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Adaptive finite element methods for fluorescence enhanced optical tomography

Fluorescence enhanced optical tomography is a promising molecular imaging
modality which employs a near infrared fluorescent molecule as an imaging agent
and time-dependent measurements of fluorescent light propagation and generation.
In this dissertation a novel fluorescence tomography algorithm is proposed to reconstruct
images of targets contrasted by fluorescence within the tissues from boundary
fluorescence emission measurements. An adaptive finite element based reconstruction
algorithm for high resolution, fluorescence tomography was developed and validated
with non-contact, planewave frequency-domain fluorescence measurements on
a tissue phantom. The image reconstruction problem was posed as an optimization
problem in which the fluorescence optical property map which minimized the
difference between the experimentally observed boundary fluorescence and that predicted
from the diffusion model was sought. A regularized Gauss-Newton algorithm
was derived and dual adaptive meshes were employed for solution of coupled photon
diffusion equations and for updating the fluorescence optical property map in
the tissue phantom. The algorithm was developed in a continuous function space
setting in a mesh independent manner. This allowed the meshes to adapt during
the tomography process to yield high resolution images of fluorescent targets and to accurately simulate the light propagation in tissue phantoms from area-illumination.
Frequency-domain fluorescence data collected at the illumination surface was used
for reconstructing the fluorescence yield distribution in a 512 cm3, tissue phantom
filled with 1% Liposyn solution. Fluorescent targets containing 1 micro-molar Indocyanine
Green solution in 1% Liposyn and were suspended at the depths of up to 2cm
from the illumination surface. Fluorescence measurements at the illumination surface
were acquired by a gain-modulated image intensified CCD camera system outfitted
with holographic band rejection and optical band pass filters. Excitation light at
the phantom surface source was quantified by utilizing cross polarizers. Rayleigh
resolution studies to determine the minimum detectable sepatation of two embedded
fluorescent targets was attempted and in the absence of measurement noise, resolution
down to the transport limit of 1mm was attained. The results of this work
demonstrate the feasibility of high-resolution, molecular tomography in clinic with
rapid non-contact area measurements.

Identiferoai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4419
Date30 October 2006
CreatorsJoshi, Amit
ContributorsSevick-Muraca, Eva M.
PublisherTexas A&M University
Source SetsTexas A and M University
Languageen_US
Detected LanguageEnglish
TypeBook, Thesis, Electronic Dissertation, text
Format4850217 bytes, electronic, application/pdf, born digital

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