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Comparative Study
. 2002 Spring;3(2):63-72.
doi: 10.1120/jacmp.v3i2.2578.

Verification of dynamic and segmental IMRT delivery by dynamic log file analysis

Dale W Litzenberg  1 , Jean M Moran, Benedick A Fraass
Affiliations
Comparative Study

Verification of dynamic and segmental IMRT delivery by dynamic log file analysis

Dale W Litzenberg et al. J Appl Clin Med Phys. 2002 Spring.

Abstract

A program has been developed to evaluate the delivered fluence of step-and-shoot segmental and sliding window dynamic multileaf collimator (MLC) fields. To automate these checks, a number of tools have been developed using data available from the dynamic log files that can be created each time a dynamic delivery occurs. Experiments were performed with a Varian 2100EX with a 120 leaf MLC equipped with dynamic capabilities. A dynamic leaf sequence is delivered and measured with film or an amorphous silicon imager. After delivery, the dynamic log file is written by the accelerator control system. The file reports the expected and actual position for each leaf and the dose fraction every 0.055 seconds. Leaf trajectories are calculated from this data and expected and actual fluence images are created from the difference of opposing leaf trajectories. These images can be compared with the expected delivery, measurements, and calculations of fluence. Tools have been developed to investigate other aspects of the delivery, such as specific leaf errors, beam hold-off flags sent by the control system to the MLC, and gap widths. This program is part of a semi-automated quality assurance (QA) system for pretreatment fluence verification and daily treatment verification of dynamic multileaf collimation (DMLC) delivery.

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Figures

Figure 1
Figure 1
(Color) The primary DynaLog File Analysis interface and automatically displayed result images. The fluence distributions shown at the top are reconstructed from a dynamically delivered sequence. The difference of the expected and actual fluence distributions is shown in the middle, while leaf position deviations are shown in the bottom two images.
Figure 2
Figure 2
(Color) The Graphing Interface and the displays generated when the “Histogram Deviations” button is clicked. These types of displays show data for each leaf in each bank. Values may be obtained using the cursors at the bottom of the graph.
Figure 3
Figure 3
(Color) This figure shows the cumulative dose fraction index in the top graph (blue line). From this cumulative index, the incremental change (top graph, red line) in the index is determined to evaluate variations in the dose rate during delivery. The MLC beam hold‐off flag is displayed at the bottom for easy comparison.
Figure 4
Figure 4
(Color) The “Leaf Position Explorer” displays the desired and actual positions vs time for each leaf in a pair, the deviations from the desired position, the user‐set tolerance, and the MLC beam hold‐off flag.
Figure 5
Figure 5
(Color) The “Gap Explorer” display shows the desired and actual gap for a given leaf pair and the error in the gap. It also shows the deviation in position for each leaf, the desired and actual velocities of each leaf in the pair, the change in the dose fraction index, and the MLC beam hold‐off flag.
Figure 6
Figure 6
(Color) The figure on the left shows a desired distribution that was reconstructed from the DynaLog File data. The figure on the right shows the difference between an a‐Si imager measurement and the desired distribution.
See this image and copyright information in PMC

References

    1. Ma L., Geis P. B., and Boyer AL., “Quality assurance for dynamic multileaf collimator modulated fields using a fast beam imaging system,” Med. Phys. 24, 1213–1220 (1997). - PubMed
    1. Patridge M., Evans P. M., Mosleh‐Shirazi A., and Convery D., “Independent verification of intensity‐modulated beam delivery by the dynamic MLC technique,” Med. Phys. 25, 1872–1879 (1998). - PubMed
    1. Pasma K. L., Kroonwijk M., de Boer J. C., Visser A. G., and Heijmen B. J., “Accurate portal dose measurement with a fluoroscopic electron portal imaging device (EPID) for open and wedged beams and dynamic multileaf collimation,” Phys. Med. Biol. 43, 2047–2060 (1998). - PubMed
    1. James H. V., Atherton S., Budgell G. J., Kirby M. C., and Williams P. C., “Verification of dynamic multileaf collimation using an electronic portal imaging device,” Phys. Med. Biol. 45 (2), 495–509 (2000). - PubMed
    1. Papatheodorou S., Rosenwald J. C., Zefkili S., Murillo M. C., Drouard J., and Gaboriaud G., “Dose calculation and verification of intensity modulation generated by dynamic multileaf collimators,” Med. Phys. 27 (5), 960–971 (2000). - PubMed

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