Study of robust optimization in brachytherapy / 中华放射肿瘤学杂志

ABSTRACT

Objective:To evaluate the application value of robost optimization of brachytherapy for cervical cancer.Methods:Twenty patients who completed radical treatment were recruited in this study. The dose volume histogram (DVH) parameters were statistically compared between the conventional and robust optimization plans, and the robustness between the conventional and robust optimization plans was evaluated using DVH and DVH bands. The robust optimization method utilized the worst dose distribution to consider the dose in the presence of uncertainties. In each optimization iteration, the dose distributin when the radioactive source shifted along the X, Y, and Z directions (±2 mm), and the dose distribution when the radioactive source was not shifted were calculated. The worst dose distribution for each voxel was the lowest dose in the target and the highest dose outside the target under all circumstances. The iterative objective function was calculated by the worst dose distribution.Results:In the scenario of no shifting of radioactive source position, the mean value of robust optimization was significantly lower and that of V 150% was significantly higher than those of conventional optimization (both P<0.05). When considering the shifting of radioactive source position, the worst dosimetric parameters of multiple dose distributions were statistically compared. The mean HR-CTV D 100% values did not significantly differ between the robust and conventional optimization plans, whereas the mean D 90% value (range 0.02-0.03 Gy) of robust optimization was significantly higher than that of conventional optimization ( P<0.05). Robust optimization increased the D 2cm 3 of the bladder and small intestine, and the rectum dose was increased with the shifting of the radioactive source position in the robust optimization. The DVH bands did not significantly differ between the conventional and robust optimization plans for all patients. Conclusions:Robust optimization based on the worst dose distribution fails to significantly improve the robustness of brachytherapy for cervical cancer. Alternative methods are required to minimize the dosimetric effect of uncertainties in brachytherapy.