ABSTRACT
In this study, the physical compensator made with the high density material, Cerrobend, and the electronic compensator realized by the movement of a dynamic multileaf collimator were analyzed in order to verify the properness of a design function in the commercial RTP (radiation treatment planning) system, Eclipse. The CT images of a phantom composed of the regions of five different thickness were acquired and the proper compensator which can make homogeneous dose distribution at the reference depth was designed in the RTP. The frame for the casting of Cerrobend compensator was made with a computerized automatic styrofoam cutting device and the Millennium MLC-120 was used for the electronic compensator. All the dose values and isodose distributions were measured with a radiographic EDR2 film. The deviation of a dose distribution was +/-0.99 cGy and +/-1.82 cGy in each case of a Cerrobend compensator and a electronic compensator compared with a +/-13.93 cGy deviation in an open beam condition. Which showed the proper function of the designed compensators in the view point of a homogeneous dose distribution. When the absolute dose value was analyzed, the Cerrobend compensator showed a +3.83% error and the electronic compensator showed a -4.37% error in comparison with a dose value which was calculated in the RTP. These errors can be admtted as an reasonable results that approve the accuracy of the compensator design in the RTP considering the error in the process of the manufacturing of the Cerrobend compensator and the limitation of a film in the absolute dosimetry.
ABSTRACT
Objective To establish the isodose curves and dose calculation models of()~(125)I seed plane implantation using the three-dimensional treatment planning system(3D-TPS). Methods The isodose cures of 1 000 cGy,3 000 cGy,6 000 cGy,9 000 cGy,12 000 cGy,15 000 cGy,and 20 000 cGy and dose calculation models of triangular,quadrilateral,hexagon,and dodecagon patterns of()~(125)I seed plane implantation were created using the 3D-TPS.The isocenter dose pattern of 0,0.5,1.0,1.5,2.0,2.5,3.0,and 4.0 cm from the plane center was calculated with 3D-CRT. Results The study showed that if doses were less than 10 Gy at 2.0 cm,2.5 cm,3.0 cm and 4.0 cm apart from the center of triangular,quadrilateral,hexagon,and dodecagon patterns and the distance was beyond 1 cm between seeds,there was a low dose region in the centeral point. Conclusions The study showed that the isodose distribution curves and dose calculation models in plane implantation were primarily established using the seed implantation 3D-TPS.