The expected benefit of this study is an improvement in the patient's care. Indeed, the additional information provided by Position Emission Tomography (PET) could allow for healthcare professionals to more precociously test for recurrence and thus diminish the delay in therapeutic care. Conversely, the PET could allow for healthcare professionals to avoid over-treatment of patients for whom the MRI would wrongly indicate a recurrence. Furthermore, imagery by PET should bring a new level of additional information allowing for an increase in the confidence index when being diagnosed, thus comforting the collective therapeutic attitude proposed in the MM.