Reproducibility of tumor blood flow quantification with¹⁵O-water PET

Noninvasive methods for quantifying tumor blood flow (TBF) have a potentially important role in the field of drug development. ¹⁵O-water PET has been used in several studies aimed at monitoring response to novel treatments. Assessing the significance of changes in TBF requires knowledge of the reproducibility of the technique. This article quantifies the reproducibility of the ¹⁵O-water technique for TBF applications. Methods: A total of 43 pairs of replicate ¹⁵O-water studies were performed on 23 different patients with cancer. TBF was estimated using a standard, single-compartment model, and the replicate data were used to assess the reproducibility of the method. Results: The magnitude of the differences between replicate flow measurements was found to be proportional to their means. TBF was measured with a within-subject coefficient of variation of 13.4% and a repeatability of 37.1%. The volume of distribution was measured with a within-subject coefficient of variation of 8.6% and a repeatability of 24.0%. Conclusion: ¹⁵O-water PET can be used to measure TBF with a reproducibility that is consistent with other applications of the technique. The short half-life of the isotope permits multiple replicate studies to be performed during the same imaging session, allowing the reproducibility of the average flow estimate to be adapted to the required task. ¹⁵O-water PET is a powerful and robust tool for TBF quantification.