Intensity-modulated Total Body Irradiation (TBI) with TomoDirect™

Abstract

Background: The new TomoDirect™ modality offers a non-rotational option with discrete beam angles. We have investigated this mode for TBI with the intention to test the feasibility and to establish it as a clinical routine method. Special foci were directed onto treatment planning, dosimetric accuracy and practical aspects. Patients and methods: TBI plans were calculated with TomoDirect™ for a Rando™ phantom and all patients with an intended fractionated total body irradiation between November 2013 and May 2014 (n=8). Finally, four of these patients were irradiated with TomoDirect™. Additionally we studied variations in the modulation factor, pitch, field width of Y-jaws and dose grid during optimization. Dose measurements were performed using thermoluminescent rods in the Rando™ phantom, with the Delta4® and with ionization chambers in a solid water phantom. Results: For all eight calculated plans with a prescribed dose of 12Gy Dmean was 12.09-12.33Gy (12,25±0.08Gy), D98 11.2-11.6Gy (11.45±0.12Gy) and D2 12.6-13.1Gy (12.94±0.13Gy). Dmean of inner lungs was 8.73±0.22Gy on the left side and 8.69±0.27Gy on the right side. Conclusion: TBI with TomoDirect™ allows a superior homogeneity compared to conventional methods, where lung blocks are widely accepted. The treatment is performed only in supine position and is robust and comfortable for the patient.