VMAT-like plans for magnetic resonance guided radiotherapy: Addressing unmet needs

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Technology

Background:

• Volumetric Modulated Arc Therapy (VMAT) is not currently feasible with Magnetic Resonance-guided radiotherapy (MRgRT) hybrid systems.
• Developing alternative delivery techniques for MRgRT is crucial for advancing treatment capabilities.

Purpose of the Study:

• To evaluate an innovative VMAT-like (VML) delivery technique for MRgRT systems.
• To compare the dosimetric and planning characteristics of VML with Intensity-Modulated Radiation Therapy (IMRT).

Main Methods:

• Dosimetric evaluation of VML plans across 10 disease sites compared to IMRT.
• Retrospective re-planning of 10 challenging locally advanced pancreas cancer cases using VML.
• Assessment of VML plan robustness against a 5mm lateral positioning error.

Main Results:

• VML plans met all organ at risk (OAR) constraints in initial evaluations.
• VML provided equal or superior planning target volume (PTV) coverage compared to IMRT in 50% of cases, with minimal undercoverage in others.
• VML plans demonstrated improved target coverage in pancreas cancer cases while respecting OAR constraints, with acceptable treatment time variations.

Conclusions:

• The VMAT-like (VML) technique is an efficient planning solution for MRgRT.
• Clinical implementation of VML is recommended, especially for hypofractionated treatments.
• While VML does not enhance plan robustness, its planning efficiency and dosimetric benefits support its adoption.