An Analytical Comparison of Two Daily Pre-Treatment Image Verification Approaches Utilizing Radixact™ Tomotherapy-Based Megavoltage Computed Tomography for Head and Neck Cancer Patients

<i>Introduction:</i> Ensuring accurate patient setup is crucial in radiotherapy for head and neck cancer (HNC) due to the intricate anatomy and the closeness to vital organs. This study aimed to assess and compare the effectiveness of two different daily pre-treatment auto image registration techniques utilizing Radixact TomoTherapy-based megavoltage computed tomography (MVCT) to enhance setup accuracy and treatment consistency. <i>Materials and Methods:</i> A prospective analysis was performed on a cohort of twenty HNC patients undergoing treatment with Radixact TomoTherapy. Two image verification techniques were assessed: one focused on aligning bony anatomy (Method A) and the other on adjusting the cross-wire at the center of the planning target volume (PTV) for automatic registration (Method B). Daily MVCT images were taken and analyzed to determine translational setup corrections, which were documented for further analysis. <i>Results:</i> Method B exhibited slightly lower mean systematic errors in both the longitudinal and lateral directions, although the differences were not statistically significant. Method A demonstrated significantly lower errors in the vertical (Z-axis) direction (p = 0.013). Overall displacement vectors favored Method A, yet multivariate analysis indicated no significant difference between the two methods. Therefore, both methods were found to perform similarly, with Method A showing superior vertical alignment. <i>Conclusions:</i> Both auto image registration techniques provide accuracy and dependability, bolstered by reproducible anatomy and clinician supervision. For optimal precision, Method A is suggested for initial gross alignment, followed by Method B for fine-tuning around the target volume, thereby improving dose precision and safety in high-accuracy radiotherapy treatments. <i>Key Messages:</i> Combining initial alignment with Method A and refinement with Method B enhances precision and safety in head and neck radiotherapy, optimizing setup accuracy using Radixact TomoTherapy MVCT imaging.