Optimum reckoning of contra lateral breast dose using physical wedge and enhanced dynamic wedge in radiotherapy treatment planning system

ABSTRACT

It was intended to investigate the effect of physical wedge [PW] and enhanced dynamic wedges [EDW] on contralateral breast dose during primary breast irradiation in radiotherapy treatment, using high energy photon beams. The Varian's Clinac dual mode linear accelerator model 2100 C/D and Siemen's Primus accelerators were used for radiation doses with 6 MV and 15 MV. Doses were delivered using Tangential field techniques and asymmetric collimator jaws. Eclipse three-dimensional Treatment Planning System [3DTPS] was used to measure contralateral breast dose for all fiend settings. Sixty five patients [with cancerous breast as well as chest wall] were taken and their contralateral breast doses were measured at a point 5 cm across, at 2 cm depth from the end of the medial field. The contralateral breast dose mean difference was 0.25 cGy and 0.24 cGy during the comparison of PW and EDW on Varian's Clinac and 0.19 cGy and 0.18 cGy were found for medial EDW and without medial EDW for the same machine in breast cases and chest wall cases respectively as per total prescribed dose. The mean difference for PW [Clinac] and PW [Primus] was found 0.08 cGy and 0.31 cGy and during the comparison of medial PW and without medial PW on primus machine this mean difference was 0.25 cGy and 0.51 cGy in breast cases and chest wall cases respectively as per total prescribed dose. The investigation demonstrates the significance that the EDW produces less scattered dose, which can cause second breast malignancy, compared to PW. Furthermore, the medial wedge, too, can cause second breast malignancy and should be avoided in planning