Williams KM, et al. - This study was carried out to assess whether ¹⁸F-fluorothymidine (¹⁸F-FLT) imaging was safe during allogenic haemopoietic stem-cell transplantation (HSCT) and allowed visualisation of early cellular proliferation and detection of patterns of cellular engraftment after HSCT. In human beings, ¹⁸F-FLT allowed quantification and tracking of subclinical bone-marrow repopulation. New insights into the biology of haemopoietic stem cells (HSCs) recovery after HSCT were gained with this imaging technique.