Effect of lithium chloride inorganic salt on the performance of N-(Hydroxymethyl)acrylamide polymer-gel dosimeter in radiation therapy

Enhancement of the dosimetric properties of N-vinyl caprolactam polymer gel dosimeter for clinical practice

In this study, the impact of Lithium Chloride inorganic salt sensitizer on the performance of N-vinyl caprolactam polymer-gel dosimeter was evaluated in terms of dose-response combined with spin-spin relaxation rate (R2) obtained from nuclear magnetic resonance relaxometry technique. The irradiation experiments were conducted using a medical linear accelerator, and the improved polymer gel dosimeters were exposed to various doses, photon beam energies, and dose rates. The signal development of the dosimeters was analyzed using a 0.5 T nuclear magnetic resonance instrument. The dose response of the improved gel at different concentration of co-monomers and at different types of gelatins was investigated. Results showed that the R2 sensitivity of the dosimeter was improved with an increase in Lithium Chloride concentration. With 6 % Lithium Chloride, the sensitivity was improved by more than one and half to two times in the linear dose response rang of (0-10 Gy). Furthermore, no significant impact was seen from varying dose rates and photon energy with the improved dosimeter, and R2 was not affected by changing the irradiation temperature from 10 to 30 °C. Additionally, the dose-response and hence R2 data decreased with increasing scanning temperature and the response was stable for up to five days after irradiation. The polymer gel dosimetry accuracy was estimated by calculating the overall uncertainty and found to be 4.06 % (2σ, 95 % confidence level).

Magnetic properties of polymeric acrylic acid hydrogel dosimeter for radiotherapy applications

The present study introduces the first magnetic characterization of a hydrogel dosimeter comprising acrylic acid synthesized within a polyvinyl alcohol matrix. The study aims to accurately assess ionizing radiation dose distributions, making it a valuable tool for radiotherapy treatment. The hydrogel was irradiated to a 1-60 Gy dose range using a medical linear accelerator with dose rates of 100-600 MU/min and radiation beam energies of 6, 10, and 15 MV. The developed dosimeter was synthesized by irradiation-triggered polymerization, and the polymerization degree was indirectly quantified by monitoring the positive alterations in the nuclear magnetic resonance spin‒spin relaxation rate. The polymeric hydrogel dosimeter demonstrated an exceptional dose response with an NMR sensitivity of 0.26 Gy⁻¹s⁻¹, which is 20 times more than the sensitivity of the same gel when measured optically in our previous study. Moreover, it exhibited consistent performance regardless of the beam energy or dose rate.

Recent Advances in Hydrogel-Based Sensors Responding to Ionizing Radiation

Ionizing radiation and its applications are widely spread throughout life. Similar to many other things, both the positive and negative aspects of ionizing radiation should always be kept in mind. For example, a proper radiation dose can be delivered to tumor tissue to kill malignant cells in radiotherapy. On the other hand, exceeding this dose can damage the normal tissues of a human organism. Therefore, the application of sensors for measuring ionizing radiation doses is of utmost importance in many fields, especially in cancer therapy. Traditional dosimeters, such as ionization chambers, silicon diodes and thermoluminescence dosimeters, are widely used. However, they have limitations in certain aspects. Hydrogel-based sensors (or dosimeters) for measuring ionizing radiation doses attract extensive attention for decades due to their equivalence to living tissue and biocompatibility. In this review, we catalog hydrogel-based dosimeters such as polymer, Fricke, radio-chromic, radio-fluorescence and NPs-embedded dosimeters. Most of them demonstrate desirable linear response and sensitivity regardless of energy and dose rate of ionizing radiation. We aim to review these dosimeters and their potential applications in radiotherapy as well as to stimulate a joint work of the experts from different fields such as materials science, chemistry, cancer therapy, radiobiology and nuclear science.

Improved Dose Response of N-(Hydroxymethyl)acrylamide Gel Dosimeter with Calcium Chloride for Radiotherapy

The impact of calcium chloride (CaCl₂) on the performance of N-(hydroxymethyl)acrylamide (NHMA) polymer gel dosimeter is studied in this article. The dosimeter was exposed to doses of up to 10 Gy with radiation beam-energy of 10 MV and dose-rates of 300 cGy/min. The relaxation rate (R₂) parameter was utilized to explore the performance of irradiated NHMAGAT gels. The dose response in terms of R₂ increased from 0.29 to 0.63 Gy⁻¹·s⁻¹ with increasing calcium chloride concentration from 0 to 1000 mM. The results show no substantial impact of dose-rates as well as radiation energies on NHMAGAT samples. For the steadiness of irradiated NHMAGAT dosimeters, it was found that there is no apparent variation in R₂ (less than ±3%; standard deviation) up to 3 days. The overall uncertainty of the gel dosimeter with calcium chloride is 4.96% (double standard deviation, 95% confidence level).

Whole Three-Dimensional Dosimetry of Carbon Ion Beams with an MRI-Based Nanocomposite Fricke Gel Dosimeter Using Rapid T1 Mapping Method

MRI-based gel dosimeters are attractive systems for the evaluation of complex dose distributions in radiotherapy. In particular, the nanocomposite Fricke gel dosimeter is one among a few dosimeters capable of accurately evaluating the dose distribution of heavy ion beams. In contrast, reduction of the scanning time is a challenging issue for the acquisition of three-dimensional volume data. In this study, we investigated a three-dimensional dose distribution measurement method for heavy ion beams using variable flip angle (VFA), which is expected to significantly reduce the MRI scanning time. Our findings clarified that the whole three-dimensional dose distribution could be evaluated within the conventional imaging time (20 min) and quality of one cross-section.