MAGIC-type polymer gel for three-dimensional dosimetry: intensity-modulated radiation therapy verification.

Research output: Contribution to journalArticle

Abstract

A new type of polymer gel dosimeter, which responds well to absorbed dose even when manufactured in the presence of normal levels of oxygen, was recently described by Fong et al. [Phys. Med. Biol. 46, 3105-3113 (2001)] and referred to by the acronym MAGIC. The aim of this study was to investigate the feasibility of using this new type of gel for intensity-modulated radiation therapy (IMRT) verification. Gel manufacturing was carried out in room atmosphere under normal levels of oxygen. IMRT inverse treatment planning was performed using the Helios software. The gel was irradiated using a linear accelerator equipped with a dynamic multileaf collimator, and intensity modulation was achieved using sliding window technique. The response to absorbed dose was evaluated using magnetic resonance imaging. Measured and calculated dose distributions were compared with regard to in-plane isodoses and dose volume histograms. In addition, the spatial and dosimetric accuracy was evaluated using the gamma formalism. Good agreement between calculated and measured data was obtained. In the isocenter plane, the 70% and 90% isodoses acquired using the different methods are mostly within 2 mm, with up to 3 mm disagreement at isolated points. For the planning target volume (PTV), the calculated mean relative dose was 96.8 +/- 2.5% (1 SD) and the measured relative mean dose was 98.6 +/- 2.2%. Corresponding data for an organ at risk was 34.4 +/- 0.9% and 32.7 +/- 0.7%, respectively. The gamma criterion (3 mm spatial/3% dose deviation) was fulfilled for 94% of the pixels in the target region. Discrepancies were found in hot spots the upper and lower parts of the PTV, where the measured dose was up to 11% higher than calculated. This was attributed to sub optimal scatter kernels used in the treatment planning system dose calculations. Our results indicate great potential for IMRT verification using MAGIC-type polymer gel.

Details

Authors
Organisations
External organisations
  • Copenhagen University Hospital
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Biophysics

Keywords

  • Ascorbic Acid, Copper Sulfate, Equipment Failure Analysis, Feasibility Studies, Gelatin, Humans, Hydroquinones, Linear Energy Transfer, Magnetic Resonance Imaging, Methacrylates, Models, Theoretical, Phantoms, Imaging, Polymers, Radiometry, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted, Radiotherapy, Conformal, Reproducibility of Results, Sensitivity and Specificity, Comparative Study, Evaluation Studies, Journal Article, Research Support, Non-U.S. Gov't, Validation Studies
Original languageEnglish
Pages (from-to)1264-1271
Number of pages8
JournalMedical Physics
Volume30
Issue number6
Publication statusPublished - 2003
Publication categoryResearch
Peer-reviewedYes

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Emergency medicine/Medicine/Surgery (013240200), Medical Radiation Physics, Malmö (013243210)