Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB) · 2019
Volumetric modulated arc therapy with robust optimization for larynx cancer.
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Miura Hideharu, Doi Yoshiko, Ozawa Shuichi, Nakao Minoru, Ohnishi Keiichi, Kenjo Masahiko, Nagata Yasushi
Аннотация
PURPOSE: The aim of this study was to perform a comparison between robust optimization and planning target volume (PTV)-based optimization plans using volumetric modulated arc-therapy (VMAT) by evaluating perturbed doses induced by localization offsets for setup uncertainties in larynx cancer radiation therapy.
METHODS: Ten patients with early-stage (T1-2N0) glottis carcinoma were selected. The clinical target volume (CTV), carotid arteries, and spinal cord were contoured by a radiation oncologist. PTV-based and robust optimization plans were normalized at D50% to the PTV and D98% to the CTV, respectively. Both optimization plans were evaluated using perturbed doses by specifying user defined shifted values from the isocenter. CTV dose (D98%, D50%, and D2%), homogeneity index (HI) and conformity index (CI95%, CI80%, and CI50%), as well as doses to the carotid arteries and spinal cord were compared between PTV-based and robust optimization plans.
RESULTS: The robust optimization plans exhibited superior CTV coverage and a reduced dose to the carotid arteries compared to the PTV-based optimization plans (p < 0.05). HI, CI95% and the dose to the spinal cord did not significantly differ between the PTV-based and robust optimization plans (p > 0.05). The robust optimization plans showed better CI80% and CI50% compared to the PTV-based optimization plans (p < 0.05). Plan perturbed evaluations showed that the robust optimization plan has small variations in the doses to the CTV, carotid arteries, and spinal cord compared to the PTV-based optimization plan.
CONCLUSIONS: The robust optimization plan may be a suitable treatment method in radiotherapy for larynx cancer patient.
METHODS: Ten patients with early-stage (T1-2N0) glottis carcinoma were selected. The clinical target volume (CTV), carotid arteries, and spinal cord were contoured by a radiation oncologist. PTV-based and robust optimization plans were normalized at D50% to the PTV and D98% to the CTV, respectively. Both optimization plans were evaluated using perturbed doses by specifying user defined shifted values from the isocenter. CTV dose (D98%, D50%, and D2%), homogeneity index (HI) and conformity index (CI95%, CI80%, and CI50%), as well as doses to the carotid arteries and spinal cord were compared between PTV-based and robust optimization plans.
RESULTS: The robust optimization plans exhibited superior CTV coverage and a reduced dose to the carotid arteries compared to the PTV-based optimization plans (p < 0.05). HI, CI95% and the dose to the spinal cord did not significantly differ between the PTV-based and robust optimization plans (p > 0.05). The robust optimization plans showed better CI80% and CI50% compared to the PTV-based optimization plans (p < 0.05). Plan perturbed evaluations showed that the robust optimization plan has small variations in the doses to the CTV, carotid arteries, and spinal cord compared to the PTV-based optimization plan.
CONCLUSIONS: The robust optimization plan may be a suitable treatment method in radiotherapy for larynx cancer patient.