The somatostatin analog diethylenetriaminepentaacetic acid (DTPA)-D-Phe1-octreotide labeled with 111In has been applied extensively for diagnosis of neuroendocrine tumors using SPECT or planar scintigraphy. However, the spatial resolution of planar scintigraphy and SPECT prohibits imaging of small tumors, and the quantification accuracy of both methods is limited.
Methods: We developed a method to prepare the positron-emitting radiopharmaceutical 110mIn-DTPA-D-Phe1-octreotide based on a commercially available kit. Phantom studies were done to investigate and compare the performance of 110mIn PET and 111In SPECT. A clinical imaging study using 110mIn-DTPA-D-Phe1-octreotide and PET was done to investigate the application of this radiopharmaceutical.
Results: An almost 3-fold better resolution and much better quantitative capabilities were found for 110mIn PET than for 111In SPECT. The clinical imaging study demonstrated the potential use of 110mIn-octreotide in PET to image tumors and quantify radioactivity uptake in humans using (110m)In-DTPA-D-Phe1-octreotide.
Conclusion: PET with 110mIn-DTPA-D-Phe1-octreotide greatly improved detection of small tumors and offers a possibility of more accurate quantification of tumor uptake than can be obtained with 111In-DTPA-D-Phe1-octreotide and SPECT.