Analysis of the Effect of Tomotherapy Plan Parameters on Patient-Specific Delivery Quality Assurance (DQA)

When Delivery Quality Assurance (DQA) results do not coincide with specific criteria, re-measurement and re-treatment planning are required because incorrect beam delivery to the patient may occur. Therefore, an analysis of the plan parameters to find reasons for failure is essential. In this paper, we examine the effect of plan parameters on the DQA passing rate and clarify the plan parameters that should be adjusted mainly for each Tomotherapy when DQA fails and re-planning is required. Two versions of Tomotherapy treatment machines, Tomotherapy Hi-art and Radixact X9, were used. An independent t-test was performed to confirm the significant difference between the DQA passing rates of Tomotherapy Hi-art and Radixact X9. Also, a regression analysis was performed to analyze the correlation between plan parameters and passing rates. The average passing rate for Radixact X9 was 99.82 (standard deviation [SD] = 0.32) and that for Tomotherapy Hi-art was 98.46 (SD = 1.76). The passing rate of Radixact X9 was significantly higher than that of Tomotherapy Hi-art (P = 0.000). Statistically significant independent variables adopted from Tomotherapy Hi-art were IEC Yf (p = 0.025), the modulation factor (p = 0.003), and the number of control points (p = 0.006). The statistically significant parameter for Radixact X9 was IEC Xf (p = 0.000). According to the results, the new version of Tomotherapy(Radixact X9) has a relatively higher DQA pass rate than the old version (Tomotherapy Hi-art), and if the DQA fails and re-planning is required, each of the plan parameters can be adjusted to achieve a higher pass rate.