Development of a pinhole collimator SPECT-CT system using a CdTe detector sample

Abstract

SPECT system with a co-registered x-ray CT image allows the fusion of functional information and morphologic information. In this study, a pinhole collimator SPECT system sharing a CdTe detector with a CT was designed. Geant4 application for tomographic emission (GATE) v.6 was used for the design simulation. Sensitivity and spatial resolution were measured to evaluate the system characteristics on an ideal condition. A pinhole collimator was designed to obtain high spatial resolution and better sensitivity. The diameter of the collimator was 0.5 mm, and the distance from the center of the field of view (CFOV) was set to 25 mm. The source to detector distance was set to 69 mm. The acquisition time of each projection was 40 seconds, and 60 projections were obtained for tomographic image acquisition. The reconstruction was performed using ordered subset expectation maximization (OS-EM) algorithms. The total system sensitivity was measured in cps/kBq, and the spatial resolution was defined by the full width at half maximum (FWHM) from the point spread function (PSF) of the point source image. Modulation transfer function (MTF) was also measured from the PSF. The spatial resolution of the system calculated from the FWHM of Gaussian fitted PSF curve was 0.48 mm, and the sensitivity of the system measured 0.354 cps/kBq from a Tc-99m point source. A phantom study was performed to verify the dual modality system design. The system will be built as designed, and it can be applied for the pre-clinical imaging system.