Dual modality planar PET/optical scanner for imaging of surgical margins in extracted tissue samples

We have developed a novel approach that allows for fast estimation of margins of extracted lesions. Dual modality planar optical/PET scanner consists of a pair of detector heads, suitable for imaging positron-emitting radioisotopes, a mechanical fixture to maintain constant separation between the two cameras, an optical camera that provides an anatomical map, a sliding table with an attached sample holder and a common mobile gantry that supports all of the system components. The two identical detector heads are based on a 4×4 array of Hamamatsu R5900-C-8 position-sensitive photomultiplier tubes (PSPMTs) with 4 strip anodes in each orthogonal dimension. Each tube has an active region of ∼1 inch square. The PSPMT array is coupled to a matrix of LGSO scintillating crystals; with each crystal measuring 3×3×10 mm. The active area of the PET subsystem is 10 cm square. Anode readout strips are interconnected to provide 8 read-out lines for each dimension of the detector head. Detector heads are read out by a custom-built 16-channel FPGA-based ADC. Online laminography reconstruction is performed over five parallel planes, separated by a selectable distance, and images from each plane can be directly exported into an ImageJ software package for overlay and further analysis. System calibration process is described. Results of imaging of several tissue simulating materials are presented. The ability of the proposed dual-modality scanner to detect lesions in warm background has been demonstrated. Although the proposed system will not eliminate the need for pathology analysis, it will help to reduce time in surgery by unveiling insufficient margins in the sample tissue. The system will be soon demonstrated and tested in a realistic clinical environment.