CCD-based temperature modulated fluorescence tomography

Abstract

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.