Fluorescence Tomographic Imaging Using a Hand-Held Optical Imager: Extensive Phantom Studies

Abstract

Hand-held probe based optical imager has become popular towards breast imaging for its potential portability and maximum patient comfort (no compression involved), but are currently limited on three-dimensional (3-D) tumor localization. A novel hand-held probe based optical imager with unique source and detector set-up was recently developed in our laboratory towards tomographic breast imaging. With 3-D fluorescence tomography feasibility of this novel optical imager demonstrated in previous studies, extensive phantom studies under various conditions were performed to assess current system limitation on 3-D tumor/target recovery. The phantom studies have been performed on slab geometries (650 ml) under different target depths (1-2.5 cm), target volumes (0.45, 0.23 and 0.10 cc), fluorescence absorption contrast ratios (1:0, 1000:1 to 5:1), and number of targets (up to 3), using Indocyanine Green (ICG) as the fluorescence contrast agent. The fluorescence optical measurements acquired on phantom surface were applied towards an Approximate Extended Kalman Filter (AEKF) algorithm for 3-D mapping of fluorescence absorption coefficient over entire phantom volume. In most cases, the target was successfully reconstructed. Currently, the limitations in terms of resolution, depth, and volume recovery of the embedded target are assessed. Upon further experimental validation based on in-vitro and in-vivo studies, the clinical translation of this technology is promising.