Purpose This study aimed to test the sensitivity of a transmission detector for online dose monitoring of intensity-modulated radiation therapy (IMRT) for detecting small delivery errors. Furthermore, the correlation of changes in detector output induced by small delivery errors with other metrics commonly employed to quantify the deviations between calculated and delivered dose distributions was investigated. Methods Transmission detector measurements were performed at three institutions. Seven types of errors were induced in nine clinical step-and-shoot (S&S) IMRT plans by modifying the number of monitor units (MU) and introducing small deviations in leaf positions. Signal reproducibility was investigated for short- and long-term stability. Calculated dose distributions were compared in terms of γ passing rates and dose–volume histogram (DVH) metrics (e.g., Dmean, Dx%, Vx%). The correlation between detector signal variations, γ passing rates, and DVH parameters was investigated. Results Both short- and long-term reproducibility was within 1%. Dose variations down to 1 MU (∆signal 1.1 ± 0.4%) as well as changes in field size and positions down to 1 mm (∆signal 2.6 ± 1.0%) were detected, thus indicating high error-detection sensitivity. A moderate correlation of detector signal was observed with γ passing rates (R2 = 0.57–0.70), while a good correlation was observed with DVH metrics (R2 = 0.75–0.98). Conclusion The detector is capable of detecting small delivery errors in MU and leaf positions, and is thus a highly sensitive dose monitoring device for S&S IMRT for clinical practice. The results of this study indicate a good correlation of detector signal with DVH metrics; therefore, clinical action levels can be defined based on the presented data.
Real-time beam monitoring for error detection in IMRT plans and impact on dose-volume histograms : A multi-center study / Livia Marrazzo, Chiara Arilli, Marlies Pasler, Martijn Kusters, Richard Canters, Luca Fedeli, Silvia Calusi, Marta Casati, Cinzia Talamonti, Gabriele Simontacchi, Lorenzo Livi, Stefania Pallotta. - In: STRAHLENTHERAPIE UND ONKOLOGIE. - ISSN 0179-7158. - ELETTRONICO. - 194:(2018), pp. 243-254. [10.1007/s00066-017-1245-3]
Real-time beam monitoring for error detection in IMRT plans and impact on dose-volume histograms : A multi-center study.
Livia Marrazzo
Writing – Original Draft Preparation
;Chiara ArilliSoftware
;Silvia CalusiMethodology
;Marta CasatiData Curation
;Cinzia TalamontiMethodology
;Gabriele SimontacchiMethodology
;Lorenzo LiviMembro del Collaboration Group
;Stefania PallottaWriting – Review & Editing
2018
Abstract
Purpose This study aimed to test the sensitivity of a transmission detector for online dose monitoring of intensity-modulated radiation therapy (IMRT) for detecting small delivery errors. Furthermore, the correlation of changes in detector output induced by small delivery errors with other metrics commonly employed to quantify the deviations between calculated and delivered dose distributions was investigated. Methods Transmission detector measurements were performed at three institutions. Seven types of errors were induced in nine clinical step-and-shoot (S&S) IMRT plans by modifying the number of monitor units (MU) and introducing small deviations in leaf positions. Signal reproducibility was investigated for short- and long-term stability. Calculated dose distributions were compared in terms of γ passing rates and dose–volume histogram (DVH) metrics (e.g., Dmean, Dx%, Vx%). The correlation between detector signal variations, γ passing rates, and DVH parameters was investigated. Results Both short- and long-term reproducibility was within 1%. Dose variations down to 1 MU (∆signal 1.1 ± 0.4%) as well as changes in field size and positions down to 1 mm (∆signal 2.6 ± 1.0%) were detected, thus indicating high error-detection sensitivity. A moderate correlation of detector signal was observed with γ passing rates (R2 = 0.57–0.70), while a good correlation was observed with DVH metrics (R2 = 0.75–0.98). Conclusion The detector is capable of detecting small delivery errors in MU and leaf positions, and is thus a highly sensitive dose monitoring device for S&S IMRT for clinical practice. The results of this study indicate a good correlation of detector signal with DVH metrics; therefore, clinical action levels can be defined based on the presented data.File | Dimensione | Formato | |
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