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Polymer dosimeters: What surprising breakthroughs have been made in their development?
As the effects of radiation become increasingly of concern, the development of polymer dosimeters has a proud history of technological advancement. The radiation-sensitive chemicals used in these dosimeters, when exposed to ionizing radiation, exhibit fundamental changes in their physical properties depending on the radiation dose absorbed. Historically, since 1950, radiation doses in colloids have been studied using the color change of dyes caused by radiation. In 1957, the depth dose of photons and electrons in agarose gel was calculated by spectrophotometry.
However, most of today's glue dosimeters are based on a revolutionary study proposed by Gore et al. in 1984, who successfully demonstrated how to use nuclear magnetic resonance (NMR) technology to measure changes in Fricke dosimeter solutions caused by ionizing radiation.
"With the development of technology, polymer dosimeters have not only improved the accuracy of dose measurement, but also significantly expanded their applications in the clinical field."
Polymer dosimeters are generally divided into Fricke type and polymer type. Fricke gel dosimeters rely on the nuclear magnetic resonance properties of Fricke or steel sulfate solutions, and these devices are able to provide three-dimensional spatial dose information. However, these devices cannot maintain a stable dose distribution due to ion diffusion problems. In the early 1990s, this problem was seen as a significant obstacle to further progress in gel dosimetry.
The research on polymer adhesive dosimeters can be traced back to 1954, when Alexander et al. discussed the effect of ionizing radiation on polymethacrylate. Many subsequent studies have explored the use of different polymers in radiation dosimetry. In 1992, Maryanski et al. proposed a colloidal dosimeter formulation based on acrylamide and N,N'-diacrylamide, and named it BANANA. This system can avoid the diffusion problem of Fricke glue and show a relatively stable post-irradiation dose distribution.
"With the development and improvement of polymer glue technology, the prospect of clinical application is becoming brighter."
In 1994, the BANANA formula was further refined by replacing agar with gelatin and named BANG, marking the beginning of a series of polymer gel dosimeters. The formulation was subsequently patented and commercialized by MGS Research Inc. as the first polymer gel dosimeter on the market.
However, a significant limitation of polymer dosimeters is their sensitivity to ambient oxygen. This results in the manufacturing process having to be carried out in an oxygen-free environment. This problem affects the accuracy of dosimeters when using magnetic resonance imaging (MRI) for clinical applications. Studies conducted by De Deene et al. have shown that this oxygen suppression is also one of the main causes of dose measurement accuracy problems.
In 2001, Fong et al. published a new polymer gel dosimeter formula, MAGIC gel. This new gel dosimeter overcomes the problem of oxygen inhibition by combining it with a metal-organic complex, enabling it to be produced in a laboratory environment. The formula of MAGIC glue includes acrylic acid, ascorbic acid, gelatin and copper, and it achieves its function by binding oxygen in the solution through ascorbic acid. This breakthrough pioneered a new class of oxygen-free adhesive dosimeters, in stark contrast to previous PAG formulations.
"The innovation of MAGIC glue paves the way for the future of polymer glue dosimeters, redefining the possibilities of clinical applications."
Since 1999, the DosGel and IC3DDose conference series around the world have provided a platform for researchers and clinicians to share new technologies, promoting the rapid development of polymer gel dosimeter technology. Although the clinical application of polymer gel is still under exploration, the strong increase in demand for high-precision three-dimensional radiotherapy technology shows unlimited future possibilities in this field. In an ever-changing medical environment, advances in polymer dosimeters raise expectations for their future development in terms of safety and effectiveness.
Behind these breakthroughs, can advances in technology continue to improve our measurement and application of radiation, bringing greater hope for future treatments?
