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Radiother Oncol. 2017 Aug;124(2):302-310. doi: 10.1016/j.radonc.2017.05.019. Epub 2017 Jul 4.

Multi-centre audit of VMAT planning and pre-treatment verification.

Author information

1
Medical Physics and Radiation Protection Department, Institut Català d'Oncologia, Girona, Spain. Electronic address: djurado@iconcologia.net.
2
Servei de Física, Hospital Sant Joan, Reus, Spain.
3
Servei d'Oncologia Radioteràpica, Hospital Clínic, Barcelona, Spain.
4
Servei d'Oncologia Radioteràpica, Consorci Sanitari de Terrassa, Spain.
5
Department of Medical Physics, Institut Català d'Oncologia, l'Hospitalet de Llobregat, Spain.
6
Department of Radiation Oncology, IMOR Foundation, Barcelona, Spain.
7
Medical Physics Department, Institut Sainte Catherine, Avignon, France.
8
Département de Cancérologie Radiothérapie, CRLC Val d'Aurelle-Paul Lamarque, Montpellier, France.
9
Department of Radiation Oncology, Institut Català d'Oncologia, Badalona, Spain.
10
Servei de Radiofísica i Radioprotecció, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.

Abstract

BACKGROUND AND PURPOSE:

We performed a multi-centre intercomparison of VMAT dose planning and pre-treatment verification. The aims were to analyse the dose plans in terms of dosimetric quality and deliverability, and to validate whether in-house pre-treatment verification results agreed with those of an external audit.

MATERIALS AND METHODS:

The nine participating centres encompassed different machines, equipment, and methodologies. Two mock cases (prostate and head and neck) were planned using one and two arcs. A plan quality index was defined to compare the plans and different complexity indices were calculated to check their deliverability. We compared gamma index pass rates using the centre's equipment and methodology to those of an external audit (global 3D gamma, absolute dose differences, 10% of maximum dose threshold). Log-file analysis was performed to look for delivery errors.

RESULTS:

All centres fulfilled the dosimetric goals but plan quality and delivery complexity were heterogeneous and uncorrelated, depending on the manufacturer and the planner's methodology. Pre-treatment verifications results were within tolerance in all cases for gamma 3%-3mm evaluation. Nevertheless, differences between the external audit and in-house measurements arose due to different equipment or methodology, especially for 2%-2mm criteria with differences up to 20%. No correlation was found between complexity indices and verification results amongst centres.

CONCLUSIONS:

All plans fulfilled dosimetric constraints, but plan quality and complexity did not correlate and were strongly dependent on the planner and the vendor. In-house measurements cannot completely replace external audits for credentialing.

KEYWORDS:

Audit; Quality assurance; VMAT

PMID:
28687395
DOI:
10.1016/j.radonc.2017.05.019
[Indexed for MEDLINE]

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