A systematic review of clinical applications of polymer gel dosimeters in radiotherapy

Abstract: Radiotherapy has rapidly improved because of the use of new equipment and techniques. Hence, the appeal for a feasible and accurate three-dimensional (3D) dosimetry system has increased. In this regard, gel dosimetry systems are accurate 3D dosimeters with high resolution. This systematic review evaluates the clinical applications of polymer gel dosimeters in radiotherapy. To find the clinical applications of polymer gel dosimeters in radiotherapy, a full systematic literature search was performed on the basis of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in electronic databases up to January 31, 2017, with use of search-related terms in the titles and abstracts of articles. A total of 765 articles were screened in accordance with our inclusion and exclusion criteria. Eventually, 53 articles were included in the study. The findings show that most clinical applications of polymer gel dosimeters relate to external radiotherapy. Most of the gel dosimeters studied have acceptable dose accuracy as a 3D dosimeter with high resolution. It is difficult to judge which is the best polymer gel dosimeter to use in a clinical setting, because each gel dosimeter has advantages and limitations. For example, methacrylic acid–based gel dosimeters have high dose sensitivity and low toxicity, while their dose response is beam energy dependent; in contrast, N-isopropylacrylamide gel dosimeters have low dose resolution, but their sensitivity is lower and they are relatively toxic. Keywords: Polymer gel dosimetry Clinical application Radiotherapy Brachytherapy Neutron capture therap

Measurement of the photon and thermal neutron doses of contralateral breast surface in breast cancer radiotherapy

Introduction and purpose:During the radiation therapy of tumoral breast, the contralateral breast (CB) will receive scattered doses. In the present study, the photon and thermal neutron dose values received by CB surface during breast cancer radiation therapy were measured.Materials and methods:The right breast region of RANDO phantom was considered as CB, and the measurements of photon and thermal neutron dose values were carried out on this region surface. The phantom was irradiated with 18 MV photon beams, and the dose values were measured with thermoluminescent dosimeter (TLD-600 and TLD-700) chips for 11 � 13, 11 � 17 and 11 � 21 cm2 field sizes in the presence of physical and dynamic wedges.Results:The total dose values (photon + thermal neutron) received by the CB surface in the presence of physical wedge were 12·06, 15·75 and 33·40 of the prescribed dose, respectively, for 11 � 13, 11 � 17 and 11 � 21 cm2 field sizes. The corresponding dose values for dynamic wedge were 9·18, 12·92 and 29·26 of the prescribed dose, respectively. Moreover, the results showed that treatment field size and wedge type affect the received photon and thermal neutron doses at CB surface.Conclusion:According to our results, the total dose values received at CB surface during breast cancer radiotherapy with high-energy photon beams are remarkable. In addition, the dose values received at CB surface when using a physical wedge were greater than when using a dynamic wedge, especially for medial tangential fields. © Cambridge University Press 2019

Different Methods of Measuring Neutron Dose/Fluence Generated During Radiation Therapy with Megavoltage Beams

Medical linear accelerators (linacs) are the most frequently applied radiation therapy machines in the locoregional treatment of cancers by producing either high-energy electron or photon beams. However, with high-energy photons (>8 MeV), interaction of these photons with different high-Z nuclei of materials in components of the linac head unavoidably generates neutrons. On the other hand, the average energy of these generated neutrons has almost the highest radiation-weighting factor. Therefore, the produced neutrons should not be neglected. There are various tools for the measurement of neutron dose/fluence generated in a megavoltage linac, including thermoluminescent dosimeters, solid-state nuclear track detectors, bubble detectors, activation foils, Bonner sphere systems, and ionization chamber pairs. In this review article, each of the above-mentioned dosimetric methods will be described in detail

