Feasibility of Patient-Specific Quality Assurance Using Gamma Analysis for IMRT Plans in Laryngeal Cancer

Abstract

Purpose: Laryngeal cancer is a critical health issue, often treated using advanced radiation therapy techniques such as Intensity-Modulated Radiation Therapy (IMRT). The gamma index is a widely used metric for quality assurance in radiotherapy, assessing the agreement between planned and delivered dose distributions.

This study aims to evaluate the feasibility and accuracy of laryngeal IMRT treatment plans using three gamma analysis algorithms and varying evaluation parameters, including Dose Difference (DD%), and Distance-To-Agreement (DTA).

Materials and Methods: IMRT treatment plans for laryngeal cancer were generated using the Prowess Panther V5.5 Treatment Planning System (TPS). Patient-Specific Quality Assurance (PSQA) was conducted using EBT3 Gafchromic films scanned at 350 dpi and analyzed with RIT Complete 6.11 software. Dose distributions were evaluated using three gamma analysis algorithms under 3%/3 mm criteria and low-dose thresholds of 15%. Calibration of the films was performed to ensure accurate dose measurements.

Results: Gamma Passing Rates (GPR) for the laryngeal IMRT plans demonstrated high accuracy, with over 90% of pixels passing the criteria in most cases. Composite gamma analysis showed 53.89% of pixels meeting both DD and DTA criteria simultaneously, while individual evaluation revealed the impact of stricter thresholds on GPR. Subtraction analysis identified dose discrepancies, emphasizing the need for accurate calibration.

Conclusion: This study highlights the effectiveness of gamma analysis in ensuring the accuracy of IMRT treatment plans for laryngeal cancer. The findings underscore the importance of rigorous PSQA, parameter optimization, and advanced algorithms to enhance treatment precision.