Gastroenteropancreatic neuroendocrine tumours (GEP-NETs) are a heterogeneous group of neoplasms that arise from the endocrine cells of the gastroenteropancreatic tract.

The diagnostic work-up of these tumours include Computed Tomography (CT), Endoscopic Ultrasound (EUS), Magnetic Resonance Imaging (MRI).

The majority of these tumours express somatostatin receptors on their surface. For this reason, in addition to traditional imaging exams, diagnostic work-up of GEP-NETs should include a Positron Emission Tomography/CT with 68Ga labeled somatostatin analogues targeting somatostatin receptors with high sensitivity and specificity. 68Ga-DOTATOC PET/CT scan is a corner stone to assess GEP- NET patients at different stage of disease and it is the standard functional imaging modality to study well-differentiated Pan-NETs, as reported in the being also included in the guidelines of the European Association of Nuclear Medicine (EANM). Moreover, quantitative parameters extracted from 68Ga- DOTA-peptides PET imaging have demonstrated their prognostic utility as markers for progression-free survival and disease specific mortality in patients affected by NET.

Additionally, 18F-FDG PET can be used for evaluating the possible presence ofa high-grade component within the tumour itself. The accurate morphofunctional characterization is of utmost importance in the field of GEP-NET.

the advent of new hybrid scanners, namely PET/MRI, opens the way to an innovative diagnostic work- up that can be applied to GEP-NETs. In fact, MRI plays a role as morphological imaging modalities for a better characterization of soft-tissue and liver parenchyma compared to CT; moreover, the low radiation exposure related to MRI, makes this imaging modality more suitable for patients requiring several imaging during follow-up.

Patients requiring 68Ga-DOTA peptides (68Ga-DOTATOC) PET scan and eventually MRI scan, can be studied in a single session examination, by using 68Ga-DOTATOC PET/MRI.

Considering the rarity of GEP_NETs, it is quite difficult to collect a sufficient number of patients in order to investigate the accuracy, predictive and prognostic value of the currently available imaging technique in this scenario. Based on these considerations, the possibility to analyze PET images deriving from both PET/CT and PET/MRI scans of patients affected by GEP-NET is of fundamental relevance in order to provide answers to the currently unmet clinical needs.

Inclusion Criteria:

• Patients with either histological diagnosis of GEP-NET at radiologic imaging and referred to 68Ga-DOTATOC PET;
• Age > 18 years old;
• Willing to provide a signed informed consent.

Exclusion Criteria:

• Controindications to MR study (i.e. Pacemaker);
• Age< 18 years old.

Main selection criteria: patients with GEP-NET referred for 68Ga-DOTATOC PET.