Comparison of PMT-based TF64 and SiPM-based Vereos PET/CT systems for Y imaging and dosimetry optimization: A quantitative study.

Background: Selective internal radiotherapy based on transarterial radioembolization (TARE) with yttrium-90 ( Y) microspheres is an established treatment for primary or metastatic liver disease.

Purpose: The objective of this work is to optimize the dosimetry of patients treated with Y TARE, using positron emission tomography (PET) images.

Methods: The NEMA 2012 PET phantom was filled with nearly 3.9 GBq of Y activity and acquired at days 0, 3, 5, 7, and 9 on a classic time-of-flight PET/computed tomography (CT) scanner (Philips TF64) and on a silicon photomultiplier (SiPM)-based PET/CT scanner (Philips Vereos). Acquisitions were carried on following the guidelines proposed in a previously published multicentric trial and images were reconstructed by varying and combining the available parameters. Comparisons were performed to identify the best set(s) of parameters leading to the most accurate Y-PET image(s), in terms of activity distribution. Then, for both scanners, the best images were analyzed with Simplicit Y, a personalized dosimetry software using multicompartmental Medical Internal Radiation Dose model. The comparison between measured and true doses allowed to identify the image granting the most consistent dose estimations and, therefore, to designate the set of parameters to be applied on patients' data for the reconstruction of optimized clinical images. Posttreatment dosimetry of four patients was then realized with Simplicit Y using optimized imaging datasets.

Results: Based on activity distribution comparisons and dose estimations over phantom and patients data, the SiPM-based PET/CT system appeared more suitable than the photomultiplier tube-based TF64 for Y-PET imaging. With the SiPM-based PET/CT system, reconstructed images with a 2-mm voxel size combined with the application of the point spread function correction led to the most accurate results for quantitative Y measures.

Conclusions: For the SiPM-based PET/CT scanner, an optimized set of reconstruction parameters has been identified and applied on patients' data in order to generate the most accurate image to be used for an improved personalized Y-PET dosimetry, ensuring a reliable evaluation of the delivered doses.