Patient-specific IMRT verification using independent fluence-based dose calculation software: experimental...

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Quality Assurance

Background:

• Patient-specific quality assurance (QA) is crucial for intensity-modulated radiotherapy (IMRT).
• Experimental methods are standard for IMRT verification but can be time-consuming.

Purpose of the Study:

• To evaluate the accuracy and performance of independent dose calculation software (MUV) for patient-specific IMRT QA.
• To compare MUV's computational approach with experimental measurements.

Main Methods:

• Recalculated 52 IMRT plans using treatment planning systems (TPS) and MUV in a QA phantom.
• Performed experimental 1D/2D verification using ionization chambers and films.
• MUV's fluence-based algorithm models physical effects like collimator transmission and scatter.

Main Results:

• Average deviations between MUV and ionization chamber measurements were 0.5 +/- 1.1% for composite plans.
• Average deviations between MUV and TPS for individual beams were 1.1 +/- 2.9%, with most absolute doses < 3 cGy.
• MUV calculations are significantly faster than experimental verification methods.

Conclusions:

• Independent dose calculation software (MUV) demonstrates high accuracy for patient-specific IMRT QA.
• Proposed confidence limits for routine QA: 3% or 6 cGy, with 5% or 10 cGy for off-axis/low-dose regions.
• Independent calculations offer a time-efficient alternative to experimental verification for mature IMRT programs.