Fabricación de microresina de ⁹⁹Mo de alta actividad para la adquisición de matrices de sistema de submilímetro SPECT

Single-photon emission computed tomography (SPECT) is a pivotal molecular imaging technology in preclinical studies. Modern high-resolution systems require accurate system matrices for high-quality image reconstruction. Among available strategies, experimentally measured pointsource system responses offer the most accurate calibration. 99m Tc is the predominant radionuclide in SPECT, and high-activity 99m Tc-adsorbed resin microspheres have been widely used for geometric calibration or small-FOV system-matrix acquisition. However, the short (6.02 hrs) halflife of 99m Tc restricts measurement duration, complicating the long acquisitions needed to complete system-matrix sampling in high-resolution SPECT.In this study, we propose a generator-producible hybrid ⁹⁹Mo/⁹⁹ᵐTc point source using ⁹⁹Moadsorbable resin microspheres to provide high activity with an effectively longer usable half-life for extended acquisitions. We adsorbed ⁹⁹Mo onto AG1-X8 resin microspheres (0.37-mm diameter), achieving activities exceeding 10 mCi per bead. To evaluate potential contamination from ⁹⁹Mo high-energy emissions, we performed Monte Carlo simulations on two sub-millimeter animal SPECT platforms: a conventional multi-pinhole system and a novel self-collimating SPECT.Comparative analyses of point-source projections at both the field-of-view center and edge showed negligible impact of ⁹⁹Mo-derived high-energy photons on ⁹⁹ᵐTc system-matrix measurements. The source strength was sufficient to support a 100×100×100 system-matrix acquisition. In summary, we introduce a practical method for accurate, reproducible system-matrix calibration in state-of-art SPECT, facilitating the development of high-resolution systems with consistent imaging performance.