Biomedical Optics 5 MCQ

Low Level Laser Therapy (LLLT) Overview

• LLLT, also known as Low Level Light Therapy (LLLT) or photobiomodulation (PBM), is a low-intensity light therapy.
• The effect of LLLT is photochemical, not thermal.
• Light triggers biochemical changes in cells, comparable to photosynthesis in plants.
• Photons are absorbed by cellular photoreceptors, triggering chemical changes.

History of LLLT

• In 1903, Dr. Nils Finsen was awarded a Nobel Prize for his work using concentrated light radiation to treat diseases, specifically lupus vulgaris.
• In 1967, Mester E et al. demonstrated the phenomenon of "laser biostimulation".
• In 1999, Whelan H et al. researched the use of light-emitting diodes (LEDs) in medical applications, including use on the NASA space station.
• Since then, over 400 Phase III randomized, double-blind, placebo-controlled trials, and over 4000 laboratory studies of LLLT support its effectiveness, according to Pubmed.gov.

Mechanisms of LLLT

• LLLT is the application of light (usually from a low-powered laser or LED). The light's power range is typically 10mW to 500mW.
• Wavelengths in the red to near-infrared region (660nm-905nm) are used to penetrate skin, soft tissue, and hard tissues.
• Mitochondria, the power plant of the cell, play a vital role in LLLT.
• Mitochondria are involved in regulating oxidative stress, calcium metabolism, and apoptosis.
• In photobiomodulation (PBM), chromophores in mitochondria absorb light photons.
• Cytochrome c oxidase (COX) is the primary photoreceptor for red-NIR wavelengths in mammalian cells.
• Other signaling molecules involved include ATP, ROS, and calcium.
• Nitric oxide (NO), produced in mitochondria, can bind to COX, inhibiting respiration.
• LLLT exhibits an Arndt-Schultz law biphasic dose-response curve. This means response to treatment changes based on the dose.
• A higher number of mitochondria cells respond better to PBM than cells with fewer mitochondria.

Instrumentation

• LLLT devices and instrumentation use LEDs and/or low-powered lasers.
• Light sources vary in terms of power, focus, and beam penetration.
• Superficial tissue treatment (e.g., wounds) can use LEDs and SLDs (Super Luminescent Diodes). Laser treatment is shown to have a greater effectiveness on deep tissue.

Treatment Parameters

• Wavelength (nm): Key parameter for LLLT, often 630nm.
• Power density (W/cm²): Specific power delivered to a given surface area.
• Energy density (J/cm²): Total energy delivered to a given surface area; a more important parameter than power density for cell-level effects.
• Tissue optical properties: How the tissue interacts with light is crucial for treatment efficacy.
• Continuous or pulsed mode: Continuous light is uninterrupted, while pulsed mode involves bursts of energy.
• Treatment duration (sec or min): The length of time the light source is applied. Treatment times can vary from 30 seconds to 1 minute depending on the clinical target.
• Irradiance: The power per unit area.
• Irradiation parameters include wavelength, irradiance, pulse structure (peak power, pulse frequency, pulse width, duty cycle), coherence , and polarization
• 6 J/cm2 is a common energy density value for use with varied power density and exposure time values.

Clinical Targets

• The four clinical clinical targets for LLLT are the site of injury, lymph nodes, nerves, and trigger points.
• These targets seek to promote healing, decrease edema and inflammation, and induce analgesia (reduce pain)

Radiation Protocols

• Specific protocols for radiation-induced oral mucositis are described.

Summary

• LLLT has a photobiomodulation effect, meaning a photochemical reaction in tissue (not thermal).
• The reaction can be stimulatory or inhibitory, depending on the dosage.
• Cells with higher mitochondria counts respond better to PBM compared to cells with fewer.
• The fluence (J/cm²) is a more critical factor than irradiance (mW/cm²) for determining in vitro results.
• Ineffective in vivo studies of LLLT may be due to underdosing.

This quiz provides an overview of Low Level Laser Therapy (LLLT), also known as photobiomodulation. Explore the history, mechanisms, and the biochemical effects of this innovative therapy, which has shown promising results in various medical applications. Test your understanding of LLLT and its significance in modern science.