No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
The full text of this article is not currently available.
A clinically observed discrepancy between image-based and log-based MLC positions
E. E. Klein, J. Hanley, J. Bayouth, F. F. Yin, W. Simon, S. Dresser, and Task Group AAPM Report, “Task Group 142 report: Quality assurance of medical accelerators,” Med. Phys. 36(9), 4197–4212 (2009).
A. Agnew, C. E. Agnew, M. W. D. Grattan, A. R. Hounsell, and C. K. McGarry, “Monitoring daily MLC positional errors using trajectory log files and EPID measurements for IMRT and VMAT deliveries,” Phys. Med. Biol. 59, N49–N63 (2014).
C. E. Agnew, R. B. King, A. R. Hounsell, and C. K. McGarry, “Implementation of phantom-less IMRT delivery verification using Varian DynaLog files and R/V output,” Phys. Med. Biol. 57(21), 6761–6777 (2012).
H. C. Woodruff, T. Fuangrod, E. Van Uytven, B. M. C. McCurdy, T. Van Beek, S. Bhatia, and P. B. Greer, “First experience with real-time EPID-based delivery verification during IMRT and VMAT sessions,” Int. J. Radiat. Oncol., Biol., Phys. 93(3), 516–522 (2015).
J. F. Calvo-Ortega, T. Teke, S. Moragues, M. Pozo, and J. Casals, “A varian dynalog file-based procedure for patient dose-volume histogram-based IMRT QA,” J. Appl. Clin. Med. Phys. 15(2), 100–109 (2014).
D. W. Litzenberg, J. M. Moran, and B. A. Fraass, “Verification of dynamic and segmental IMRT delivery by dynamic log file analysis,” J. Appl. Clin. Med. Phys. 3(2), 63–72 (2002).
M. Alber et al., 2008 ESTRO Booklet No 9: Guidelines for the Verification of IMRT, ESTRO, Brussels, 2008.
Article metrics loading...
To present a clinical case in which real-time intratreatment imaging identified an multileaf collimator
(MLC) leaf to be consistently deviating from its programmed and logged position by >1 mm.
An EPID-based exit-fluence dosimetry system designed to prevent gross delivery errors was used to capture cine during treatment images. The author serendipitously visually identified a suspected MLC leaf displacement that was not otherwise detected. The leaf position as recorded on the EPID
images was measured and log-files were analyzed for the treatment in question, the prior day’s treatment, and for daily MLC test patterns acquired on those treatment days. Additional standard test patterns were used to quantify the leaf position.
Whereas the log-file reported no difference between planned and recorded positions, image-based measurements showed the leaf to be 1.3 ± 0.1 mm medial from the planned position. This offset was confirmed with the test pattern irradiations.
It has been clinically observed that log-file derived leaf positions can differ from their actual position by >1 mm, and therefore cannot be considered to be the actual leaf positions. This cautions the use of log-based methods for MLC or patient quality assurance without independent confirmation of log integrity. Frequent verification of MLC positions through independent means is a necessary precondition to trust log-file records. Intratreatment EPID
imaging provides a method to capture departures from MLC planned positions.
Full text loading...
Most read this month