Assessment of Tryptophan Uptake and Kinetics Using 1-(2-¹⁸F-Fluoroethyl)-l-Tryptophan and α-¹¹C-Methyl-l-Tryptophan PET Imaging in Mice Implanted with Patient-Derived Brain Tumor Xenografts

Biodistribution of ¹⁸F-FETrp and ¹¹C-AMT between 30 and 60 min. Two coronal slices of 14-038 glioblastoma PDX mouse showing pancreas, gallbladder, and bladder in one plane with kidneys in other. Color scale bar represents SUV range for both tracers. (A) For ¹⁸F-FETrp, high uptake is observed in both bladder and pancreas, with lesser uptake in gallbladder. Minimal uptake is seen in kidneys. (B) For ¹¹C-AMT, tracer uptake is high in bladder and kidneys, with low uptake detected in pancreas and gallbladder.

Time-dependent SUV curves characterizing ¹⁸F-FETrp and ¹¹C-AMT tracers. Averaged SUVs for indicated organs (n = 5). Error bars represent SD. (A) ¹¹C-AMT tracer uptake is initially high in kidneys and undergoes washout to bladder, where activity increases with time. (B) ¹⁸F-FETrp tracer shows increasing uptake in bladder, followed by relatively constant retention in pancreas and intestines. For both tracers, brain displays slow but steady accumulation.

Comparison of tumoral tracer uptake between ¹⁸F-FETrp and ¹¹C-AMT in the 14-038 glioblastoma PDX mouse. Mouse was injected with ¹⁸F-FETrp, followed by ¹¹C-AMT 7 d later. (A) ¹⁸F-FETrp tracer (left) and ¹¹C-AMT tracer (right). ¹⁸F-FETrp shows increased tumoral tracer accumulation compared with ¹¹C-AMT. Color scale bar represents SUV range for both tracers. (B) Corresponding time–activity curves confirm higher tracer retention for ¹⁸F-FETrp.