Evaluation of Ga-DOTATOC PET/MRI for whole-body staging of neuroendocrine tumours in comparison with Ga-DOTATOC PET/CT.

Objectives: To compare the diagnostic performance of Ga-DOTATOC PET/MRI and Ga-DOTATOC PET/CT in the whole-body staging of patients with neuroendocrine tumours (NET).

Methods: Thirty patients with histopathologically confirmed NET underwent PET/CT and PET/MRI in a single-injection protocol. PET/CT and PET/MRI scans were prospectively evaluated with regard to lesion count, localization, nature (NET/non-NET), and conspicuity (four-point scale). Histopathology and follow-up imaging served as the reference standards. The proportions of NET and non-NET lesions rated correctly were compared using McNemar's chi-squared test. The Wilcoxon test was used to assess differences in SUVmax and lesion conspicuity. The correlation between the SUVmax for the same lesions from each modality was analysed using Pearson's correlation coefficient (r).

Results: According to the reference standard, there were 197 lesions (142 NET, 55 non-NET). Lesion-based analysis showed a higher proportion of correctly rated NET lesions on PET/MRI than on PET/CT (90.8% vs. 86.7%, p = 0.031), whereas on PET/CT there was a higher proportion of correctly rated non-NET lesions (94.5% vs. 83.6%, p = 0.031). SUVmax was strongly correlated (r = 0.86; p < 0.001) and did not differ significantly (p = 0.35) between the modalities. Overall conspicuity and NET lesion conspicuity were higher on PET/MRI (both p < 0.01).

Conclusions: Ga-DOTATOC PET/MRI yielded a higher proportion of correctly rated NET lesions and should be regarded as a valuable alternative to Ga-DOTATOC PET/CT in whole-body staging of NET patients.

Key Points: • Ga-DOTATOC PET/MRI correctly identified more NET lesions than Ga-DOTATOC PET/CT. • Ga-DOTATOC PET/MRI provides better NET lesion conspicuity than Ga-DOTATOC PET/CT. • SUVmax values from the two modalities are strongly correlated and do not differ significantly.