Pinhole aperture design for /sup 131/I tumor imaging

A new pinhole aperture design for single photon imaging is introduced whose distinctive feature is a cylindrical channeled aperture. This allows greater attenuation near the pinhole aperture, which is especially important when imaging /sup 131/I with its medium and high energy emissions. The new design reduces to a conventional knife-edge aperture when the channel height is zero. Point source response functions were simulated for pinhole inserts with different pinhole diameters (0.4-2.0 mm diameter) and channel heights (0.1-3.0 mm) with acquisition parameters appropriate for /sup 131/I brain tumor imaging. A photon transport simulation code was used to comprehensively model photon transport and detection. Tradeoff curves between resolution and sensitivity suggest that varying pinhole diameter and channel height to achieve higher resolution at the expense of decreased sensitivity may be advantageous for imaging tumors with intratumoral administration of /sup 131/I radiolabeled monoclonal antibodies.