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Comparison and Analysis of Penumbra Measured with Eight Different Dosimeters in Cyberknife Robotic Radiosurgery System

M Manavalan1*, D Manigandan2, G Narayanasamy3, F Godson4, S Vikraman5, S Stathakis6, (1) Research and Development,Bharathiyar University,India (2) Medanta The Medicity Hospital,Gurgaon, India(3) University of Arkansas for Medical Sciences, Little Rock, AR, (4) Christian Medical College,Vellore,India (5) The Brunei Cancer Centre (TBCC), Jerudong, BM, BN, (6) Mays Cancer Center - MD Anderson Cancer Center, San Antonio, TX


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Cyberknife Robotic Radiosurgery system is first of its kind to treat tumors anywhere within the body with sub-millimeter accuracy. The treatment accuracy is based on the imaging system integrated into the machine, which tracks the tumor throughout the treatment. Due to its precise delivery, Cyberknife is used to treat complex tumors in between critical structures. It demands a high level of accuracy in the dosimetry. In the present study, profiles are measured with eight different dosimeters, and penumbra is compared and analyzed for 5 mm, 30 mm, and 60 mm collimators to study the efficacy of different dosimeters.

Methods: dosimeters used in this study are PTW Photon Diode, PTW Electron Diode, PTW SRS Diode, PTW PinPoint Chamber, PTW microDiamond, Scanditronix PFD, Scanditronix EFD and Scanditronix SFD detectors. PTW MP3-M water phantom is used for data acquisition and Mephysto 3.3 software is used for analysis.

Results: Penumbra Left, Penumbra Right and Field size at SID was analyzed. The Penumbra for PinPoint chamber was high when compared with that of the solid-state detectors due to volume averaging effect. Scanditronix SFD showed lesser penumbra when compared with other detectors for 5 mm and 60 mm collimators. However for 30 mm collimator the lesser penumbra was measured by PTW photon Diode. The % variance in penumbra values were high with 5 mm collimator and decreased with higher collimator sizes.

Conclusion: penumbra were measured with eight different detectors for all the twelve IRIS collimators. The variation in penumbra with different detectors was prominent in 5 mm collimator and advocating appropriate selection of dosimeters in small field dosimetry.


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