Detection of Graft Versus Host Disease With [18F]F-AraG

This is a single-center imaging study to determine utility of in vivo imaging with \[18F\]F-AraG to identify sites of Graft Versus Host Disease (GVHD) in patients highly suspected of having acute GVHD who require systemic therapy, and patients at high risk for developing acute GVHD. \[18F\]F-AraG PET scans will be compared to biopsy results to correlate T cell accumulation which is implicated in the disease. High risk patients will be followed to verify predictive potential of \[18F\]F-AraG.