Bolus Effect Caused by Use of Thermoplastic Masks in Head and Neck Radiotherapy Treatments.

This paper examines the dosimetric uncertainty arising from the use of thermoplastic masks in the treatment of head and neck cancer through radiotherapy. This study was conducted through Monte Carlo simulations using the Monte Carlo N-Particle eXtended (MCNPX code), and the theoretical results are compared with radiochromic films. Using material characterization techniques, the compounds of the thermoplastic mask were identified, confirming that most of the material corresponds to the polymer C10H16O4. The theoretical results show increases ranging from 42% to 57.4% in the surface absorbed dose for 6 and 15 MV photon beams, respectively, compared to the absorbed dose without the mask. The experimental data corroborate these findings, showing dose increases ranging from 18.4% to 52.1% compared to the expected surface absorbed dose without the mask. These results highlight the need to consider the bolus effect induced by thermoplastic masks during the precise and safe planning and application of radiotherapy treatment in order to ensure its therapeutic efficacy and minimize the associated risks to patients.

Radon activity concentration RnCA and workers lung cancer risks in SENA coal mines, Colombia.

The risk of lung cancer or pneumoconiosis mortality, increases with radioactive radon gas exposures. This article report health risk for underground workers exposed to radioactive gas and radon daughters carried by airborne dust at the coal mining in the Central Mountainous Region of Colombia. A set of 33 measurement points located in that mine galleries were selected to monitor radon gas concentration activity, by passive LR-115 detectors, during two months. Resulting values provided radon concentrations, absorbed dose, environmental equivalent dose and the effective dose; miners increased risk of contracting lung cancer is included. It is concluded that the mine ventilation system satisfies the conditions required by the current radiological protection of the miners. Our study point out that Colombia can effectively address the potential risks associated with radon exposure and ensure a safer living environment for its citizens.

Bolus 3D printing for radiotherapy with conventional PLA, ABS and TPU filaments: Theoretical-experimental study.

A theoretical-experimental study of the interaction of electron beams with 3 filaments conventionally used for 3D printing is presented in this paper. Pieces of polylactic acid (PLA), acrylonitrile butadiene styrene (ABS) and thermoplastic polyurethane (TPU) are studied using Monte Carlo simulation with Geant4 and experimental measurements with plane-parallel ionization chambers and radiochromic films. Using different printing parameters and computed tomography, the presence of air gaps and the uniformity in the bolus density made with the different materials are evaluated. The main parameters in the Percentage Depth Dose (PDDs) are determined, the manufacturing process is standardized and the printing profiles are generated for each of the materials in order to obtain uniform attenuation characteristics in the pieces and improve adaptation to irregular anatomical areas.

Development of a 3D printing process of bolus using BolusCM material for radiotherapy with electrons.

This work presents the optimized parameters of 3D printing for print bolus using BolusCM material. Printing parameters were selected of the homogeneity and absence of air gaps. The dosimetric features of printed bolus were measured with a plane-parallel ionization chamber and EBT3 radiochromic film. Measured features were compared with those estimated with Monte Carlo methods. BolusCM shows good characteristics to be used as bolus material in radiotherapy with electrons, where the printing process allows personalizing the bolus in function of patient characteristics. The material low-cost, the 3D printing and the dosimetric features are few of the advantages of using BolusCM material in radiotherapy with electrons in skin cancer treatment.

¿Son útiles los antimicrobianos en pacientes con trabajo de parto prematuro, espontáneo, membranas intactas e infección bacteriana ascendente? Una revisión narrativa / Are antibiotics useful in patients with preterm and spontaneous labor, intact membranes and ascendant bacterial infection? A narrative review

