A Multi-Function Compact Small-Animal Imaging System Incorporating Multipinhole Standard and Helical SPECT and Parallel-Hole SPECT

A small-animal imaging system suitable for SPECT imaging and multipinhole standard/helical SPECT has been designed and constructed. Copper-beryllium parallel-hole collimators suitable for imaging the ~35 keV photons from the decay of ¹²⁵I have been built and installed to achieve better spatial resolution and to reduce imaging time on our dual-detector array. To further address the limitations in the resolution of parallel-hole SPECT and the sensitivity and limited field of view of single-pinhole SPECT, we have incorporated multipinhole circular/helical SPECT in addition to expanding parallel-hole SPECT capabilities. The pinhole SPECT system is based on a 110 mm circular detector equipped with pixellated NaI(Tl) scintillator (1 times 1 times 5 mm³/pixel). The helical trajectory is accomplished by two stepping motors controlling the rotation of the detector-support gantry and displacement of the animal bed along the axis of rotation of the gantry. Results obtained in SPECT studies of various phantoms show an enlarged field of view, enhanced resolution and improved sensitivity over our earlier results. In particular, improved reconstructed resolution is obtained with the helical pinhole SPECT. Pinhole collimators with one, three and five 1 mm diameter pinholes have been used in these tests. Spatial resolution of 1.26 mm, 1.43 mm and 1.55 mm have been obtained respectively with those collimators.