Haoyang Yu

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.

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.