El parto prematuro (PP) es la principal causa de morbilidad/mortalidad perinatal y frecuentemente es espontáneo, con membranas intactas (MI). La infección intrauterina es su causa más común en un hospital público de Chile. Existe evidencia que la infección bacteriana ascendente desde la vagina es responsable de la infección/inflamación intraamniótica, del PP y de los resultados adversos maternos y perinatales. Esta revisión narrativa incluye ensayos controlados aleatorizados (ECAs), publicados en PubMed, Cochrane, Embase, Scielo, Science Direct, Wiley Online Library, sobre los mecanismos que intervienen en el ascenso de la infección vaginal, los factores infecciosos que participan en el resultado adverso materno-perinatal y la eficacia de los antimicrobianos en estos casos. Estos trabajos no recomiendan usar antimicrobianos profilácticos porque producen daño a corto y largo plazo en los hijos. Pero este resultado tiene sesgo porque no se evaluó la presencia de infección/inflamación subclínica, lo que disminuye el grado de recomendación. También existen ECAs, que erradican la infección/inflamación intraamniótica, reducen la morbilidad/mortalidad neonatal, pero son trabajos aislados, obtenidos de subanálisis, con bajo nivel de evidencia. Se requieren revisiones sistemáticas y metaanális de ECAs con estudio de infección/inflamación subclínica para evaluar si son útiles los antimicrobianos en el PP espontáneo con MI.

Preterm labor (PL) is the leading cause of perinatal morbidity/ mortality and is frequently spontaneous with intact membranes (IM). Intrauterine infection is its most common cause in a public hospital in Chile. There is evidence that ascending bacterial infection from the vagina is responsible for intraamniotic infection/inflammation, PL, and adverse maternal and perinatal outcomes. This narrative review includes randomized controlled trials (RCTs), published in PubMed, Cochrane, Embase, Scielo, Science Direct, Wiley Online Library on the mechanisms involved in the rise of vaginal infection, the infectious factors involved in adverse maternal-perinatal outcomes, and the efficacy of antibiotics in these cases. They do not recommend the use of prophylactic antibiotics because they cause short and long-term damage to children. But this result is biased because the presence of subclinical infection/inflammation was not evaluated, which lowers the degree of recommendation. There are also RCTs that eradicate intra-amniotic infection/inflammation, reduce neonatal morbidity/ mortality, but they are isolated studies, obtained from subanalyses, with a low level of evidence. Systematic reviews and meta-analyses of RCTs with subclinical infection/inflammation study are required to assess whether antibiotics are useful in spontaneous PL with IM.

Linac natW target close-in geometry photoneutron study by nuclear track distribution function.

During electron beam stopping on natW target in a linear accelerator, photonuclear (γ, xn) reactions occur; the tungsten converter provides a non-negligible neutron yield with an energy spectrum that significantly depends on surrounding mass nuclei. Reduction of the neutron radiation field is convenient to limit the side-effects that accompany the tumor or cancer radiotherapy. A close-in irradiation geometry is proposed to improve therapy effectiveness. The convenience of the proposed experimental arrangement is assessed using Monte Carlo simulation and experimental results based on nuclear track-etch methodology. Photoneutron yield for two energy groups (thermal and epithermal) are determined experimentally via boron (98%) converter and cadmium-filter employing a passive detector (poly allyl di-glicol carbonate polimer). Etched track diameter histograms are described by distribution functions to determine the ratio between thermal and higher energy neutrons. New insights are given into therapy beam quality and radiotherapy dose delivery based on bar histograms unfolding.

Characterization of a novel material to be used as bolus in radiotherapy with electrons.

Features of new material to be used as bolus in external radiotherapy were determined and their performance were evaluated. The characterization was carried out using Monte Carlo methods with the Geant4 code where the Percentage Depth Dose (PDD) due to electrons was estimated. In the Monte Carlo model the linear accelerator head was included. Calculated results were experimentally validated with measurements made for 6, 9, 12 and 16 MeV electron beams. The key characteristics of the implemented material were identified, guaranteeing a low cost bolus, easy to be customized and to be used in clinical applications. In comparison with commercial materials the new materials are superior from the cost to the effectiveness of their use in clinical treatments.

Monte Carlo evaluation of out-of-field dose in 18 MV pelvic radiotherapy using a simplified female MIRD phantom.

