Radiobiological evaluation of dose calculation algorithms in RapidArc planning of esophageal cancer treatment plans

Abstract

Purpose: The purpose of current study is to investigate the impact of tissue heterogeneity corrections in Acuros XB algorithm (AXB) and Anisotropic Analytical Algorithm (AAA) on RapidArc esophageal cancer treatment plans using equivalent uniform dose (EUD) calculations and tumor control probability (TCP).

Methods: Ten esophageal cancer cases were selected for the current study. All cases were planned using RapidArc technique in Eclipse treatment planning system (10.0.28). The treatment plans were inversely optimized using progressive resolution optimizer and each optimized plan was calculated using AAA with tissue heterogeneity correction. The AAA plans were then normalized such that prescription dose covered 95% of the planning target volume (PTV). The AXB plans were generated by recalculating the normalized AAA plans using AXB with tissue heterogeneity correction for identical monitor units and beam parameters as in the corresponding AAA plans. The EUD and TCP calculations were then performed on the AAA and AXB plans.

Results: For PTV, the EUD values in AXB plans were always lower than in AAA plans with an average difference of 1.3%. Similarly, AXB calculations produced smaller magnitude of EUD for the organs at risk (OARs) compared to AAA calculations. On average, in AXB plans, the lung EUD was lower by 3.5%, the liver EUD was lower by 2.3%, the heart EUD was lower by 2.8%, and the spinal cord EUD was lower by 1.8%. The TCP of AXB plans was lower by average difference of 7.1% compared to that of AAA plans.

Conclusion: In comparison to AAA calculations, the preliminary results presented in the current study showed that AXB calculations produced lower EUD and TCP for the PTV as well as lower EUD for OARs in the esophageal cancer treatment plans created by RapidArc planning technique.