REVEAL Biomarkers of Engraftment After Alternative Donor HSCT

The purpose of this study is to find new tests that could help determine if the newly infused bone marrow cells are growing well after bone marrow transplantation or if new bone marrow cells are needed. The Investigator will use FLT imaging, an investigational imaging test, and collect blood samples to investigate whether the cells are growing well.

Inclusion Criteria: General * Ability to undergo 18F FLT imaging without sedation * Patients \> 4 years of age and less than 80 years of age at highest risk for graft failure: cord blood HSCT, haplo HSCT, or lack of engraftment by day 28. * Diagnosed with a condition for which hematopoietic stem cell transplant (HSCT) is standard of care and HSCT is planned (Arm A) or occurred (Arm B) * In morphologic remission prior to HSCT * Patient or guardian able to give informed consent * Investigational therapies within past 28 days or planned on protocol are pre-approved by the PI or Site PI * Karnofsky or Lansky performance status \> 60% Arm A * A1 Cord blood recipients: Absence of donor specific antibodies to cord HLA * Haplo-identical recipients: ≥ 5/10 and \< 7/8 allele mismatch donor * A2- myeloablative Haplo-identical transplant is planned * A3- reduced intensity Haplo-identical transplant is planned (non-myeloablative is excluded) * A1- myeloablative or reduced intensity transplant is planned (non-myeloablative is excluded) * Diagnosed with a condition for which hematopoietic stem cell transplant (HSCT) is standard of care and HSCT is planned * Total bilirubin \< 2.5 mg/dL (unless documented Gilbert's syndrome) and transaminases (ALT and AST) \< 5 x the upper limit of normal * Creatinine clearance or GFR \> 60 ml/min/1.73 m2. (performed pre-HSCT) * FEV1 \> 80% pre or post-bronchiolator whichever is higher and DLCO Adj \> 70% (performed pre-HSCT if age appropriate) and Sa02 \> 94% on room air * Ejection fraction \> 50% (performed pre-HSCT) Arm B • Non-engraftment recipients of HCT with any donor source (related or unrelated): primary graft failure as defined by ANC not \> 500 for 3 consecutive days and at least 20 days after HSCT. Inclusion Criteria - Donors * 1-2 cords and \>.4/6 match to recipient for each (as per current National Marrow Donor guidelines), with a dose \>2 x 10e6 CD34 cells/kg for each cord OR \> 5/10 and \