Development and initial results of a dual-modality SPECT/optical small animal imager

We have developed a dual-modality single photon (SPECT)/optical (OT) small animal tomographic device to image simultaneously and from identical projection angles in vivo distributions of bioluminescent/(near-infrared) fluorescent and radiolabeled markers. For the SPECT sub-system a compact gamma detector has been developed. A custom-made pinhole (PH) collimator suitable for attachment of reflective surfaces for concurrent optical imaging has been built. The collimator's reflective surfaces filter out optical photons from the multi-energetic photon flux. These photons are directed into a system of mirrors to compose an optical projection that is aligned with the angular field of view of the PH SPECT camera. For the optical detector sub-system a high resolution cooled CCD camera is used. In addition to initial small animal imaging studies several experimental phantom studies were performed with capillary tubes filled with various isotopes and optical markers to evaluate energy/wavelength/tissue dependent spatial resolution capabilities of the sub-systems.