• Jolanta Kunikowska, Adam Bajera, Magdalena Sawicka, Piotr Czwarnowski, Bożena Pawłowicz, Dariusz Aksamit, Dariusz Pawlak, and Leszek Królicki.
• Nuclear Medicine Department, Medical University of Warsaw, Poland. jolanta.kunikowska@wum.edu.pl.
• Nucl Med Rev Cent East Eur. 2013 Jan 1; 16 (2): 70-4.

BackgroundNeuroendocrine tumors (NETs) are a heterogeneous group of neoplasms derived from endocrine stem cells.These tumors are characterized by overexpression of somatostatin receptors (SSTR), which is utilized for imaging using SSTR analogs. Peptide receptor radionuclide therapy (PRRT) somatostatin analogs labeled with 90Y and 177Lu in neuroendocrine tumors (NETs) results in symptomatic improvement, prolonged survival,and enhanced quality of life. The post-therapeutic imaging leadsto possibility of biodistribution of therapy. The aim of our study was to describe different possibilities of post-therapeutic imaging in patients underwent tandem therapy 90Y/177Lu-DOTATATE with preliminary results of 90Y PET imaging.Material And MethodsThirty patients (11 men, 19 women; the mean age 55 ± 10.9 y) with histological confirmation of metastatic neuroendocrine tumors (G1 and G2) were treated with tandem therapy 90Y/177Lu-DOTATATE. WHBA scan and SPECT acquisition of the abdomen were performed 24 hours post therapy injection, on the dual-head Varicam camera (ELSCINT) using 177Lu photopeak and 90Y bremsstrahlung. PET imaging of 90Y component was done on Siemens Biograph Truepoint PET/CT (window 511 keV ± 15%)4 hours after 90Y/177Lu-DOTATATE. Additionally phantom studies were performer to analyze the spatial resolution of different protocols.ResultsOut of all the patients, median OS was 49.8 months and median EFS time 24.3 months. Spatial resolution achieved for 90Y, 177 Lu and PET imaging of 90Y component measured using the phantom of the torso filled up with water was 20 mm, 8 mm and 4-5 mm FWHM, respectively. Spatial resolution in human body in our study was about 30 mm for 90Y, 15 mm for 177Lu and 25-30 mm for PET imaging of 90Y component.ConclusionsThe theoretically best spatial resolution offers PET scanner, however it is important to keep in mind that 90Y-imaging PET is not used for diagnosis purposes (small activities)but rather to present new possibility of post-therapeutic imaging (substantially higher activities). For post-therapeutic imaging after intravenous radiopharmaceutical administration the best spatial resolution offers standard scintigraphic camera for 90Y/177Lu DOTATATE imaging, with using 177Lu photopeaks. The worst spatial resolution offers standard scintigraphic camera for 90Y/177Lu DOTATATE imaging, with using 90Y bremsstrahlung gammas.

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