An innovative dual-modality 3D fluorescence/3D ultrasound tomography system was demonstrated in this research. The system includes an electron-multiplying charge-coupled device (EMCCD), a 660 nm wavelength fiber-coupling laser, and a 10-15 MHz frequency customized single-element ultrasound transducer on a 3D rotating scanning device. We combined multiple ultrasound images from different sections to obtain a whole-body 3D mesh of mice, which provide anatomical information. In this study, we demonstrated the accuracy of this system through a 4T1 tumor-bearing nude mice experiment.
We demonstrate dual modality of free-space fluorescence diffuse optical tomography (FDOT) and handheld ultrasound (US) imaging to reveal both functional and structural information in small animals. FDOT is a noninvasive method for examining the fluorophore inside an object from the light distribution of the surface. In FDOT, a 660-nm continuous wave diode laser was used as an excitation source and an electron-multiplying charge-coupled device (EMCCD) was used for fluorescence data acquisition. Both the laser and EMCCD were mounted on a 360-deg rotation gantry for the transmission optical data collection. The structural information is obtained from a 6- to 17-MHz handheld US linear transducer by single-side access and conducts in the reconstruction as soft priors. The rotation ranges from 0 deg to 360 deg; different rotation degrees, object positions, and parameters were determined for comparison. Both phantom and tissue phantom results demonstrate that fluorophore distribution can be recovered accurately and quantitatively using this imaging system. Finally, an animal study confirms that the system can extract a dual-modality image, validating its feasibility for further in vivo experiments. In all experiments, the error and standard deviation decrease as the rotation degree is increased and the error was reduced to 10% when the rotation degree was increased over 135 deg.