A dose verification method using a monitor unit matrix for dynamic IMRT on Varian linear accelerators

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Dosimetry

Background:

• Accurate dosimetry verification is crucial for intensity modulated radiotherapy (IMRT).
• Existing independent dose calculation methods are inefficient for dynamic multi-leaf collimator (MLC) delivery.
• There is a need for efficient verification methods for dynamic MLC-based IMRT.

Purpose of the Study:

• To develop an efficient independent dose calculation method for dynamic MLC-based IMRT on Varian linear accelerators.
• To enable accurate dosimetry verification for advanced radiotherapy techniques.

Main Methods:

• Extracted machine delivery parameters from dynamic MLC (DMLC) files.
• Calculated a monitor unit (MU) matrix including direct exposure and leakage contributions.
• Computed primary and scattered doses using a modified Clarkson technique.

Main Results:

• The developed method demonstrated high agreement with measurements (average < 2% difference).
• The standard deviation between calculated and measured doses was approximately 1.9%.
• The method showed good agreement with treatment planning system calculations for 25 plans.

Conclusions:

• The novel dose calculation method provides accurate and efficient independent dosimetry verification for dynamic MLC IMRT.
• This technique addresses limitations of existing methods for dynamic beam delivery.
• The findings support improved quality assurance in IMRT.