Evaluation of dose to the heart from breast radiotherapy
The importance of minimizing dose to heart during breast irradiation has attracted increased interest in recent years stating that major coronary events are avoided if threshold of 3Gy is kept for the mean heart dose and are increased linearly with the mean dose to the heart by 7.4% per Gy and 4% increase in risk of heart disease. A sample of 100 patients from our centre (50% right breast and 50% left breast), were treated with 6MV 3D-conformal radiotherapy planning with two tangential fields. Angles were chosen to avoid OAR from receiving unnecessary dose and not compromising target coverage or increasing contra-lateral breast dose. After evaluating the OAR doses, a simple planning technique was used by blocking heart with the use of MLCs (MbT) on the medial tangential field. After applying the MbT, dose to the heart was reduced with a max reduce on MHD of 3Gy and the criteria of V20 and V40 were achieved.