Computational Anatomy in Surgery for Childhood Tumours and Malformations

To be included, patients must meet the following criteria: * Patient aged between 5 months and 17 years * Patient with a confirmed diagnosis of : * Abdomino-pelvic tumour * Pelvic malformation * Patient whose parents or legal guardians have read, accepted and signed the study consent form * Patients whose parents or legal guardians are beneficiaries of a social security scheme. To be included, control patients (patients other than those suffering from an abdomino-pelvic tumour or malformation) must meet the following criteria: * Patient aged between 5 months and 17 years inclusive. * A patient being followed in the visceral surgery department for a pathology other than tumour or malformation, and requiring MRI as part of his or her diagnosis, extension assessment or monitoring. * Patient whose parents or legal guardians have read, accepted and signed the study consent form. * Patient whose parents or guardians are beneficiaries of a social security scheme. Non inclusion criteria : Patients * Patient with a contraindication to MRI: metallic ocular foreign body, pacemaker, mechanical cardiac valve, old vascular clips on cerebral aneurysm, etc. * Patient having participated in a therapeutic clinical trial involving a new molecule in the 30 days prior to inclusion. Controls : * Patient with a contraindication to MRI: ocular metallic foreign body, pacemaker, cardiac mechanical valve, old vascular clips on cerebral aneurysm, etc. * Patient having participated in a therapeutic clinical trial involving a new molecule in the 30 days prior to inclusion.