A polycapillary x-ray optics-based integrated micro-SPECT/CT scanner

To show the feasibility of a combined micro-CT and micro-SPECT scanner based on use of polycapillary optics we inserted an optic between the radio-labeled specimen and our micro-CT scanner's imaging system. The micro-CT x-ray focal spot was placed at the focal point of the optic so that x-ray micro-CT of the specimen could also be performed without having to move the specimen. Using this set-up we scanned a 2 cm diameter Plexiglas cylinder with three (177 μCi) prostate brachytherapy seeds embedded in it. Each seed was 0.5 mm diameter, 4 mm long and filled with 0.4 mm diameter ceramic beads coated with ¹²⁵Iodine. The SPECT images clearly resolve the layer of ¹²⁵Iodine on the beads. That the SPECT image is spatially correct was confirmed by the concurrent CT image. We also used a parallel polycapillary optic to scan a 1.5cm Plexiglas cylinder with holes (2, 1, and 0.5 mm diameter, parallel to the cylinder axis) filled with a solution containing 11.56μCi/mm³ of ¹²⁵Iodine. These data indicate a spatial resolution of 5 line pairs per mm at 10% modulation. Based on these results we propose a design that is more efficient at acquiring the scintigraphic image data.