MAGIC‐type polymer gel for three‐dimensional dosimetry: Intensity‐modulated radiation therapy verification

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.

MAGAT gel and EBT2 film‐based dosimetry for evaluating source plugging‐based treatment plan in Gamma Knife stereotactic radiosurgery

“…In recent times, 3D dosimetry, such as gel dosimetry, has gained popularity because it has the potential to measure highly complex treatments, which is particularly significant in situations where steep dose gradients exist such as intensity‐modulated radiation therapy (IMRT) and SRS 20 , 21 , 22 , 23 , 24 , 25 , 26 . This 3D measurement method simulates all major aspects of the treatment process, and provides 3D dose distributions measurements with high resolution.…”

MAGIC polymer gel for dosimetric verification in boron neutron capture therapy

“…The gel was prepared in normal room atmosphere in a fume cupboard using the gel preparation method described by Fong et al (24) The chosen MAGIC gel composition was previously used and characterized by Gustavsson et al ( 25 , 26 ) Table 1 shows the composition.…”

“…( 2 , 23 ) Polymer gel dosimeters known by the acronym MAGIC (methacrylic and ascorbic acid in gelatin initiated by copper) can be prepared in normal‐room atmosphere more easily and faster than BANG‐type gel. ( 24 , 25 ) …”

3D Dosimetric Tools in Radiotherapy for Photon Beams

“…In 1992, formulations like BANANA, BANG and PAG polymer gels were proposed [25,26]. The suppression of polymerization by oxygen, present in these gels, was improved with a proposition of MAGIC gel (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) [27], which allows the MAGIC polymeric gels to be prepared in normal weather conditions [28][29][30], which for higher temperatures beyond 25 °C loss stability. Thus, was add formaldehyde to the original formulation of the MAGIC, re-calling as MAGIC-f, which led to a rise in its melting point to 69 °C [31].…”