Validating the algorithms AAA and Acuros for calculation of dose from flattening filter free beams in heterogenous tissue - Application to stereotactic radiotherapy of lung tumors

Abstract

In radiation therapy of cancer, modeling the dose to the patient is very important. Several computational algorithms are available, where some model dose in heterogeneous tissue better than others. After implementation of stereotactic radiotherapy of lung cancer at the University Hospital of North Norway, where high dose are given with high precision, it is desirable to look at the difference in the calculated dose for the established algorithm AAA, and newcomer Acuros, in heterogeneous tissue. Dose measurements were made using radiochromic film and ionization chambers in a lung phantom, and compared with calculated dose distributions for different energies which can be used in the treatment of lung tumors. In addition, patients previously treated stereotactically to the lung was replanned using Acuros and volume doses were compared. Results from the lung phantom show that Acuros calculates lower dose in light lung tissue compared to AAA but it is difficult to make measurements the dose in low density media for absolute comparisons. Patient plans calculated by Acuros show correspondingly a much lower dose to lung tissue surrounding a tumor and an overall lower dose given to heterogeneous tissue relative to AAA calculations. To acquire better estimations of actual doses given during radiotherapy of lung tumors, the implementation of Acuros should be considered.