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Direct Comparison Between Elekta IViewDose and PTW OCTAVIUS 4D for Dosimetric Verification of IMRT and VMAT Treatments

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I Olaciregui Ruiz

I Olaciregui Ruiz*, B Mijnheer , J Kaas , T Perik , B Vivas-Maiques , A Mans , The Netherlands Cancer Institute, Amsterdam, Noord Holland


SU-I-GPD-T-252 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: iViewDose (Elekta AB, Stockholm, Sweden) uses EPID measurements made behind a patient or a phantom to reconstruct in vivo or phantom 3D dose distributions, respectively. The purpose of this study is to present a direct comparison of this EPID based dosimetry system against a conventional ionisation chamber (IC) based system for dosimetric verification of IMRT and VMAT treatments .

Methods: Measurements were performed on an Elekta Versa HDTM linac using plans generated with Pinnacle 9.10 (Philips Medical Systems, Eindhoven, The Netherlands). iViewDose was commissioned following the vendor’s instructions, i.e. using Template Calibration Models (TCMs) to create 6MV and 10MV linac-specific models. The created models passed the criteria of the recommended set-to-work tests. 7 IMRT and 6 VMAT clinical treatments of 7 different tumor sites were randomly selected and measured with the OCTAVIUS 4D System, consisting of an OCTAVIUS 4D phantom in combination with the OCTAVIUS 1500 or 1000 SRS 2D IC arrays (PTW, Freiburg, Germany). For iViewDose, EPID images behind an adapted OCTAVIUS 4D phantom, which contains no air cavities, were acquired using iViewGT software. The resulting OCTAVIUS and iViewDose 3D dose distributions were directly compared using γ-analisis (3% global dose/3mm) with statistics calculated on the volume within the 50% isodose surface of the OCTAVIUS dose distributions.

Results: The average isocentre dose difference between iViewDose and OCTAVIUS was -0.5±1.4%(1SD). The maximum detected deviation was 2.8%. In the direct 3D dose comparison, the average γ-mean and γ-pass rate values were 0.39±0.11%(1SD) and 97.9±2.1%(1SD).

Conclusion: Good agreement was observed between iViewDose and the OCTAVIUS 4D System in the dosimetric verification of the selected treatments. Although more measurements are needed, we may tentatively conclude that the new EPID-based iViewDose system is equivalent to an established IC-based system for dosimetric verification of IMRT and VMAT treatments.

Funding Support, Disclosures, and Conflict of Interest: iViewDose was developed by Elekta in conjunction with the Netherlands Cancer Institute.

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