Impact of dose calculation accuracy during optimization on lung IMRT plan quality.

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Intensity-modulated radiation therapy (IMRT) is a cornerstone of lung cancer treatment.
• Accurate dose calculation is crucial for optimizing IMRT plan quality.
• The impact of intermediate dose calculation steps during optimization on lung IMRT plans requires further investigation.

Purpose of the Study:

• To evaluate the effect of dose calculation accuracy and an intermediate dose calculation step during IMRT optimization on final plan quality for lung cancer patients.
• To compare dosimetric parameters between plans optimized with and without an intermediate dose calculation step.

Main Methods:

• Re-planning of 11 free-breathing lung IMRT cases using Varian Eclipse v11 TPS.
• Comparison of plans optimized with a fast pencil beam convolution algorithm (original) versus those using an intermediate analytical anisotropic algorithm (AAA) dose calculation during optimization (new).
• Analysis of dosimetric parameters including planning target volume (PTV) coverage, organs-at-risk (OARs) sparing, and monitor units (MU).

Main Results:

• New plans showed improved PTV dose homogeneity (HI: 0.08 vs. 0.12) and conformity (CI: 0.69 vs. 0.59).
• Significant reduction in dose to lungs (V5, V10, V30, mean dose), esophagus (mean dose, max dose, V20, V60), heart (mean dose, max dose, V40), and spinal cord (max dose) in new plans.
• Optimization efficiency improved, with a 50% reduction in iterations and 30% faster planning time (10-15 min savings).

Conclusions:

• Utilizing an intermediate dose calculation step during lung IMRT optimization improves PTV dose homogeneity and spares organs at risk.
• This method enhances planning efficiency and reduces overall treatment preparation time.
• Accurate dose calculation during optimization is vital for both IMRT plan quality and efficiency in lung cancer treatment.