Iranian Journal of Medical Physics

Iranian Journal of Medical Physics

Dosimetric and Treatment Delivery Analysis of Volumetric Modulated Arc Therapy systems for Pharyngeal Carcinoma

Document Type : Original Paper

Authors
Srikanth Guduru 1
Rohith Singareddy 2
Madhusudhana Sresty N.V.N. 1
Deleep Kumar Gudipudi 2
Aparna Dode 3
1 Department of Radiation Physics, Basavatarakam Indo-American Cancer Hospital and Research Institute, Hyderabad, Telangana,500034, India
2 Department of Radiation Oncology, Basavatarakam Indo-American Cancer Hospital and Research Institute, Hyderabad, Telangana,500034, India
3 Department of Physics, University College of Science, Osmania University, Hyderabad, Telangana,500007, India
10.22038/ijmp.2026.88260.2554
Abstract
Introduction: This study evaluated the dosimetric performance and delivery efficiency of three volumetric modulated arc therapy (VMAT) techniques using different multileaf collimator (MLC) systems: MLCi2, Agility and HDMLC for the treatment of pharyngeal cancer.
Material and Methods: A retrospective analysis of 21 pharyngeal cancer patients was performed. For each patient, three VMAT plans were generated using a simultaneous integrated boost (SIB) technique, delivering 66 Gy, 60 Gy and 54 Gy to PTV66, PTV60 and PTV54 respectively, over 30 fractions. Plans were created in Monaco treatment planning system (TPS) with MLCi2 (VMAT1) and Agility (VMAT2) and in Eclipse TPS with HDMLC (RapidArc). Plan quality was evaluated using conformity index (CI), homogeneity index (HI) and mean dose for target volumes. Organ-at-risk (OAR) doses were assessed according to RTOG criteria, while treatment efficiency was analyzed using monitor units (MUs) and beam-on time (BOT).
Results: All techniques produced clinically acceptable plans. RapidArc demonstrated superior conformity for PTV66 and significantly improved homogeneity for PTV60 and PTV54. It also achieved reduced maximum doses to the spinal cord and decreased low- and medium-dose spillage to normal tissue compared with VMAT1 and VMAT2. RapidArc required fewer MUs and achieved shorter BOT (p < 0.05), indicating enhanced delivery efficiency.
Conclusion: While all techniques met clinical requirements, RapidArc with HDMLC achieved superior conformity, better OAR sparing and improved delivery efficiency. These findings underscore the pivotal role of MLC design and configuration in optimizing VMAT plan quality and treatment performance for head and neck cancers.
Keywords
Pharyngeal Neoplasms
Radiotherapy Planning
Multileaf Collimator
Volumetric Modulated Arc Therapy
Organs at Risk
Subjects
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Iranian Journal of Medical Physics
Volume 22, Issue 6 - Serial Number 6
November and December 2025
Pages 423-429

  • Receive Date 18 May 2025
  • Revise Date 10 February 2026
  • Accept Date 02 January 2026