Pilot Prospective Study for PET-CT Imaging in Participants With Relapsed/Refractory Acute Leukemias

Background Acute lymphoblastic leukemia (ALL) accounts for about 25 percent of childhood cancers and for about 20 percent of adult leukemias. The disease can be treated with CAR T-cell infusion but non-central nervous system (CNS) extramedullary disease (EMD) is associated with lower rates of complete remission. 18-fludeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET-CT) has been shown to be effective for detection of non-CNS EMD in ALL. Pre and post CAR T-cell infusion may help to predict outcomes and risk of early progression. Objectives To describe the number of adults with relapsed/refractory B-cell ALL who proceed to CAR T-cell therapy. Eligibility Participants \>=18 years with relapsed/refractory B-cell ALL who are being screened for CAR T-cell clinical trial enrollment, and Participants \

* INCLUSION CRITERIA: * Diagnosis: Participants must have a B cell ALL (inclusive of CML with ALL transformation) * Age: 5-39 years * All participants \>=18 years old with relapsed/refractory B cell ALL potentially proceeding to CAR therapy at the NIH, or * Any participant \