Introduction: Nowadays radiosensitive polymer gels are used as a reliable dosimetry tool for verification of 3D dose distributions. Special characteristics of these dosimeters have made them useful for verification of complex dose distributions in clinical situations. The aim of this work was to evaluate the capability of a Normoxic polymer gel to determine electron dose distributions in different slab phantoms in presence of small heterogeneities. Materials and Methods: Different cylindrical phantoms consisting gel were used under slab phantoms during each irradiation. MR images of irradiated gel phantoms were obtained to determine their R2 relaxation maps. 1D and 2D lateral dose profiles were acquired at depths of 1 cm for an 8 MeV beam and 1 and 4 cm for the 15 MeV energy, and then compared with the lateral dose profiles measured using a diode detector. In addition, 3D dose distributions around these heterogeneities for the same energies and depths were measured using a gel dosimeter. Results: Dose resolution for MR gel images at the range of 0-10 Gy was less than 1.55 Gy. Mean dose difference and distance to agreement (DTA) for dose profiles were 2.6% and 2.2 mm, respectively. The results of the MAGIC-type polymer gel for bone heterogeneity at 8 MeV showed a reduction in dose of approximately 50%, and 30% and 10% at depths 1 and 4 cm at 15 MeV. However, for air heterogeneity increases in dose of approximately 50% at depth 1 cm under the heterogeneity at 8 MeV and 20% and 45% respectively at 15 MeV were observed. Discussion and Conclusion: Generally, electron beam distributions are significantly altered in the presence of tissue inhomogeneities such as bone and air cavities, this being related to mass stopping and mass scattering powers of heterogeneous materials. At the same time, hot and cold scatter lobes under heterogeneity regions due to scatter edge effects were also seen. However, these effects (increased dose, reduced dose, hot and cold spots) at deeper depths, are compensated with the contributions of scattered electrons. Our study showed that Normoxic polymer gels are reliable detectors for determination of electron dose distributions due to their characteristics such as tissue equivalence, energy independence, and 2D and 3D dose visualization capabilities.

Cardiosphere-derived cells (CDCs) have emerged as one of the most promising stem cell types for cardiac protection and repair. Exosomes are required for the regenerative effects of human CDCs and mimic the cardioprotective benefits of CDCs such as anti-apoptotic effect in animal myocardial infarction (MI) models. Here we aimed to investigate the anti-apoptotic effect of the hypoxic and Normoxic human CDCs-derived exosomes on induced apoptosis in human embryonic stem cell-derived cardiomyocytes (hESC-CMs). In this study, CDCs were cultured under Normoxic (18% O2) and hypoxic (1% O2) conditions and CDC-exosomes were isolated from conditioned media by differential ultracentrifugation. Cobalt chloride as hypoxia-mimetic agents at a high concentration was used to induce apoptosis in hESC-CMs. The caspase-3/7 activity was determined in apoptosis-induced hESC-CMs. The results indicated that the caspase-positive hESC-CMs were significantly decreased from 30.63 ± 1.44% (normalized against untreated cardiomyocytes) to 1.65±0.1 and 1.1±1.09 in the presence of Normoxic exosomes (N-exo) at concentration of 25 and 50 mg/mL, respectively. Furthermore, hypoxic exosomes (H-exo) at concentration of 25 and 50 μg/mL led to 8.75 and 12.86 % reduction in caspase-positive cells, respectively. The anti-apoptotic activity of N-exo at the concentrations of 25 and 50 μg/mL was significantly higher than H-exo. These results could provide insights into optimal preparation of CDCs which would greatly influence the anti-apoptotic effect of CDC-exosomes. Totally, CDC-secreted exosomes have the potential to increase the survival of cardiomyocytes by inhibiting apoptosis. Therefore, CDC-exosomes can be developed as therapeutic strategy in ischemic cardiac disease.

Radiotherapy includes all methods that can deliver a particular amount of ionizing radiation to malignant tissues, assuming that minimal damage hurts healthy tissues. We are looking for a valuable and reliable method to measure absorbed dose and the ability to measure the distribution of absorbed dose in three dimensions which nowadays is one of the three-dimensional dosimetry methods in using radiation-sensitive polymer gels. The purpose of the present study was to calculate the amount of increase of absorbed dose in the presence of gold nanoparticles and to investigate the type of gold nanoparticles arrangement (uniformly and shells) in the polymer gel of Normoxic. In this study from both experimental and simulation approaches, a dosimeter of a Normoxic polymer type gel was used to measure the amount of absorbed dose changes of Gamma rays in the presence of gold nanoparticles irradiated with Iridium-192 source beams. Thermolominans dosimetry reading system was used to read steps of dose value and then MCNPX computational code was simulated by using Monte Carlo method. The results were compared and investigated by experimental experiments. In the presence of gold nanoparticles uniformly distributed in polymer gel, with 0. 1mM to 1. 5mM, the maximum absorbed dose was 0. 24% and in shell state it was 20%. The result and investigation of both experimental and simulation studies showed that the optimum density of gold nanoparticles in the Normoxic polymer gel is 1. 5mM, which can be used for clinical trials.

