@article{oai:nagoya.repo.nii.ac.jp:02001911, author = {Kamomae, Takeshi and Matsunaga, Takuma and Suzuki, Junji and Okudaira, Kuniyasu and Kawabata, Fumitaka and Kato, Yutaka and Oguchi, Hiroshi and Shimizu, Morihito and Sasaki, Motoharu and Takase, Yuki and Kawamura, Mariko and Ohtakara, Kazuhiro and Itoh, Yoshiyuki and Naganawa, Shinji}, journal = {Physica medica}, month = {Jun}, note = {Purpose: Equipment refurbishment was performed to remove the beam-hardening filter (BHF) from the CyberKnife system (CK). This study aimed to confirm the change in the beam characteristics between the conventional CK (present-BHF CK) and CK after the BHF was removed (absent-BHF CK) and evaluate the impact of BHF removal on the beam quality correction factors kQ. Methods: The experimental measurements of the beam characteristics of the present- and absent-BHF CKs were compared. The CKs were modeled using Monte Carlo simulations (MCs). The energy fluence spectra were calculated using MCs. Finally, kQ were estimated by combining the MC results and analytic calculations based on the TRS-398 and TRS-483 approaches. Results: All gamma values for percent depth doses and beam profiles between each CK were less than 0.5 following the 3%/1 mm criteria. The percentage differences for tissue-phantom ratios at depths of 20 and 10 cm and percentage depth doses at 10 cm between each CK were −1.20% and −0.97%, respectively. The MC results demonstrated that the photon energy fluence spectrum of the absent-BHF CK was softer than that of the present-BHF CK. The kQ values for the absent-BHF CK were in agreement within 0.02% with those for the present-BHF CK. Conclusions: The photon energy fluence spectrum was softened by the removal of BHF. However, no remarkable impact was observed for the measured beam characteristics and kQ. Therefore, the previous findings of the kQ values for the present-BHF CK can be directly used for the absent-BHF CK.}, pages = {98--105}, title = {Dosimetric impacts of beam-hardening filter removal for the CyberKnife system}, volume = {86}, year = {2021} }