Comparison of 3DCRT Dose Distribution in Radiotherapy for Lung Cancer Patient by Using AAA and PBC Algorithms

The Pencil Beam Convolution (PBC) algorithm in radiation treatment planning system is widely used to calculate the radiation dose distribution in radiotherapy planning. A new photon dose calculation algorithm known as Anisotropic Analytical Algorithm (AAA) by Varian Medical Systems is applied to investigate the difference of dose distribution by using AAA and PBC algorithms for the lung cancer with an inhomogeneity of its low density. In the present work, radiotherapy treatment planning of 10 lung cancer patients are designed with 6 MV photon beam using three-dimensional conformal radiation therapy (3DCRT) and dose distribution was calculated by the AAA and the PBC Algorithms. The dose distribution performance is evaluated by dose profile curve along transversal slice of PTV and Dose Volume Histogram (DVH) covered by the 95% isodose of PTV. The mean dose of organ at risks did not changed significantly but the volume of the PTV covered by the 95% isodose curve was decreased by 6% with inhomogeneity due to the algorithms. The dose distribution and the accuracy in calculating the absorbed dose of the AAA algorithm of the Varian Eclipse treatment planning system is analyzed and discussed.