Dosimetric evaluation of MobiusFX in the RapidArc delivery quality assurance comparing with 3DVH

Abstract

The dosimetric characteristics of MobiusFX, which uses the treatment machine log file to calculate the dose inside the patient body, were analyzed for use in the RapidArc delivery quality assurance (DQA) process. The accuracy and usefulness of MobiusFX in clinical cases was evaluated by comparing the dose calculated by MobiusFX with that calculated by the conventional measurement dose based program, 3DVH. The results of gamma evaluation with three different criteria (3%–3 mm, 4%–3 mm, 5%–3 mm) were analyzed, and the dose changes were calculated while simulating variable position errors (6 mm, 3 mm) and dosimetric output increases (6%, 3%). Although the doses calculated by each tool were not identical due to differences in the calculation algorithms, the doses calculated by MobiusFX were generally similar to those calculated by 3DVH. Based on these results, MobiusFX exhibited the required accuracy for clinical application. However, it could not determine the dosimetric output variation. It should therefore be considered a supplementary DQA tool that can verify the error in the daily treatment process, but not an ideal DQA tool that can replace conventional measurement based DQA methods.

Cross verification of independent dose recalculation, log files based, and phantom measurement‐based pretreatment quality assurance for volumetric modulated arc therapy

“…MobiusFX and 3DVH were not identical, they were generally similar to each other in their verification for 10 prostate, 10 head-and-neck, and 10 chest cancer patients who underwent VMAT. 26 Gamma index evaluation results further demonstrated that independent dose check with Mobius3D and log files based QA with…”

“…25 Similarly, Song et al demonstrated that although the dose reconstructed from MobiusFX and 3DVH were not identical, they were generally similar to each other in their verification for 10 prostate, 10 head-and-neck, and 10 chest cancer patients who underwent VMAT. 26 Gamma index evaluation results further demonstrated that inde-…”

“…23 It could also partly due to the output variations during treatment delivery which was not considered in log files. 26 Although independent TPS check and log files based QA achieved higher accuracy than phantom measurement-based QA for VMAT patients. DVH metrics with relative high dosimetric errors…”

“…M3D, Mobius3D software; MFX, MobiusFX software; TPS, treatment planning system. deviations could be partly due to the limitation of 3DVH software, which uses preloaded kernel libraries for various Linacs with intrinsic discrepancies, as pointed out by Tyagi et al23 It could also partly due to the output variations during treatment delivery which was not considered in log files 26. Although independent TPS check and log files based QA achieved higher accuracy than phantom measurement-based QA for VMAT patients.…”

Assessment of DLG Correction Factor in Mobius3D Commissioning Affected by Couch Top

“…Mobius3D can calculate a dose distribution for a patient CT dataset directly by using an independent dose calculation algorithm from the primary radiation treatment planning system. Mobius3D has been widely implemented in various institutions and has been applied as a primary-and secondary-checking QA tool to evaluate not only conventional radiotherapy techniques but also advanced ones, such as intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) [9][10][11][12][13][14][15].…”