Monte-Carlo based assessment of MAGIC, MAGICAUG, PAGATUG and PAGATAUG polymer gel dosimeters for ovaries and uterus organ dosimetry in brachytherapy, nuclear medicine and Tele-therapy

The Role of Molecular Structure in Monte Carlo Simulations of the Secondary Electron Yield and Backscattering Coefficient from Methacrylic Acid

In this paper, we show the influence of the chemical structure of four different conformers on the secondary electron emission and backscattering of an electron beam from a gel of methacrylic acid. The conformers have different permanent dipole moments, which determines the cross sections for elastic collisions with electrons. The cross sections are used in Monte Carlo simulations of an electron beam, which enters the gel of methacrylic acid. The secondary electron yield and the backscattering coefficient are computed as a function of the beam energy.

A review study on application of gel dosimeters in low energy radiation dosimetry

INTRODUCTION

The accuracy of dose delivered to tumors and surrounding normal tissues is vital in either radiotherapy using low energy photons and radiological techniques as well as radiotherapy with mega voltage energies. This systematic review focuses on applications of gel dosimetry in low energy radiation contexts applied either through radiotherapy or interventional radiology.

METHODS

Literature was reviewed based on electronic databases: Google Scholar, Scopus, Embase, PubMed, Science Direct, Research Gate and IOP science. The search was conducted on relevant terms in the title and keywords. 82 articles related to our criteria has been extracted and included in the study.

RESULTS

The findings demonstrated that almost all types of gel dosimeters had an acceptable accuracy and high resolution in low energy radiation contexts with their own limitations and advantages.

CONCLUSION

Gel dosimeters compete well with other conventional dosimeters in terms of tissue equivalence and energy dependence; however, choosing the best gel dosimeter for use in low energy radiation dosimetry depends on their different limitation and advantages. There are some general features about each gel group which can help to select the suitable gel related to our work. For example, methacrylic acid based gel dosimeters show higher sensitivity compared to other types of gel dosimeters but have more toxicity and are dose rate dependent in the range of dose rates applied in low energy contexts. In addition, Fricke gel dosimeters exhibit less sensitivity while they are independent of dose rate and energy applied in low energy situations.

Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry

Radiation-sensitive gels are among the most recent and promising developments for radiation therapy (RT) dosimetry. RT dosimetry has the twofold goal of ensuring the quality of the treatment and the radiation protection of the patient. Benchmark dosimetry for acceptance testing and commissioning of RT systems is still based on ionization chambers. However, even the smallest chambers cannot resolve the steep dose gradients of up to 30-50% per mm generated with the most advanced techniques. While a multitude of systems based, e.g., on luminescence, silicon diodes and radiochromic materials have been developed, they do not allow the truly continuous 3D dose measurements offered by radiation-sensitive gels. The gels are tissue equivalent, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some of them are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gels). Other formulations consist of monomers dispersed in a gelatinous medium (Polyacrylamide gels) and rely on radiation-induced polymerization, which creates a stable polymer structure. In both gel types, irradiation causes changes in proton relaxation rates that are proportional to locally absorbed dose and can be imaged using magnetic resonance imaging (MRI). Changes in color and/or opacification of the gels also occur upon irradiation, allowing the use of optical tomography techniques. In this work, we review both Fricke and polyacrylamide gels with emphasis on their chemical and physical properties and on their applications for radiation dosimetry.