TABLE 2

Sequential Quantitative PET Data

Organ activity (kBq/mL)
Liver/thyroid*BrainYolk
TracerDay of incubationInjected activity (MBq)Time between injection and acquisitionScan durationMaxMeanMaxMeanMaxMean
18F-FDG2730.328 min10 min160.4133.4151.0136.300
2836.729 min10 min163.8139.4155.3140.30.20.1
2940.130 min10 min178.8159.1159.8136.200
3234.830 min10 min5,225.3729.60000
124I-NaI290.992 h10 min4.32.01.10.50.010
300.9920 h10 min3.01.40.60.20.60.1
310.9944 h10 min7.92.40.40.20.90.2
330.9996 h10 min10.96.20.20.11.60.4
  • * Data are liver for 18F-FDG and thyroid for 124I-NaI.

  • Mean data are for 1.5-mL spheric volume of interest for 18F-FDG in liver, 1.0-mL spheric volume of interest for 18F-FDG and 124I-NaI in brain, 5.0-mL spheric volume of interest for 18F-FDG and 124I-NaI in yolk, and isocontour volume of interest (threshold, 35% of maximum activity) for 124I-NaI in thyroid.

  • Sequential 18F-FDG PET/CT with 4 injections of 18F-FDG on different days produces homogeneous results for representative volumes of interest in first 3 studies. Fourth study, without brain uptake, is associated with embryo’s death between days 29 and 32 of incubation. High liver uptake is attributable to adjacent blood-pool activity in heart and thus represents artifact. Sequential 124I-NaI PET/CT with 1 injection of NaI and 4 scans on different days produces increasing thyroid activity over time, attributable to continuous iodine trapping within thyroid. Gradually decreasing brain activity is presumably due to reduction of blood-pool activity over time. Increasing yolk activity over time is most likely attributable to unspecific tracer distribution and partial excretion within this compartment.