Radioembolization and the Dynamic Role of 90Y PET/CT

Abstract

Before the advent of tomographic imaging, it was postulated that decay of 90 Y to the 0+ excited state of 90Zr may result in emission of a positron–electron pair. While the branching ratio for pair-production is small (~32 × 10−6), PET has been successfully used to image 90 Y in numerous recent patients and phantom studies. 90 Y PET imaging has been performed on a variety of PET/CT systems, with and without time-of-flight (TOF) and/or resolution recovery capabilities as well as on both bismuth-germanate and lutetium yttrium orthosilicate (LYSO)-based scanners. On all systems, resolution and contrast superior to bremsstrahlung SPECT has been reported. The intrinsic radioactivity present in LYSO-based PET scanners is a potential limitation associated with accurate quantification of 90 Y. However, intrinsic radioactivity has been shown to have a negligible effect at the high activity concentrations common in 90 Y radioembolization. Accurate quantification is possible on a variety of PET scanner models, with or without TOF, although TOF improves accuracy at lower activity concentrations. Quantitative 90 Y PET images can be transformed into 3-dimensional (3D) maps of absorbed dose based on the premise that the 90 Y activity distribution does not change after infusion. This transformation has been accomplished in several ways, although the most common is with the use of 3D dose-point-kernel convolution. From a clinical standpoint, 90 Y PET provides a superior post-infusion evaluation of treatment technical success owing to its improved resolution. Absorbed dose maps generated from quantitative PET data can be used to predict treatment efficacy and manage patient follow-up. For patients who receive multiple treatments, this information can also be used to provide patient-specific treatment-planning for successive therapies, potentially improving response. The broad utilization of 90 Y PET has the potential to provide a wealth of dose–response information, which may lead to development of improved radioembolization treatment-planning models in the future.

Selective Internal Radiation Therapy: Quantifying Distal Penetration and Distribution of Resin and Glass Microspheres in a Surrogate Arterial Model

“…Kokabi et al (2) found significantly greater tumor uptake for 99m Tc-MAA doses than for glass 90 Y microspheres (1.4:1). Among other factors, particle size, density, and morphology have been identified as key factors in these differences (3,4).…”

Computational simulation of the predicted dosimetric impact of adjuvant yttrium-90 PET/CT-guided percutaneous ablation following radioembolization

“…Several studies [30, 31] have described changes in tumor volume and SUV in 18 FDG PET/CT when respiratory gating was used. However, investigation into the feasibility of respiratory gating in 90 Y PET/CT has been limited to a few examples [32, 33]. The usefulness of 90 Y PET respiratory gating may be limited by the small branching ratio of positron emission in 90 Y [34] and the clinical difficulty of increasing an already long acquisition time.…”

Réalisation d’une référence nationale pour les microsphères de 90Y utilisées en radiothérapie interne sélective

“…Comme c'est le cas pour l'ensemble des radiopharmaceutiques, les laboratoires nationaux de métrologie ont pour mission d'établir une traçabilité métrologique entre les références nationales et les utilisateurs tels que les services de médecine nucléaire [3]. L'intérêt de l'étude était également de répondre aux besoins d'une traçabi-lité métrologique en imagerie quantitative par tomographie, utilisée pour l'estimation de la biodistribution des microsphères marquées avec 90 Y après injection théra-peutique [4] pour le développement d'une dosimétrie personnalisée [5], et d'aller vers une meilleure connaissance de la relation dose-effet thérapeutique.…”