Contribution of 3D Modeling in Surgical Management of Pediatric Retroperitoneal and Pelvic Tumors

This study's purpose is the comparison of the automatically segmented 3D model to the reference manual segmentation, based on the Dice precision index. It is implemented by making parents' patients, surgeons and surgical helpers answer specific questions comparing 3D images to usual 2D images of the patient's tumor.

Inclusion Criteria: Children: * Children between 3 months and less than 18 years old * Children with a pelvic tumor requiring an MRI for a possible surgical intervention * Children with a retroperitoneal tumor requiring a CT scan or MRI with a view to surgical intervention * Children with no contraindication for a CT scan and/or 3T MRI * Children whose parents do not object to their participation in the study Other participants: * Operating surgeon agreeing to participate in the study * Caregiver agreeing to participate in the study * External surgeon agreeing to participate in the study Exclusion Criteria: Children : * Contraindication to MRI: metallic ocular foreign body, pacemaker, mechanical heart valve, old vascular clips on cerebral aneurysm * Need for an MRI under general anaesthesia * Contraindication for a CT scan with injection: renal failure, allergy to iodinated contrast products * Patients having participated in a therapeutic clinical trial involving a new molecule within 30 days before inclusion * Emergency situation