High resolution 4-head pinhole SPECT system for small animal studies

We describe a newly developed ultra-high resolution SPECT system using four pinhole collimators for small animal studies. Methods:Thesystemutilizesa clinicalfour-headSPECTscan ner with Specially designed pinhole collimators. Four types of pinholes with different configurations were designed with differ ant effective aperture sizes (1.0, 2.0 and 4.0 mm) and rotating radii (40 mm and 50 mm). The distance from the axis of rotation to the scintillatorwas fixed to 180 mm. A fltteredbackprojection algorithm was used to reconstruct SPECT images after fan beam-to-parallel-beam data conversion. Results The system provided a reconstructed spatial resolution of 1.65 mm (FWHM) and sensitivity of 4.3 kcps/@tCVmlwith the best type of pinholes, respectively. The @rc-HMPAOSPECT image in rat studies clearly visualized small brain structures, and the left ventricular myocardium and cardiac cavity were clearly separated with @Tc-MlBl. IYynamic SPECT imaging of rat brain with r23oiom@enilwas also feasible.Conclusion:This uttra-high resolution SPECT system can be used to measure the regional distribution of radiolabeled tracers in small animals in vn,o and may play a significantrole in the development of new radio pharmaceuticals and in studies of various disease models using living animals.