open access

Vol 23, No 5 (2018)
Original research articles
Published online: 2018-09-01
Submitted: 2017-06-17
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Trajectory log file sensitivity: A critical analysis using DVH and EPID

Wui Ann Woon, Paul B. Ravindran, Piyasiri Ekanayake, Subramani Vikraman, Siti Amirah, Yivonne Y.F. Lim, Christopher H.S. Vun, Jamsari Khalid
DOI: 10.1016/j.rpor.2018.07.006
·
Rep Pract Oncol Radiother 2018;23(5):346-359.

open access

Vol 23, No 5 (2018)
Original research articles
Published online: 2018-09-01
Submitted: 2017-06-17

Abstract

Aim

The aim of this study was to investigate the sensitivity of the trajectory log file based quality assurance to detect potential errors such as MLC positioning and gantry positioning by comparing it with EPID measurement using the most commonly used criteria of 3%/3 mm.

Materials and methods

An in-house program was used to modified plans using information from log files, which can then be used to recalculate a new dose distribution. The recalculated dose volume histograms (DVH) were compared with the originals to assess differences in target and critical organ dose. The dose according to the differences in DVH was also compared with dosimetry from an electronic portal imaging device.

Results

In all organs at risk (OARs) and planning target volumes (PTVs), there was a strong positive linear relationship between MLC positioning and dose error, in both IMRT and VMAT plans. However, gantry positioning errors exhibited little impact in VMAT delivery. For the ten clinical cases, no significant correlations were found between gamma passing rates under the criteria of 3%/3 mm for the composite dose and the mean dose error in DVH (r < 0.3, P > 0.05); however, a significant positive correlation was found between the gamma passing rate of 3%/3 mm (%) averaged over all fields and the mean dose error in the DVH of the VMAT plans (r = 0.59, P < 0.001).

Conclusions

This study has successfully shown the sensitivity of the trajectory log file to detect the impact of systematic MLC errors and random errors in dose delivery and analyzed the correlation of gamma passing rates with DVH.

Abstract

Aim

The aim of this study was to investigate the sensitivity of the trajectory log file based quality assurance to detect potential errors such as MLC positioning and gantry positioning by comparing it with EPID measurement using the most commonly used criteria of 3%/3 mm.

Materials and methods

An in-house program was used to modified plans using information from log files, which can then be used to recalculate a new dose distribution. The recalculated dose volume histograms (DVH) were compared with the originals to assess differences in target and critical organ dose. The dose according to the differences in DVH was also compared with dosimetry from an electronic portal imaging device.

Results

In all organs at risk (OARs) and planning target volumes (PTVs), there was a strong positive linear relationship between MLC positioning and dose error, in both IMRT and VMAT plans. However, gantry positioning errors exhibited little impact in VMAT delivery. For the ten clinical cases, no significant correlations were found between gamma passing rates under the criteria of 3%/3 mm for the composite dose and the mean dose error in DVH (r < 0.3, P > 0.05); however, a significant positive correlation was found between the gamma passing rate of 3%/3 mm (%) averaged over all fields and the mean dose error in the DVH of the VMAT plans (r = 0.59, P < 0.001).

Conclusions

This study has successfully shown the sensitivity of the trajectory log file to detect the impact of systematic MLC errors and random errors in dose delivery and analyzed the correlation of gamma passing rates with DVH.

Get Citation

Keywords

Intensity-modulated radiation therapy; Volumetric arc therapy; Trajectory log files; Dose error; Multileaf collimator

About this article
Title

Trajectory log file sensitivity: A critical analysis using DVH and EPID

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 23, No 5 (2018)

Pages

346-359

Published online

2018-09-01

DOI

10.1016/j.rpor.2018.07.006

Bibliographic record

Rep Pract Oncol Radiother 2018;23(5):346-359.

Keywords

Intensity-modulated radiation therapy
Volumetric arc therapy
Trajectory log files
Dose error
Multileaf collimator

Authors

Wui Ann Woon
Paul B. Ravindran
Piyasiri Ekanayake
Subramani Vikraman
Siti Amirah
Yivonne Y.F. Lim
Christopher H.S. Vun
Jamsari Khalid

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