The goal of the unit is to devise new approaches for noninvasive, quantitative optical spectroscopic and tomographic imaging of deep tissue structures for clinical screening and monitoring of physiological parameters. To achieve this goal, the laboratory has undertaken a multifaceted theoretical, computational, experimental, and clinical research program. These areas of inquiry include time-resolved transillumination of thick tissue applied to quantitative spectroscopy of breast tumors; the use of specific fluorescent markers (e.g., ligands) for identifying molecular biology of disease processes applied to noninvasive biopsy of Sjøgren's syndrome; and lymphatic imaging for sentinel node detection. We are involved in several clinical studies, including an NCI protocol to use oblique angle reflectometry for noninvasive monitoring of inflammation in the oral cavity, an NIDCR/NINDS clinical study to evaluate the drug response of patients experiencing complex regional pain syndrome, and another NCI-sponsored clinical trial to evaluate the effectiveness of anti-angiogenesis drug treatment for Kaposi's sarcoma.

Time-Resolved Tomography of Thick Tissue
Chernomordik, Hattery, Rinneberg ^a Zaccanti,^b Gandjbakhche
In collaboration with researchers at the PTB of Berlin, who have provided in vivo measurements on human breast, we used random walk methodology that we developed to quantify optical properties of breast tumors (invasive ductal carcinoma). By using time-domain scanning mammography developed by the Berlin group, we performed data analysis on distributions of times of flight for photons transmitted through the breast in vivo at 670 and 785 nm. The size of the tumors, their optical properties, and those of the surrounding tissue were reconstructed at both wave lengths. The tumors showed increased absorption and scattering. From the absorption coefficients at both wave lengths, blood oxygen saturation was estimated for the tumors and the surrounding tissue. We found that both tumors were hypoxic. Whether this is true generally for the particular tumor type (invasive ductal carcinoma) cannot be deduced at this time because of limited data. Furthermore, in both tumors, relative blood volume was found to be increased by about a factor of two in comparison with surrounding tissue, which could be explained by increased vascularization.

3D Reconstruction of Localized in Vivo Fluorescence
Chernomordik, Hattery, Gannot I, Gannot G, Gandjbakhche
The development of specific fluorescently labeled cell surface markers has opened the possibility of specific and quantitative noninvasive diagnosis of tissue changes. We are pursuing the development of a fluorescence scanning imaging system that can perform a "noninvasive optical biopsy" of Sjøgren's syndrome (SS) that can replace the currently used histological biopsy. We are also developing and using IR-dependent fluorescent detection methods to determine the position of sentinel node(s) in the lymphatic system of cancer patients to replace currently used detection by radioactive particles. Analysis of different phantom data and ex vivo tissue confirms potential of the random walk-based theoretical approach to reconstruct with good accuracy 3D positions of deeply embedded fluorophores.

Oblique Angle Reflectometry for Noninvasive Monitoring of Inflammation: Application to Chemopreventative Drugs
Hattery, Hekmat, Mulshine,^c Gandjbakhche
Inflammatory cell populations produce cytokines that can specifically stimulate growth of evolving cancer clones. Since the normal epithelium shares many biological properties with cancer cells, it also responds to the chronic presence of mitogenically active cytokines by accelerated growth (hyperplasia); normal cell hyperplasia provides a measure of the promotional environment of a cancer clone. At NCI, a Phase II trial is under way to determine the effectiveness of cyclooxygenase (COX) inhibitor on oral leukoplakia. The effectiveness will be monitored by surgical biopsy with its associated complications. To monitor patient response less invasively, we have developed a quantitative epithelial inflammation measuring device that may be used to evaluate the general state of the oral mucosa and to monitor the effectiveness of chemopreventative treatment regimes. The device measures diffuse reflectance from a low-power optical wave-length source that inserts photons into the tissue at specific angles. As the angle of insertion becomes parallel to the epithelial surface, the mean penetration of the photons becomes smaller, and the photons spend more time in the epithelial layer. Wave lengths of interest are those with high tissue absorption, thus limiting detected photons to those with few scattering events. This confines to the surface layers the tissue volume that has been interrogated, which, from a theoretical point of view, permits the use of integral equations to describe photon migration in a two-layer tissue model. We performed several experiments using acrylamide gel phantoms with high absorption and covered with a thin liquid layer simulating the epithelial layer of tissue. We compared the data with theoretical predictions. Ten sets of data from five patients and two controls were collected and analyzed by using our theoretical model. Initial results indicate that the model is effective in measuring the level of inflammation in patients.

Laser Doppler Blood Flow Measurements and Thermography for Monitoring Angiogenesis in Kaposi's Sarcoma and Complex Regional Pain Syndrome, Type I
Hattery, Hekmat, Paollela, Gelderman, Besharatian, Yarchoan,^d Dionne,^e Gandjbakhche
Kaposi's sarcoma is a highly vascular skin disease for which there is an NCI-sponsored clinical trial to evaluate the effectiveness of anti-angiogenesis drug treatment. A direct measure of reduction of blood flow is desired. Thus, we are acquiring blood flow images by using laser Doppler measurements at two wave lengths, 690nm and 780nm. The probes are used to sample slightly different tissue volumes, with the near-infrared sampling a larger volume. The measurements have been compared with thermography images to look for corresponding changes in skin temperature. For this study, we acquired 20 sets of data from 12 patients who are imaged at the start of treatment, at 18-week intervals during treatment, and at the end of treatment. Initial results indicate a variety of tissue responses depending on location in and near the tumor.

Another collaboration involves an NIDCR/NINDS clinical study to evaluate the response of patients experiencing complex regional pain syndrome, type I, to the drug Neurotropin. The patients generally experience pain near the tissue surface, which is accessible to both laser Doppler blood flow and thermography. In addition to static masurements, patient blood-flow response to neurostimuli (such as the sympathetic neural response to cold water immersion) is being imaged. Patients are seen at the start of treatment, at the midpoint of the study, and at the end of treatment.