Introduction: Despite the fact that the clinical implementation of polymer gel dosimetry has been facilitated after the introduction of Normoxic gels, there are still complications in its clinical routine use that are under investigation. In the current work, the feasibility of using a Normoxic polymer gel dosimeter named MAGICA has been investigated for use in our clinical brachytherapy applications at Imam Hospital and the deviations between the results obtained from two different calibration methods were investigated. Materials and Methods: The gel fabrication was performed at Novin Medical Radiation Institute and 4 Perspex walled phantoms designed especially for brachytherapy irradiations were filled with the same gel, together with 15 plastic calibration test tubes. The test tubes were irradiated with a range of known doses using a cobalt-60 teletherapy unit and the phantoms were irradiated with two brachytherapy remote-after-loaders using Cs137 and Co60 brachytherapy sources according to the treatment planning data. Imaging was performed with a Multi-spin-echo protocol using a Siemens 1.5T MRI machine. Image processing was performed in MATLAB environment to extract R2 maps of the dose distributions. Gel fabrication, irradiation and imaging were performed at three different centers, so the dosimeters and test tubes were transferred from one center to another under non-uniform conditions. R2 values of the first dosimeter which was irradiated with a single cesium source were extracted from different distances from the source along a horizontal profile and correlated to the dose values at the same distances in treatment planning data. This was used as the second calibration method to extract the absolute measured values of the other three dosimeters. Diagrams of the absorbed dose versus distance were plotted for each dosimeter and the results obtained from the two calibration methods were compared. Results: Results of the measured values that were calibrated with the test tubes show a 3 to 6 Gy dose difference in plateaus and more than 2 mm distance to agreement gap in steep dose gradients. However, the results of using the second calibration method show at most a 0.36 Gy dose difference in plateaus and less than 2 mm distance to agreement gap in steep dose gradients. Discussion and Conclusion: As the gel fabrication, irradiation and imaging conditions were the same for all the gel dosimeters and the calibration tubes, the unexpected deviations between the results of the two calibration methods deserves more investigations. It seems plausible to attribute this deviation to the difference in the size of calibration test tubes and original dosimeters. From a practical point of view, as the origin of this effect has not yet been investigated, it would be best to use a calibration phantom with the same size and characteristics as the original dosimeters.

IntroductionThe use of cut-outs in electron applicators make changes on output, isodose, and percentage depth dose (PDD) curves. These changes and electron beam dose distribution in the form of three-dimensional (3D) can be measured by gel dosimeters.Materials and MethodsDosimetry was performed with and without a square shield (6×6 cm2 field). The energies were 4, 9, and 16 MeV and phantom was filled with MAGIC gel polymer. For each section, transverse relaxation rate (R2) maps were obtained from MRI images and percentage depth doses and isodose curves were plotted.ResultsAverage energy was 3.029 MeV for the energy of 4 MeV and 8.155 MeV for the energy of 9 MeV. Surface dose was higher in shielded field compared with the open one (due to electron scattering between the phantom and lead) which increased with increasing of energy. In the open field, for energies equal to 4, 9, and 16 MeV, the surface dose was 6.40, 6.48, and 7.20 Gy and for the shielded mode, they were 6.63, 7.04, and 7.31 Gy, respectively. Also error values showed less errors and higher accuracy on curves by increasing of energy.ConclusionInvestigation of an isodose pattern in the shielded mode showed scattering due to the lead, which is on the applicator. Overall, the results of this study demonstrated the value and potential of this dosimetric method with respect to characteristics such as stability, responsiveness and specially ability to show three dimensional electron beam dose distribution.

Introduction: The purpose of this work was to study the ability of MRI Normoxic polymer gel dosimetry for evaluating the dose distribution in HDR brachytherapy of esophagial cancer at Imam Reza brachytherapy center (Mashhad, Iran). Materials and Methods: Initially, 2liters of Normoxic gel (MAGIC) was fabricated and then poured into 12 calibration test tubes and placed in a perspex walled phantom. The gel phantom was irradiated with a brachytherapy remote-afterloader unit using a cobalt-60 brachytherapy source and the test tubes were irradiated with a range of known doses with a cobalt-60 teletherapy unit. Imaging was performed with a multi-spin-echo protocol and a T2 quantitative technique using a Siemens 1.5 T MRI machine. The MRI images were transferred to a computer and then image processing was performed in the MATLAB environment to extract R2 maps of the irradiated area. Results: In this study and at the reference point, the dose deviation between the gel dosimetry and the calculated data was 4.5%. The distance to agreement (DTA) for dose profiles was 2.7 mm. Also, dose sensitivity of the MAGIC gel dosimeter was 0.693 S-1Gy-1 (R2=0.9376). Conclusion: In this work, the data obtained from TPS calculations were found in very good agreement with the measured results provided by gel dosimetry. It was evaluated using a comparison of isodoses and dose at the reference point, and dose profile verification. It is also concluded that the gel dosimetry systems have proven to be a useful tool for dosimetry in clinical radiotherapy applications.