Lecture

Light Dosimetry in Tissues

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In course

CH-448: Photomedicine

The most important clinical diagnostic and therapeutic applications of light will be described. In addition, this course will address the principles governing the interactions between light and biological tissues, their optical properties and basic concept ...

Description

This lecture covers the importance of light dosimetry in tissues for medical laser treatments, focusing on parameters like light dose, fluence rate, and mechanisms of interaction. It explains the impact of parameters such as geometry, wavelength, and tissue optical properties on light dosimetry. The lecture also discusses the classification of medical lasers based on their interactions with tissues and the accuracy of laser/light therapy models. Additionally, it explores the thermal relaxation time, laser pulse duration, and the influence of laser beam diameter on treatment outcomes.

Instructor

Georges Wagnières

Georges Wagnières received his diploma degree (MSc) in physics from the University of Lausanne, Switzerland, in 1986. He obtained his doctorate in science (PhD) in physics (Biomedical optics) from the Swiss Federal Institute of Technology at Lausanne (EPFL) in 1992 and did a postdoctoral work in the Wellman Laboratories of Photomedicine (Harvard Medical School), Boston, USA, from 1993 to 1994. He also obtained a Master degree in Management of Technology delivered by the Ecole des Hautes Etudes Commerciales (HEC) of Lausanne University and the EPFL in 2001. Georges Wagnières manages a research group active in the fields of: - Detection of early superficial cancers by fluorescence imaging. - Characterization of early superficial cancers by high magnification narrow band imaging. - In vivo and in vitro measurement of the vascular and tissular oxygen concentration by time-resolved luminescence spectroscopy and imaging. - Preclinical and clinical study of new photosensitizers for photodynamic therapy (PDT). - Treatment of neurodegenerative conditions (Alzheimer, Parkinson's diseases) by photobiomodulation. - Preclinical and clinical photodynamic therapy of inflammatory bowel diseases and atheroscerotic plaque. - Improvement of the selective vascular extravasation of chemotherapeutic agents by PDT. - Monitoring the light dosimetry during PDT by fluorescence spectroscopy and imaging. - Monitoring laser treatments of the retina by reflectance imaging. - Light dosimetry and tissue optical spectroscopy. - Radiometry. - Development of light delivery systems for biomedical applications. Georges Wagnières is also co-founder and was chairman of one spin-off companies: - Medlight SA, founded in July 1997, which develops, produces and commercializes light distributors for photodynamic therapy. Georges Wagnières has currently authored more than 235 papers (more than 150 in international journals with review board) and is inventor of 18 patents. He supervised 12 PhD students up to now, and currently teaches biomedical optics and photomedicine in master programs and doctoral schools. In addition, he gives the course entitled "Physique Générale I" to biology first year students registered to the Biology School of the Lausanne's University. MAIN PUBLICATIONS Please visit: https://www.epfl.ch/labs/lifmet/wagnieres/publications/

Official source

Related concepts (32)

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word laser is an anacronym that originated as an acronym for light amplification by stimulated emission of radiation. The first laser was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light that is coherent.

Laser medicine

Laser medicine consists in the use of lasers in medical diagnosis, treatments, or therapies, such as laser photodynamic therapy, photorejuvenation, and laser surgery. The word laser stands for "light amplification by stimulated emission of radiation". The laser was invented in 1960 by Theodore Maiman, and its potential uses in medicine were subsequently explored. Lasers benefit from three interesting characteristics: directivity (multiple directional functions), impulse (possibility of operating in very short pulses) and monochromaticity.

Pulsed laser

Pulsed operation of lasers refers to any laser not classified as continuous wave, so that the optical power appears in pulses of some duration at some repetition rate. This encompasses a wide range of technologies addressing a number of different motivations. Some lasers are pulsed simply because they cannot be run in continuous mode. In other cases the application requires the production of pulses having as large an energy as possible.

Dye laser

A dye laser is a laser that uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths, often spanning 50 to 100 nanometers or more. The wide bandwidth makes them particularly suitable for tunable lasers and pulsed lasers. The dye rhodamine 6G, for example, can be tuned from 635 nm (orangish-red) to 560 nm (greenish-yellow), and produce pulses as short as 16 femtoseconds.

Ultrashort pulse

In optics, an ultrashort pulse, also known as an ultrafast event, is an electromagnetic pulse whose time duration is of the order of a picosecond (10−12 second) or less. Such pulses have a broadband optical spectrum, and can be created by mode-locked oscillators. Amplification of ultrashort pulses almost always requires the technique of chirped pulse amplification, in order to avoid damage to the gain medium of the amplifier. They are characterized by a high peak intensity (or more correctly, irradiance) that usually leads to nonlinear interactions in various materials, including air.

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