This study was devoted to determining the unwanted dose due to scattered photons to the out-of-field organs and subsequently estimate the risk of secondary cancers in the patients undergoing pelvic radiotherapy. A typical 18 MV Medical Linear Accelerator (Varian Clinac 2100 C/D) was modeled using MCNPX®code to simulate pelvic radiotherapy with four treatment fields: anterior-posterior, posterior-anterior, right lateral, left lateral. Dose evaluation was performed inside Medical Internal Radiation Dose (MIRD) revised female phantom. The average photon equivalent dose in out-of-field organs is 8.53 mSv Gy-1, ranging from 0.17 to 72.11 mSv Gy-1, respectively, for the organs far from the Planning Treatment Volume (Brain) and those close to the treatment field (Colon). Evidence showed that colon with 4.3049% and thyroid with 0.0020% have the highest and lowest risk of secondary cancer, respectively. Accordingly, this study introduced the colon as an organ with a high risk of secondary cancer which should be paid more attention in the follow-up of patients undergoing pelvic radiotherapy. The authors believe that this simple Monte Carlo (MC) model can be also used in other radiotherapy plans and mathematical phantoms with different ages (from childhood to adults) to estimate the out-of-field dose. The extractable information by this simple MC model can be also employed for providing libraries for user-friendly applications (e.g. '.apk') which in turn increase the public knowledge about fatal cancer risk after radiotherapy and subsequently decrease the concerns in this regard among the public.

[Fetal death from ascending bacterial infection. Diagnostic method, a narrative review. Why is the method that includes placental study, evaluation of clinical and laboratory data efficient in identifying ascending bacterial infection as the cause of fetal death?] / Muerte fetal por infección bacteriana ascendente. Método diagnóstico, una revisión narrativa. ¿Por qué el método que incluye estudio placentario, evaluación de datos clínicos y de laboratorio es eficiente en identificar la infección bacteriana ascendente como causa de muerte fetal?

This narrative review includes published studies of stillbirth classification methods and their efficiency in identifying ascending bacterial infection (ABI), as a cause of fetal death (FD), by searching PubMed, Cochrane, Embase, ScienceDirect, Wiley Online Library, Scielo. Many children die before birth around the world and it has not been possible to reduce FD because the methods used have not been adequate and because ABI, the most frequent cause of FD in a public hospital in Chile, is not diagnosed. Systems using clinical, laboratory and placental study data, INCODE, CORM, are more efficient in identifying ABI as the origin of FD. Specific markers of infection/placental inflammation, histologic chorioamnionitis/acute funitis have been shown to be more efficient in diagnosing ABI than fetal autopsy, that amniotic fluid culture is more efficient than placental culture for detect microbial invasion of the amniotic cavity and that the cord blood sample is efficient for the etiological diagnosis of the infection. The knowledge of the ABI as the initial cause of FD helps to develop guidelines and norms for preventing FD due to this condition.

Muerte fetal por infección bacteriana ascendente: método diagnóstico, una revisión narrativa. ¿Por qué el método que incluye estudio placentario, evaluación de datos clínicos y de laboratorio es eficiente en identificar la infección bacteriana ascendente como causa de muerte fetal? / Fetal death from ascending bacterial infection: diagnostic method, a narrative review. Why is the method that includes placental study, evaluation of clinical and laboratory data efficient in identifying ascending bacterial infection as the cause of fetal death?

Resumen Esta revisión narrativa incluye estudios publicados sobre métodos de clasificación de mortinatos y su eficiencia para identificar la infección bacteriana ascendente (IBA) como causa de muerte fetal (MF), mediante búsqueda en PubMed, Cochrane, Embase, ScienceDirect, Wiley Online Library, Scielo. Muchos niños mueren antes de nacer en todo el mundo y no se ha logrado reducir la MF porque los métodos empleados no han sido los adecuados y porque no se diagnostica la IBA, la causa más frecuente de MF en un hospital público de Chile. Los sistemas que utilizan los datos clínicos, de laboratorio y estudio placentarios, INCODE, CORM, son los más eficientes para identificar la IBA como origen de la MF. Se ha demostrado que los marcadores específicos de infección/inflamación placentaria, corioamnionitis histológica/funisitis aguda son de mayor eficiencia para diagnosticar la IBA que la autopsia fetal, que el cultivo de líquido amniótico es más eficiente que el cultivo de la placenta para detectar invasión microbiana de la cavidad amniótica y que la muestra de sangre de cordón es eficiente para el diagnóstico etiológico de la infección. El conocimiento de la IBA como causa inicial de MF, ayuda a elaborar guías y normas de prevención de la MF por esta condición.

