  A new strategy for radiation therapy dosimetry planning (RTDP) used to reduce
dose estimation errors due to respiratory motion in breast treatment was
illustrated and evaluated in this study. On CT data set acquired for breast
treatment, six different RTDP tangential techniques were performed: (i)
three-dimensional conformal radiotherapy (3DCRT) with physical wedge, (ii)
3DCRT with virtual wedge, (iii) motion management technique (MMT) with physical
wedge, (iv) MMT with virtual wedge, (v) 3DCRT with field-in-field, and (vi)
intensity-modulated radiation therapy (IMRT) with direct aperture optimization.
These anti-motion techniques were considered to generate continuous dose
degradation to avoid drastic changes in the delivered doses that involve the
edge regions of the beams. A comparison was made between the delivered and
simulated doses, with and without the presence of motions simulations. This
study demonstrates that techniques without motion management can be affected by
motions that can lead to a difference equal to 19 % between the delivered and
the planned doses in a point located near to the beams collimators edges, and
to a difference up to 3 % on multi-leaf collimators (MLCs) edges (gamma pass
rates were 87.9 % for 3%/3mm). These differences were reduced to 11 % and to
less than 3 % (gamma pass rates were 100 % for 3%/3mm) when MMT were used. As a
conclusion, in tangential techniques motion can affect dose estimations on the
MLCs and beams collimators edges. The proposed MMT reduce this effect to
estimate the delivered dose accurately.

Medical Physics