Radiotherapy & Oncology
Volume 95, Issue 2 , Pages 142-148, May 2010

Single Arc Volumetric Modulated Arc Therapy of head and neck cancer

  • Anders Bertelsen

      Affiliations

    • Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
    • Laboratory of Radiation Physicsand
    • Corresponding Author InformationCorresponding author. Address: Institute of Clinical Research, University of Southern Denmark, Odense, Denmark.
    • ,
  • Christian R. Hansen

      Affiliations

    • Laboratory of Radiation Physicsand
    • ,
  • Jørgen Johansen

      Affiliations

    • Department of Oncology, Odense University Hospital, Odense, Denmark
    • ,
  • Carsten Brink

      Affiliations

    • Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
    • Laboratory of Radiation Physicsand

Received 24 August 2009; received in revised form 14 January 2010; accepted 17 January 2010. published online 26 February 2010.

Abstract 

Background

The quality of Volumetric Modulated Arc Therapy (VMAT) plans is highly dependent on the performance of the optimization algorithm used. Recently new algorithms have become available which are capable of generating VMAT plans for Elekta accelerators. The VMAT algorithm in Pinnacle3® is named SmartArc and its capability to generate treatment plans for head and neck cancer was tested.

Methods

Twenty-five patients with oropharyngeal or hypopharyngeal carcinoma, previously treated with IMRT by means of Pinnacle3® and Elekta accelerators, were replanned with single arc VMAT. The VMAT planning objectives were to achieve clinical target coverage and sparing of the organs at risk (OAR). Comparison with the original clinically used IMRT was made by evaluating (1) dose–volume histograms (DVHs) for PTVs, (2) DVHs for OARs, (3) delivery time and monitor units (MU), and (4) treatment accuracy.

Results

Equivalent or superior target coverage and sparing of OARs were achieved with VMAT compared to IMRT. Volumes in the healthy tissues receiving between 17.3Gy and 49.4Gy were significantly reduced and the conformity (CI95%) of the elective PTV was improved from 1.7 with IMRT to 1.6 with VMAT. Compared to step-and-shoot IMRT, VMAT reduced the number of MUs by 8.5% to 460±63MUs per fraction, and delivered on an Elekta Synergy accelerator, the treatment time was on average reduced by 35% to 241±16s. In Delta4® measurements of the VMAT treatments, 99.6±0.5% of the detector points passed a 3mm and 3% gamma criterion, identical to the results of IMRT.

Conclusions

The target coverages obtained in the IMRT and VMAT plans were found to be very similar. SmartArc generated single arc VMAT plans with equivalent or better target coverage and sparing of OARs compared to IMRT, while both delivery time and MUs were decreased. Very good dose accuracy results were obtained delivering the plans on an Elekta accelerator.

Keywords: Volumetric Modulated Arc Therapy, VMAT, SmartArc, Head and neck, Step-and-shoot intensity modulated radiotherapy

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PII: S0167-8140(10)00062-9

doi:10.1016/j.radonc.2010.01.011

Radiotherapy & Oncology
Volume 95, Issue 2 , Pages 142-148, May 2010

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