Impact on Undefined Normal Tissue by using different combination of Normal Tissue Objective and Dose Control Ring in IMRT Plans for Cervix cancer
Introduction: The normal tissue objective (NTO) is a tool used in inverse planning of Intensity Modulated Radiation Therapy (IMRT) to reduce dose spreading to surrounding normal tissues. The multitude of potential NTO setting combinations challenges optimal NTO tunning. In addition to NTO, Dose Control Ring (DCR) around the target may impact plan quality.
Aim and Objective: To find the impact on Undefined Normal Tissue (UNT) by using the different combinations of NTO and DCR in IMRT Plans for Cervical cancer plans.
Materials and Methods: Our sample consists of 30 patients with similar treatment prescription doses. Varian Eclipse Treatment Planning System (TPS) of Version13.6 was used in this study. 5 different plans were created for each patient. In every plan beam energy, several beams, Beam angle, Optimization algorithm - Photon optimizer (PO), Calculation algorithm – Anisotropic analytic algorithm (AAA)and evaluation methods were maintained constant. 5 plans were different only in the optimization process. Before generating plans DCR of thickness 1.0 cm and 0.5 cm away from the Planning Target Volume (PTV) was created. The plan with different combinations between NTO and DCR were A. Without NTO, B. Automatic NTO, C. Manual NTO, D. Automatic NTO + DCR, E. Manual NTO + DCR generated. The plan quality was evaluated by comparing PTV: Conformity Index (CI), Homogeneity Index, OAR Doses and mean dose to UNT.
Results: HI was better without NTO plans compared to all other plans. CI and OAR doses show a significant difference in Manual NTO along with DCR plans. The mean dose of UNT was less in Manual NTO along with DCR compared to all other plans and it was significantly less.
Conclusion: This study shows that manual NTO + Dose Control Ring gives better plan quality in terms of PTV coverage and less dose to Undefined Normal Tissue by maintaining Organ at Risk dose within the tolerance limits.
2. Khan FM, Gibbons JP. Khan's the physics of radiation therapy. Lippincott Williams & Wilkins; 2014.
3. Bell JP, Patel P, Higgins K, McDonald MW, Roper J. Fine-tuning the normal tissue objective in eclipse for lung stereotactic body radiation therapy. Med Dosim. 2018 Winter;43(4):344-350. doi: 10.1016/j.meddos.2017.11.004. Epub 2017 Dec 23. PMID: 29277249.
4. Gerdán M, Pócza T, Polgár C, Major T. The effects of nor¬mal tissue objective parameters on lung stereotactic body radiotherapy dose distributions. MagyOnkol 65:14-22, 2021
5. Fogliata A, Nicolini G, Clivio A, Vanetti E, Cozzi L. Critical appraisal of Acuros XB and Anisotropic Analytic Algorithm dose calculation in advanced non-small-cell lung cancer treatments. Int J Radiat Oncol Biol Phys. 2012 Aug 1;83(5):1587-95. doi: 10.1016/j.ijrobp.2011.10.078. Epub 2012 Jan 31. PMID: 22300575.
Copyright (c) 2022 Author (s). Published by Siddharth Health Research and Social Welfare Society
This work is licensed under a Creative Commons Attribution 4.0 International License.