RESUMEN
Objective To compare the dosimetric difference in planning target volume(PTV)and organ at risk(OAR)with conventional and the three-dimensional treatment planning for limlted-stage small cell lung cancer.Methods Ten patients with limited-stage small cell lung cancer were chosen in the present study.Two treatment planning were designed twice respectively with the Cadplan R 3.1.2 treatment planning system for each patient in two-course.The total radiation dose was 50 Gy.The dosimetric parameters were assessed with dose volume histograms in PIT and OAR.Results For the first course,the dose homogeneity indices(HI)of PTV1,conformal indices(CI)of PTV2,contralateral lung V3o and eontralateral mean lung dose in the three-dimensional treatment planning were better than that in the conventional treatment planning.For the second course,the HI,CI and mean dose of PTV1,CI and mean dose of PTV2 in the three-dimensional treatment planning were better than that in the conventional treatment planning.Conclusions By comparison with conventional treatment planning,the three-dimensional conformal treatment planning could meet the demands of dosimetrie requirements well for limited-stage small cell lung cancer with three-dimensional conformal radiotherapy,but with no significant dnsimetric differences in the OAR.
RESUMEN
Objective To develop a beam orientation optimization algorithm for the gantry orientation in three-dimensional conformal radiotherapy(3 DCRT).Methods Patients' data were imported from the Pinnacle v 7.2 treatment planning system.including the DICOMRT and dose distribution files.These imported files were merged using a uniforiB coordinate system.The algorithm determined the optimized beam weight for each beam group and optimized the beam orientation with genetic algorithm.The optimized parameters,including the optimized beam orientations and weights,were exposed back to the Pinnacle v 7.2 to compare with the conventional 3DCRT plan.The optimized algorithm was implemented with our in-house program. The dose distributions, the DVH diagram and the conformity index of two lung cancer patients were compared. Results for the two lung cancer patients,the conformity index of the optimized plan(0.59 and 0.7)was higher than the conwentional 3DCRT plan(0.36 and 0.58).The maximum dose in spinal cord was reduced by 17.8%and 22.4%,the lung V20 reduced by 3.12%and 4.35%,and V30 reduced by 4.47%and 1.49%.For the brain tumor patient. the dose of lens and eyes was also decreased significantly. Conclusion This beam orientation optimization can be used as an assistant planning tool.