The role of melatonin on doxorubicin-induced cardiotoxicity: A systematic review

Purpose: Doxorubicin, as an effective chemotherapeutic drug, is commonly used for combating various solid and hematological tumors. However, doxorubicin-induced cardiotoxicity is considered as a serious adverse effect, and it limits the clinical use of this chemotherapeutic drug. The use of melatonin can lead to a decrease in the cardiotoxic effect induced by doxorubicin. The aim of this review was to evaluate the potential role of melatonin in the prevention of doxorubicin-induced cardiotoxicity. Methods: This review was conducted by a full systematic search strategy based on PRISMA guidelines for the identification of relevant literature in the electronic databases of PubMed, Web of Science, Embase, and Scopus up to January 2019 using search terms in the titles and abstracts. 286 articles were screened in accordance with our inclusion and exclusion criteria. Finally, 28 articles were selected in this systematic review. Results: The findings demonstrated that doxorubicin-treated groups had increased mortality, decreased body weight and heart weight, and increased ascites compared to the control groups; the co-administration of melatonin revealed an opposite pattern compared to the doxorubicin-treated groups. Also, this chemotherapeutic agent can lead to biochemical and histopathological changes; as for most of the cases, these alterations were reversed near to normal levels (control groups) by melatonin co-administration. Melatonin exerts these protection effects through mechanisms of anti-oxidant, anti-apoptosis, anti-inflammatory, and mitochondrial function. Conclusion: The results of this systematic review indicated that co-administration of melatonin ameliorates the doxorubicin-induced cardiotoxicity. © 2019 Elsevier Inc

Measuring the dose�width product and proposing the local diagnostic reference level in panoramic dental radiography: a multi-center study from Iran

Objective: Although radiation exposure associated with dental radiography is relatively low, patient exposure must be kept practically low. Therefore, it is necessary for each country to establish its own diagnostic reference levels (DRLs) suitable for its equipment and practice. In the present study, dose-width product (DWP) values for panoramic dental radiography were measured and a local DRL was established. Methods: Five panoramic devices from five radiology clinics of Kashan, Iran were selected to measure the DWP values of panoramic dental radiography. To investigate the DWP values, the parameters of each patient�s exposure (e.g., tube voltage, tube current, and exposure time) at these five radiology clinics were extracted. Then, the dose value received by each patient was measured based on a CT pencil chamber. Finally, the overall median DWP values for the patients with small, medium, and large sizes were obtained, and these values were considered as the local DRLs for panoramic dental radiography. Results: A total of 99 adult patients were included in the present study. The findings demonstrated that the median and third-quartile DWP values for these five radiology clinics ranged from 42.3 to 94.3 and 49.7 to 142.8 mGy mm, respectively. The local DRL values, which were established as the overall median DWP values, were 43.4, 52.0, and 80.3 mGy mm for the adults with small, medium, and large sizes, respectively. Conclusion: The local DRL proposed in this study for the adult with standard/medium size was lower than those proposed by other reports and seemed acceptable for panoramic radiography in Kashan, Iran. © 2020, Japanese Society for Oral and Maxillofacial Radiology and Springer Nature Singapore Pte Ltd

Heme oxygenase-1 induction in hepatocytes and non-parenchymal cells protects against liver injury during endotoxemia

INTRODUCTION:Heme oxygenase-1 (HO-1) is a stress response enzyme, which catalyses the breakdown of heme into biliverdin-IX alpha, carbon monoxide and ferrous iron. Under situations of oxidative stress, heat stress, ischemia/reperfusion injury or endotoxemia, HO-1 has been shown to be induced and to elicit a protective effect. The mechanism of how this protective effect is executed is unknown.RESULTS:HO-1 induction with cobalt protoporphorin (Co-PP) dose-dependently protected against apoptotic cell death as well as neutrophil-mediated oncosis in the galactosamine/endotoxin (Gal/ET) shock model. Induction of HO-1 with Co-PP dose-dependently protected against neutrophil-mediated oncosis as indicated by attenuated ALT release and TNF-mediated apoptotic cell death as indicated by reduced caspase-3 activation. HO-1 induction did not attenuate Gal/ET-induced TNF-alpha formation. Furthermore, a similar protective effect with the high dose of Co-PP was observed when animals were treated with Gal/TNF-alpha.CONCLUSIONS:HO-1 induction attenuates apoptosis and neutrophil-mediated oncosis in the Gal/ET shock model. However, the protective effect is not due to the reduction of TNF-alpha release or the attenuation of neutrophil accumulation in the liver sinusoids.This item is part of the UA Faculty Publications collection. For more information this item or other items in the UA Campus Repository, contact the University of Arizona Libraries at [email protected]

