Can a commercial gel dosimetry system be used to verify stereotactic spinal radiotherapy treatment dose distributions?

Tanya Kairn ,Daniel Papworth ,Bess Sutherland ,Steven Sylvander ,A G Livingstone ,Rick Franich ,Scott Crowe ,Shaun Smith ,Andre Asena ,Jamie Trapp

doi:10.1088/1742-6596/847/1/012071

Abstract

This study investigated the use of the TruView xylenol-orange-based gel and VISTA optical CT scanner (both by Modus Medical Inc, London, Canada), for use in verifying the accuracy of planned dose distributions for hypo-fractionated (stereotactic) vertebral treatments. Gel measurements were carried out using three stereotactic vertebral treatments and compared with planned doses calculated using the Eclipse treatment planning system (Varian Medical Systems, Palo Alto, USA) as well as with film measurements made using Gafchromic EBT3 film (Ashland Inc, Covington, USA), to investigate the accuracy of the gel system. The gel was calibrated with reference to a moderate-dose gradient region in one of the gel samples. Generally, the gel measurements were able to approximate the close agreement between the doses calculated by the treatment planning system and the doses measured using film (which agreed with each other within 2%), despite lower resolution and bit depth. Poorer agreement was observed when the dose delivered to the gel exceeded the range of doses delivered in the calibration region. This commercial gel dosimetry system may be used to verify hypo-fractionated treatments of vertebral targets, although separate gel calibration measurements are recommended.

Highlights

Radiotherapy treatments of vertebral targets are challenging to plan and deliver, due to the geometry of the anatomy involved
Three different stereotactic ablative body radiotherapy (SABR) treatments were planned for vertebral targets, for delivery using a volumetric modulated arc therapy (VMAT) technique, using a Varian Truebeam linac with Millennium MLC (Varian Medical Systems, Palo Alto, USA)
This measurement result provides a strong indication that the dose-response of the TruView gel and VISTA readout system was non-linear

Summary

Introduction

Radiotherapy treatments of vertebral targets are challenging to plan and deliver, due to the geometry of the anatomy involved. While valuable dose gradient information can be derived from two-dimensional film measurements in the coronal and sagittal planes [2, 3], the three-dimensional measurement capability of dosimetry gels gives them the potential to provide information about the consistency of the dose gradient, along the whole treatment volume, as well as a more comprehensive indication of the accuracy and deliverability of the planned dose. This study investigated the use of a commercial gel dosimetry [4] system, for use in verifying the accuracy of planned dose distributions for vertebral treatments. Gel measurements were carried out and compared with planned doses and film measurements, to investigate the accuracy of the gel system and evaluate the suitability of a simple calibration method.

Methods

Results

Conclusion