Thesis (Ph.D.)--Tufts University, 2004. / Adviser: David A. Boas. Submitted to the Dept. of Electrical Engineering. Includes bibliographical references (leaves 407-416). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

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.

Optical imaging of soft biological tissues is highly desirable since it is nonionizing and provides sensitive contrast information which enables detection of physiological functions and abnormalities, including potentially early cancer detection. However, due to the diffusion of light, it is dificult to achieve simultaneously both good spatial resolution and good imaging depth with the pure optical imaging modalities. This work focuses on the ultrasound-modulated optical tomography - a hybrid technique which combines advantages of ultrasonic resolution and optical contrast. In this technique, focused ultrasound and optical radiation of high temporal co-herence are simultaneously applied to soft biological tissue, and the intensity of the ultrasound-modulated light is measured. This provides information about the optical properties of the tissue, spatially localized at the interaction region of the ultrasonic and electromagnetic waves. In experimental part of this work we present a novel implementation of high-resolution ultrasound-modulated optical tomography that, based on optical contrast, can image several millimeters deep into soft biological tissues. A long-cavity confocal Fabry-Perot interferometer was used to detect the ultrasound-modulated coherent light that traversed the scattering biological tissue. Using 15-MHz ultrasound, we imaged with high contrast light absorbing structures placed 3 mm below the surface of chicken breast tissue. The resolution along the axial and the lateral directions with respect to the ultrasound propagation direction was better than 70 and 120¹m, respectively. This technology is complementary to other imaging technologies, such as confocal microscopy and optical-coherence tomography, and has potential for broad biomedical applications. In the theoretical part we present various methods to model interaction be-tween the ultrasonic and electromagnetic waves in optically scattering media. We first extend the existing theoretical model based on the diffusing-wave spectroscopy approach to account for anisotropic optical scattering, Brownian motion, pulsed ul-trasound, and strong correlations between the ultrasound-induced optical phase in-crements. Based on the Bethe-Salpeter equation, we further develop a more general correlation transfer equation, and subsequently a correlation diffusion equation, for ultrasound-modulated multiply scattered light. We expect these equations to be applicable to a wide spectrum of conditions in the ultrasound-modulated optical tomography of soft biological tissues.

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Η οπτική τομογραφία διάχυσης είναι μια πρόσφατη μέθοδος απεικόνισης που χρησιμοποιεί φωτόνια κοντά στο φάσμα των υπερύθρων για τον υπολογισμό ορισμένων ιδιοτήτων των ιστών και η οποία ανακατασκευάζει τρισδιάστατες εικόνες βάση αυτών. Σε αυτή τη διπλωματική εργασία αναλύονται πρόσφατες μελέτες που έχουν πραγματοποιηθεί γύρω από τη νέα αυτή τεχνική, οι οποίες περιλαμβάνουν μια ιστορική αναδρομή στην εξέλιξή της, τις προσπάθειες μαθηματικής βελτίωσης των τεχνικών χαρακτηριστικών της, καθώς και πειραματικές εφαρμογές της στην παρακολούθηση εγκεφαλικών βλαβών σε νεογνό, στην ανταπόκριση μιας ασθενούς με καρκίνο του μαστού στη χημειοθεραπεία και στην πορεία ασθενών με ρευματοειδή αρθρίτιδα. Τα πορίσματα αυτής της εργασίας οδηγούν στο συμπέρασμα ότι σε μετέπειτα χρόνια μετά από βελτιώσεις στην τεχνολογία και στην επεξεργασία των σημάτων, η DOT θα αποδειχθεί μια χρήσιμη μέθοδος διάγνωσης και παρακολούθησης πολλών ασθενειών. / Diffuse optical tomography (DOT) is a recent imaging method which uses near-infrared photon emission in order to measure certain tissue properties, and processes them to reconstruct 3-D images. In this project, we analyze five studies on this method which include: a historic overview, the efforts of mathematical optimization of its technical features as well as some of the clinical trials using it, such as the observation of a neonate with brain lesions, the response of a breast-cancer patient to chemotherapy and the progress of patients suffering from rheumatoid arthritis. Based on this project’s conclusions, after several years and several improvements in its features and data-processing, DOT will prove to be a useful diagnostic and observational method for many illnesses.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 50-51). / xi, 51 leaves, bound ill. 29 cm

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 11, 2008) Includes bibliographical references.

Thesis (Ph. D.)--Northeastern University, 2008. / Title from title page (viewed May 21, 2009). Graduate School of Engineering, Dept. of Electrical and Computer Engineering. Includes bibliographical references (p. [138] - 156).

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.