Evaluation of Different Strategies to Reduce the Dose to Normal Tissues in VMAT Planning of Esophageal Carcinoma Using the Eclipse Treatment Planning System

Md. Mahmudul H. Manna, Mohammad A. Islam, Md O. Rahman

Abstract


The aim of this study is to quantify the dosimetric impact of the normal tissue objective (NTO) on volumetric‑modulated arc therapy (VMAT) for mid‑thoracic esophageal cancer and to identify an optimal NTO configuration in Varian Eclipse Planning System. VMAT plans with prescription dose 50.40 Gy in 28 fractions were generated in Eclipse v15.1 for 22 patients using dual 6‑MV arcs and the Anisotropic Analytical Algorithm (AAA). Organs at risk (OARs) included lungs, heart, liver, spinal cord and normal tissue (NT). All plans were normalized such that 95% of the planning target volume (PTV) received ≥95% of the prescription dose. Five strategies were compared per patient: (1) without NTO, (2) ring only, (3) Auto‑NTO, (4) Auto‑NTO + ring, and (5) manual NTO (ManNTO). Systematic parameter sweeps were performed for ManNTO. Among non‑manual strategies, Auto‑NTO + ring provided the most favorable balance between PTV coverage and OAR sparing. ManNTO further improved plan quality. The optimal ManNTO setting (start dose 105%, end dose 10%, 1‑mm distance from the PTV, fall‑off 1.0 mm⁻¹, priority 150) yielded superior PTV coverage (D95% = 98.95%), lower mean normal‑tissue dose (13.125 Gy), reduced 50% isodose volume (60.47 cc), and enhanced delivery efficiency (MU/PD = 2.378) compared with all other strategies. A carefully optimized manual NTO configuration in Eclipse planning system significantly enhances OAR sparing, steepens normal‑tissue dose fall‑off, and improves delivery efficiency while maintaining or exceeding target coverage, and can reduce planning time significantly.


Keywords


Normal Tissue Objective (NTO); ring structure; esophageal cancer; VMAT; treatment plan evaluation

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References


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DOI: http://dx.doi.org/10.52155/ijpsat.v55.1.7728

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