<p>Background: Currently, CBCT system is an indispensable component of radiation therapy units. Because of that, it is important</p><p>in treatment planning and diagnosis. CBCT is also an crucial tool for patient positioning and verification in image-guided</p><p>radiation therapy (IGRT). Therefore, it is critical to investigate the patient organ doses arising from CBCT imaging. The purpose</p><p>of this study is to evaluate patient organ doses and effective dose to patients from three different protocols of Elekta Synergy</p><p>XVI system for kV CBCT imaging examinations in image guided radiation therapy.</p><p>Materials and methods: Organ dose measurements were done with thermoluminescent dosimeters in Alderson RA NDO</p><p>male phantom for head &amp; neck (H&amp;N), chest and pelvis protocols of the Elekta Synergy XVI kV CBCT system. From the measured</p><p>organ dose, effective dose to patients were calculated according to the International Commission on Radiological Protection</p><p>103 report recommendations.</p><p>Results: For H&amp;N, chest and pelvis scans, the organ doses were in the range of 0.03–3.43 mGy, 6.04–22.94 mGy and 2.5–25.28</p><p>mGy, respectively. The calculated effective doses were 0.25 mSv, 5.56 mSv and 4.72 mSv, respectively.</p><p>Conclusion: The obtained results were consistent with the most published studies in the literature. Although the doses to</p><p>patient organs from the kV CBCT system were relatively low when compared with the prescribed treatment dose, the amount</p><p>of delivered dose should be monitored and recorded carefully in order to avoid secondary cancer risk, especially in pediatric</p><p>examinations.</p><p>Key words: kV CBCT; equivalent organ dose; effective dose; image guided radiation therapy; Alderson Rando phantom</p><p>Rep Pract Oncol Radiother 2021;26(2):251–258</p>