en Medical Physics Medical Physics تحقيق بديع Original Research <div style="text-align: justify;">Background: Accurate dosimetry in CyberKnife&reg; is challenging because of the unavailability of suitable detectors to satisfy all the criteria of small-field dosimetry. In this work, eight different small-field detectors from PTW and IBA Dosimetry were used to determine the dosimetric parameters for twelve fixed collimators in the CyberKnife&reg; radiosurgery system. The scope of this work was to assist medical physicists in detector selection in small-field dosimetry. Materials and Methods: Dosimetric parameters such as the surface dose (D_s), dose buildup (D_B), percentage dose at 100 mm (D₁₀₀), percentage dose at 200 mm (D₂₀₀), depth of dose maximum (D_max), and total scatter factor (S_cp) were compared and analyzed from the acquired Percentage Depth Dose(PDD). Results: Large variations in D_s were observed with different detectors for smaller collimator sizes. On analyzing the dose buildup, considerable differences were observed with all detectors from the surface to&nbsp; 6 mm depth for the smallest cone of 5 mm diameter. The D₁₀₀ and D₂₀₀values obtained using ion chambers were higher than those using diodes, likely due to the volume averaging effect. The depth of dose maximum was found to increase with increase in the field size for most of the detectors. Considerable variation in S_cp was noticed with all detectors in smaller field ranges. Conclusion: For small fields, the selection of detector is crucial, and awareness of the advantages, disadvantages and limitations of the detectors used is crucial. As in absolute dosimetry, the relative dosimetry in small fields is challenging and requires further studies and recommendations.</div> CyberKnife®, detectors, PinPoint chamber, diodes, PDD, small field dosimetry. 437 447 http://ijrr.com/browse.php?a_code=A-10-2055-30&slc_lang=en&sid=1 M. Manavalan emailmuthukumaran@gmail.com 7900319475328460017269 7900319475328460017269 Yes Research and Development Centre, Bharathiar University, Coimbatore, India M. Duraisamy 7900319475328460017270 7900319475328460017270 No Medanta The Medicity Hospital, Gurgaon, India V. Subramani 7900319475328460017271 7900319475328460017271 No Brunei National Cancer Centre, Brunei H.F. Godson 7900319475328460017272 7900319475328460017272 No Department of Radiotherapy, Christian Medical College, Vellore, India G. Krishnan 7900319475328460017273 7900319475328460017273 No Department of Radiation Oncology, Apollo Proton Cancer Centre, Chennai, India M. Venkataraman 7900319475328460017274 7900319475328460017274 No Department of Radiation Oncology, Apollo Speciality Hospitals, Chennai, India T. Ganesh 7900319475328460017275 7900319475328460017275 No Manipal Hospitals Dwarka, India