Cancer stem cells (CSCs) in cancer progression and therapy

Cancer stem cells (CSCs) are self-renewable cell types that are identified in most types of liquid and solid cancers and contributed to tumor onset, expansion, resistance, recurrence, and metastasis after therapy. CSCs are identified from the expression of cell surface markers, which is tumor-type dependent. The transition between CSCs with cancer cells and other non-CSCs occurs in cancers, which is possibly under the control of signals from CSCs and tumor microenvironment (TME), including CSC niche. Cancer-associated fibroblasts are among the most influential cells for promoting both differentiation of CSCs and dedifferentiation of non-CSCs toward attaining a CSC-like phenotype. WNT/β-catenin, transforming growth factor-β, Hedgehog, and Notch are important signals for maintaining self-renewal in CSCs. An effective therapeutic strategy relies on targeting both CSCs and non-CSCs to remove a possible chance of tumor relapse. There are multiple ways to target CSCs, including immunotherapy, hormone therapy, (mi)siRNA delivery, and gene knockout. Such approaches can be designed for suppressing CSC stemness, tumorigenic cues from TME, CSC extrinsic and/or intrinsic signaling, hypoxia or for promoting differentiation in the cells. Because of sharing a range of characteristics to normal stem/progenitor cells, CSCs must be targeted based on their unique markers and their preferential expression of antigens. © 2018 Wiley Periodicals, Inc

Disruption of the redox balance with either oxidative or anti-oxidative overloading as a promising target for cancer therapy

Abstract Oxidative stress acts as a double edged sword by being both a promoter and a suppressor of cancer. Moderate oxidative stress is beneficial for cancer cell proliferative and invasiveness features, while overexposure of the cells to oxidative insults could induce cancer cell apoptosis and reduce hypoxia along with modulating the immune system for regression of tumor. Cancer cells and cancer stem cells have highly efficient redox systems that make them resistant to oxidative insults. The redox disruptive approach is an area of current research and key for oxidative targeted cancer therapies. This disruption is applicable by using either oxidative or anti oxidative overloading strategies, specifically on cancer cells without influencing normal cells or tissues around tumor. The activity of tumor suppressor cells within tumor microenvironment is needed to be maintained in patients receiving such approaches. KEYWORDS: cancer, oxidative stress, reactive oxygen species (ROS), redo

Targeting of cellular redox metabolism for mitigation of radiation injury

Accidental exposure to ionizing radiation is a serious concern to human life. Studies on the mitigation of side effects following exposure to accidental radiation events are ongoing. Recent studies have shown that radiation can activate several signaling pathways, leading to changes in the metabolism of free radicals including reactive oxygen species (ROS) and nitric oxide (NO). Cellular and molecular mechanisms show that radiation can cause disruption of normal reduction/oxidation (redox) system. Mitochondria malfunction following exposure to radiation and mutations in mitochondria DNA (mtDNA) have a key role in chronic oxidative stress. Furthermore, exposure to radiation leads to infiltration of inflammatory cells such as macrophages, lymphocytes and mast cells, which are important sources of ROS and NO. These cells generate free radicals via upregulation of some pro-oxidant enzymes such as NADPH oxidases, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Epigenetic changes also have a key role in a similar way. Other mediators such as mammalian target of rapamycin (mTOR) and peroxisome proliferator-activated receptor (PPAR), which are involved in the normal metabolism of cells have also been shown to regulate cell death following exposure to radiation. These mechanisms are tissue specific. Inhibition or activation of each of these targets can be suggested for mitigation of radiation injury in a specific tissue. In the current paper, we review the cellular and molecular changes in the metabolism of cells and ROS/NO following exposure to radiation. Furthermore, the possible strategies for mitigation of radiation injury through modulation of cellular metabolism in irradiated organs will be discussed. © 2020 Elsevier Inc