 The primary purpose is to perform PET imaging of CD34-TK transduced allogeneic donor T cells in patients who have relapsed hematologic malignancies after allogeneic hematopoietic stem cell transplantation SCT. At this time the limited amount of cGMP quality virus produced by the NGVL will likely permit the imaging of only 3 patients. Consequently our current objective will be to establish that the TK-expressing cells can be detected by 18FHBG-PET in patient organs relevant for performing additional studies that are currently in the planning stages and for which we are working to produce additional virus. 