles compress during the  -press. peaks followed expansion of bubbles during  -press. troughs </li></ul></ul><ul><ul><li>Unstable (transient) – compression of bubbles during  -press. Peaks, but is followed by total collapse during trough (BAD!) </li></ul></ul>
  29. 29. Pulsed Ultrasound <ul><li>Acoustical Streaming: stable cavitation leads this; one-directional flow of tissue fluids, & is most marked around cell membranes </li></ul><ul><ul><li>Facilitates passage of calcium potassium & other ions, etc. in/out of cells </li></ul></ul><ul><ul><li>Collagen synthesis, chemotactics secretion,  update of calcium in fibroblasts,  fibroblastic activity </li></ul></ul><ul><li>Eddies (Eddy) – circular current of fluid often moving against the main flow </li></ul><ul><ul><li>Flows around the cell membranes & its organelles </li></ul></ul><ul><ul><li>Flow of bubbles in stream cause change in cell membrane permeability </li></ul></ul>
  30. 30. Clinical Applications – Soft Tissue <ul><li>Stimulates release of histamine from mast cells </li></ul><ul><ul><li>May be due to cavitation & streaming </li></ul></ul><ul><ul><li> transport of calcium ions across membrane that stimulates histamine release </li></ul></ul><ul><ul><li>Histamine attracts leukocytes, that clean up debris, & monocytes that release chemotactic agens & growth factors that stimulate fibroblasts & endothelial cells to form a collagen-rich, well-vascularized tissue </li></ul></ul>
  31. 31. Clinical Applications – Soft Tissue & Plantar Warts <ul><li>Pitting edema -  temp. makes thick edema liquefy thus promoting lymphatic drainage </li></ul><ul><li> fibroblasts = stimulation of collagen production = gives CT more strength </li></ul><ul><li>Plantar Warts - 0.6 W/cm 2 for 7-15 min. </li></ul>
  32. 32. Clinical Applications – Scar Tissue, Joint Contracture, & Pain Reduction <ul><li> mobility of mature scar </li></ul><ul><li> tissue extensibility </li></ul><ul><li>Softens scar tissue </li></ul><ul><li> pain threshold </li></ul><ul><li>Stimulates large-diameter myelinated n. fibers </li></ul><ul><li> n. conduction velocity </li></ul>
  33. 33. Clinical Applications <ul><li>Chronic Inflammation - Pulsed US has been shown to be effective with  pain &  ROM </li></ul><ul><ul><li>1.0 to 2.0 W/cm 2 at 20% duty cycle </li></ul></ul><ul><li>Bone Healing – Pulsed US has been shown to accelerate fracture repair </li></ul><ul><ul><li>0.5 W/cm 2 at 20% duty cycle for 5 min., 4x/wk </li></ul></ul><ul><ul><li>Caution over epiphysis – may cause premature closure </li></ul></ul>
  34. 34. Treatment Duration & Area <ul><li>Length of time depends on the </li></ul><ul><ul><li>Size of area </li></ul></ul><ul><ul><li>Output intensity </li></ul></ul><ul><ul><li>Goals of treatment </li></ul></ul><ul><ul><li>Frequency </li></ul></ul><ul><li>Area should be no larger than 2-3 times the surface area of the sound head ERA </li></ul><ul><li>If the area is large, it can divided into smaller treatment zones </li></ul><ul><li>When vigorous heating is desired, duration should be 10-12 min. for 1 MHz & 3-4 min. for 3 MHz </li></ul><ul><li>Generally a 10-14 day treatment period </li></ul>
  35. 35. Thermal Applications
  36. 37. Treatment Goal & Duration <ul><li>Adjust the intensity & time according to specific outcome </li></ul><ul><li>Desired temp.    /min. = treatment min. </li></ul><ul><ul><li>Ex. For 1.5 W/cm 2 : 2°C  .3°C = 6.67 min. </li></ul></ul>
  37. 38. Phonophoresis <ul><li>US is used to deliver a medication via a safe, painless, noninvasive technique </li></ul><ul><li>Opens pathways to drive molecules into the tissues </li></ul><ul><li>Not likely to damage or burn skin as with iontophoresis </li></ul><ul><li>Usually introduces an anti-inflammatory drug </li></ul><ul><li>Preheating the area may enhance delivery of medication </li></ul><ul><ul><li>Encourages vascular absorption & distribution of meds. </li></ul></ul><ul><li>Some medications are poor conductors </li></ul>
  38. 39. Phonophoresis <ul><li>Factors affecting rate of medication diffusion </li></ul><ul><ul><li>Hydration – higher water content = skin more penetrable </li></ul></ul><ul><ul><li>Age – better with younger ages </li></ul></ul><ul><ul><li>Composition – better near hair follicles, sebaceous glands & sweat ducts </li></ul></ul><ul><ul><li>Vasularity – higher vascular areas are better </li></ul></ul><ul><ul><li>Thickness – thinner skin is better </li></ul></ul><ul><li>Types of medications </li></ul><ul><ul><li>Corticosteroids – hydrocortisone, dexamethasone </li></ul></ul><ul><ul><li>Salicylates - </li></ul></ul><ul><ul><li>Anesthetics - lidocaine </li></ul></ul>