Cyberknife® ve Varian RapidArc® TrilogyTM Cihazında Üç Boyutlu Uzaysal Fraksiyone Grid Terapi Doz Karakteristiklerinin Karşılaştırılması

Abstract

. Lattice therapy is an innovative method to increase the effectiveness of radiotherapy by delivering a high dose to the target volume irradiated through small spaces in one or more fractions.In this study, we investigated the feasibility of 3D Grid therapy dose distributions with CyberKnife and Varian RapidArc. The valley-peak ratios were compared. This is a dosimetric study. For this reason, 8 cm and 12 cm target volumes were defined on the rando phantom. Valley-peak dose distribution patterns were obtained by creating Grid dose vertices and avoidance in target volume. By changing hole diameter,center-to-center distance and open-closed area ratio, seven different Grid designs were generated. Treatment plans were made with CyberKnife and Varian RapidArc. TLD and EBT3 film were employed for dosimetric treatment verification. The measured and calculated doses from TPS were compared. In comparison of DVH, the highest difference in the maximum dose and mean dose was found to be 3% for 8 cm diameter target volume. For 12 cm diameter target volume, the highest difference in the maximum dose was 11%, while the highest difference in the mean dose was 2%. By changing hole diameter (1 cm, 1.5 cm, 2 cm) and center-to-center distance (1 cm, 2.2 cm, 3.5 cm), the valley-peak ratio was found to be 5% smaller decreasing hole diameter and center-to-center distance for CyberKnife. By changing hole diameter (1 cm, 1.5 cm, 2 cm) and open-closed area ratio (0.08, 0.2, 0.5), the valley-peak ratio was found to be 5% lower increasing the hole diameter and open-closed ratio for CyberKnife. Gama analysis resulted above the tolerance value of 90% gamma passing rate in all plans. Point dose measurements were found less than 10% in all plans. In this study, we concluded that although smaller valley-peak ratios were obtained with CyberKnife, the overall shape of dose volume histograms was similar in both systems. Furthermore, when we evaluated the treatment duration, the RapidArc plans were more appropriate for clinical routine. In addition, we recommend that the valley-peak ratios should be analyzed by radiobiological studies to evaluate how they change the therapeutic rate.