Laser Technology in Biomedical Applications

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is excimer laser radiation and how does it differ from conventional lasers?

Excimer lasers use a mixture of reactive gases to produce ultraviolet light, differing from conventional lasers that typically use solid, liquid, or gas mediums for a range of wavelengths.

What are two key properties of laser radiation that make it effective in biomedical applications?

Two key properties are coherence, which allows focused energy delivery, and monochromaticity, which ensures a single wavelength for targeted treatments.

What is the primary role of the LSO/MLSO in relation to lasers?

To direct the safe use of lasers and ensure compliance with laser hazard standards.

Identify one potential qualification that an LSO/MLSO could have.

A Medical Physicist's license. Signup and view all the answers

Explain how photodynamic therapy (PDT) utilizes laser radiation.

PDT uses laser radiation to activate photosensitizing agents, which produce reactive oxygen species that selectively destroy cancerous or abnormal tissues. Signup and view all the answers

Discuss a biomedical application of excimer laser technology and its advantage.

One application is in refractive eye surgery, where excimer lasers reshape the cornea; the advantage is its precision and ability to minimize damage to surrounding tissues. Signup and view all the answers

How does the LSO/MLSO contribute to laser hazard management?

By implementing safety standards and controls to mitigate risks associated with laser use. Signup and view all the answers

Why is it important for the LSO/MLSO to ensure compliance with laser hazard standards?

To prevent accidents and ensure the safe operation of laser equipment. Signup and view all the answers

How does the wavelength of laser radiation influence its interaction with biological tissues?

Shorter wavelengths, like those from excimer lasers, are absorbed more by tissues, leading to effective ablation and alteration of cellular structures. Signup and view all the answers

What responsibilities might extend to the LSO/MLSO beyond directing laser safety?

They may also be involved in training staff on laser usage and safety protocols. Signup and view all the answers

Study Notes

Photodynamic Therapy (PDT)

PDT is a 120-minute second session
Presented by Dr. Marjaneh Hejazi
It involves the use of light to activate a photosensitizing drug that has accumulated within cells, causing oxidative cell injury.

Learning Objectives

Understanding the necessity of radiation dosimetry and treatment planning.
Applications of lasers in biomedicine
Role of medical physicists in hospital therapeutic departments

Keywords

Photodynamic therapy
Physics
Dosimetry

Content of the Presentation

Introductory remarks
Laser radiation, definition, properties and biomedical applications
Laser-tissue interactions & photobiological mechanisms
Biomedical laser applications in phototherapy
Current areas of basic PDT research
PDT dosimetry
PDT future research
Summary

PDT - Laser Radiation

Definition, properties, and biomedical applications
Lasers for cosmetic applications (wrinkle-removal, hair-removal)
All light-based technologies are applied to life sciences and form an area called biophotonics. The combination of 'bios' (life) and 'photons' (light).
The link between therapeutics and diagnostics leads to a new field called theranostics

PDT - Laser Radiation: Biomedical Applications

All light-based technologies applied to life sciences and medicine, named biophotonics
Combines Greek syllables "bios" (standing for life) and “phos” (standing for light).
Theranostics

PDT - Laser - Tissue Interactions & Photobiological Mechanisms

Relationships between power density and exposure time.
Photomechanical interaction
Photoablation
Photothermal interaction
Photochemical interaction

PDT - Photochemical Effects

Photochemical processes result from molecular photo-excitation, following absorption of one or more photons
Leads to a variety of chemical reactions, including the generation of free radicals and reactive oxygen species (ROS)

PDT - Biomedical Laser Applications

Main applications based on photochemical mechanism of laser-tissue interaction
Photodynamic therapy (PDT) of tumors
Biostimulation for wound healing (low-level laser therapy (LLLT))
Photochemical ablation and photodisruption

PDT - Definition of PDT

Light-activated chemotherapy using light to activate a photosensitive drug within cells to cause oxidative injury to the cell.

PDT - Involvement of Dosimetry

PDT is a non-invasive technique, based on the simultaneous action of three factors:
Photosensitizing agent (PS)
Molecular oxygen (O2)
Non-thermal monochromatic light irradiation

PDT - Energy Level Diagram (Type II Mechanism)

Shows how a sensitizer absorbs light, becomes excited, and transfers energy to oxygen to create reactive singlet oxygen.

PDT - Singlet Oxygen

A reactive form of oxygen with a paired electron spin
Kinetically unstable at ambient temperatures
Important component of PDT effects

PDT - Dosimetry Methodology

Three methods for assessing PDT dosimetry:
Implicit dosimetry
Explicit dosimetry
Direct dosimetry

PDT - Implicit Dosimetry

Uses a metric like photobleaching to implicitly assess dose parameters without explicitly measuring each.

PDT - Explicit Dosimetry

Measures each parameter directly during treatment to determine the resultant dose metric via model of how photodynamic response depends on each variable.

PDT - Direct Dosimetry

Involves direct measurement of each parameter during treatment.

PDT - Current Areas of Basic PDT Research and Dosimetry

600-850nm (near-infrared) light region for photons
Diode lasers with wavelengths important for excitation
Clinical diode lasers provide up to 1 W cm-2
415-690nm output wavelengths suitable for PDT

PDT - Light Source, Transport, and Delivery

Different delivery devices (e.g., non-contact, contact, interstitial).
Modes defined as spatial profiles of electromagnetic fields repeated at intervals along fibers and are either single- or multimode.

PDT - Current Areas of Basic PDT Research and the Involvement of Dosimetry

Using commercial IR navigation allows tracking of light delivery during pleura PDT.

PDT - Future PDT Research and Dosimetry

Studies show some efficacy in a range of malignant and pre-malignant pathologies
Further research aims for targeted delivery of photosensitizers and drugs via nanotechnology for superior selectivity.

PDT - Future Steps

Overcoming shallow light penetration suggests combining PDT with external-beam radiation therapy.
Using radioluminescence of nanoparticles (scintillation or persistent luminescence) or induced Cerenkov radiation to activate photosensitizers for PDT initiation
4-5 orders of magnitude higher energy delivered by standalone PDT treatment than typical ionizing radiation therapy

PDT - Conclusion

Advances in physics will likely bridge the gap between ionizing and non-ionizing radiation in oncology, necessitating a well-trained medical physicist
This expertise is essential for dosimetry, treatment planning, and patient safety in PDT.

PDT - Summary

Safety for patients and healthcare personnel is dependent on efficient use of lasers.
Laser Safety Officer or Medical Laser Safety Officer for safe laser operation and compliance
A greater understanding of basic biophysical mechanisms of light in biological media is important for improving safety and efficacy

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the fundamentals of laser technology, focusing on excimer lasers and their unique properties. Learn about the role of Laser Safety Officers (LSOs) and Medical Laser Safety Officers (MLSOs) in ensuring safe practices in biomedical applications. It also delves into the significance of compliance with laser hazard standards and the interaction of laser radiation with biological tissues.