A portable secondary dose monitoring system using scintillating fibers for proton therapy of prostate cancer: A Geant4 Monte Carlo simulation study

Purpose: The main purpose of this study was to monitor the secondary dose distribution originating from a water phantom during proton therapy of prostate cancer using scintillating fibers.Methods: The Geant4 Monte Carlo toolkit version 9.6.p02 was used to simulate a proton therapy of prostate cancer. Two cases were studied. In the first case, 8 × 8 = 64 equally spaced fibers inside three 4 × 4 × 2.54 cm3 Delrin® blocks were used to monitor the emission of secondary particles in the transverse (left and right) and distal regions relative to the beam direction. In the second case, a scintillating block with a thickness of 2.54 cm and equal vertical and longitudinal dimensions as the water phantom was used. Geometrical cuts were implemented to extract the energy deposited in each fiber and inside the scintillating block.Results: The transverse dose distributions from the detected secondary particles in both cases are symmetric and agree to within <3.6%. The energy deposited gradually increases as one moves from the peripheral row of fibers towards the center of the block (aligned with the center of the prostate) by a factor of approximately 5. The energy deposited was also observed to decrease as one goes from the frontal to distal region of the block. The ratio of the energy deposited in the prostate to the energy deposited in the middle two rows of fibers showed a linear relationship with a slope of (-3.55±2.26) × 10-5 MeV per treatment Gy delivered. The distal detectors recorded a negligible amount of energy deposited due to higher attenuation of the secondary particles by the water in that direction.Conclusion: With a good calibration and with the ability to define a good correlation between the radiation flux recorded by the external fibers and the dose delivered to the prostate, such fibers can be used for real time dose verification to the target. The system was also observed to respond to the series of Bragg Peaks used to generate the Spread Out Bragg Peak inside the water phantom. Such Bragg Peaks were detected by the fibers. The energy deposited inside the lateral blocks were also observed to decrease as one goes away from the beam nozzle due to increased attenuation

Scintillating fiber based in-vivo dose monitoring system to the rectum in proton therapy of prostate cancer: A Geant4 Monte Carlo simulation

Purpose: To construct a dose monitoring system based on an endorectal balloon coupled to thin scintillating fibers to study the dose to the rectum in proton therapy of prostate cancer.Method: A Geant4 Monte Carlo toolkit was used to simulate the proton therapy of prostate cancer, with an endorectal balloon and a set of scintillating fibers for immobilization and dosimetry measurements, respectively.Results: A linear response of the fibers to the dose delivered was observed to within less than 2%. Results obtained show that fibers close to the prostate recorded higher dose, with the closest fiber recording about one-third of the dose to the target. A 1/r2 (r is defined as center-to-center distance between the prostate and the fibers) decrease was observed as one goes toward the frontal and distal regions. A very low dose was recorded by the fibers beneath the balloon which is a clear indication that the overall volume of the rectal wall that is exposed to a higher dose is relatively minimized. Further analysis showed a relatively linear relationship between the dose to the target and the dose to the top fibers (total 17), with a slope of (-0.07 ± 0.07) at large number of events per degree of rotation of the modulator wheel (i.e., dose).Conclusion: Thin (1 mm × 1 mm), long (1 m) scintillating fibers were found to be ideal for real time in-vivo dose measurement to the rectum during proton therapy of prostate cancer. The linear response of the fibers to the dose delivered makes them good candidates as dosimeters. With thorough calibration and the ability to define a good correlation between the dose to the target and the dose to the fibers, such dosimeters can be used for real time dose verification to the target.-----------------------------------Cite this article as: Tesfamicael BY, Avery S, Gueye P, Lyons D, Mahesh M. Scintillating fiber based in-vivo dose monitoring system to the rectum in proton therapy of prostate cancer: A Geant4 Monte Carlo simulation. Int J Cancer Ther Oncol 2014; 2(2):02024.DOI: http://dx.doi.org/10.14319/ijcto.0202.

Coordination mechanisms for COVID-19 in the WHO Regional office for Africa

Aim: this study describes the coordination mechanisms that have been used for management of the COVID-19 pandemic in the WHO AFRO region; relate the patterns of the disease (length of time between onset of coordination and first case; length of the wave of the disease and peak attack rate) to coordination mechanisms established at the national level, and document best practices and lessons learned. Method: We did a retrospective policy tracing of the COVID-19 coordination mechanisms from March 2020 (when first cases of COVID-19 in the AFRO region were reported) to the end of the third wave in September 2021. Data sources were from document and Literature review of COVID-19 response strategies, plans, regulations, press releases, government websites, grey and peer-reviewed literature. The data was extracted to Excel file database and coded then analysed using Stata (version 15). Analysis was done through descriptive statistical analysis (using measures of central tendencies (Mean, DS, and median) and measures of central dispersion (range)), multiple linear regression, and thematic analysis of qualitative data. Results: There are three distinct layered coordination mechanisms (strategic, operational, and tactical) that were either implemented singularly or in tandem with another coordination mechanism. 87.23% (n=41) of the countries initiated strategic coordination, and 59.57% (n=28) initiated some form of operational coordination. Some of countries (n=26,55.32%) provided operational coordination using functional Public Health Emergency Operation Centres (PHEOCs) which were activated for the response. 31.91% (n=15) of the countries initiated some form of tactical coordination which involved the decentralisation of the operations at the local/grassroot level/district/ county levels. Decentralisation strategies played a key role in coordination, as was the innovative strategies by the countries; some coordination mechanisms built on already existing coordination systems and the heads of states were effective in the success of the coordination process. Financing posed challenge to majority of the countries in initiating coordination. Conclusion: Coordinating an emergency is a multidimensional process that includes having decision-makers and institutional agents define and prioritise policies and norms that contain the spread of the disease, regulate activities and behaviour and citizens, and respond to personnel who coordinate prevention

