Dosimetric comparison of the field-in-field technique and tangential wedged beams for breast irradiation

Purpose To analyze tangential wedged beam and field-in-field (FIF) technique doses using dose-volume histograms and conformality indices for target volume and healthy tissues within the irradiated volume. Materials and methods Thirty patients treated with breast-conserving surgery and postoperative whole breast radiotherapy were enrolled. Three plans were generated: a standard tangential plan with either one outer field wedge or bilateral wedges, and an FIF plan. Three indices were used: the dose homogeneity index (DHI), PTV dose improvement index (PDI index ) and geometric conformity index ( g ). Also ipsilateral lung, heart and contralateral breast doses were compared for each plan. Results Dose homogeneity index was significantly lower for the FIF (0.117 ± 0.021) than for the single wedge (0.131 ± 0.025, p = 0.02) and double wedged plan (0.128 ± 0.025, p = 0.04), respectively. The g was significantly less in the FIF (0.70 ± 0.14) compared to the wedge plans (0.80 ± 0.17, p = 0.02 and 0.83 ± 0.16, p = 0.003). Contralateral breast doses were significantly lower in the FIF plan. The FIF plan significantly lowered MU compared to both the single wedge and bilateral wedge plans. Conclusion The dose distribution within the target was more homogenous, and the doses for healthy tissue were less in the FIF plan compared to the tangential wedge plans.