Contents I. Introduction
Pinhole cameras are widely used for small animal imaging [1], [2]. They offer a high spatial resolution that is necessary for small animal single photon emission computed tomography (SPECT) applications. Comparing with dedicated small animal PET, they also benefit from a wide range of readily available radiotracers and the use of longer-lived isotopes. However, the biggest disadvantage of small animal pinhole SPECT system is the very low detection efficiency. The use of multiple pinholes aperture has been studied as an alternative to the pinhole cameras to improve the detection sensitivity [3]–[5]. This leads to an improved raw sensitivity at the price of increased data multiplexing and reduced information content per detected photon. As a result, the multiple openings in apertures may sometimes lead to a worse signal to noise ratio in reconstructed images. In the context of three-dimensional (3-D) tomographic imaging applications, it is important to note that even a single pinhole aperture results in multiplexed data sets. Projections from different points in the object space to the detector space may be severely overlapped. Many studies have shown that the use of multiple pinhole apertures lead to improved imaging performances for certain tasks [6], [7]. The intention of this work is to develop and examine an analytical approach for quantifying system performances. This may serve as a step toward systematic optimization of multiple pinhole apertures.
