The value of 18F-FDG PET/MR whole body imaging in staging of pediatric neuroblastoma

122 Objectives: To evaluate the value of a Hybrid 18F-FDG PET/MR in staging of pediatric neuroblastoma. Methods: The clinical data of 72 patients who were diagnosed as NB were retrospectively analyzed from April 2017 to July 2019.Patients were divided into the pre-treatment group ( =18) and post-treatment group ( =55). The PET/MR characteristics was analyzed, and the size,shape, signal characteristics, relationship with surrounding tissues, SUVmax value, metastasis and staging characteristics of the tumor were observed. Pathological and clinical diagnosis results are the gold standard. The diagnostic staging criteria was based on standards developed by the international neuroblastoma staging system (INSS) which was revised in 1988. Results: PET/MR showed that most of the patients (17/18,94.4%) in the pre-treatment group were in the middle and late stages; 16 of the 18 primary tumors occurred in the retroperitoneal sympathetic chain distribution, 1 in the mediastinum and 1 in the pelvic cavity; the size of the primary tumors varied greatly, the mean maximum diameter was 9.86±3.87cm, and the largest diameter was mostly the upper and lower diameter. The largest one was located in the right adrenal gland, with a long diameter of about 19.9cm.The tumor morphology was mostly round (12/18, 66.7%).Hemorrhage and necrosis were easy to occur in tumors, and the signal characteristics were mostly mixed. In the pre-treatment group, 18F-FDG uptake was increased (18/18, 100%), and the SUVmax average was 5.47±1.64.PET/MR showed that 38 of 73 patients had recurrence or metastasis. Staging after PET/MR imaging: 12 patients (12/18, 66.7%) in the pre-treatment group had stage changes, 9 of them increased from 3 to 4, 2 from 2B to 4, and 1 from 1 to 3. In the post-treatment group, 18 cases (18/55, 32.7%) had stage changes, of which 12 cases increased from stage 0 to stage 4, 3 cases decreased from stage 1 to stage 4 due to negative PET/MR uptake, 1 case increased from stage 1 to stage 4, and 2 case increased from stage 3 and stage 2B to stage 4 respectively due to tumor recurrence and extensive systemic metastasis. Conclusions: 18F-FDG PET/MRI is superior to clinical in staging of pediatric neuroblastoma.It has more advantages in detecting the invasion and distant metastasis around the tumor, and obviously improves the accuracy of the primary staging and re-staging of the NB.Fig.A 2-year-old female presented with neuroblastoma of the left adrenal.1) From left to right, T2WI/PET coronal fusion image,T2WI coronal image,T2WI sagittal fusion image and T2WI sagittal image show clearly the involved left kidney;2)From left to right, T2WI/PET axial fusion image and T2WI axial image show that the signal of the focus is not uniform (red arrow), and it surrounds the renal portal vessels (green arrow); 3) 4)Retroperitoneal multiple lymph node metastasis (yellow arrow) , right meningeal metastasis (blue arrow), right pleura metastasis (white arrow), whole body diffuse bone marrow infiltration;5)The whole-body PET-MIP image clearly shows multiple body metastases and bone marrow infiltration.