Super Spatial Resolution (SSR) method for small animal SPECT imaging: A Monte Carlo study

Abstract

This work used Monte Carlo (MC) simulations in order to investigate the feasibility of the application of a super-resolution method, namely Super Spatial Resolution (SSR), to a preclinical SPECT system. The SSR method is used to obtain a resolution enhancement by combining several images containing slightly different perspectives of the same scene.MC simulations are a useful tool in the development of new imaging devices, as well as in the assessment of new reconstruction methods. In this respect, GATE (Geant4 Application for Emission Tomography) is an open source platform dedicated to numerical MC simulations that has become a well validated toolkit for the simulation of SPECT and PET systems.We modelled a four-headed preclinical SPECT scanner capable of the proper movements in order to obtain the SSR acquisition sequences. Each detector is based on a CsI(Tl) pixelated scintillator coupled to a low-energy tungsten collimator with parallel square holes.Several phantoms and radioactive sources were simulated, in order to assess the performance of the proposed SPECT scanner. In addition, a complex voxelized phantom of a mouse was used to obtain realistic images with the aim of evaluating the system as a suitable tool for small animal imaging.The whole system sensitivity was 164.1 cps/MBq. In order to assess the impact of the SSR this value must be divided by the number of the images acquired to perform this method. The average value of the trans-axial resolution improves from 2.4 mm to 1.54 mm, 1.21 mm and 1.03 mm by respectively applying the SSR based on two, three or four images. While the average axial resolution changes from 1.69 mm to 1.49 mm, 1.15 mm and 0.98 mm by respectively using the SSR based on two, three or four images. The mouse images obtained by using the voxel phantom have demonstrated the good capability of the system as a suitable tool for small animal imaging.Finally, a comparison with commercial preclinical scanners has proved that the presented SSR scanner provides an alternative to pinhole SPECT systems for many preclinical research studies.