Deep Heat Ultrasound- Therapeutic Procedures – Flashcards
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Waves used in ultrasound:
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Sound waves are mechanical pressure waves. US waves are high frequency, inaudible to the human ear. US requires a medium such as gel to transmit acoustic energy.
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Medical frequency
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800,000 to 3,000,000 Hz
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Audible sound frequency
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16,000-20,000 Hz
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Ultrasound frequency
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<20,000 Hz
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How do sound waves travel?
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Travel mechanically by deforming or vibrating moleulces. A vibrating molecule "bumps" into adjacent molecule, a chain reaction through the tissue. Mollecules closer together collide more quickly.
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Relationship between tissue density and energy transfer speed?
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Sound energy travels faster through denser connective tissues such as tendon and bone.
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Ultrasound on a large area?
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Not appropriate for large surface areas- its inefficient way of heating becuase of hte small area of the transducer.
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How are sound waves produced in US?
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Waves are produced by a piezoelectric cystal: - Alternating current impressed on crystal causes molecules to collide & transfer energy - Crystal vibrates and produces mechanical waves equal to sound waves
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2 kinds of effects from a piezoelectric crystal:
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1. thermal 2. mechanical
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What kind of pattern do sound waves travel in?
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sinusoidal pattern through a medium. Positive pressure phase followed by a negative pressure phase.
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Condensations
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areas of compression or increased molecular density
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Rarefractions
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areas of decreased molecular density
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Frequency: 1 MHz
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Deeper penetration Diverges more as leaves transducer
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Penetration of 1 MHz:
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1-2 inches (greater than 2cm)
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Tissues used for 1 MHz:
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Soleus, deep hip rotators for example
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Frequency: 3 MHz
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Superficial Absorbed more easily, raises temp faster, less penetration
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Tissues used for 3 MHz:
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Plantar fasciitis, patellar tendonitis, epicondylitis
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Higher frequencies
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At higher frequencies, more frequent molecular oscillations occur, and increased work is required for sound waves to overcome molecular friction. This means more energy is absorbed in superficial tissues and less is available for deeper tissues.
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Penetration of 3 MHz:
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1-2 cm
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Temperature and frequency:
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At 3 MHz (superficial), tissue temperature increases much quicker and to a higher temperature. At 1 MHz (deep), tissue temperature takes much longer to increase, but stays heated for a longer time.
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Continuous mode
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Uninterrupted stream of sound waves. Used for thermal effects.
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Pulsed mode
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Periodic interruptions in sound waves. Energy flows for a brief duration, then no energy flows. Used for non-thermal effects, but has a mechanical effect on movement of ions across cell membranes. Characterized by a duty cycle
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Duty cycle
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- Fraction of time during single pulse period that US beam is present - % of pulsed duration - On-time to the sum of on-time plus off-time Ex: 10 sec on, & 30 sec off (sum = 40 sec total time) 10/40 = 25% duty cycle
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Intensity watts/cm2
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Determined by quantity of energy or acoustic power Not uniform across sound head (lower intensity around the sound head)
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ERA: Effective Radiating Area
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A measure of the actual cross-sectional area of the US beam as it exits the metal plate Expressed in square centimeters (cm2)
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Where does the sound head have highest/lowest intensity? why?
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Around the sound head = lowest Middle of sound head = highest Crystal is cemented around the periphery of the transducer, it cannot vibrate much so you don't get as much intensity out to the edge.
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Biophysical characteristics of US:
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Can be transmitted, absorbed, reflected and refracted Depends on angle and type of tissue: greater energy is reflected at mm/bone interface 2° more drastic change in impedance
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Acoustic Impedance
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Material / tissue's ability to transmit sound Molecular density & structure of material / tissue
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Low impedance:
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If acoustic impedance is low, transmission is high & material absorbs little sound
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Penetration and frequency:
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Lower frequency, deeper penetration Higher frequency, ↓'d penetration 2° ↑'d attenuation
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Attenuation:
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A measure of the decrease in sound energy as the sound wave travels by absorption, reflection, or refraction ex: 3 MHz would be more appropriate to treat carpal tunnel.
