Stanbridge - T4 - Modalities - W3 - Laser & Ultrasound

Modalities (PTA 1009)

• The presentation covers Ultrasound and Laser therapy.
• Students will learn about the physical principles of ultrasound, physiological responses, indications, contraindications, precautions, adverse reactions, and general application, dosage and frequency.

Ultrasound

• Sound is the vibration of a medium.
• Frequency is the rate at which something repeats over a period.
• Ultrasound is a frequency of vibration beyond audible sound (above 20,000 cps).
• Human ears detect vibrations up to 20,000 cycles per second (cps).
• Therapeutic ultrasound typically operates between 1 MHz and 3.3 MHz (millions of cycles per second - or megahertz).
• A sound wave creates pressure in a medium, compressing molecules.
• Each molecule transfers energy to its neighbour causing a chain reaction throughout the medium.
• Sound waves can travel through liquids, gases, and solids.
• Ultrasound machines use piezoelectric ceramic crystals to generate sound waves.
• Current applied to the crystal causes it to distort and vibrate producing mechanical waves which are sent into the body.
• During treatment, waves impart energy to the target tissue molecules.
• Ultrasound can generate thermal and non-thermal tissue effects.

Ultrasound: Indications

• Deep Heating: Joint contracture, scar tissue, pain, muscle spasm, subacute/chronic tissue disorders requiring increased temperature or blood flow.
• Healing Facilitation: Acute injury or inflammation of soft tissues, peripheral nerves, and open wounds.

Ultrasound: Instrumentation

• Includes a console, coaxial cable, and transducer (5 cm² or 10 cm²).
• The presentation mentions coupling gel (a medium that allows sound waves to travel effectively through tissues, typically water-based).
• Using coupling gel prevents air pockets that reflect/absorb the ultrasound waves

Ultrasound: Beam Nonuniformity Ratio (BNR)

• BNR is the ratio of peak power to the average power in an ultrasound beam.
• It is measured 0.5 cm from the transducer, indicating transducer quality.
• Acceptable BNRs in Ultrasound range from 2.1:1 to 8:1; with an average of 5:1 to 6:1.
• A "hot spot" in tissue can receive 6 times more energy than intended.

Ultrasound: Effective Radiating Area (ERA)

• The effective radiating area (ERA) is the part of the ultrasound beam that delivers clinically effective power.
• The treatment area must be smaller than 4x the ERA, to maximize the effectiveness.
• This is because treatment time increases if the area to be treated is significantly larger than the size of the treatment head.

Ultrasound: Biophysical Effects

• Thermal: Increased metabolism, reduced muscle spasms, decreased joint stiffness, alteration of nerve conduction velocity, increased circulation, and increased soft tissue extensibility.
• Thermal effects depend on tissue temperature changes and factors like type of device/ modality used.
• Non-thermal (usually with pulsed ultrasound): Increased cell membrane permeability, increased intracellular calcium levels, facilitation of tissue repair, and promotion of normal cell function.

Ultrasound: Effects on Different Tissues

• Tissues with high protein content and dense tissues absorb ultrasound waves best, resulting in significant heat production.

Ultrasound: Effects on Fluids/Bone

• Fluid elements have low resistance and absorption, minimizing heat effects.
• Bone's high impedance and absorption can result in quick heating and if intensity is too high, it can lead to a prickling sensation.

Ultrasound: Frequency

• Higher frequency (3.3 MHz): absorbed more effectively in superficial tissues (with penetration of 1-3 cm), and accelerates temperature rise.
• Lower frequency (1 MHz): penetrates deeper into tissues (up to 3-5 cm in tissue)

Ultrasound: Mode

• Continuous: produces primarily thermal effects.
• Pulsed: produces both thermal and nonthermal effects. This means the output of the Ultrasound is not constantly applied but rather in short bursts.

