This glossary has not changed much from what Martin Ostermeyer put together. Other obvious terms to define are attenuation, chromophore, diffraction, diffuse imaging, diffusion, diffusion coefficient, fluorescence imaging, fluorophore, photodynamic therapy (PDT), refraction, scattering coefficient, specular reflectance, thermotherapy. It may or may not be expanded upon and still needs work. In fact, even I disagree with a couple of definitions below.

ablation - removal of a layer of material. Ablation of tissue with a laser is a rich field of its own. We will have a section on ablation in the future, right now we only have a sequence of pictures of a water surface that is hit with a short laser pulse so that a plume of ablated water forms.

absorption - here: absorption of light. If a beam of light goes through an absorbing substance like a dye, the light gets weaker. The reason is that molecules interact with the light and transform it into different forms of energy, like heat or chemical energy.

absorption coefficient - describes how strong a material absorbs light of a certain color. In medical optics the absorption coefficient is often represented with the greek letter 'mu' and a subscript 'a'. The units [1/cm] are common.

albedo - the ratio of scattering coefficient and reduced total interaction coefficient.

Monte Carlo - see our page devoted to the randomly bouncing photons around.

photon - a light 'particle'. Often it is reasonable to describe light as a beam of photons. They behave similar to base balls: while base balls can be scattered by collisions with other things like bats, heads, or trees, photons in tissues are scattered by cells and objects inside the cells. Baseballs can be absorbed by a glove (or by bushes or lakes); photons are absorbed by molecules like chromophores and fluorophores.
Sometimes the photon-model for light fails and one has to resort to a model that describes light as an electromagnetic wave. This is usually the case when diffraction at very small structures occurs or light beams 'interfere' with each other.

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