The effect of multi-leaf collimator leaf width on VMAT treatment plan quality

Area of Science:

• Radiotherapy physics and technology
• Medical physics
• Radiation oncology

Background:

• Volumetric modulated arc therapy (VMAT) is a widely adopted radiotherapy technique.
• Previous studies indicated narrower multi-leaf collimator (MLC) widths improve intensity-modulated radiation therapy (IMRT) plan quality.
• The impact of MLC leaf width on VMAT plans requires re-evaluation in a global context.

Purpose of the Study:

• To assess the effect of different MLC leaf widths on VMAT treatment plan quality.
• To determine if wider MLC leaf widths yield clinically acceptable VMAT plans.
• To explore implications for radiotherapy in resource-limited settings.

Main Methods:

• VMAT treatment plans were generated for 51 cancer patients using MLC leaf widths of 2.5, 5, and 10 mm.
• Plans were evaluated using dose metrics (D2, D50, D98), homogeneity index (HI), conformity index (CI), average leaf pair opening (ALPO), modulation factor (MF), and estimated treatment delivery time.
• Statistical analysis was performed to compare plan quality across different leaf widths.

Main Results:

• Target dose coverage showed minimal differences between 2.5 and 5 mm MLCs; 10 mm MLCs resulted in a statistically significant increase in D2 and D50.
• Organs at Risk (OAR) sparing was comparable, though 10 mm MLCs showed increased dose to the bladder and heart at low percentages.
• Wider MLCs (10 mm) exhibited smaller average leaf pair openings and shorter leaf travel distances, with no significant difference in estimated treatment delivery time.

Conclusions:

• MLC leaf width has a minimal impact on overall VMAT treatment plan quality.
• Wider MLC leaf widths (up to 10 mm) can produce clinically acceptable VMAT plans.
• This finding is significant for improving radiotherapy accessibility and efficiency in low- and middle-income countries.