Room: Exhibit Hall
Purpose: The present study is to investigate the influence of Bremsstrahlung energies on 3D-CRT (FIF) and Hybrid plans for breast cancer regional node and estimation of Photoneutron Dose Equivalent (PNDE) in an Elekta Versa HD linear using BD-PND bubble detector for 10 and 15 MV photon beam.
Methods: In the current study, breast cancer patient having higher separation was selected retrospectively. The planning target volume (PTV) and organ at risk (OAR) were contours using RTOG protocol. Using Monaca planning system V.5.1, treatment techniques were generated using collapsed cone convolution (CCC) algorithm. 3D-CRT (FIF) and hybrid techniques (combination of conventional CRT and IMRT beams) were planned. Plan evaluations were carried out using dose volume histogram. The bubble detectors were used to measure the out-of-field photoneutron dose equivalent (PNDE) along the patient plane with the source to detector distance of 100cm for both energies.
Results: Compare to 3D-CRT (FIF), hybrid techniques have better conformity and homogeneity indexes, V95% to PTV were 92.44 and 94.32 for both energies. Dose received by OAR did not have higher significant variations in both techniques and energies. Furthermore, in 10 and 15 MV photon beams, the 3D-CRT technique exhibits lesser contamination of neutrons compare to a hybrid plan due to lesser monitor units were delivered.
Conclusion: The study concludes, with regard to PTV that: hybrid plan has a better uniform dose distribution than the 3D-CRT technique. The PNDE estimation was found to be almost two-three folds higher for 15 MV compare to 10 MV. Use of 15 MV beam should be employed only for specific cases to meet the requirements. It is advisable to use either low or medium beam which proves to be more effective dose homogeneity and reduced secondary neutron dose to the patients and the radiation workers.