Small field output factor measurement and verification for CyberKnife robotic radiotherapy and radiosurgery system using 3D polymer gel, ionization chamber, diode, diamond and scintillator detectors, Gafchromic film and Monte Carlo simulation. (February 2023)

• Record Type: Journal Article
• Authors: Al Kafi, Md Abdullah; Arib, Mehenna; Al Moussa, Akram; Alzorkany, Faisal; Shehadeh, Mamoun; Mohd Yusof, Mohd Fahmi; Moftah, Belal
• Is Part Of: Applied radiation and isotopes. Volume 192(2023)
• Publication Date: 2023-02
• Subjects: Small field dosimetry -- Robotic radiotherapy/radiosurgery -- Field output factor -- Monte Carlo simulation; Radiology -- Periodicals; Radiation -- Industrial applications -- Periodicals; Nuclear chemistry -- Periodicals; Internet resource; Periodical; 660.298
• DOI: 10.1016/j.apradiso.2022.110576
• Languages: English
• ISSNs: 0969-8043

Abstract

Abstract: The dosimetry of small fields has become tremendously important with the advent of intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery, where small field segments or very small fields are used to treat tumors. With high dose gradients in the stereotactic radiosurgery or radiotherapy treatment, small field dosimetry becomes challenging due to the lack of lateral electronic equilibrium in the field, x-ray source occlusion, and detector volume averaging. Small volume and tissue-equivalent detectors are recommended to overcome the challenges. With the lack of a perfect radiation detector, studies on available detectors are ongoing with reasonable disagreement and uncertainties. The joint IAEA and AAPM international code of practice (CoP) for small field dosimetry, TRS 483 (Alfonso et al., 2017) provides guidelines and recommendations for the dosimetry of small static fields in external beam radiotherapy. The CoP provides a methodology for field output factor (FOF) measurements and use of field output correction factors for a series of small field detectors and strongly recommends additional measurements, data collection and verification for CyberKnife (CK) robotic stereotactic radiotherapy/radiosurgery system using the listed detectors and more new detectors so that the FOFs can be implemented clinically. The present investigation is focused on using 3D gel along with some other commercially available detectors for the measurement and verification of field output factors (FOFs) for the small fields available in the CK system. The FOF verification was performed through a comparison with published data and Monte Carlo simulation. The results of this study have proved the suitability of an in-house developed 3D polymer gel dosimeter, several commercially available detectors, and Gafchromic films as a part of small field dosimetric measurements for the CK system. Highlights: Different commercial small field detectors are used to measure the field output factors for robotic CyberKnife system. Tissue equivalent radiochromic EBT3 films were calibrated, and measurements of field output factor are performed. Locally fabricated and patented 3D polymer is also used to measure the field output factors for CK. The measured data were compared with Monte Carlo simulated data using BEAMnrc and DOSRZnrc codes. The measured field output factors with all the detectors and techniques are found suitable for CK.