^110mIn-DTPA-D-Phe¹-octreotide for imaging of neuroendocrine tumors with PET

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 ^11OmIn-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 ^110mIn-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.