OCTAVIUS 4D: Commissioning and routine clinical use of a device for VMAT verifications

Purpose: To commission OCTAVIUS 4D and its arrays 729 and 1000 SRS for VMAT patient-specific QA verifications, and to provide clinical results obtained with this device. Methods: The performance of both arrays was analysed by evaluating: homogeneity, linearity, reproducibility and leakage current. The accuracy of the dose reconstruction of OCTAVIUS 4D with array 729 was evaluated through ion chamber measurements at several points of interest. The performance of both arrays was compared for the same clinical plans. Finally, results of the 3D gamma analysis performed in our hospital for more than 900 patient plans are provided. Results: Both arrays present good homogeneity, linearity, reproducibility, and negligible leakage current. Dose differences between OCTAVIUS-calculated doses and ion chamber measurements or TPS-calculated doses were within 2% for single field plans, and within 4% for clinical plans. The mean value of the local gamma passing rate (3%/3 mm) of clinical plans verified with array 729 is 89.7%, whereas for 1000 SRS it is 97.8%. Conclusions: OCTAVIUS 4D provides accurate 3D dose reconstructions from 2D dose measurements. Clinical results here presented may be used to establish reference levels for VMAT verifications with this device. (Author)