Introduction: The brain is the main part of the central nervous system. In oncology, radiotherapy, alongside surgery and systemic therapy, is one of the three fundamental methods of treating cancer. Successful local treatment requires high precision in radiation procedures, which is ensured during the treatment with image-guided radiotherapy. The patient's position on the treatment table is corrected before each session by adjusting the table based on the measured shifts in alignment of daily images on the device with the simulator images. Automatic alignment can optimize the radiation process in terms of time. Objective: To determine the accuracy of automatic image alignment in image verification using a tabletop imaging system and cone-beam computed tomography during the treatment of primary brain tumors on the TrueBeam STx linear accelerator. We will also investigate the accuracy of image verification with the tabletop imaging system and cone-beam computed tomography. Methods: At the radiotherapy department of the Oncology Institute Ljubljana, we conducted an observational prospective non-interventional clinical study on the selected linear accelerator during radical radiotherapy of primary brain tumors in the period from February 1, 2023, to November 1, 2023. We included data from 29 patients with 18 to 30 treatment fractions. Results: In all translational and two rotational directions, the average shift between automatic and manual alignment during image verification with the tabletop imaging system did not differ. In the roll direction, the difference in average shifts was statistically significant. Differences in average shifts between automatic and manual alignment in image verification with cone-beam computed tomography were not statistically significant in any of the six measured movement directions (p < 0.05). The total percentage of translational manual additional adjustments that exceeded the threshold value of 0.05 cm was 0.05% for verification with the tabletop imaging system and 0.04 % for verification with cone-beam computed tomography. The total percentage of rotational manual additional adjustments exceeding the threshold value of 0.2° was 0.01% for both verification with the tabletop imaging system and with cone-beam computed tomography. Discussion and Conclusion: Based on the results and findings, we can confirm that the image verification protocol for the treatment of primary brain tumors at the Oncology Institute Ljubljana is safe and appropriate. We found that there is no need for manual adjustments after automatic alignment.
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