<abstract xmlns="http://www.w3.org/1999/xhtml">

<italic>Introduction:</italic> The purpose of this study was to determine the best normal tissue objective (NTO) values based on the dose distribution from brain tumor radiation therapy.
<italic>Material and methods:</italic> The NTO is a constraint provided by Eclipse to limit the dose to normal tissues by steepening the dose gradient. The multitude of NTO setting combinations necessitates optimal NTO settings. The Eclipse supports manual and automatic NTOs. Fifteen patients were re-planned using NTO priorities of 1, 50, 100, 150, 200, and 500 in combination with dose fall-offs of 0.05, 0.1, 0.2, 0.3, 0.5, 1 and 5 mm-1. NTO distance to planning target volume (PTV), start dose, and end dose were 1 mm, 105%, and 60%, respectively, for all plans. In addition, planning without the NTO was arranged to find out its effect on planning. The prescription dose covered 95% of the PTV. Planning was evaluated using several indices: conformity index (CI), homogeneity index (HI), gradient index (GI), modified gradient index (mGI), comprehensive quality index (CQI), and monitor unit (MU). Differences among automatic NTO, manual NTO, and without NTO were evaluated using the Wilcoxon signed-rank test.
<italic>Results:</italic> Comparisons obtained without and with manual NTO were: CI of 0.77 vs. 0.96 (p = 0.002), GI of 4.52 vs. 4.69 (p = 0.233), mGI of 4.93 vs. 3.95 (p = 0.001), HI of 1.10 vs. 1.10 (p = 0.330), and MU/cGy of 3.44 vs. 3.42 (p = 0.460). Planning without NTO produced a poor conformity index. Comparisons of automatic and manual NTOs were: CI of 0.92 vs. 0.96 (p = 0.035), GI of 5.25 vs. 4.69 (p = 0.253), mGI of 4.46 vs. 3.95 (p = 0.001), HI of 1.09 vs. 1.10 (p = 0.004), MU/cGy of 3.31 vs. 3.42 (p = 0.041).
<italic>Conclusions:</italic> Based on these results, manual NTO with a priority of 100 and dose fall-off 0.5 mm-1 was optimal, as indicated by the high dose reduction in normal tissue.
</abstract>

Introduction: The purpose of this study was to determine the best normal tissue objective (NTO) values based on the dose distribution from brain tumor radiation therapy.
Material and methods: The NTO is a constraint provided by Eclipse to limit the dose to normal tissues by steepening the dose gradient. The multitude of NTO setting combinations necessitates optimal NTO settings. The Eclipse supports manual and automatic NTOs. Fifteen patients were re-planned using NTO priorities of 1, 50, 100, 150, 200, and 500 in combination with dose fall-offs of 0.05, 0.1, 0.2, 0.3, 0.5, 1 and 5 mm-1. NTO distance to planning target volume (PTV), start dose, and end dose were 1 mm, 105%, and 60%, respectively, for all plans. In addition, planning without the NTO was arranged to find out its effect on planning. The prescription dose covered 95% of the PTV. Planning was evaluated using several indices: conformity index (CI), homogeneity index (HI), gradient index (GI), modified gradient index (mGI), comprehensive quality index (CQI), and monitor unit (MU). Differences among automatic NTO, manual NTO, and without NTO were evaluated using the Wilcoxon signed-rank test.
Results: Comparisons obtained without and with manual NTO were: CI of 0.77 vs. 0.96 (p = 0.002), GI of 4.52 vs. 4.69 (p = 0.233), mGI of 4.93 vs. 3.95 (p = 0.001), HI of 1.10 vs. 1.10 (p = 0.330), and MU/cGy of 3.44 vs. 3.42 (p = 0.460). Planning without NTO produced a poor conformity index. Comparisons of automatic and manual NTOs were: CI of 0.92 vs. 0.96 (p = 0.035), GI of 5.25 vs. 4.69 (p = 0.253), mGI of 4.46 vs. 3.95 (p = 0.001), HI of 1.09 vs. 1.10 (p = 0.004), MU/cGy of 3.31 vs. 3.42 (p = 0.041).
Conclusions: Based on these results, manual NTO with a priority of 100 and dose fall-off 0.5 mm-1 was optimal, as indicated by the high dose reduction in normal tissue.

Normal tissue objective (NTO) tool in Eclipse treatment planning system for dose distribution optimization

Department of Physics, Faculty of Sciences and Mathematics

Department of Applied Physics and Medical Imaging

California State University Channel Islands

Polish Journal of Medical Physics and Engineering

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Introduction: The purpose of this study was to determine the best normal tissue objective (NTO) values based on the dose distribution from brain tumor...

Normal tissue objective (NTO) tool in Eclipse treatment planning system for dose distribution optimization

Published Online: Jun 21, 2022

Page range: 99 - 106

Received: Dec 28, 2021

Accepted: May 11, 2022

DOI: https://doi.org/10.2478/pjmpe-2022-0012

Keywords
normal tissue objective, priority, fall off, external beam radiation therapy, IMRT

© 2022 Liza Indrayani et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Normal tissue objective (NTO) tool in Eclipse treatment planning system for dose distribution optimization

Published Online: Jun 21, 2022

Page range: 99 - 106

Received: Dec 28, 2021

Accepted: May 11, 2022

DOI: https://doi.org/10.2478/pjmpe-2022-0012

Keywordsnormal tissue objective, priority, fall off, external beam radiation therapy, IMRT

© 2022 Liza Indrayani et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Keywords
normal tissue objective, priority, fall off, external beam radiation therapy, IMRT