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Aim <p>This study investigates the impact of gantry speed (GS) and dose rate (DR) variations on VMAT RapidArc plan quality and delivery using the Photon Optimizer (PO) and Progressive Resolution Optimizer (PRO) algorithms in the Varian TrueBeam LINAC.</p> Materials and methods <p>Five treatment sites (brain, head and neck, Hodgkin’s lymphoma, advanced lung, and cervix) were planned using PO and PRO algorithms. Plans were generated with varying GS (0.5 and 6.0&#xa0;deg/s) and DR (100–600 MU/min) combinations, resulting in 24 plans per site. Plan quality was assessed using DVH parameters and isodose distributions. Technical delivery aspects, including MU/deg, total MU, DR, and GS patterns, were analyzed. Trajectory log files provided data on planned vs. delivered dose, gantry angle deviations, and MLC position deviations. Pre-treatment QA was performed using Portal dosimetry, with a 3%/3&#xa0;mm gamma criterion.</p> Results <p>Both PO and PRO algorithms demonstrated similar dose distributions and PTV coverage D95% (differences &lt; 3%) across all sites and GS/DR combinations. Minor variations in OAR doses were observed. Maximum MU/deg limits varied with GS and DR levels, with PO showing higher limits at slower GS. PO generally exhibited higher MU/deg and DR compared to PRO. Gantry speed remained constant at the set value during delivery. Trajectory log analysis confirmed accurate dose delivery, with deviations in gantry angle and MLC positions within tolerances. Portal dosimetry yielded high gamma passing rates (&gt; 98.6%) for both algorithms across all sites and GS/DR combinations, indicating accurate dose calculation and delivery.</p> Conclusion <p>This study provides valuable insights into the technical aspects of VMAT delivery and supports the clinical use of both PO and PRO algorithms for a wide range of treatment sites and delivery conditions. Truebeam LINAC controller systems data confirmed any variation of GS and DS deliver better accuracy for both optimizers. Current Truebeam platform LINAC can deliver any extreme mechanical limits without causing or reducing accuracy plans can be delivered very accurately.</p>

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Evaluation of dose rate and gantry speed variations in volumetric modulated Arc therapy optimization algorithms for a modern linear accelerator

  • 期刊论文

  • 发表日期：

    2026年1月5日

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  • Venugopal Sundaram,
  • David Khanna,
  • Mohandass Palanisamy

摘要

Aim

This study investigates the impact of gantry speed (GS) and dose rate (DR) variations on VMAT RapidArc plan quality and delivery using the Photon Optimizer (PO) and Progressive Resolution Optimizer (PRO) algorithms in the Varian TrueBeam LINAC.

Materials and methods

Five treatment sites (brain, head and neck, Hodgkin’s lymphoma, advanced lung, and cervix) were planned using PO and PRO algorithms. Plans were generated with varying GS (0.5 and 6.0 deg/s) and DR (100–600 MU/min) combinations, resulting in 24 plans per site. Plan quality was assessed using DVH parameters and isodose distributions. Technical delivery aspects, including MU/deg, total MU, DR, and GS patterns, were analyzed. Trajectory log files provided data on planned vs. delivered dose, gantry angle deviations, and MLC position deviations. Pre-treatment QA was performed using Portal dosimetry, with a 3%/3 mm gamma criterion.

Results

Both PO and PRO algorithms demonstrated similar dose distributions and PTV coverage D95% (differences < 3%) across all sites and GS/DR combinations. Minor variations in OAR doses were observed. Maximum MU/deg limits varied with GS and DR levels, with PO showing higher limits at slower GS. PO generally exhibited higher MU/deg and DR compared to PRO. Gantry speed remained constant at the set value during delivery. Trajectory log analysis confirmed accurate dose delivery, with deviations in gantry angle and MLC positions within tolerances. Portal dosimetry yielded high gamma passing rates (> 98.6%) for both algorithms across all sites and GS/DR combinations, indicating accurate dose calculation and delivery.

Conclusion

This study provides valuable insights into the technical aspects of VMAT delivery and supports the clinical use of both PO and PRO algorithms for a wide range of treatment sites and delivery conditions. Truebeam LINAC controller systems data confirmed any variation of GS and DS deliver better accuracy for both optimizers. Current Truebeam platform LINAC can deliver any extreme mechanical limits without causing or reducing accuracy plans can be delivered very accurately.