90Y bremsstrahlung imaging for absorbed-dose assessment in high-dose radioimmunotherapy

Abstract

This feasibility study demonstrates 90Y quantitative bremsstrahlung imaging of patients undergoing high-dose myeloablative 90Y-ibritumomab treatment. Methods: The study includes pretherapy 111In SPECT/CT and planar whole-body (WB) imaging at 7 d and therapy 90Y SPECT/CT at 6 d and 90Y WB imaging at 1 d. Time-activity curves and organ-absorbed doses derived from 90Y SPECT images were compared with pretherapy 111In estimates. Organ activities derived from 90Y WB images at the first day were compared with corresponding pretherapy estimates. Results: Pretherapy 111In images from 3 patients were similar to the 90Y images. Differences between absorbed-dose estimates from pretherapy 111In and 90Y 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. Copyright © 2010 by the Society of Nuclear Medicine, Inc.