The goal of this study is to understand why some people receiving chimeric antigen receptor (CAR) T-cell therapy for cancer experience neurotoxicity. The main question it aims to answer is: Can a novel tool be developed to identify early the patients who will develop immune effector cell-associated neurotoxicity syndrome (ICANS, also called neurotoxicity) after chimeric antigen receptor (CAR) T-cell therapy? Participants already scheduled for chimeric antigen receptor (CAR) T-cell therapy as part of the medical care for their cancer will be evaluated with advanced neuroimaging techniques. In addition, neurocognitive assessments using questionnaires and measurement of biomarkers in blood (liquid biomarkers) will be performed to provide a comprehensive characterization of neurotoxicity following chimeric antigen receptor T-cell therapy. Assessments will be performed in the acute phase (2 to 14 days after chimeric antigen receptor (CAR) T-cell therapy) and after approximately 3 months.