| Summary: | 碩士 === 國立陽明大學 === 生物醫學影像暨放射科學系暨研究所 === 98 === Objectives: 90Y-SIR-Spheres® are currently used in the treatment of solid liver tumors. However, they cannot be clearly imaged in vivo post injection. Gamma imaging with 99mTc-MAA is currently adopted to predict the distribution of 90Y-SIR-Spheres® in vivo. This study aims to develop a novel 68Ga/111In-SIR-Spheres® as PET/SPECT imaging surrogate for distribution assessment and radiation dose estimation of 90Y-SIR-Spheres®. The distribution pattern of 68Ga-SIR-Spheres® and 99mTc-MAA was also evaluated.
Methods: 68Ga/111In-SIR-Spheres® were prepared with high radiochemical yield and radiochemical purity (both >95%) after incubating 90Y-SIR-Spheres® with 68GaCl3 or 111InCl3. The in-vivo stability of 68Ga/111In-SIR-Spheres® was assessed based on the small animal PET/gamma imaging of normal SD rats after i.v. injection of radiotracers. The biodistribution study and PET/SPECT/CT imaging were performed in N1S1 hepatoma-bearing SD rats after intra-hepatic artery (i.a.) co-injection of 68Ga-SIR-Spheres® and 99mTc-MAA.
Results: 68Ga- and 111In-SIR-Spheres® has the same size distribution (30.1±6.0 μm), similar to that of 90Y-SIR-Spheres® (30.1±9.1μm), and both showed good in vivo stability (> 90% at 1 h and 80% at 78 h, respectively). The tumor-to-liver ratios determined in biodistribution studies of 68Ga-SIR-Spheres® and 99mTc-MAA showed only weak correlation (r2=0.35, n=8). Similar results were found for the tumor-to-lung ratio (r2=0.31, n=8) after i.a. co-injection of 68Ga-SIR-Spheres® and 99mTc-MAA. However, co-injection of 68Ga-SIR-Spheres® and 111In-SIR-Spheres® resulted in highly correlated particle distribution in tumor and liver with a r2 of 0.997 (tumor-to-liver ratio).
Conclusion: Significantly different distribution pattern between 68Ga-SIR-Spheres® and 99mTc-MAA (size distribution 26.6±18.2 μm) were observed, probably due to the difference in the size and the shape between radiolabeled SIR-Spheres® and 99mTc-MAA. Our study clearly indicated that 99mTc-MAA is not an ideal imaging surrogate of 90Y-SIR-Spheres® in the orthotopic hepatoma animal model.
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