Inclusion Criteria:  All patients affiliated to the French social security system will be eligible, after signing a consent form, and presenting the following criteria  Introduction within the last 3 months of at least one of the following ICIs: nivolumab, pembrolizumab, cemiplimab, avelumab, atezolizumab, ipilimumab, tremelimumab, durvalumab.  Suspicion of myocarditis defined by the presence of at least one of the following criteria adapted from the European Society of Cardiology guidelines:  Symptomatic patients (chest pain, dyspnea, palpitations, syncope/lipothymia) within 7 days of ICI administration New ECG abnormality (ST-segment elevation, ST-segment undershift, arrhythmia, conductive disturbances, T-wave inversion) Elevation of troponin above the 99th percentile of the laboratory reference value or, if troponin is already elevated before treatment, an increase of more than 30% of the baseline value Recent LVEF decline or recent LV contraction abnormality on a TTE Patient has given no objection  Translated with www.DeepL.com/Translator (free version)  Exclusion Criteria:  Age <18 years Major under guardianship or curatorship Pregnant or breastfeeding women Patient not covered by a social security plan Hemodynamic or rhythmic instability Estimation of glomerular filtration rate by the MDRD formula <30ml/min/1.73m2 Implantable equipment that does not allow for cMRI