Intensity-modulated Total Body Irradiation (TBI) with TomoDirectTM

Background:
The new TomoDirectTM 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 methodsTBI plans were calculated with TomoDirectTM for a RandoTM 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 TomoDirectTM. 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 RandoTM phantom, with the Delta4� and with ionization chambers in a solid water phantom.
Results:
For all eight calculated plans with a prescribed dose of 12�Gy Dmean was 12.09-12.33�Gy (12,25?�?0.08�Gy), D98 11.2-11.6�Gy (11.45?�?0.12�Gy) and D2 12.6-13.1�Gy (12.94?�?0.13�Gy). Dmean of inner lungs was 8.73?�?0.22�Gy on the left side and 8.69?�?0.27�Gy on the right side.When single planning parameters are varied with otherwise constant parameters, the modulation factor showed the greatest impact on dose homogeneity and treatment time. The impact of the pitch was marginally, and almost equal homogeneity can be obtained with field width of Y-jaws 5�cm and 2.5�cm.Measurements with thermoluminescent rods (n?=?25) in the RandoTM phantom showed a mean dose deviation between measured and calculated dose of 0.66?�?2.26%. 18 of 25 TLDs had a deviation below 3%, seven of 25 TLDs between 3% and 5%.
Conclusion:
TBI with TomoDirectTM 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.TomoDirectTM allows the implementation of organ-specific dose prescriptions. So the discussion about the balance between the need for aggressive treatment and limited toxicity can be renewed with the new potentials of TomoDirectTM - for children as well as for adults ? and possibly yield a better clinical outcome in the future.

Source: http://www.ro-journal.com/content/10/1/58

auto sport medical rehab