New dosimetry planning strategy based on continuous dose gradient used to reduce dose estimation errors due to respiratory motion in breast radiation therapy
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.