Abstract This narrative review includes published studies of stillbirth classification methods and their efficiency in identifying ascending bacterial infection (ABI), as a cause of fetal death (FD), by searching PubMed, Cochrane, Embase, ScienceDirect, Wiley Online Library, Scielo. Many children die before birth around the world and it has not been possible to reduce FD because the methods used have not been adequate and because ABI, the most frequent cause of FD in a public hospital in Chile, is not diagnosed. Systems using clinical, laboratory and placental study data, INCODE, CORM, are more efficient in identifying ABI as the origin of FD. Specific markers of infection/placental inflammation, histologic chorioamnionitis/acute funitis have been shown to be more efficient in diagnosing ABI than fetal autopsy, that amniotic fluid culture is more efficient than placental culture for detect microbial invasion of the amniotic cavity and that the cord blood sample is efficient for the etiological diagnosis of the infection. The knowledge of the ABI as the initial cause of FD helps to develop guidelines and norms for preventing FD due to this condition.

A new graph of soil Rn-gas transport: Radon-rose plot.

Soil radon gas movement depends on soil geology, environmental thermodynamic parameters and, micro-seismic telluric activity. Mapping radon time dependent concentration at the relaxation depth in a selected area, provide transport direction in a seismically high-risk region. Nuclear track methodology is employed to determine main gradient vector for radon transport. Applying the gradient definition, a "radon rose" graph is constructed from which prone area can be promptly identified. Results show that short time interval, Rn-transport direction may change unpredictably, however, the length of each "spoke" around the circle provides information on the soil Rn-gas probable shifts towards or from a direction per time interval. The new graph is a novelty and provide improved approach for environmental protection and radon dosimetry.

New target with low photoneutron yield for LINAC radiotherapy applications.

This paper presents three new materials composed of TiXV0,035XCuX-1,035 (X = 2, 4 and 6%), is proposed as Linear Accelerator target. Its response to electron beam based on photoneutron production, is assessed by MC simulation and nuclear track-etch methodology. The outcome is compared to a tungsten target irradiated by energetic 16 MeV electron beam. Photoneutron yield, of two energy groups (thermal and epithermal) were determined via converter matter 10B (98%) and Cd-filter by PADC-track density comparison. The multi-metal Ti2V0,07Cu97.93 target related to therapy beam quality, resulted advantageous in comparison to that provided by W-target, commonly used in the LINAC.

Seasonal variation of the S-index as it relates to the concentration of 222Rn inside a bunker that stores radioactive material.

In this work, the seasonal variation of the concentration of radon in soil and its contribution to concentrations inside of a bunker used for the storage and operation of radioactive material was studied. The measurements obtained inside and outside of the installation allowed establish a method for the calculation of the diffusion coefficient for the concrete, variable that directly influences the concentration of radon gas inside of the bunker. With the obtained results of the gamma dose rate and the concentration of radon inside the bunker, the S-index was calculated in order to determine whether the bunker would require some remediation process. The high radon gas concentration rates to which workers are exposed led to study the relative risk of contracting lung cancer (RRLC).

Shielding for transporting an 241Am-Be source for industrial applications.

Paraffin, water and water-extended polyester (WEP) were used as main moderator to design a mobile shielding for a 666 GBq 241Am-Be source used in oil industry. The shielding performance was estimated using Monte Carlo methods where the γ-rays induced by the neutron interaction with the shielding materials were also included. The spectra of neutrons and γ-rays around the shielding were estimated, as well as the total neutron and g-ray total fluences per history. The neutron source strength was used to calculate ambient dose equivalent rates, aiming to satisfy the international recommendation (2 mSv/h at the shielding surface). Moderators modify the neutron spectrum of the source reducing the amount of fast neutrons (0.5-11 MeV) and producing epithermal and thermal neutrons. During neutron transport in the moderator neutron capture and inelastic scattering produce gamma-rays. Paraffin has the best shielding performance however it is not suitable because can be affected by extreme temperatures. WEP and water have similar shielding performance, however water do not satisfy the international recommendations because at one site the neutron and γ-ray doses rates are larger than 2 mSv/h. WEP is the best option because fulfill the international recommendations, it is stable and temperatures where paraffin fails. The WEP-based shielding weights 66 kg.

Removal of iron and manganese in groundwater through magnetotactic bacteria.

