On the performance of two multi-pinhole SPECT systems for small animal research

Molecular imaging calls for imaging systems with both high resolution and high sensitivity. In small-animal SPECT high resolution is typically achieved using pinhole collimation. In order to improve the sensitivity of single-pinhole systems we employ a novel collimation approach called multi-pinhole imaging. This imaging technique extends conventional single-pinhole collimation through the addition of pinholes on each collimator. An important feature of multi-pinhole imaging is the overlap of projections on the detector. This overlap results in a more efficient coverage of the detector and thus a considerable increase in sensitivity. In this contribution we report on the performance of two multi-pinhole imaging systems: a dual-headed Siemens ECAM and a triple-headed Trionix TRIAD. The big-headed ECAM being upgraded with two 10-pinhole collimators, while the medium-sized detectors of the TRIAD were equipped with three 7-pinhole apertures. Image reconstruction is performed using a dedicated OSEM algorithm. Both systems are characterized by a series of phantom measurements and tested on numerous animal studies. We will show that both systems yield excellent image quality with a reconstructed resolution of 1.2 mm and a sensitivity of up to 1600 cps/MBq. In addition to regular semi-quantitative single-isotope studies, we will present data on dual-isotope imaging, absolute tracer quantification and the fusion of the SPECT images with MR data of the same animal