Summary

Current [F-18]-fluorodeoxyglucose positron emission tomography (FDG-PET) procedures in tumor-bearing mice typically includes fasting, anesthesia, and standardized uptake value (SUV)-based quantification. Such procedures may be inappropriate for prolonged multiscan experiments. The working hypothesis was that normalization of tumor FDG retention relative to a suitable reference tissue may improve accuracy as this method may be less susceptible to uncontrollable day-to-day changes in blood glucose levels, physical activity, or unnoticed imperfect tail vein injections.

Conclusions

Multimodality scanners allow tissue delineation and normalization of tumor FDG uptake relative to reference tissues. Normalization to brain, but not liver or kidney, improved scan reproducibility considerably and was superior to traditional SUV quantification in i.v. tracer-injected animals. Day-to-day variability in SUV’s was lower in i.p. than in i.v. injected animals, and i.p. injections may therefore be a valuable alternative in prolonged rodent studies, where repeated vein injections are undesirable.

Results from the nanoScan PET/MRI 1T

• tumor FDG retention is quantified relative to brain signal, rather than to ID and body weight (SUV) in i.v. tracer administered mice
• SUV quantification showed less day-to-day variability in mice administered FDG i.p. than in i.v. injected animals

Figure 2. Reproducibility of Mediso PET/MRI-based quantification of tumor FDG retention in control mice during repeated scans on consecutive days. (A) Brain and tumors were manually delineated based on the MR images. (B and D) Whole tumor tracer retention expressed relative to the whole brain uptake (T/B ratio) or relative to weight-normalized injected dose (SUV) in i.v. (B) and i.p. (D) injected animals. Absolute mean percentual change and range (in parentheses) is shown. (C and E) There was a good correlation between the PET-deduced T/B and the ratio determined in dissected tissues following the scans in both i.v. (C) and i.p. (E) administered animals [n¼6 (i.v.) or 7 (i.p.)].

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