Jared Strydhorst1, Thomas Carlier2, Arnaud Dieudonné3, Maurizio Conti4, Irène Buvat1. 1. IMIV, U1023 Inserm/CEA/Université Paris-Sud and ERL 9218 CNRS, Université Paris-Saclay, CEA/SHFJ, Orsay 91401, France. 2. Department of Nuclear Medicine, Centre Hospitalier Universitaire de Nantes and CRCNA, Inserm U892, Nantes 44000, France. 3. Department of Nuclear Medicine, Hôpital Beaujon, HUPNVS, APHP and Inserm U1149, Clichy 92110, France. 4. Siemens Healthcare Molecular Imaging, Knoxville, Tennessee, 37932.
Abstract
PURPOSE: Accurate reconstruction of the dose delivered by 90Y microspheres using a postembolization PET scan would permit the establishment of more accurate dose-response relationships for treatment of hepatocellular carcinoma with 90Y. However, the quality of the PET data obtained is compromised by several factors, including poor count statistics and a very high random fraction. This work uses Monte Carlo simulations to investigate what impact factors other than low count statistics have on the quantification of 90Y PET. METHODS: PET acquisitions of two phantoms-a NEMA PET phantom and the NEMA IEC PET body phantom-containing either 90Y or 18F were simulated using gate. Simulated projections were created with subsets of the simulation data allowing the contributions of random, scatter, and LSO background to be independently evaluated. The simulated projections were reconstructed using the commercial software for the simulated scanner, and the quantitative accuracy of the reconstruction and the contrast recovery of the reconstructed images were evaluated. RESULTS: The quantitative accuracy of the 90Y reconstructions were not strongly influenced by the high random fraction present in the projection data, and the activity concentration was recovered to within 5% of the known value. The contrast recovery measured for simulated 90Y data was slightly poorer than that for simulated 18F data with similar count statistics. However, the degradation was not strongly linked to any particular factor. Using a more restricted energy range to reduce the random fraction in the projections had no significant effect. CONCLUSIONS: Simulations of 90Y PET confirm that quantitative 90Y is achievable with the same approach as that used for 18F, and that there is likely very little margin for improvement by attempting to model aspects unique to 90Y, such as the much higher random fraction or the presence of bremsstrahlung in the singles data.
PURPOSE: Accurate reconstruction of the dose delivered by 90Y microspheres using a postembolization PET scan would permit the establishment of more accurate dose-response relationships for treatment of hepatocellular carcinoma with 90Y. However, the quality of the PET data obtained is compromised by several factors, including poor count statistics and a very high random fraction. This work uses Monte Carlo simulations to investigate what impact factors other than low count statistics have on the quantification of 90Y PET. METHODS: PET acquisitions of two phantoms-a NEMA PET phantom and the NEMA IEC PET body phantom-containing either 90Y or 18F were simulated using gate. Simulated projections were created with subsets of the simulation data allowing the contributions of random, scatter, and LSO background to be independently evaluated. The simulated projections were reconstructed using the commercial software for the simulated scanner, and the quantitative accuracy of the reconstruction and the contrast recovery of the reconstructed images were evaluated. RESULTS: The quantitative accuracy of the 90Y reconstructions were not strongly influenced by the high random fraction present in the projection data, and the activity concentration was recovered to within 5% of the known value. The contrast recovery measured for simulated 90Y data was slightly poorer than that for simulated 18F data with similar count statistics. However, the degradation was not strongly linked to any particular factor. Using a more restricted energy range to reduce the random fraction in the projections had no significant effect. CONCLUSIONS: Simulations of 90Y PET confirm that quantitative 90Y is achievable with the same approach as that used for 18F, and that there is likely very little margin for improvement by attempting to model aspects unique to 90Y, such as the much higher random fraction or the presence of bremsstrahlung in the singles data.