Algorithm-based gantry angle range determination in volumetric modulated arc therapy for liver stereotactic body...

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Volumetric Modulated Arc Therapy (VMAT) is a radiotherapy technique used for liver cancer treatment.
• Optimizing gantry angle selection in VMAT is crucial for minimizing dose to organs at risk, such as normal liver tissue.
• Current methods for gantry angle selection can be subjective and vary between treatment planners.

Purpose of the Study:

• To develop and evaluate an algorithm-based method for determining optimal gantry angle ranges in VMAT for liver cancer.
• The primary goal is to minimize the beam path length through normal liver tissue.

Main Methods:

• An algorithm was developed to calculate shortest beam paths from liver surface to target center using DICOM contours.
• Three VMAT plans were generated for 15 liver cancer patients: automated (algorithm-based), expert manual, and novice manual.
• Plans were compared based on gantry angle ranges, liver path length, dose-volume parameters, monitor units, and Jaccard similarity for angle agreement.

Main Results:

• The automated plan achieved a mean normal liver path length comparable to expert plans (35.0 mm vs. 34.6 mm) and shorter than novice plans (39.3 mm).
• Jaccard similarity coefficients showed high agreement between automated and expert plans (0.86) and good agreement with novice plans (0.80).
• Dosimetric parameters and monitor units were similar across all plan types, with no significant differences.

Conclusions:

• The algorithmic approach offers a simple, quantitative, and reproducible method for determining gantry angles in liver VMAT.
• This method effectively replicates expert planner decisions, reduces inter-planner variability, and can standardize gantry angle selection.
• The algorithm has the potential to streamline the VMAT treatment planning process for liver cancer.