Ultrasound PDF

Ultrasound Objectives Review the indications of Ultrasound Review the contraindications of Ultrasound Understand the principles behind the clinical application of Ultrasound in physical therapy  Continuous - Ultrasound &...

Ultrasound Objectives Review the indications of Ultrasound Review the contraindications of Ultrasound Understand the principles behind the clinical application of Ultrasound in physical therapy  Continuous - Ultrasound & L Pulsed Acoustic Thermal Can produce biophysical Can provide deep mechanical agent: uses heating (nonthermal) - sound waves effects as well > - For Pain control Frequency and Wavelength  Frequency (Remember these Numbers Most common Frequency used in PT are 1 MHz and 3 MHz G1MHz penetrates deeper and is used to impact deeper tissues - Example of when you would use this? O3 MHz is used to impact superficial tissues - Example of when you would use this? exi- Finger extensor tendon Power and Intensity Same thing, but reported using different units of measure Power: Measured in Watts; amount of energy produced but he - ultrasound generator - Intensity: Describes the strength of the sound wave at a given location within the tissue treated; Intensity is expressed in W/cm2. (Uses spatial - Average Intensity) Lower Intensity is effective at higher frequency and vice versa - – 1 MHz = 1.5 to 2 W/cm2 - – 3 MHz= 0.5 W/cm2 - ↓ Intensity ↑ Frequency = ↳ Frequent tensity  · Continuous is used for thermal heat tassue effects I can up to 5 en Deep Duty Cycle Continuous: 100% duty cycle Thermal: think back to thermal - lecture of when you would want this Can heat tissue up to 5 cm deep Pulsed: often 20% or 50% - Non-thermal (good during acute - inflammation) - Transmission of Acoustical Energy Uses a sound head with a piezoelectric crystal Requires a medium to transmit Medium must be denser than air EDirectly on stim What mediums have you seen used can cause periosteium sound head to transmit ultrasound waves? burn burns or out the.  Concept that ultrasound output has peaks and valleys of high and low energy Ultrasound Beam Calculated by Spatial peak intensity/Spatial average Nonuniformity rece intensity FDA requires that Beam Nonuniformity is < 5:1 - - - # L5 : / Influences on the transmission of energy Target tissue is just below the transducer. The deeper the tissue, the less absorption because of dispersion, refraction ,reflection, and divergence Coupling Agents Gel Used as Medium for Bladder Ultrasound Water Immersion Bladder Water Immersion Gel Effective Radiating Area (ERA) : Will be tested ON. ERA is the proportion of the transducer’s surface area that produces ultrasonic energy (Always slightly smaller than the actual transducer head) Area that gets therapeutic effects Most concentrated area of energy is the center of the ultrasound head Treatment area should be NO MORE treatment area wide than -4x the than Dont ERA go 4 too big or Used to calculate the spatial average intensity (W/cm2) DONT MEMORIZE SCIDR Describes the amount of energy passing through the sound head’s effective area This is an expression of energy density Spatial Average Intensity SAI= total watts (W)/Effective radiating area (ERA)= W/cm2 Key point: Ultrasound units can display total output as EITHER Watts or Watts/centimeters2 Ultrasound Head Sizes - Consider the body part and target area before choosing the ultrasound head Move the sound head 4 cm/second  Ultrasound Attenuation Tissue Attenuation (%/cm) Blood 3 Fat 13 As ultrasound travels through tissue, the intensity and the Muscle 24 amplitude of the wave decreases. Skin 39 Happens due to absorption, redlection, deflection, etc. Tendon 59 Cartilage 68 Bone 96 *US is more effective at heating more protein rich and low water content tissues 15 Key Points Bone periosteum can Gel should be on US head become injured with before turning it on to prolonged exposure, so prevent burning out the be sure to continuously crystal move the US transducer due to reflection Treatment Algorithm (Cameron 2009) - Ultrasound Indications – Local inflammation and pain Carpal tunnel, tendinopathy, bursitis, arthritis, · -- myofascial pain, muscle spasm, trigger points – Soft tissue shortening Should be combined with other interventions (e.g., stretch) - – Smaller body of literature for soft tissue healing, wounds, scar tissue remodeling, calcium deposits mumm – Less evidence supporting non-thermal use of US, but still used as rationale for use 18 Ultrasound Precaution: – Pulsed US in active inflammation (acute conditions) – Regenerating nerves (poor evidence) – Skin disease – Impaired sensation, cognition, communication – Adverse effects: if soundhead is not moved, periosteal burning OR may result in gas bubble formation, unstable cavitation and damage to endothelial lining of blood vessels 19  – Tumor – Pregnancy (over pelvis, low back, abdomen) – Breast implants – Over CNS tissue, eyes, heart, reproductive organs – Pacemaker – Site of active bone growth (epiphysis) – Joint cement or plastic implant components Contraindications (absorb US well and will heat tissue more) – Metal implants (will reflect US and create standing waves) – Hemorrhagic conditions – Continuous US use in acute injury – US over spinal cord or regenerating/superficial nerves – Decreased local circulation – Recently irradiated tissue (s/p radiation therapy) 20 Heating of the Tissue Thermal effects Tissue Absorption Occur mainly with continuous High collagen content absorbs US well ultrasound (though to a much (e.g. tendon, capsules, ligaments, fascia, smaller extent in pulsed US) scar tissue) Produces deep heat (up to 5 cm) Not absorbed well by tissues with high by heating tissues which absorb it well (increasing molecular water content and low collagen content movement and friction and (e.g. fat) or those with higher water spreading by conduction to content and good vascularization to surrounding tissues) dissipate heat (e.g. muscle) 21 Non-thermal effects Increase in intracellular calcium level (may increase metabolic cellular activity and protein synthesis) Increase in skin and cell membrane permeability Increase in mast cell degranulation, macrophage responsiveness, protein synthesis by fibroblasts (may increase healing and decrease time spent in inflammation phase) Increases nitric oxide synthesis in endothelial cells (may lead to vasodilation); ex: increases blood flow to fracture site and ischemic muscle tissue in animals Placebo? Patient expectation? Thermal Effects Pain modulation Decreased muscle spasm, joint stiffness Increased tissue extensibility, circulation, metabolic rate Ultrasound: Expected Patient Response Should feel warmth if continuous US Will probably just feel gentle pressure of sound head being moved (like a massage?) if US is pulsed Very few adverse effects/incidences of discomfort Pay immediate attention if patient reports ache, burn, or discomfort – may indicate too much heating in tissue/formation of standing wave! 24 Documentation Include: – All parameters (intensity, frequency, duty cycle, etc) – Treatment duration – Treatment area size – Sound head size – Coupling agent – Patient position – Patient response  Ultrasound WILL affect body tissues through thermal mechanisms; non-thermal mechanisms have demonstrated effects in vitro, but less in vivo But…growing body of literature questioning US clinical utility US: What We Know Very capable of heating a small volume of tissue but not large muscle mass Additive effect to a multimodal package? 26 Ultrasound: Study Limitations Body of literature to be explored – Studies at a patient-level (as opposed to tissue level) plagued with multiple pervasive flaws – Poor/no blinding – Inconsistency in dosage and rationale (often not even using a demonstrated therapeutic dosage!) – Confounding with placebo effect – Small sample sizes – Findings indicate that results MAY be dependent upon the unit itself – Does not mean ineffective, just not consistently shown to be better than alternatives and still safe for use 29 But Despite What We Don’t Know… Amijo-Olivo et al 2013 – 82.4% PTs report US use – 36.4% PTs report daily use – Of those who use US routinely, 40% use clinical experience to justify use vs. 13% use research studies 31 Any Questions?