Practical use of dynalogs analysis in seven linacs in IMRT and VMAT techniques over than 20 months

Abstract

Introduction Dynalog files’s (DLGf) analysis can provide important information about deviations from planned and actual movement (positioning and velocity) of the MLC, during an IMRT or VMAT treatment delivery. Pre-treatment verification (QA) allows the comparison of the calculated and delivered dose distributions. In case of failure, the treatment plan must be reviewed and possible sources of fault must be tracked. Purpose The aim of this study is to substantiate a possible correlation between MLC behavior (through the analysis of the DLGf using FractionCheck software) and the failure of the QA procedure. Materials and methods Data from IMRT and VMAT DLGf acquired from May 2014 to February 2016 in 7 linacs was statistical analyzed as a complementary data source for the QA procedures. The analyzed results were expressed in “Warning” and “Fail” accordingly to the tolerances in TG142 report. Other parameters were also analyzed by the software: RMS, Beam-On, 95P, MaxRMS, MaxLag and Gamma-function distribution. Results were reviewed considering several factors: gantry angle, MLC maintenance, day time, pathology’s type, mechanical and dosimetric tests results and network upgrade. Results No correlation between Dynalog information and the results obtained from the QA measurements (VerySoft analysis) was verified. For an increase in the dose rate, the 95P’s, MaxRMS’s and RMS’s (for each leaf) parameters worsen. Conclusion Although the information obtained from DLGf can be very useful in some particular situations, it does not predict the outcome of IMRT or VMAT QA procedures. MLC’s performance does not depend on the treatment’s pathology, gantry angle, or day time due to possible linac’s overheating. Disclosure The authors have no relevant financial or non-financial relationships to disclose.