Coded Aperture Imaging is a technique originally developed for X-ray astronomy where typical imaging problems are characterized by far-field geometry and an object made of point sources distributed over a mainly dark background. These conditions provide, respectively, the basis of artifact-free and high Signal-to-Noise Ratio (SNR) imaging.

When the coded apertures successful in far-field problems are used in near-field geometry, images are affected by extensive artifacts. The classic remedy is to move away from the object until far-field geometry is restored, but this is at the expense of counting efficiency and, thus, of the SNR of the images. This seminar will address how the application to near-field of a technique originally developed to mitigate the effects of non-uniform background in far-field applications results in a considerable reduction of near-field artifacts. This result opens the way to the exploitation in near-field problems of the favorable SNR characteristics of coded apertures: images comparable to those provided by state-of-the-art imagers can be obtained in a shorter time or with a lower dose.

Further developments follow when the SNR increase is traded for better resolution at constant time and dose. The main focus will be on a coded aperture camera specifically designed for high-resolution single-photon planar imaging with a pre-existing gamma (Anger) camera. Original theoretical findings and the results of computer simulations led to an optimal coded aperture that was tested experimentally in phantom as well as in-vivo studies. Results include, but are not limited to, 1.66-mm-resolution images of 99mTc-labeled blood and bone agents in a mouse.

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