Purpose: To compare dose distribution to organs at risk (OAR) while irradiating lungs for cancer treatment by using different planning techniques offered by a Varian Trilogy and Accuray Radixact. Also, a comparison of the V5 (percentage of lung receiving dose greater than 5 Gy) and V20 (percentage of lung receiving dose greater than 20 Gy)for both the total lung and contralateral lung among the different treatment planning techniques.
Methods: Thirty SBRT lung tumor patients were planned on a Varian Trilogy, fifteen for left lung and fifteen for right lung tumor, using 9 3D conformal MLC treatment fields.These treatments will be re-planned with both Radixact-Tomotherapy Helical and TomoDirect -IMRT methods and the resulting OAR data will be compared with the Trilogy data. The dose prescription for the PTV will be same for the Radixact planning techniques. The dose distribution to the OARs along with the V5 and V20 values for the total lung and contralateral lung will be compared for different techniques.
Results: As the irradiation greater than 20Gy can be associated with the occurrence of Radiation Pneumonitis which can be fatal, the focus of our study is on finding the technique that is 1) best at keeping the contralateral lung dose below 20 Gy, 2) which technique is best for lung tumor treatment while giving minimum dose to organs at risk.
Conclusion: We will analyze which technique provides the best target coverage, lowest dose to the OARs, as well as keeping the total lung and contralateral lung V5 and V20 values at acceptable levels.