Fabrizia Bevilacqua

We report coregistration of near-infrared diffuse optical spectroscopy and magnetic resonance imaging for the study of animal model tumors. A combined broadband steady-state and frequency-domain apparatus was used to determine tissue oxyhemoglobin, deoxyhemoglobin, and water concentration locally in tumors. Simultaneous MRI coregistration provided structural and contrast-enhanced images of the tumor that were correlated with the optical measurements. By use of Monte Carlo simulations, the optically sampled volume was superimposed on the MR images, showing precisely which tissue structure was probed optically. DOS and MRI coregistration measurements were performed on seven rats over 20 days and were separated into three tumor tissue classifications: viable, edematous, and necrotic. A ratio of water concentration to total hemoglobin concentration, as measured optically, was performed for each tissue type and showed values for edematous tissue to be greater than viable tissue. Tissue hemoglobin oxygen saturation also showed a large variation between tissue types: viable tissue had an optically measured StO2 value of 61 ± 5%, whereas StO2 determined for necrotic tissue was 43 ± 6%. © 2003 Optical Society of America.

We present a combined near-infrared diffuse optical spectroscopy and Magnetic Resonance Imaging system for the study of animal model tumors. A combined broad-band steady-state and frequency domain optical spectroscopy apparatus was integrated with the MRI. The physiological properties of tissue rendered by MRI, including vascular volume fraction and water, were compared with chromophore concentrations as determined from the parameters obtained by optical measurements. DOS measurements provided oxyhemoglobin, deoxy-hemoglobin, and water concentration locally in tumors. A method for coregistration of the information obtained by both modalities was developed. Using Monte Carlo simulations, the optically sampled volume was superimposed on the MR images, illustrating which tissue structure was probed optically. Finally, two optical contrast agents, indocyanine green and methylene blue, were employed and their kinetics were measured by DOS system from different locations on the tumor and compared with Gd-DTPA enhancement maps obtained from MRI.

Presurgical chemotherapy is widely used in the treatment of locally advanced breast cancer. Monitoring the response to therapy can improve survival and reduce morbidity. We employ a noninvasive, near-infrared method based on diffuse optical spectroscopy to quantitatively monitor tumor response to neoadjuvant chemotherapy. DOS was used to monitor tumor response in one patient with locally advanced breast cancer throughout the course of her therapy. Measurements were performed prior to doxorubicin-cyclophosphamide therapy and at several time points over the course of three treatment cycles. Our results show strong tumor to normal tissue contrast in total hemoglobin concentration, water fraction, tissue hemoglobin oxygen saturation, S tO 2, and lipid fraction prior to treatment. Over a 10-week period, the peak total hemoglobin and water dropped 56 and 67%, respectively. Lipid content nearly returned to baseline while S tO 2 exceeded pretreatment levels. Approximately half of the hemoglobin and water changes occurred within 5 days of treatment. These data suggest that noninvasive, quantitative optical methods that characterize tumor physiology may be useful in assessing and optimizing individual response to neoadjuvant chemotherapy. © 2004 Society of Photo-Optical Instrumentation Engineers.

We introduce a novel and efficient method to provide solutions to inverse photon migration problems in heterogeneous turbid media. The method extracts derivative information from a single Monte Carlo simulation to permit the rapid determination of rates of change in the detected photon signal with respect to perturbations in background tissue optical properties. We then feed this derivative information to a nonlinear optimization algorithm to determine the optical properties of the tissue heterogeneity under examination. We demonstrate the use of this approach to solve rapidly a two-region inverse problem of photon migration in the transport regime, for which diffusion-approximation-based approaches are not applicable. © 2001 Optical Society of America.

Absorption and reduced scattering spectra of turbid media were quantified with a noncontact imaging approach based on a Fourier-transform interferometric imaging system. The FTIIS was used to collect hyperspectral images of the steady-state diffuse reflectance from turbid media. Spatially resolved reflectance data from Monte Carlo simulations were fitted to the recorded hyperspectral images to quantify ma and m9s spectra in the 550-850-nm region. A simple and effective calibration approach was introduced to account for the instrument response. With reflectance data that were close to and far from the source, μa and μ‘s of homogeneous, semi-infinite turbid phantoms with optical property ranges comparable with those of tissues were determined with an accuracy of ±7% and ±3%, respectively. Prediction accuracy for μa and μ‘s degraded to ±12% and ±4%, respectively, when only reflectance data close to the source were used. Results indicate that reflectance data close to and far from the source are necessary for optimal quantification of μa and μ‘s. The spectral properties of μa and μ‘s values were used to determine the concentrations of absorbers and scatterers, respectively. Absorber and scatterer concentrations of two-chromophore turbid media were determined with an accuracy of ±5% and ±3%, respectively. © 2000 Optical Society of America.