A phylogenetic framework of the legume genus Aeschynomene for comparative genetic analysis of the Nod-dependent and Nod-independent symbioses

Background : Among semi-aquatic species of the legume genus Aeschynomene, some have the property of being nodulated by photosynthetic Bradyrhizobium lacking the nodABC genes necessary for the synthesis of Nod factors. Knowledge of the specificities underlying this Nod-independent symbiosis has been gained from the model legume Aeschynomene evenia but our understanding remains limited due to the lack of comparative genetics with related taxa using a Nod factor-dependent process. To fill this gap, we combined different approaches to perform a thorough comparative analysis in the genus Aeschynomene. Results: This study significantly broadened previous taxon sampling, including in allied genera, in order to construct a comprehensive phylogeny. In the phylogenetic tree, five main lineages were delineated, including a novel lineage, the Nod-independent clade and another one containing a polytomy that comprised several Aeschynomene groups and all the allied genera. This phylogeny was matched with data on chromosome number, genome size and low-copy nuclear gene sequences to reveal the diploid species and a polytomy containing mostly polyploid taxa. For these taxa, a single allopolyploid origin was inferred and the putative parental lineages were identified. Finally, nodulation tests with different Bradyrhizobium strains revealed new nodulation behaviours and the diploid species outside of the Nod-independent clade were compared for their experimental tractability and genetic diversity. Conclusions: The extended knowledge of the genetics and biology of the different lineages sheds new light of the evolutionary history of the genus Aeschynomene and they provide a solid framework to exploit efficiently the diversity encountered in Aeschynomene legumes. Notably, our backbone tree contains all the species that are diploid and it clarifies the genetic relationships between the Nod-independent clade and the Nod-dependent lineages. This study enabled the identification of A. americana and A. patula as the most suitable species to undertake a comparative genetic study of the Nod-independent and Nod-dependent symbioses

The role of bioreductive activation of doxorubicin in cytotoxic activity against leukaemia HL60-sensitive cell line and its multidrug-resistant sublines

Clinical usefulness of doxorubicin (DOX) is limited by the occurrence of multidrug resistance (MDR) associated with the presence of membrane transporters (e.g. P-glycoprotein, MRP1) responsible for the active efflux of drugs out of resistant cells. Doxorubicin is a well-known bioreductive antitumour drug. Its ability to undergo a one-electron reduction by cellular oxidoreductases is related to the formation of an unstable semiquionone radical and followed by the production of reactive oxygen species. There is an increasing body of evidence that the activation of bioreductive drugs could result in the alkylation or crosslinking binding of DNA and lead to the significant increase in the cytotoxic activity against tumour cells. The aim of this study was to examine the role of reductive activation of DOX by the human liver NADPH cytochrome P450 reductase (CPR) in increasing its cytotoxic activity especially in regard to MDR tumour cells. It has been evidenced that, upon CPR catalysis, DOX underwent only the redox cycling (at low NADPH concentration) or a multistage chemical transformation (at high NADPH concentration). It was also found, using superoxide dismutase (SOD), that the first stage undergoing reductive activation according to the mechanism of the redox cycling had the key importance for the metabolic conversion of DOX. In the second part of this work, the ability of DOX to inhibit the growth of human promyelocytic-sensitive leukaemia HL60 cell line as well as its MDR sublines exhibiting two different phenotypes of MDR related to the overexpression of P-glycoprotein (HL60/VINC) or MRP1 (HL60/DOX) was studied in the presence of exogenously added CPR. Our assays showed that the presence of CPR catalysing only the redox cycling of DOX had no effect in increasing its cytotoxicity against sensitive and MDR tumour cells. In contrast, an important increase in cytotoxic activity of DOX after its reductive conversion by CPR was observed against HL60 as well as HL60/VINC and HL60/DOX cells

Case Report: COVID-19 and Lassa Fever Coinfection in an Ebola Suspected Patient in Guinea

ABSTRACT. In this case report, we describe a clinical presentation and therapeutic history of a unique case diagnosed with Lassa fever and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a 23-year-old man from Yomou prefecture in southeast Guinea identified with suspected Ebola Virus Disease (EVD) in the midst of an ongoing outbreak of that disease in the same region. On May 3, 2021, he was admitted to the Nzérékoré Epidemic disease treatment center where his clinical condition deteriorated significantly. Laboratory testing performed on the same day reveals a negative EVD polymerase chain reaction (PCR). Three days later, the patient was tested positive for SARS-CoV-2 and Lassa fever by reverse transcriptase PCR (RT-PCR) assays. Laboratory examination also indicated severe hematological and biochemical deteriorations in the patient. This case substantiates the need for systematic differential diagnosis during epidemic-prone disease outbreaks to better manage severely unwell patients.</jats:p