Diffraction Tomography adapted to Technical Applications
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XVII IMEKO World Congress
Imaging and especially tomographic methods play a very important part in both, medical and technical examinations. To overcome the disadvantages of the widely used ionizing radiation, more and more research work is focused on diffraction tomography allowing to utilize low energy and thus harmless but still sufficiently penetrating light radiation. Visible and near infrared (NIR) wavelengths between 600 nm and 1000 nm are chosen for medical applications which comprise soft tissue testing for malignant masses as applicable to breast tissue scans for example. The primary intention of our examinations was to rather quickly obtain clear 2 dimensional images with respect to the absorption and scattering properties than to determine the exact values of these parameters.
A light intensity modulation technique is employed to achieve imaging of the absorption and additionally even the scattering properties of better resolution than usual transillumination images of technical process monitoring. Since the understanding of photon migration in strongly scattering media has improved much lately, it is now possible to utilize inversion methods to solve for optical parameters out of a series of measurements. The discetisized volume of the probe and the modeling of the light propagation by the diffusion equation gives a linear system of equations which is solved by singular value decomposition.
We will present an approach of a diffuse optical tomography system using NIR wavelengths capable to image heterogenities in various kinds of turbid volumes, such as a wide rang of biological substances, many translucent technical substances like plastics, foams and fluids.