Ultrasound in Physical Therapy

Ultrasound

• Ultrasound is a biophysical agent using sound waves.
• Objectives include reviewing indications, contraindications, and clinical application principles in physical therapy.
• Ultrasound can be continuous or pulsed.
• Continuous ultrasound provides deep heating, while pulsed ultrasound is non-thermal.
• Frequency and wavelength are inversely proportional.
• 1MHz is used for deeper tissue impact, while 3MHz is used for superficial tissue impact.
• Ultrasound intensity (W/cm²) and frequency have an inverse relationship; higher frequency corresponds to lower intensity.
• Duty cycle is either continuous (100%) or pulsed (20-50%).
• Ultrasound uses a piezoelectric crystal to transmit acoustic energy.
• The medium for transmission must be denser than air.
• Coupling agents like gel or water immersion ensure proper transmission.
• ERA (Effective Radiating Area) should be approximately 4 times smaller than the treatment area. Spatial Average Intensity (SAI) is calculated as total watts divided by the effective radiating area (ERA) as a measurement of energy density.
• Ultrasound head size should be selected based on the target area.
• Sound heads move at approximately 4 cm/second during application.
• Ultrasound attenuation occurs as the energy passes through tissue, and the intensity decreases due to absorption, reflection, and deflection.
• Ultrasound-specific attenuation coefficients are shown for different tissues (blood is the lowest, bone is highest).
• Key points include gel application before activation to prevent crystal damage and continuous transducer movement to prevent periosteal injury.
• Treatment guidelines are available, including frequency, intensity, duration, and other parameters.
• Ultrasound indications include local inflammation, soft tissue shortening, and specific pain conditions (e.g., carpal tunnel syndrome).
• Contraindications include pregnancy, tumor locations, pacemaker implantation, metal implants, and other conditions.
• Thermal effects include pain modulation, decreased muscle spasm, and increased tissue extensibility.
• Heat is produced directly in the tissues.
• Non-thermal effects include intracellular calcium level increase, membrane permeability, mast cell degranulation, increase fibroblast activity, increased nitric oxide and vasodilation.
• Patients should feel warmth (continuous) or gentle pressure (pulsed) during application.
• Discomfort, burning, or intense ache often indicates too much heating (standing wave formation).
• Documentation of treatment parameters (intensity, frequency, duty cycle) and response is essential.
• Ultrasound devices often produce differing levels of intensity or different ranges for output.
• Ultrasound's efficacy for different conditions is still under investigation and debated.