High scattering in biological tissues severely degrades the spatial resolution of optical fluorescence imaging in thick tissue. As one of the most sensitive in vivo molecular imaging modalities, Fluorescence Tomography plays an essential role in preclinical studies. To overcome the limitations of FT, we introduced a novel method termed, temperature modulated fluorescence tomography (TMFT). TMFT is based on two key elements: 1) temperature sensitive fluorescent agent (ThermoDots) and 2) high intensity focused ultrasound (HIFU). TMFT localizes the position of the fluorescent ThermoDots by scanning a HIFU beam across the tissue while monitoring the variation in the measured fluorescence signals. Actually, a binary mask is built by monitoring the sudden jumps in the fluorescence signal corresponding to the HIFU scan over a position containing ThermoDots. This binary map is used as functional a priori during the FT image reconstruction process. TMFT not only allowed us to resolve ThermoDots with high spatial resolution (~1.3 mm), deep in tissue (~ 60 mm) but with high quantitative accuracy as well (< 3% error). In this paper, we present the latest prototype of TMFT. Here, the fluorescence signals are acquired using a CCD camera, which increases the sensitivity of the system compared to the previous fiber-based system.
Although diffuse optical tomography (DOT) is able to obtain valuable functional information, its routine use in clinic is hampered by its poor spatial resolution and quantitative accuracy. Previously, our team introduced Photo-Magnetic Imaging (PMI) to overcome the limitation of DOT. PMI is a hybrid modality that synergistically utilizes optics and Magnetic Resonance Imaging (MRI). While illuminating the imaged medium by near-infrared laser, the induced internal temperature increase is measured using Magnetic Resonance Thermometry (MRT). Using these MRT maps, optical absorption maps at the laser's wavelength can be recovered using the dedicated PMI image reconstruction algorithm. In this paper, we present the result of the first validation simulation study of multi-wavelength PMI that utilizes five different laser wavelengths ranging between 760 and 980 nm. Using the high resolution wavelength specific absorption maps, PMI successfully recovered the concentration of three dyes, used as chromophore in the composition of our phantom, with high spatial resolution and quantitative accuracy. By providing functional information at high resolution, multi-wavelength PMI will be a valuable tool for monitoring tissue physiology, cancer detection and monitoring.