title: A standardized method for in vivo mouse pancreas imaging and semiquantitative β cell mass measurement by dual isotope SPECT.
abstract: OBJECTIVE
  In order to evaluate future β cell tracers in vivo, we aimed to develop a standardized in vivo method allowing semiquantitative measurement of a prospective β cell tracer within the pancreas.
  
  
  METHODS
  2-[(123)I]Iodo-L-phenylalanine ([(123)I]IPA) and [Lys(40)([(111)In]DTPA)]exendin-3 ([(111)In]Ex3) pancreatic uptake and biodistribution were evaluated using SPECT, autoradiography, and an ex vivo biodistribution study in a controlled unilaterally nephrectomized mouse β cell depletion model. Semiquantitative measurement of the imaging results was performed using [(123)I]IPA to delineate the pancreas and [(111)In]Ex3 as a β cell tracer.
  
  
  RESULTS
  The uptake of [(123)I]IPA was highest in the pancreas. Aside from the kidneys, the uptake of [(111)In]Ex3 was highest in the pancreas and lungs. Autoradiography showed only uptake of [(111)In]Ex3 in insulin-expressing cells. Semiquantitative measurement of [(111)In]Ex3 in the SPECT images based on the delineation of the pancreas with [(123)I]IPA showed a high correlation with the [(111)In]Ex3 uptake data of the pancreas obtained by dissection. A strong positive correlation was observed between the relative insulin positive area and the pancreas-to-blood ratios of [(111)In]Ex3 uptake as determined by counting with a gamma counter and the semiquantitative analysis of the SPECT images.
  
  
  CONCLUSIONS
  [(123)I]IPA is a promising tracer to delineate pancreatic tissue on SPECT images. It shows a high uptake in the pancreas as compared to other abdominal tissues. This study also demonstrates the feasibility and accuracy to measure the β cell mass in vivo in an animal model of diabetes.
authors: Cell Differentiation Unit, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090, Brussels, Belgium, Iris.mathijs@vub.ac.be.
authors: Iris
authors: I
authors: Mathijs
authors: Catarina
authors: C
authors: Xavier
authors: Cindy
authors: C
authors: Peleman
authors: Vicky
authors: V
authors: Caveliers
authors: Maarten
authors: M
authors: Brom
authors: Martin
authors: M
authors: Gotthardt
authors: Pedro L
authors: PL
authors: Herrera
authors: Tony
authors: T
authors: Lahoutte
authors: Luc
authors: L
authors: Bouwens
mesh_terms: D000818:Animals; D005260:Female; D005720:Gamma Rays; D006579:Heterozygote; D007205:Indium Radioisotopes / Q000737:chemistry; D007328:Insulin / Q000235:genetics / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000166:cytology*; D008297:Male; D051379:Mice; D010179:Pancreas / Q000000981:diagnostic imaging; D010455:Peptides / Q000737:chemistry*; D010649:Phenylalanine / Q000031:analogs & derivatives / Q000737:chemistry; D015203:Reproducibility of Results; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed
chemical_list: C496694:2-iodophenylalanine; D007205:Indium Radioisotopes; D007328:Insulin; D010455:Peptides; C066448:exendin 3; D010649:Phenylalanine