Inclusion Criteria:  Female or male patients diagnosed with sickle cell anemia (HbSS, HbS/β0, HbS/β+, HbSC) with or without known avascular lesions Age ≥ 7 and < 18 years at the moment of signed consent Written informed consent/assent, according to local guidelines, signed by patient and/or guidelines, signed by the patient and/or at least one parent or legal guardian  Exclusion Criteria:  - Any contraindication to perform Nuclear Magnetic Resonance Magnetic Resonance Imaging (MRI) Inability to obtain informed consent/assent