A Novel Method for Improving VMAT Plan Quality and Deliverability

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Planning

Background:

• A novel Volumetric Modulated Arc Therapy (VMAT) technique, termed Augmented Arc (Aug Arc), is introduced.
• Aug Arc involves augmenting specific portions of a VMAT arc with an additional arc to enhance treatment plan quality.
• The identification of these Aug Arc portions relies on an objective function-based scoring method, the 'ψ - score'.

Purpose of the Study:

• To demonstrate the clinical validity and effectiveness of the proposed Augmented Arc (Aug Arc) VMAT method.
• To evaluate Aug Arc's performance across diverse clinical scenarios, including Lung, Abdomen, Gynecologic (Gyn), and Pancreas cases.
• To assess the impact of Aug Arc on plan quality and deliverability compared to conventional VMAT techniques.

Main Methods:

• Four clinical cases (Lung, Abdomen, Gyn, Pancreas) were used to validate the Aug Arc approach.
• Different plan configurations were generated: Single Arc (S Arc), Double Arc (D Arc), Partial Arc (P Arc), and Augmented Arc (P+Aug Arc or S+Aug Arc).
• The 'ψ - score' was computed using initial optimization with a full arc and 4-degree gantry spacing to identify optimal Aug Arc portions.

Main Results:

• The Augmented Arc (Aug Arc) method significantly improved plan quality and deliverability for both central and non-central tumors.
• Key improvements included reductions in Organs at Risk (OAR) dose, monitor units (MUs), and beam-on time.
• Low dose volume was reduced without compromising target coverage, indicating enhanced treatment precision.

Conclusions:

• The proposed Augmented Arc (Aug Arc) approach offers a balanced solution between single/partial arc and full double arc VMAT techniques.
• Planners can leverage Aug Arc to identify optimal delivery parameters, achieving a 'sweet spot' for superior plan quality.
• This method enhances radiotherapy planning by optimizing efficiency and therapeutic ratio.