SURVEY OF THE FIRST 300 QUALITY ASSURANCE CASES USING THE COMPASS/DOLPHIN 3D DOSIMETRY TOOL

Introduction: one of the great differentials of the 3D Compass dosimetric quality assurance system (Ion Beam Applications - IBA Dosimetry GMBH, Germany) is its own modeling and to contain all linear accelerator dosimetric parameters fed into its database in the same way as a conventional planning system (TPS). This feature allows an independent verification of the case to be evaluated using secondary calculation or by measurements performed on the linear accelerator. Rapidly increasing clinical use of VMAT technology demands a complete dosimetric check to ensure correct and safe dose delivery to the patient. Objective: the aim of this work was to conduct a survey and general analysis of the first 300 cases of 3D dosimetry using the Compass/Dolphin tool for patient-specific quality assurance. Materials and Method: between August 2018 and July 2019, 303 quality assurance cases were registered with the Compass/Dolphin 3D dosimetry system. Compass is a 3D anatomy-based dose verification software and, in this work, it was used in conjunction with the Dolphin system, an array of 1513 ionization chambers, with a spacing of 5mm in the central region and 10mm in the peripheral portion, allowing measurements of fields up to 40x40cm². Compass uses a collapsed cone convolution-based calculation algorithm and, by using the segments and monitor unit information from the TPS DICOM RT Plan file, it generates a file called predicted dose based on the dosimetric information of its independent modeling. The measured dose in Dolphin can be reconstructed later in the tomography allowing for 3D gamma analysis and comparison of dose-volume histograms (DVHs) with statistical data. Results: the most measured and evaluated cases were, respectively, breasts planned with vmat (25.1%), 13.5% cases of hypofractionation, prostate (23.1%), most of the cases (10.9%) with irradiation of pelvic lymph nodes and 5.3% of hypofractionation, head and neck (9.6%) and cranial cases (16.2%). Conclusion: The data presented summarize the one-year experience of using Compass/Dolphin 3D dosimetry technology that has been effective for a wide range of clinical cases, from small fields of cranial radiosurgery to large and more than one isocenter targets such as craniospinal patients planned with VMAT.

Publication History

Article published online:
23 October 2019