Impact of Integrated Whole Body 68 Ga PET/MR Imaging in Comparison with 68 Ga PET/CT in Lesions Detection and Diagnosis of Suspected Neuroendocrine Tumours

Abstract

Combined PET/MR is a relatively new technique and so far there has been a very limited report of the potential simultaneous PET/MR and PET/CT application in the evaluation of neuroendocrine tumours. The present study aimed to compare Ga-DOTATATE PET/CT and PET/MR imaging in patients with known neuroendocrine tumours (NET) and assess the confidence in anatomic lesion detection and localization. We analysed the data of 37 NET patients who underwent both 68Ga-DOTATATE PET/CT and PET/MR using the same injected activity. Visual findings by two observers of the two modalities were recorded. SUV max of both primary tumour and liver lesions for both modalities and PET/MR derived apparent diffusion coefficient (ADC) values were measured. To study the value of additional MRI sequences, the differences in performance between PET with T1+T2w, PET with DWI reads, and PET with post contrast was assessed. No significant differences between the two modalities were seen regarding the number of patients affected by primary or metastatic disease. However, counting the number of lesions per patient, both observers were able to recognize more liver lesions in MRI T1 and T2. The interclass correlation coefficient (ICC) demonstrated a strong correlation between SUV max derived from PET/CT and PET/MR in both primary lesions (ICC = 0.92; p = 0.001) and liver (ICC = 0.882; p = 0.001). In the evaluation of lesion per patient, PET+ contrast and DWI detected more metastasis than the evaluation of PET +T1 and T2 alone. There was no significant correlation between ADC values and PET/MR SUV max of the tumour (respectively: p = 0.43, p 0.88 and p = 0.295). PET/MRI has comparable accuracy in localization and staging to PET/CT, and has a potential to become a valid alternative to PET/CT in staging and follow up of NET patients, with advantages in the characterization of liver lesions. In our study DWI and contrast helped to detect more lesions.