Fabrication of Optical Phantoms with Specific Oxygenation Levels

Abstract: By making use of optical technologies, much about the human body can be understood and treated. In the near-infrared part of the spectrum, hemoglobin is the most important absorber of light, acting as a bio-marker or indicator of tissue health in many photonic diagnostic techniques, like photoacoustic imaging, hyperspectral imaging and near-infrared spectroscopy (NIRS).

In order to calibrate the photonic devices, simulate light distributions in a medium and set a reference to optical properties, ‘Optical Phantoms’ are constructed. Fabricating phantoms that mimic the absorption properties of oxy- and deoxyhemoglobin – which determine the oxygen saturation in blood – over a wide spectral range present a challenge.

In this project, 11 different biocompatible silicon-soluble color pastes have their optical properties characterized. To achieve that, thin phantoms made of biocompatible silicone containing the individual colors are case and evaluated, with the help of a spectrometer. Concentration independent optical coefficients of these colors are then defined.

Knowing the individual absorption and scattering coefficients of each color allowed for the programming of a user interface, which allows one to create a recipe of a silicone phantom, with selected optical properties.

Finally, this user interface is put to proof by creating an optical phantom with a specific oxygen saturation.