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Attenuation ex of 1 MHz
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lowest in blood, fat, muscle, blood vessel highest in bone, cartilage, tendon, skin
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Angle of the US beam should be:
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should be <15 degrees from the perpendicular (more perpendicular to the tissue, best intensity)
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Thermal effects of US:
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Deep heat
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Tissue temp increase of 1 C:
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Increases metabolic rates
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Tissue temp increase of 2-3 C:
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Decrease muscle spasm Decrease pain Increase blood flow
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Tissue temp increase of >4 C:
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Necessary to increase collagen extensibility & inhibit sympathetic activity *stretch after or during to increase collagen extensibility
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2 mechanical effects of US:
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1. microstreaming 2. cavitation
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Microstreaming
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Small magnitude movements of ions & cellular fluids Alters cellular activity & cell membrane permeability
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Cavitation
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Small gas bubbles present in body fluids are subject to compression during condensations & expansion during rarefactions, when exposed to US When exposed to high intensity US, may cause violent collapse or implosion of gas bubbles, leads to tissue destruction
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US effects on muscle are dependent on:
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intensity, duration, frequency ex: 1 MHz can penetrate deeper but longer treatment times with higher intensities are required to achieve vigorours muscle heating
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US effects on connective tissue:
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CT heats up faster & to higher temp than muscle
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Differences between CT and muscle:
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CT more dense than mm (CT heats faster) Higher collagen content in CT CT more avascular (less blood vessels, blood flow not increased as much, also not as easy to cool down)
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How does ERA effect temp?
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When Rx area 2 x ERA, aver temp ↑ 8 °C after Rx & returned to baseline after 20 min When Rx area 4 x ERA, temp ↑ 5 °C after Rx & returned to baseline after 15 min
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If the intent of US is to maximize stretching...
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Stretching should be immediately after US or begin concurrently with it and continue for at least 4 min afterwards.
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US effects on joint pain:
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May reduce pain in arthritis and stiffness
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US effects on hemodynamics:
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Temp ↑'s in tissue as US energy is absorbed Local blood flow then increases to area to dissipate heat
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US non-thermal effects:
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Reflexive vasodilation Local histamine release changes vascular tone
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How long does it take blood flow to return to normal?
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Regardless of mechanism, blood flow returns to baseline < 1 minute after US
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US effects on neurological system motor nerve conduction velocity:
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Motor nerve conduction velocities (MNCV) change Can ↑, ↓, or stay the same *Depends on parameter; pulse will stay the same, continuous mode may increase NCV.
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US effects on neurological system sensory nerve conduction velocity
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Sensory nerve conduction velocities (SNCV) appear to ↑ with thermal US (Unclear whether solely due to temp changes, or other factors also) Somewhat unknown
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US effects on pain threshold:
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Pain threshold increased 2° US effects / vascular / thermal changes Somewhat unknown
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Thermal vs. non thermal:
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Thermal is achieved with continuous US 0.75-3.0 W/cm2 Non-thermal is achieved with pulsed US or low intensity continuous US
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Treatment goal: thermal
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Gentle tissue temperature rise Low enough not to cause pain High enough for depth of penetration Long enough for heating to occur penetrate deeper? choose 1 MHz (longer wavelength). Increase duration for temperature increase.
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Clinical uses: inflammation
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- Decrease pain with thermal, increase blood flow & nutrition (pain fibers more sensitive to US) - Edema has thermal & nonthermal effects
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Clinical uses: tissue healing
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- ↑ # of tissue repair cells - ↑ collagen (need cont US), good for tendon/ligament healing - ↑ protein synthesis low intensity pulsed ultrasound can be used for fracture ealing.
