Low-dose : a phantom study to assess the feasibility of pretherapy imaging to plan the therapeutic dose90: a phantom study to assess the feasibility of pretherapy imaging to plan the therapeutic doseY PET/CT imaging optimized for lesion detectability and quantitative accuracy: a phantom study to assess the feasibility of pretherapy imaging to plan the therapeutic dose

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Abstract

Objective

The overall aim of this work is to optimize the reconstruction parameters for low-dose yttrium-90 (90Y) PET/CT imaging, and to determine 90Y minimum detectable activity, in an endeavor to investigate the feasibility of performing low-dose 90Y imaging in-vivo to plan the therapeutic dose in radioembolization.

Materials and methods

This study was carried out using a Siemens Biograph 6 True Point PET/CT scanner. A Jaszczak phantom containing five hot syringes was imaged serially over 15 days. For 128 reconstruction parameters/algorithms, detectability performance and quantitative accuracy were evaluated using the contrast-to-noise ratio and the recovery coefficient, respectively.

Results

For activity concentrations greater than 2.5 MBq/ml, the linearity of the scanner was confirmed while the corresponding relative error was below 10%. Reconstructions with smaller numbers of iterations and smoother filters led to higher detectability performance, irrespective of the activity concentration and lesion size. In this study, the minimum detectable activity was found to be 3.28±10% MBq/ml using the optimized reconstruction parameters. Although the recovered activities were generally underestimated, for lesions with activity concentration greater than 4 MBq/ml, the amount of underestimation is limited to −15% for optimized reconstructions.

Conclusion

90Y PET/CT imaging, even with a low activity concentration, is feasible for depicting the distribution of 90Y implanted microspheres using optimized reconstruction parameters. As such, in-vivo PET/CT imaging of low-dose 90Y in the pretherapeutic stage may be feasible and fruitful to optimally plan the therapeutic activity delivered to patients undergoing radioembolization.

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