10.6084/m9.figshare.1623057.v1 Sarah O. S. Osman Sarah O. S. Osman Eleftheria Astreinidou Eleftheria Astreinidou Peter C. Levendag Peter C. Levendag Ben J. M. Heijmen Ben J. M. Heijmen Impact of geometric variations on delivered dose in highly focused single vocal cord IMRT Taylor & Francis Group 2014 ptv mu cl equivalent uniform dose planning CT scans exhale CT scans V 40 Gy CTV dose reductions Monte Carlo dose simulations glottic carcinoma patients 66 Gy cord IMRT Purpose reference dose distribution 2014-02-01 00:00:00 Journal contribution https://tandf.figshare.com/articles/journal_contribution/Impact_of_geometric_variations_on_delivered_dose_in_highly_focused_single_vocal_cord_IMRT/1623057 <div><p></p><p><i>Purpose.</i> To investigate the robustness of single vocal cord intensity modulated radiation therapy (IMRT) treatment plans for set-up errors, respiration, and deformation. <i>Material and methods.</i> Four-dimensional computed tomography (4D-CT) scans of 10 early glottic carcinoma patients, previously treated with conventional techniques, were used in this simulation study. For each patient a pre-treatment 4D-CT was used for IMRT planning, generating a reference dose distribution. Prescribed PTV dose was 66 Gy. The impact of systematic set-up errors was simulated by applying shifts of ± 2 mm to the planning CT scans, followed by dose re-calculation with original beam segments, MUs, etc. Effects of respiration and deformation were determined utilizing extreme inhale and exhale CT scans, and repeat scans acquired after 22 Gy, 44 Gy, and 66 Gy, respectively. All doses were calculated using Monte Carlo dose simulations. <i>Results.</i> Considering all investigated geometrical perturbations, reductions in the clinical target volume (CTV) V<sub>95%</sub>, D<sub>98%</sub>, D<sub>2%</sub>, and generalized equivalent uniform dose (gEUD) were limited to 1.2 ± 2.2%, 2.4 ± 2.9%, 0.2 ± 1.8%, and 0.6 ± 1.1 Gy, respectively. The near minimum dose, D<sub>98%</sub>, was always higher than 89%, and gEUD always remained higher than 66 Gy. Planned contra-lateral (CL) vocal cord D<sub>Mean</sub>, gEUD, and V<sub>40 Gy</sub> were 38.2 ± 6.0 Gy, 43.4 ± 5.6 Gy, and 42.7 ± 14.9%. With perturbations these values changed by −0.1 ± 4.3 Gy, 0.1 ± 4.0 Gy, and −1.0 ± 9.6%, respectively. <i>Conclusions.</i> On average, CTV dose reductions due to geometrical perturbations were very low, and sparing of the CL vocal cord was maintained. In a few observations (6 of 103 simulated situations), the near-minimum CTV-dose was around 90%, requiring attention in deciding on a future clinical protocol.</p></div>