Development of an x-ray-opaque-marker system for quantitative phantom positioning in patient-specific quality assurance. (November 2021)

• Record Type: Journal Article
• Authors: Suzuki, Kentaro; Kamomae, Takeshi; Oguchi, Hiroshi; Kawabata, Fumitaka; Sugita, Kazuma; Okudaira, Kuniyasu; Mori, Masaki; Abe, Shinji; Komori, Masataka; Kawamura, Mariko; Ohtakara, Kazuhiro; Itoh, Yoshiyuki; Naganawa, Shinji
• Is Part Of: Physica medica. Volume 91(2021)
• Page Start: 121
• Page End: 130
• Publication Date: 2021-11
• Subjects: Patient-specific QA -- Fiducial marker -- CyberKnife -- Monte Carlo simulation; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2021.10.017
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: We developed x-ray-opaque-marker (XOM) system for quantitative phantom positioning. Seven tungsten carbide spherical markers were inserted in XOM system. Phantom positioning accuracy and dose perturbation from markers were evaluated. The results were sufficient for clinical use in CyberKnife or general-purpose linac. XOM also contributes to minimizing phantom positioning variation and human errors. Abstract: Purpose: We developed an x-ray-opaque-marker (XOM) system with inserted fiducial markers for patient-specific quality assurance (QA) in CyberKnife (Accuray) and a general-purpose linear accelerator (linac). The XOM system can be easily inserted or removed from the existing patient-specific QA phantom. Our study aimed to assess the utility of the XOM system by evaluating the recognition accuracy of the phantom position error and estimating the dose perturbation around a marker. Methods: The recognition accuracy of the phantom position error was evaluated by comparing the known error values of the phantom position with the values measured by matching the images with target locating system (TLS; Accuray) and on-board imager (OBI; Varian). The dose perturbation was evaluated for 6 and 10 MV single-photon beams through experimental measurements and Monte Carlo simulations. Results: The root mean squares (RMSs) of the residual position errors for the recognition accuracy evaluation in translations were 0.07 mm with TLS and 0.30 mm with OBI, and those in rotations were 0.13° with TLS and 0.15° with OBI. The dose perturbation was observed within 1.5 mm for 6 MV and 2.0 mm for 10 MV from the marker. Conclusions: Sufficient recognition accuracy of the phantom position error was achieved using our system. It is unnecessary to consider the dose perturbation in actual patient-specific QA. We concluded that the XOM system can be utilized to ensure quantitative and accurate phantom positioning in patient-specific QA with CyberKnife and a general-purpose linac.