Total body irradiation (TBI) is a standard part of the conditioning regimen for bone marrow transplantation (BMT). Several randomized trials have shown superior outcomes using TBI compared with non TBI-containing regimens. Standard TBI is usually delivered over three days for a total dose of 12 Gy with two daily fractions. However, as demonstrated by our group, increasing the TBI dose above 10 Gy is not necessarily associated with better outcome in patients undergoing allogenic BMT for hematologic malignancies. For this reason, patients older than 40 or grafted after relapse are treated at our center with a reduced-dose 10 Gy TBI regimen. This pilot study wishes to investigate in 10 patients with hematological malignancies unfit for a standard 12 Gy TBI conditioning regimen a more targeted, conformal form of treatment, referred as total marrow (TMI), using volumetric Arc Therapy (VMAT). Our hypothesis is that using this technique that can allow deliver a higher total dose to the target while at the same time assuring to the organs at risk (OAR) the same dose normally delivered with a 10 Gy TBI we will improve the therapeutic ratio in these patients.