Analysis of plan parameters affecting the delivery quality assurance passing rate of the Tomo direct method in Radixact X9

Abstract

Delivery quality assurance (DQA) is the process of establishing a treatment plan and verifying that the pre-treatment dose is delivered without any problems through a simulation. If the result does not meet certain criteria, the dose delivered to the patient is judged to be inaccurate, and the measurement or the treatment plan should be reconsidered. Therefore, it is important to analyze the plan parameters that influence the DQA outcome. The plan parameters have been studied for LINAC-based intensity-modulated radiation therapy and the Tomo helical method but not for the Tomo direct (TD) method. In this study, we perform this investigation using the TD method. A Radixcat X9 machine was used to collect data. Furthermore, in the TD method, we set the passing rate for each gamma analysis criterion as 2%/2 mm and 3%/3 mm. Next, the plan parameters influencing the DQA passing rate were confirmed by Pearson's correlation analysis and regression analysis. Based on the gamma analysis, the mean passing rates of 2%/2 mm and 3%/3 mm were 97.9299 and 99.8472, respectively. The plan parameters influencing the DQA passing rate during the Pearson correlation analysis were IECZ (2%/2 mm: p = 0.008), duration (2%/2 mm: p = 0.002), and planning target volume (2%/2 mm: p = 0.030 and 3%/3 mm: p = 0.034). Based on these results, a regression analysis was performed. As a result of the regression analysis, duration (2%/2 mm: p = 0.047) was identified as the most significant plan parameter for the DQA passing rate. However, statistically for the gamma analysis criterion of 3%/3 mm, there were no significant plan parameters. As the beta of the duration has a negative relationship with the passing rate, reducing the duration improves the passing rate. When confirming the passing rate for each group in a duration of 60 s, it was confirmed that the passing rate was high if it was set to less than 240 s. So, we recommend setting the duration to 240 s or less.