Evaluation of three VMAT-TMI planning methods to find an appropriate balance between plan complexity and the resulting dose distribution.

PURPOSE

Evaluation of different planning methods of treatment plan preparation for volumetric modulated arc therapy during total marrow irradiation (VMAT-TMI).

METHOD

Three different planning methods were evaluated to establish the most appropriate VMAT-TMI technique, based on organ at risk (OAR) dose reduction, conformity and plan simplicity. The methods were: (M) the sub-plan method, (M) use of eight arcs optimised simultaneously and (M) M with monitor unit reduction. Friedman ANOVA comparison, with Nemenyi's procedures, was used in the statistical analysis of the results.

RESULTS

The dosimetric results obtained for the planning target volume and for most OARs do not differ statistically between methods. The M method was characterized by the lowest numbers of monitor units (3259 MU vs. 4450 MU for M and 4216 MU for M) and, in general, the lowest complexity. The variability of the monitor units from control points was almost half for M than M and M (i.e. 0.33 MU vs. 0.61 MU for M and 0.58 for M). Analysing the relationship between the dose distributions obtained for the plans and their complexity, the best result was observed for the M method.

CONCLUSION

The use of eight simultaneously optimised arcs with MU reduction allows to obtain VMAT-TMI plans that are characterized by the lowest complexity, with dose distributions comparable to the plans generated by other methods.