Analysis of various dosimetric parameters using multiple detectors in the cyberknife® roboticradiosurgery system

Background: accurate dosimetry in cyberknife® is challenging because ofthe unavailability of suitable detectors to satisfy all the criteria of small-fielddosimetry. in this work, eight different small-field detectors from ptw andiba dosimetry were used to determine the dosimetric parameters for twelvefixed collimators in the cyberknife® radiosurgery system. the scope of thiswork was to assist medical physicists in detector selection in small-fielddosimetry. materials and methods: dosimetric parameters such as thesurface dose (ds), dose buildup (db), percentage dose at 100 mm (d100),percentage dose at 200 mm (d200), depth of dose maximum (dmax), and totalscatter factor (scp) were compared and analyzed from the acquiredpercentage depth dose(pdd). results: large variations in ds were observedwith different detectors for smaller collimator sizes. on analyzing the dosebuildup, considerable differences were observed with all detectors from thesurface to 6 mm depth for the smallest cone of 5 mm diameter. the d100 andd200 values obtained using ion chambers were higher than those using diodes,likely due to the volume averaging effect. the depth of dose maximum wasfound to increase with increase in the field size for most of the detectors.considerable variation in scp was noticed with all detectors in smaller fieldranges. conclusion: for small fields, the selection of detector is crucial, andawareness of the advantages, disadvantages and limitations of the detectorsused is crucial. as in absolute dosimetry, the relative dosimetry in small fieldsis challenging and requires further studies and recommendations.