Amit Joshi, Wolfgang Bangerth, Alan B. Thompson, Eva Sevick-Muraca
Experimental fluorescence optical tomography using adaptive finite elements and planar illumination with modulated excitation light.
Progress in Biomedical Optics and Imaging, vol. 6 (2005), pp. 351-358.

Fluorescence enhanced optical tomography is rapidly advancing as a research tool for investigating molecular tissue environments in vivo as well as a molecular medical imaging tool. Owing to the scattering nature of near infrared radiation in tissue, iterative tomography approaches must employ the coupled diffusion equations for three-dimensional recovery of fluorescent properties from tissue boundary measurements. Unfortunately, the inverse problem suffers from computational inefficiency and ill-posed ness. Furthermore, the resolution attained in fluorescence tomography is limited by a priori fixed discretization of finite element/finite difference schemes used. These difficulties can be ameliorated by employing adaptive discretization strategies. To date, the efficacy of adaptive mesh refinement techniques has yet to be demonstrated in clinically relevant medical imaging situations. In this contribution we present a novel fluorescence tomography scheme which employs dual adaptive finite element meshes for three dimensional reconstructions of fluorescent targets beneath the simulated tissue surface. We demonstrate the tomographic reconstruction from actual experimental data. Frequency domain fluorescence data collected at the illumination surface was used for reconstructing the fluorescence yield distribution in an 8cm x 8cm x 8cm cubical tissue phantom filled with 1% Liposyn solution. Fluorescent targets contained 1 micro-molar Indocyanine Green solution. The tissue phantom was illuminated at the top surface by an expanded 785nm laser modulated at 100 MHz. Fluorescence measurements at the illumination surface were taken by an image intensified CCD camera system outfitted with holographic band rejection and optical band pass filters. Excitation source was quantified by utilizing cross polarizers. Adaptive mesh refinement allows efficient reconstructions for buried fluorescent targets. Image reconstructions for 1cm3 fluorescent target placed at the depth of 1cm from the illumination surface are presented for the perfect and imperfect (100:1) uptake of the fluorescent contrast agent.



Wolfgang Bangerth
Sun Aug 20 15:19:54 MDT 2017