en Radiation Biology Radiation Biology تحقيق بديع Original Research <div style="text-align: justify;"><span style="font-size:10pt"><span style="text-justify:newspaper"><span style="text-kashida-space:50%"><span style="line-height:119%"><span style="font-family:Calibri"><span style="color:black"><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Background:</span></span></span></span></span></span> <span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">Precise patient positioning is essential to effective head radiotherapy. However, helical tomotherapy lacks six-degree-of-freedom (6DoF) correction, limiting its ability to adjust for pitch and yaw errors. Optical surface imaging (OSI) enables non-invasive, real-time monitoring of patient position but exhibits limitations. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Materials and Methods: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">A rotational correction device (RCD) was developed consisting of acrylic and steel adjustment components integrated into a carbon-fiber head-fixation baseplate. The phantom head is immobilized using a thermoplastic mask and positioned on the RCD. The setup accuracy and time were compared between the megavoltage computed tomography (MVCT)-based image-guided correction and OSI-assisted correction using an RCD. Ten trials were conducted for each system to measure the setup errors (translational and rotational magnitudes) and the total setup time. Treatment plans with a yaw error of 3&deg; assessed the dosimetric impact on three spherical clinical target volumes (CTVs) and compared them with plans corrected using the RCD.&nbsp; </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Results: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">The RCD system significantly reduced setup errors (0.24&deg; &plusmn; 0.16&deg; vs. 0.49&deg; &plusmn; 0.14&deg;; p=0.001) and setup time by approximately 40% (7 min 48 s vs. 19 min 37 s; p<0.001) compared with MVCT. Dosimetric analysis revealed improved D99% recovery in CTVs with RCD correction (e.g., CTV3: 24.74 Gy with RCD vs. 23.89 Gy without correction, against a reference of 24.74 Gy). </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Conclusion: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">The RCD could provide an effective and accurate solution for correcting pitch and yaw rotational errors during head radiotherapy. This approach enhanced setup precision and efficiency without requiring repeated imaging, thereby improving treatment accuracy in multitarget brain irradiation.</span></span></span></span></span></span></span></span></span></div> Surface-guided radiation therapy, megavoltage computed tomography, tomotherapy, patient setup, rotational errors. 1081 1086 http://ijrr.com/browse.php?a_code=A-10-1-1618&slc_lang=en&sid=1 D. Kim 7900319475328460035017 7900319475328460035017 No Department of Radiation Oncology, Soonchunhyang University Hospital Bucheon, Bucheon, Republic of Korea K.H Cho 7900319475328460035018 7900319475328460035018 No Department of Radiation Oncology, Soonchunhyang University Hospital Bucheon, Bucheon, Republic of Korea J.H Jung 7900319475328460035019 7900319475328460035019 No Department of Radiation Oncology, Soonchunhyang University Hospital Bucheon, Bucheon, Republic of Korea S. Kim ksc@gachon.ac.kr 7900319475328460035020 7900319475328460035020 Yes Department of Radiological Science, Gachon University Medical Campus, Incheon, Republic of Korea