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Clinical uses: scar tissue
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relaxation of polypeptide vonds, increase mobility
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Clinical uses: collagen extensibility
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Collagen good absorber of US Window for adding stretching to US
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US Indications
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Contractures / scarring Chronic arthritis Muscle strain, spasm, hematoma MM guarding / trigger points / neuromas Subacute & chronic inflammation Wound healing
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Contraindications
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Pacemaker (can use in more remote areas) Pregnancy Over pelvic/abd/ lumbar areas Malignancies / tumors (don't want to increase blood flow) DVT or thrombophlebitis Infected areas Spinal cord - laminectomy
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Contraindications cont
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Growing bone, epiphyseal plate (damaging) Areas with tendency to bleed Eyes Over heart, carotid sinus, or cervical ganglia (HR influence)
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Precautions
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Unhealed fx sites Primary repair of tendon or ligament Osteoporosis Plastic implants Metal implants
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Repair of tendons/ligaments?
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Human studies of low-intensity US using treatment parameters similar to those found to be beneficial in animal models of tendon and ligament healing are absent in the literature.
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3 methods of application:
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1. direct 2. indirect 3. phonophoresis
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Indirect application: water immersion
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Irregular surface, small area Keep sound head 1-2 cm away Delivers only 32% as much energy vs. direct contact (need to increase duration due to decreased intensity)
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Other methods of indirect application
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Fluid-Filled bag Fluid or gel filled Glove Gel pad MIST therapy-(Non contact) 40 kHz (low frequency/low intensity/nonthermal)
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Phonophoresis
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Use Hydrocortisone (10%) dexamethosone or lidocaine with US gel Drives whole molecules into tissues, not ions Not supported by the literature
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Deep heat rx set up:
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Explain Rx to patient Position the patient comfortably Remove clothing Appropriately drape Inspect area to be treated Determine patient's ability to respond to changes in temperature
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US procedures:
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Follow general deep heat Rx set-up Select appropriate frequency Select continuous vs. pulsed If pulsed select duty cycle Use alcohol wipes to clean skin if oily or lotion on Apply coupling medium
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Size of treatment area?
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Should be less than or greater to 2x ERA
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Keep the transducer moving:
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smooth, rhymthmical area, longitudinal stroking or circular movements
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Appropriate dosage time?
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5-10 minutes per site < 3 minutes no physiological effects 1 MHz takes 10 minutes to reach therapeutic temp 3 MHz faster **** LOOK AT CHART IN PPT for time/duration!!!
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Procedures: US intensity
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Lower with more acute conditions, higher with chronic conditions or connective tissue shortening Patient dependent, ↓ if pain or dull ache 0.75-3.0 W/cm2 (↑ slowly if needed) Make sure transducer head is in contact when US is started, keep it moving!
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Procedures cont
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Do not remove transducer from pt without shutting off machine first Conclusion of treatment: Shut off power Clean off gel Inspect the skin Clean the transducer Towel to remove gel Transducer cleaner spray
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Document?
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Treatment area Pt position Frequency Mode Intensity (duty cycle) Treatment duration Application technique Transducer size Sequence within treatment session
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Purpose of the gel?
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eliminate as much air as possible between the transducer & skin, maximizing US into pt body.
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document example:
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1Mhz, 100% duty cycle, 2.0 W/cm2, 2cm2 sound head, 10 min
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Frequency of treatments:
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Not well researched Usually max of 10-14 treatments recommended, but no evidence to support. Every other day, 2-3 x/week. Some suggest 2 week break before initiating US again What other options do you have? Is the patient progressing toward outcomes / goals?
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Summary points:
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Need a larger sound head for larger area (treats 2x ERA size of sound head)
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Why use an indirect treatmetn?
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Bony prominence. ALways use direct moethod unless you are on a bony prominence. Direct on muscle.
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Acute ankle fracture?
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You can use US, but should use pulsed in the acute stages for non-thermal effects.
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How do we get vasodilation with non-thermal?
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No temp increase- vasodilation due to muscle tone relaxing.
