STEREOTACTIC IRRADIATION OF LUNG CANCER
Abstract
Objective: To investigate the best stereotactic irradiation (STI) technique in treatment of small lung tumors, using dose-volume statistics.
Methods: Dose-volume histogram (DVH) of the study phantom consisting of CT using the software of FOCUS-3D planning system. The beam was a 6MV X-ray from a Varian 2300C. The analysis data of Dose-volume statistics was from the technique used for: (1) 2-12 arcs; (2) 200--45 . separation angle of arcs; (3) 80°-160 . of gantry rotation. Then we studied the difference of DVH with various irradiation techniques and the influence of target positions and field size by calculated to the distribution of dose from 20%-90% of the six targets in the lung with 3x3 cm 2, 4x4 cm 2 and 5x5 cm 2 field size.
Results: The volume irradiated pulmonary tissue was the smallest using a six non-coplanar 120 ° arcs with 30" separation between arcs in the hypothetical set up, the non-coplanar SRI was superiority than conventional one's. The six targets were chosen in the right lung, the volume was the largest in geometric center and was decreased in hilus, bottom, anterior chest wall, lateral wall and apex of the lung in such an order. The DVH had significant change with an increasing field size.
Conclusion: the irradiation damage of normal pulmonary tissue was the lowest using the six non-coplanar 120 ° arcs with a 30 ° separation between arcs by <5x5 cm 2 field and the position of target was not a restricting factor.
Methods: Dose-volume histogram (DVH) of the study phantom consisting of CT using the software of FOCUS-3D planning system. The beam was a 6MV X-ray from a Varian 2300C. The analysis data of Dose-volume statistics was from the technique used for: (1) 2-12 arcs; (2) 200--45 . separation angle of arcs; (3) 80°-160 . of gantry rotation. Then we studied the difference of DVH with various irradiation techniques and the influence of target positions and field size by calculated to the distribution of dose from 20%-90% of the six targets in the lung with 3x3 cm 2, 4x4 cm 2 and 5x5 cm 2 field size.
Results: The volume irradiated pulmonary tissue was the smallest using a six non-coplanar 120 ° arcs with 30" separation between arcs in the hypothetical set up, the non-coplanar SRI was superiority than conventional one's. The six targets were chosen in the right lung, the volume was the largest in geometric center and was decreased in hilus, bottom, anterior chest wall, lateral wall and apex of the lung in such an order. The DVH had significant change with an increasing field size.
Conclusion: the irradiation damage of normal pulmonary tissue was the lowest using the six non-coplanar 120 ° arcs with a 30 ° separation between arcs by <5x5 cm 2 field and the position of target was not a restricting factor.