Beam controlled arc therapy--a delivery concept for stationary targets

Area of Science:

• Radiation oncology
• Medical physics
• Cancer treatment technology

Background:

• Volumetric modulated arc therapy (VMAT) assumes continuous radiation delivery from all angles.
• Continuous delivery may lead to suboptimal dose distribution due to radiation from undesirable angles.
• Current VMAT techniques may compromise treatment efficacy and patient safety.

Purpose of the Study:

• To introduce and evaluate beam-controlled arc therapy (BCAT) as an alternative to VMAT.
• To challenge the necessity of continuous beam delivery during arc radiotherapy.
• To assess BCAT's impact on plan quality and delivery efficiency.

Main Methods:

• Developed BCAT, modulating beam on/off status and dose rate during gantry rotation.
• Employed linear-programming-based dose optimization for aperture weights, allowing zero weights.
• Tested BCAT on ten head and neck cancer cases, comparing with VMAT.

Main Results:

• BCAT achieved significant improvements: up to 17% in organ-at-risk sparing (p=0.001) and 57% in target dose uniformity (p=0.018).
• BCAT used a comparable number of apertures to VMAT (109 vs. 175 on average) with less than 4% difference in total Monitor Units (MUs).
• Post-delivery analysis confirmed plan quality with over 99% agreement using gamma analysis.

Conclusions:

• BCAT offers superior plan quality and delivery efficiency compared to VMAT for head and neck cancers.
• The beam-off capability at zero-weight apertures in BCAT optimizes dose delivery.
• BCAT represents a promising advancement in intensity-modulated arc therapy.