sup 90^Y Bremsstrahlung Imaging for Absorbed-Dose Assessment in High-Dose Radioimmunotherapy

This feasibility study demonstrates ^sup 90^Y quantitative bremsstrahlung imaging of patients undergoing high-dose myeloablative ^sup 90^Y-ibritumomab treatment. Methods: The study includes pretherapy ^sup 111^In SPECT/CT and planar whole-body (WB) imaging at 7 d and therapy ^sup 90^Y SPECT/CT at 6 d and ^sup 90^Y WB imaging at 1 d. Time-activity curves and organ-absorbed doses derived from ^sup 90^Y SPECT images were compared with pretherapy ^sup 111^In estimates. Organ activities derived from ^sup 90^Y WB images at the first day were compared with corresponding pretherapy estimates. Results: Pretherapy ^sup 111^In images from 3 patients were similar to the ^sup 90^Y images. Differences between absorbed-dose estimates from pretherapy ^sup 111^In and ^sup 90^Y therapy were within 25%, except for the lungs. Corresponding activity differences derived from WB images were within 25%. Differences were ascribed to incomplete compensation methods and real differences in pharmacokinetics between pretherapy and therapy. Conclusion: Quantitative bremsstrahlung imaging to estimate organ activities and absorbed doses is feasible. [PUBLICATION ABSTRACT]