The amount of carrier-added 2 requires careful calibration. On one-hand, we have shown that decreasing MA prevents blood oxidation of the aldehyde, maintaining a sufficient pool of the ALDH substrate. However, a low MA has the potential to block ALDH-mediated oxidation of [ 18 F]1 due to increased competition at the enzyme's active site. To test the effect of MA on SKOV3-TRip2 cell uptake, we incubated [ 18 F]2 with varying concentrations of non-radioactive 2. A decrease in MA proportionally decreased SKOV3-TRip2 [ 18 F]2 cell uptake. High radiotracer uptake, however, was still present with a MA of 0.11 GBq/µmol (Supplementary Fig. ).