Ultrasound: Dosage & Duty Cycles

• Duty cycle = (On time/ total treatment time) x 100.
• Common duty cycles use 1:1 (50%) or 1:4 ratios (20%) to deliver pulsed ultrasound.
• Intensity (the amount of energy per unit area), is typically between 0.5-3.0W/cm2
• Duration in minutes (5-10 per point) is dependent on the frequency and the intended target area's size.
• More intense treatment at chronic conditions.

Ultrasound: Contraindications/Precautions

• Contraindications: Anesthetic areas, impaired arterial circulation, over epiphyseal plates of growing bones, active bleeding, over eyes, testes, spinal cord after laminectomy (may cause cavitation).
• Pregnancy, malignancy/infection, over carotid sinus, heart, stellate, cervical ganglia, pacemaker, over regions of thrombophlebitis or DVT, abscesses.
• Precautions: Maintain consistent energy transfer, keep transducer moving, avoid bony prominences, use low doses for acute inflammatory pathologies, and avoid epiphyses of growing bones.

Ultrasound: General Instructions for Application

• Inspect/check equipment (calibration)
• Instruct the patient about the procedure, sensation and expected outcomes.
• Position and drape the patient.
• Identify the area, palpate the skin, consider depth.
• Adjust patient position as needed, if necessary.
• Select an appropriate frequency (1 MHz or 3.3 MHz).

Ultrasound: Application Technique

• Apply gel to the transducer head, and maintain skin parallel contact.
• Apply dosage, and keep transducer moving (approximately ~4 cm/sec).

Ultrasound: Response to Intervention & Documentation

• Document patient responses.
• Monitor for warmth (normal response).
• If sharp pain, decrease the intensity and pause the treatment before changing frequencies.

Laser Therapy

• Focuses on biostimulation (cellular-level tissue growth) instead of heat.
• Types of lasers: different wavelengths have varying tissue depth.
• Wavelengths: 400-700 nm - effective on superficial tissues; 700-1200 nm - effective on deeper tissues.
• Classification: Class 1 is safe for any potential exposure; class 2 - safe to blink reflex (visible light); class 3a and 3b increase in power and potential hazard to eyes; and class 4 poses a risk of burns and permanent eye damage.

Laser Therapy: Purpose & Effects

• Light is absorbed into mitochondria, triggering biochemical reactions and physiological responses within the cells.

Laser Therapy: Physiological Responses

• LLLT & HILT lead to increased ATP production, resulting in increased cellular energy with increased fibroblast activity.
• Increased cell proliferation, aiding tissue healing (fibroblasts, endothelial cells, keratinocytes, macrophages, mast cells).
• Increased local blood circulation and muscle relaxation, with an anti-inflammatory response and pain reduction.

Laser Therapy: Precautions

• Dark pigmented skin (less depth of beam penetration)
• Impaired sensation
• Photophobia, check for skin rashes
• Diabetes, check sensation
• Over tattoos.

Laser Therapy : Applications and Technique

• Direct contact approach: (LLLT)
• Indirect contact approach: (LLLT & HILT)
• Sweeping technique: (LLLT & HILT).

Laser Therapy Dosage and Frequency

• The frequency is typically determined by the specific laser and manufacturer.
• A common way to represent dosage is in joules per cm2.

Laser Therapy: Frequency

• Acute conditions benefit from high frequency at lower doses.
• Sub-acute conditions may benefit from every other day treatment
• Chronic conditions usually benefit from lower frequency but higher doses.
• If there is no response after two weeks, re-evaluation is necessary.

Laser Therapy: Documentation

• Record the location, surface area, dosage in joules/cm², laser power in watts, frequency and type of laser, mode, and the patient response to therapy.

Test your knowledge on the applications and effects of laser and ultrasound therapies. This quiz covers the principles of Low Level Laser Therapy (LLLT), the differences among various laser types, and the characteristics of ultrasound treatment. Dive into the specific conditions treated and the physiological responses associated with these modalities.