Derivation of input function for FDG-PET studies in mice with intraperitoneal injection

Objectives To derive the plasma time-activity curve in mouse PET studies with intraperitoneal (IP) injection of FDG.

Methods In 4 C57BL/6 isoflurane anesthetized mice (nonfasted; 29.1±2.2 g), dynamic PET scans were performed for 60 minutes after IP injection of FDG (15.2±1.5 MBq) and serial blood samples were drawn from the femoral artery. Image data were reconstructed using filtered backprojection with CT-based attenuation correction. Volumes of interest were defined frame-by-frame on the bladder whose total activity data was fitted to a renal compartmental model with the last blood sample so as to determine the blood FDG clearance described by an 1-exponential function. A linear 9-compartment whole-body model that described FDG kinetics in peritoneal cavity, liver, bladder and lumped tissues upon IP injection was fitted to the measured data, whereas the kinetics in the central plasma pool was determined based on the simultaneous fitting of tissue kinetics to the model and the estimated plasma samples from the blood FDG clearance equation.

Results The volume of FDG in bladder increased linearly with time from ~10 to 60 min with a rate of 3.49±0.32 uL/min. The total activity of FDG in bladder also increased linearly during the same period of time. The estimated blood samples using a renal compartmental model and the whole-body model agreed well with the actual measurements.

Conclusions The proposed modeling approach maybe useful for derivation of plasma input function for IP injection of FDG mouse PET studies.

Research Support NIBIB grant R01-EB001943