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Validation of Linac Small-Field Commissioning with a Commercial Plastic Scintillator Detector

J Van Schelt*, A Templeton, D Bernard, G Cifter, J Turian, Rush University Medical Center, Chicago, IL


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: The recently commercialized Exradin W1 plastic scintillator detector is nearly water equivalent and offers an opportunity to perform small-field dosimetry with minimal correction. Our goal is to use it validate the prior commissioning of a Varian TrueBeam STx linac with BrainLab stereotactic cones, which was performed with other small-field detectors.

Methods: Output factors were measured in water for MLC-defined fields from 0.5 cm to 4 cm at 10 cm depth and for cone fields from 0.5 cm to 1.5 cm diameter at dmax with the W1 scintillator. For comparison they were also measured with an IBA SFD unshielded diode and a PTW 31016 Pinpoint 3D microionization chamber via the intermediate field method with a PTW 31010 ionization chamber. Beam energies include 6 and 10 MV, both with and without flattening filters. The scintillator Cerenkov light correction was performed according to the manufacturer’s procedure with the features of the Standard Imaging SuperMax two-channel electrometer, which was also used for measurement. Output correction factors were applied to the non-scintillator measurements according to TRS-483 when available.

Results: The scintillator measurements are broadly consistent with the other small-field detectors after their corrections. Under the assumption of the water-equivalence for the W1, output correction factors were determined for the IBA SFD and PTW 31016 for all beam energies for both MLC-defined and cone-defined fields at 10 cm depth and dmax, respectively.

Conclusion: The W1 scintillator is abundantly suited for commissioning or validating small-field dosimetry in linacs, and its results relative to an unshielded diode and microionization chamber are as expected from the predictions of TRS-483.

Funding Support, Disclosures, and Conflict of Interest: Funds for scintillator provided by Rush Radiosurgery LLC.


Scintillators, Small Fields, Dosimetry


TH- External beam- photons: Small/nonstandard field experimental dosimetry

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