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Evaluating the dosimetric consequences of MLC leaf positioning errors in dynamic IMRT treatments

Published online by Cambridge University Press:  12 February 2019

Arpita Agarwal ,
Nikhil Rastogi ,
KJ Maria Das ,
SA Yoganathan ,
D Udayakumar ,
R Naresh  and
Shaleen Kumar
Arpita Agarwal*
Affiliation:
Department of Physics, School of Sciences, IFTM University, Moradabad, Uttar Pradesh, India
Nikhil Rastogi
Affiliation:
Department of Physics, School of Sciences, IFTM University, Moradabad, Uttar Pradesh, India
KJ Maria Das
Affiliation:
Department of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
SA Yoganathan
Affiliation:
Department of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
D Udayakumar
Affiliation:
Department of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
R Naresh
Affiliation:
Department of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
Shaleen Kumar
Affiliation:
Department of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
*
Author for correspondence: Ms. Arpita Agarwal, Department of Physics, School of Sciences, IFTM University, Moradabad, Uttar Pradesh, India. Tel: 12253605730. E-mail: arpitagrwl@gmail.com
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Abstract

Purpose

The purpose of this study was to evaluate the dosimetric impact of multileaf collimator (MLC) positional errors on dynamic intensity-modulated radiotherapy (IMRT) treatments through planning simulation. Secondly the sensitivity of IMRT MatriXX device for detecting the MLC leaf positional errors was also evaluated.

Materials and methods

In this study five dynamic IMRT plans, each for brain and head–neck (HN), were retrospectively included. An in-house software was used to introduce random errors (uniform distribution between −2·0 and +2·0 mm) and systematic errors [±0·5, ±0·75, ±1·0 and ±2·0 mm (+: open MLC error and −: close MLC error)]. The error-introduced MLC files were imported into the treatment planning system and new dose distributions were calculated. Furthermore, the dose–volume histogram files of all plans were exported to in-house software for equivalent uniform dose (EUD), tumour control probability and normal tissue complication probability calculations. The error-introduced plans were also delivered on LINAC, and the planar fluences were measured by IMRT MatriXX. Further, 3%/3 mm and 2%/2 mm γ-criteria were used for analysis.

Results

In planning simulation study, the impact of random errors was negligible and ΔEUD was <0·5±0·7%, for both brain and HN. The impact of systematic errors was substantial, and on average, the maximum change in EUD for systematic errors (close 2 mm) was −10·7±3·1% for brain and −15·5±2·6% for HN.

Conclusions

It can be concluded that the acceptable systematic error was 0·4 mm for brain and 0·3 mm for HN. Furthermore, IMRT MatriXX device was able to detect the MLC errors ≥2 mm in HN and >3 mm errors in brain with 2%/2 mm γ-criteria.

Keywords

IMRTMLCrandomsystematicuncertainties
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 18 , Issue 3 , September 2019 , pp. 225 - 231
Copyright
© Cambridge University Press 2019 

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Footnotes

Cite this article: Agarwal A, Rastogi N, Maria Das KJ, Yoganathan SA, Udayakumar D, Naresh R, Kumar S. (2019) Evaluating the dosimetric consequences of MLC leaf positioning errors in dynamic IMRT treatments. Journal of Radiotherapy in Practice18: 225–231. doi: 10.1017/S1460396918000705

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