Nowadays approximately 80% of children and adolescents with acute lymphoblastic leukaemia (ALL) or lymphoblastic lymphoma (LBL) can be cured and become long-term survivors. Avascular osteonecroses (ON) appear as serious side-effect of antileukaemic treatment. Frequently ON are first diagnosed at higher and than irreversible stages (ARCO III, IV). At these advanced stages curative treatment options are not available. Hence ON are associated with considerable morbidity concerning pain and immobility and go along with long-term impairment of quality of life. Therefore early diagnosis of ON in the follow-up of children and young adults with ALL or LBL is a pressing object.

Within the prospective multicentric observational OPAL-trial patients at risk (aged 10 years or older) treated according to the clinical trials ALL-BFM(Berlin-Frankfurt-Muenster Study Group), COALL or NHL (Non Hodgkin Lymphoma)-BFM in Germany should be examined with regard to the development of ON. By using a treatment associated, risk orientated assessment and examination incidence, symptoms and the clinical course of ON are investigated. The validity of MRI screening in the early diagnosis of ON in children and young adults is analysed.

Systematical investigation of patients under antileukaemic treatment is intended to contribute to risk adapted diagnostic strategies and to serve as data base for the subsequent evaluation of preventive and interventional approaches for the treatment of ON. Long-term objective is the reduction of ON-associated morbidity.

Inclusion Criteria:

• diagnosis of ALL or LBL
• age at diagnosis of ALL or LBL ≥ 10 and < 18 years
• study patient of AIEOP( Associazione Italiana Ematologia ed Oncologia Pediatrica)-BFM, COALL or NHL-BFM in Germany
• treatment in a hospital participating in OPAL
• written informed consent

Exclusion Criteria:

• relapse of ALL or LBL
• every non evidence based treatment (pharmacological, orthopaedic-conservative, orthopaedic operative) aiming at the prevention of ON during study participation
• pacemaker, other MRI prohibited devices
• metal implants in the field of view, other MRI prohibited implants
• pregnancy
• claustrophobia

Pediatric patients with acute lymphoblastic leukemia or lymphoblastic lymphoma, aged >= 10 and < 18 years