The lofthole: A novel shaped pinhole geometry for optimal detector usage without multiplexing and without additional shielding

Multi-pinhole collimator based SPECT systems are nowadays used for pre-clinical and clinical imaging. Overlap of the different projections of the pinholes should generally be avoided. This can be done by either positioning the pinholes far from each other or by using additional shielding. The first method does not allow to use the detector area efficiently while the second method introduces additional cost, weight and design complexity. We investigate a new pinhole geometry, the lofthole, that has a circular aperture but whose entrance and/or exit opening is shaped by the desired irradiated detector area. The lofthole is designed using a ray-tracer and can be manufactured with traditional manufacturing techniques. A lofthole and two regular pinholes have been made in two tungsten-alloy plates. Production of these plates indicates that the manufacturing cost of a pinhole is roughly similar to the manufacturing cost of a lofthole. Measurements on the lofthole and pinhole plates show the rectangular projection of the lofthole versus the circular projection of the pinhole. Penetration measurements indicate that the lofthole has less penetration than a pinhole that irradiates the same detector area.