Development and Initial Results of a Tomographic Dual-Modality Positron/Optical Small Animal Imager

A novel concept for integrating PET and optical detection devices in a single instrument is presented. It is intended for simultaneous tomographic imaging of positron-labeled and optical probes in vivo. The optical imaging units consist of a microlens array (MLA) defining the field-of-view, a large area CMOS chip for light detection, and a transferable filter for excitation light blocking. The CMOS sensor array is positioned at the focal plane of the MLA. In a final design proposal optimized for fully tomographic mouse imaging the optical detector size is chosen to be 8.2 mm (transaxially) x 82.0 mm (axially) and has an effective thickness of 3.0 mm. A multitude of such ultra-thin detectors is allocated orthogonally with respect to the imaged object´s long axis for tomographic whole body data acquisition of small animals (mice). PET detector blocks are located in radial extension to the optical detectors and mounted on a common rotatable gantry. Laser(s) used for probe excitation are positioned at radial extension behind the PET rings and are translatable along the axis of rotation allowing for arbitrary probe excitation and improved spatial sampling, particularly of the optical system. Both, the optical detector arrangement as well as the PET detectors are mounted so that excitation light can be introduced through the gaps between individual blocks. An experimental setup has been assembled in our laboratory and phantom data were acquired.