ABSTRACT
Objective To delineate and measure the left anterior descending coronary artery (LAD) on CT angiography (CTA) and evaluate the dose delivered to LAD by different radiotherapy techniques for left-sided breast cancer.Methods Twenty-nine left-side breast cancer women with mean age of 54.71 years (range:30-80 years) were included.CTA was performed, and LAD was contoured and the distances were measured between LAD and chest wall (posteroanterior diameter,PD), between LAD and internal mammary artery (horizontal diameter,HD), between LAD and interventricular groove (oblique diameter,OD) at the level of T7-T8,T8-T9,T9-T10 and at level of nipple and lower boundary of the breast.The dose delivered to LAD was calculated on three-dimensional plans for two patients with mastectomy whose chest wall and internal mammary chain (IMC) were irradiated and one patient with breast-conserving surgery who received whole breast irradiation.Results The LAD arose at the level of the third rib in 40% of patients and at the fourth rib in 60% of patients.The mean length of LAD was 7.49±0.58 cm.At the level of T7-T8,T8-T9,T9-T10,the mean PD were 2.99±1.11 cm, 1.26±0.65 cm,0.68±0.39 cm, the mean HD were 2.27±0.84 cm, 2.81±0.65 cm, 3.37±1.21 cm, and the mean OD were 0.47±0.25 cm,0.38±0.21 cm,0.42±0.19 cm respectively.At the level of the breast nipple and the lower boundary of the breast, the mean PD were 2.94±1.06 cm, 0.79±0.46 cm, the mean HD were 2.45±0.89 cm, 3.31±1.22 cm,and the mean OD were 0.56±0.30 cm,0.57±0.24 cm respectively.The mean dose to the LAD was 5 Gy and 14 Gy for patients with mastectomy whose IMC was irradiated with 9 MeV electron and whose IMC was irradiated with 6 MV photon tangential beams.The mean dose to the LAD was 26 Gy for patients with breast conserving surgery.Conclusions To contour the LAD, the interventricular groove could be the reference point.Tangential technique can be giving a higher dose of LAD when compared with other radiation techniques