90Y microsphere therapy: does 90Y PET/CT imaging obviate the need for 90Y Bremsstrahlung SPECT/CT imaging?

BackgroundTransarterial radioembolization using Y-90 microspheres is a novel therapeutic option for inoperable hepatic malignancies. As these spheres are radiolucent, real-time assessment of their distribution during the infusion process under fluoroscopic guidance is not possible. Bremsstrahlung radiations arising from Y-90 have conventionally been used for imaging its biodistribution. Recent studies have proved that sources of Y-90 also emit positrons, which can further be used for PET/computed tomography (CT) imaging. This study aimed to assess the feasibility of Y-90 PET/CT imaging in evaluating microsphere distributions and to compare its findings with those of Bremsstrahlung imaging.Materials and methodsThirty-five sessions of Y-90 microsphere transarterial radioembolization were performed on 30 patients with hepatic malignancies. Y-90 PET/CT imaging was performed within 3 h of therapy. Bremsstrahlung imaging was also performed for each patient. The imaging findings were compared for concordance in the distribution of microspheres.ResultsExact one-to-one correspondence between Y-90 PET/CT imaging and Y-90 Bremsstrahlung imaging was observed in 97.14% of cases (i.e. in 34/35 cases). Discordance was observed only in one case in which Y-90 PET/CT imaging resolved the microsphere uptake in the inferior vena cava tumor thrombus, which was, however, not visualized on Bremsstrahlung imaging.ConclusionThere is good concordance in the imaging findings of Y-90 PET/CT and Y-90 Bremsstrahlung imaging. Y-90 PET/CT imaging scores over the conventionally used Bremsstrahlung imaging in terms of better resolution, ease of technique, and comparable image acquisition time. This makes it a preferred imaging modality for assessment of the distribution of Y-90 microspheres. (C) 2013 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.