open access

Vol 20, No 1 (2015)
Original research articles
Published online: 2015-01-01
Submitted: 2014-03-23
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A study on the correlation between plan complexity and gamma index analysis in patient specific quality assurance of volumetric modulated arc therapy

Dhanabalan Rajasekaran, Prakash Jeevanandam, Prabakar Sukumar, Arulpandiyan Ranganathan, Samdevakumar Johnjothi, Vivekanandan Nagarajan
DOI: 10.1016/j.rpor.2014.08.006
·
Rep Pract Oncol Radiother 2015;20(1):57-65.

open access

Vol 20, No 1 (2015)
Original research articles
Published online: 2015-01-01
Submitted: 2014-03-23

Abstract

Aim

To evaluate the new Octavius 4D system for patient specific quality assurance and to study the correlation between plan complexity and gamma index analysis in patient specific quality assurance of VMAT using the Octavius 4D system.

Background

McNiven (2010) proposed a study to evaluate the utility of a complexity metric, the Modulation Complexity Score, to evaluate the relationship of the metric with deliverability in IMRT.

Materials and methods

Evaluation of the Octavius 4D system was carried out by gamma evaluation of user defined MLC created patterns and AAPM TG 119 benchmark plans. The relationship between plan complexity expressed as Modulation Complexity Score (MCS) and the gamma index analysis was established by a planar and volumetric gamma analysis of 106 clinically approved VMAT patient plans of different sites.

Results

Average volumetric 3D global gamma evaluation (3[[ce:hsp sp="0.25"/]]mm/3%) results for the evaluation plans was 97.41% for 6[[ce:hsp sp="0.25"/]]MV X-rays and 98.30% for 15[[ce:hsp sp="0.25"/]]MV X-rays. Average MCS values for the head and neck, pelvic and thoracic plans were 0.2224, 0.3615 and 0.1874. Average volumetric 3D global gamma analysis (3[[ce:hsp sp="0.25"/]]mm/3%) results for the head and neck, pelvic and thoracic VMAT plans were 95.45%, 97.51% and 96.98%, respectively. Out of 90 correlation analyses between the MCS and gamma passing rate, only 3 had the r value greater than 0.5.

Conclusions

The Octavius 4D system is a suitable device for patient specific pretreatment QA. Global and local gamma analysis results showed a weak correlation with the MCS.

Abstract

Aim

To evaluate the new Octavius 4D system for patient specific quality assurance and to study the correlation between plan complexity and gamma index analysis in patient specific quality assurance of VMAT using the Octavius 4D system.

Background

McNiven (2010) proposed a study to evaluate the utility of a complexity metric, the Modulation Complexity Score, to evaluate the relationship of the metric with deliverability in IMRT.

Materials and methods

Evaluation of the Octavius 4D system was carried out by gamma evaluation of user defined MLC created patterns and AAPM TG 119 benchmark plans. The relationship between plan complexity expressed as Modulation Complexity Score (MCS) and the gamma index analysis was established by a planar and volumetric gamma analysis of 106 clinically approved VMAT patient plans of different sites.

Results

Average volumetric 3D global gamma evaluation (3[[ce:hsp sp="0.25"/]]mm/3%) results for the evaluation plans was 97.41% for 6[[ce:hsp sp="0.25"/]]MV X-rays and 98.30% for 15[[ce:hsp sp="0.25"/]]MV X-rays. Average MCS values for the head and neck, pelvic and thoracic plans were 0.2224, 0.3615 and 0.1874. Average volumetric 3D global gamma analysis (3[[ce:hsp sp="0.25"/]]mm/3%) results for the head and neck, pelvic and thoracic VMAT plans were 95.45%, 97.51% and 96.98%, respectively. Out of 90 correlation analyses between the MCS and gamma passing rate, only 3 had the r value greater than 0.5.

Conclusions

The Octavius 4D system is a suitable device for patient specific pretreatment QA. Global and local gamma analysis results showed a weak correlation with the MCS.

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Keywords

Octavius 4D system; VMAT QA; 3D dosimetry; Dose verification; Plan complexity

About this article
Title

A study on the correlation between plan complexity and gamma index analysis in patient specific quality assurance of volumetric modulated arc therapy

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 20, No 1 (2015)

Pages

57-65

Published online

2015-01-01

DOI

10.1016/j.rpor.2014.08.006

Bibliographic record

Rep Pract Oncol Radiother 2015;20(1):57-65.

Keywords

Octavius 4D system
VMAT QA
3D dosimetry
Dose verification
Plan complexity

Authors

Dhanabalan Rajasekaran
Prakash Jeevanandam
Prabakar Sukumar
Arulpandiyan Ranganathan
Samdevakumar Johnjothi
Vivekanandan Nagarajan

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