Quantification of head leakage radiation in CyberKnife robotic radiosurgery systems using a multimodal approach

This study aims to measure the head leakage radiation of a CyberKnife system (Model-S7 (without MLC)) in-patient and out-of-patient planes using optically stimulated luminescence dosimeters (OSLDs), vented ionization chambers, and a pressurized ionization chamber-based survey meter, and to compare the measured leakage levels with the limits specified by the International Electrotechnical Commission (IEC) standards. In this study, a CyberKnife LINAC equipped with a 6 MV flattening filter-free (FFF) beam and a maximum circular field size of 6 cm in diameter was utilized. Leakage radiation was assessed for both IRIS and FIXED collimators in their fully closed positions. Three independent measurement techniques were employed to quantify leakage: optically stimulated luminescence dosimeters (OSLDs), vented ionization chambers (ICs), and a pressurized ionization chamber-based survey meter (SM). Leakage measurement points were taken as per the IEC 60601-2-1 report both for in-patient plane and out-of-patient plane. The total number of monitor units (MU) delivered were 500 MU's. The measured average in-patient plane leakage was 0.015% using IC, 0.100% using OSLD and 0.010% using SM, that is well within the tolerance limit of 0.1% according to IEC guidelines. The average leakage for out of patient plane was 0.037%, which is well within the limit of 0.5% as per IEC guidelines. The study measured head leakage radiation of the CyberKnife System using OSLD, ionization chambers, and a survey meter. Leakage levels for both in-patient and out-of-patient planes were significantly below the IEC 60601-2-1 standard limits. This confirms the system's compliance with safety guidelines, ensuring minimal radiation exposure.