Effects of Collimator and Gantry on Dose Delivery Accuracy for Patients Undergoing Radiation Therapy of the Breast on Theratron Equinox 80 cm SSD

Introduction In some developing countries the problem of low cure rate of breast cancer might be compounded by manual placement of the beam during treatment using anatomical land marks. The combination of manual placement of the beam and patient positioning inevitably introduce collimator and gantry adjustments errors. Material and Methods Breast phantom of dimensions 35 cm x 50 cm was fabricated by using bee wax. The phantom was positioned at source-surface distance (SSD) 80 cm using the information obtained from the Tera-Six simulator and the phantom irradiated and diode collected the readings. Mismatch was then created by increasing the gantry and collimator angles to 1, 2, 3, 4 to 5 degree. On each increase the phantom irradiated and diodes readings were recorded. Conclusion Accuracy of dose delivery to the breast cancer patients undergoing radiation therapy could be reached when adjustments of both gantry and collimator angles caused by mismatch of the simulator and the cobalt-60, Theratron Equinox 80 minimized not to exceed 2 degree.