Quality Assurance for Small-Field VMAT SRS AndConventional-Field IMRT Using the Exradin W1 Scintillator
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PO-GePV-P-2 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: The plastic scintillator detector Exradin W1 has been provento provide good dosimetry for a small field owing to its good waterequivalence and small sensitive volume. However, few studies havereported on its dosimetry for fields of conventional size. The purpose ofthis study is to assess the accuracy of the Exradin W1 in measuringconventional-field IMRT plans and small-field VMAT SRS plans, and thento assess its clinical value in dose verification and providing qualityassurance for clinical radiotherapy plans for different field sizes.
Methods: 47 cases (i.e., 29 cases with IMRT clinical plans forconventional fields and 18 cases with VMAT SRS plans for a PTV < 8cm3) in our center were included in this study. The Exradin W1 andExradin A19 standard ionization chamber were used for IMRT plans, andthe Exradin W1 and Exradin A16 microchamber were used for the VMATSRS plans. Finally, the measurements were compared with those of theTPS and the average differences were calculated.
Results: For the 29 IMRT plans, the mean difference between theExradin W1 and TPS was 0.16 ± 1.83%; while for Exradin A19 chamberradio was 0.97 ± 1.77%, which was significantly higher than that of theExradin A19 chamber (p = 0.048). For the 18 VMAT SRS plans, themean difference between the Exradin W1 and TPS was 1.13 ± 1.33%and the radio for Exradin A19 microchamber was 0.93 ± 1.57%. Theaccuracy of the Exradin W1 was nearly the same as that of the ExradinA16 and no statistical difference was observed.
Conclusion: The Exradin W1 has good accuracy in measuring doses forconventional-field IMRT plans and small-field VMAT SRS plans, whichmakes it a more comprehensive radiation detector than others availableand will be convenient for use in a clinic.
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