Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology | 2019
Effect of setup and inter-fraction anatomical changes on the accumulated dose in CT-guided breath-hold intensity modulated proton therapy of liver malignancies.
Abstract
PURPOSE\nTo evaluate the effect of setup uncertainties including uncertainties between different breath holds (BH) and inter-fractional anatomical changes under CT-guided BH with intensity-modulated proton therapy (IMPT) in patients with liver cancer.\n\n\nMETHODS AND MATERIALS\nThis retrospective study considered 17 patients with liver tumors who underwent feedback-guided BH (FGBH) IMRT treatment with daily CT-on-rail imaging. Planning CT images were acquired at simulation using FGBH, and FGBH CT-on-rail images were also acquired prior to each treatment. Selective robust IMPT plans were generated using planning CT and re-calculated on each daily CT-on-rail image. Subsequently, the fractional doses were deformed and accumulated onto the planning CT according to the deformable image registration between daily and planning CTs. The doses to the target and organs at risk (OARs) were compared between IMRT, planned IMPT, and accumulated IMPT doses.\n\n\nRESULTS\nFor IMPT plans, the mean of D98% of CTV for all 17 patients was slightly reduced from the planned dose of 68.90\u202f±\u202f1.61\u202fGy to 66.48\u202f±\u202f1.67\u202fGy for the accumulated dose. The target coverage could be further improved by adjusting planning techniques. The dose-volume histograms of both planned and accumulated IMPT doses showed better sparing of OARs than that of the IMRT.\n\n\nCONCLUSIONS\nIMPT with FGBH and CT-on-rail guidance is a robust treatment approach for liver tumor cases.