After dual isotope acquisition of SPECT images, 99mTc-demobesin-4 was used to define a volume of interest for the pancreas in SPECT images subsequently the 111In-exendin-3 uptake within this region was quantified.  Quantification of both ex vivo and in vivo SPECT images resulted in an excellent linear correlation between the pancreatic uptake, determined with ex vivo counting and 111In-exendin-3 uptake, determined from the quantitative analysis of the SPECT images (Pearson r = 0.97, Pearson r = 0.92).



SPECT
Accurate assessment of the 111In-exendin-3 uptake within the pancreas requires exact delineation of the pancreas, which is highly challenging by MRI and CT in rodents. 
MRI
Improved Quantification of the Beta Cell Mass after Pancreas Visualization with 99mTc-demobesin-4 and Beta Cell Imaging with 111In-exendin-3 in Rodents.OBJECTIVE
 Accurate assessment of the 111In-exendin-3 uptake within the pancreas requires exact delineation of the pancreas, which is highly challenging by MRI and CT in rodents.  In this study, the pancreatic tracer 99mTc-demobesin-4 was evaluated for accurate delineation of the pancreas to be able to accurately quantify 111In-exendin-3 uptake within the pancreas.


 Healthy and alloxan-induced diabetic Brown Norway rats were injected with the pancreatic tracer 99mTc-demobesin-4 ([99mTc-N4-Pro1,Tyr4,Nle14]bombesin) and the beta cell tracer 111In-exendin-3 ([111In-DTPA-Lys40]exendin-3).  After dual isotope acquisition of SPECT images, 99mTc-demobesin-4 was used to define a volume of interest for the pancreas in SPECT images subsequently the 111In-exendin-3 uptake within this region was quantified.  Quantification of both ex vivo and in vivo SPECT images resulted in an excellent linear correlation between the pancreatic uptake, determined with ex vivo counting and 111In-exendin-3 uptake, determined from the quantitative analysis of the SPECT images (Pearson r = 0.97, Pearson r = 0.92).


 This method provides a straightforward, reliable, and objective method for preclinical beta cell mass (BCM) quantification with 111In-exendin-3.
CT