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
Sat Apr 20 09:13:53 MDT 2024