RT Journal Article SR Electronic T1 Time Evolution of DOTATOC Uptake in Neuroendocrine Tumors in View of a Possible Application of Radioguided Surgery with β− Decay JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1501 OP 1506 DO 10.2967/jnumed.115.160481 VO 56 IS 10 A1 Francesco Collamati A1 Fabio Bellini A1 Valerio Bocci A1 Erika De Lucia A1 Valentina Ferri A1 Federica Fioroni A1 Elisa Grassi A1 Mauro Iori A1 Michela Marafini A1 Silvio Morganti A1 Riccardo Paramatti A1 Vincenzo Patera A1 Luigi Recchia A1 Andrea Russomando A1 Alessio Sarti A1 Adalberto Sciubba A1 Martina Senzacqua A1 Elena Solfaroli Camillocci A1 Annibale Versari A1 Cecilia Voena A1 Riccardo Faccini YR 2015 UL http://jnm.snmjournals.org/content/56/10/1501.abstract AB A novel radioguided surgery (RGS) technique exploiting β− radiation has been proposed. To develop such a technique, a suitable radiotracer able to deliver a β− emitter to the tumor has to be identified. A first candidate is represented by 90Y-labeled DOTATOC, a compound commonly used today for peptide radioreceptor therapy. The application of this β− RGS to neuroendocrine tumors (NET) requires study of the uptake of DOTATOC and its time evolution both in tumors and in healthy organs and evaluation of the corresponding performance of the technique. Methods: Uptake by lesions and healthy organs (kidneys, spleen, liver and healthy muscle) was estimated on 177Lu-DOTATOC SPECT/CT scans of 15 patients affected by NET with different localizations, treated at IRCCS–Arcispedale Santa Maria Nuova, Reggio Emilia, Italy. For each patient, SPECT/CT images, acquired at 0.5, 4, 20, 40, and 70 h after injection, were studied. For each lesion, the tumor-to-nontumor ratio (TNR) with respect to all healthy organs and its time evolution were studied. A subset of patients showing hepatic lesions was selected, and the TNR with respect to the nearby healthy tissue was calculated. By means of a Monte Carlo simulation of the probe for β− RGS, the activity that is to be administered for a successful detection was estimated lesion-by-lesion. Results: Uptake of DOTATOC on NETs maximized at about 24 h after injection. The cases of hepatic lesions showed a TNR with respect to the tumor margins compatible with the application of β− RGS. In particular, 0.1-mL residuals are expected to be detectable within 1 s with 5% false-negative and 1% false-positive by administering the patient as little as 1 MBq/kg. Conclusion: The balance between tumor uptake and metabolic washout in healthy tissue causes the TNR to increase with time, reaching its maximum after 24 h, and this characteristic can be exploited when a radiotracer with a long half-life, such as 90Y, is used. In particular, if 90Y-DOTATOC is used with liver NET metastases, the proposed RGS technique is believed to be feasible by injecting an activity that is one third of that commonly used for PET imaging.