It is presented an alternative biological method based on biomineralization mechanisms of Magnetotactic Bacteria (MTB) for the removal in groundwater, of soluble elements such as Fe+2and Mn+2. In first place, it was compared the effectiveness of MTB retention methods for obtention of concentrated volumes in microorganisms, then, it was carried out an inoculation process in groundwater samples and evaluate the removal rate of Fe+2 and Mn+2 in constant conditions of pH and temperature. It was identified electromagnetic method is more efficient in MTB retention, and that the inoculation processes of an enriched solution with MTB in groundwater samples allow to get average removal rates of 47.86% for Fe+2 and 15.26% for Mn+2. In addition, it was evaluated the removal rate of other metals due to magnetic properties of biominerals inside of MTB magnetosome. The highest removal in all cases occurred between the interval of 3 and 5 min of interaction and tended to stabilize in time.

Study of X-ray scattered in a phantom as function of its maximum energy during bimodal PET/CT imaging.

In a simultaneous Bimodal System with Positron Emission Tomography and Computed Tomography, the X-rays from a collimated X-ray tube are scattered over an anatomical region on the patient being scanning and cause a contamination effect on the signal received by the detectors distributed in the shape of a ring of the PET system. To study this phenomenon, each of the components of a bimodal system was modeled and simulated by the Monte Carlo method in Geant4 an X-ray beam produced in a RTW tube MCBM 65B with typical fluences used in medical diagnosis of small animals hitting a cylindrical phantom with a diameter greater than Field of View (FOV) in the tomographic center. The number of ionization events that occur in each of the phoswich detectors of the PET were obtained, the spatial distribution of the scattered X-rays was studied according to three maximum energies of the spectrum and calculation was made to find a filter that was located at the input of the phoswich detector that attenuates the X-rays by 98% and that would allow transmitting the gamma rays of annihilation also by 98%. For this, simulations were carried out using various filter materials, finding that copper is an excellent candidate and were found an optimum thicknesses between 0.5 mm and 1.3 mm, according to the average energy of the X-rays used in the different exploration techniques.

Radon concentration in hydrogeothermal deposit and spas of Boyacá, Colombia.

Inhaled radon and its progenies induce health concern due to high activity-concentration in selected thermal spas of Boyacá region. Hydrogeothermal water sources in a high risk seismic area, are studied to determine by water bubbling method radon concentration values; their occurrence is between few hundreds and 2000 Bq dm-3. Deposits, existing in this area, reach at the surface soil gas radon concentration up to 210 kBq m-3. Maintenance workers, health tourists and visitor's possible detrimental health effects, are discussed in relation to radon balneotherapy beneficial aspects.

PERFORMANCE OF THE INSTADOSETM DOSEMETER FOR INTERVENTIONAL RADIOLOGY AND CARDIOLOGY APPLICATION.

The aim of this article was to verify the performance of the Mirion InstadoseTM dosemeter under clinical conditions and to compare its response in typical X-ray fields used during interventional and cardiology procedures with the TLD-100, usually used for radiation dosimetry. It was also objective of this study to verify the feasibility of using the InstadoseTM dosemeter response at the chest level for estimation of occupational eye lens dose in cardiology and interventional radiology. Initially the response of the dosemeter was tested using continuous X-ray beams and the results showed that the Instadose dosemeter present a satisfactory behavior of the most important dosimetric properties based on the tests as described in the IEC 62387 standard. The measurements performed in clinical conditions showed that the InstadoseTM dosemeter response was comparable to that of TL dosemeters used in interventional radiology and cardiology procedures and there is a correlation between the eye lens doses and the chest doses measured with the InstadoseTM. Based on the results obtained, we recommend the use of the InstadoseTM dosemeter for purposes of occupational whole-body monitoring of medical staff in interventional radiology and cardiology procedures.

El método de clasificación de mortinatos "Condición Obstétrica Relevante de la Muerte Fetal" (CORM) reduce la frecuencia de muerte fetal de causa inexplicable / The stillbirth classification method "Relevant Obstetric Condition of Stillbirth" (CORM) reduces the frequency of unexplained fetal death

RESUMEN Introducción: La muerte fetal (MF) es el principal contribuyente de la mortalidad perinatal. Objetivo: Analizar la eficiencia del método de clasificación de mortinatos, condición obstétrica relevante de la MF (CORM). Métodos: Estudio cohorte retrospectivo, de las MF ocurridas en la Maternidad del Hospital San Borja Arriarán durante 10 años. Los datos provienen de los informes de las auditorías de mortinatos. Se aplicó el método de clasificación CORM, que usa la biopsia placentaria, los datos clínicos y de laboratorio analizados por un obstetra y un patólogo. Resultados: Ocurrieron 56.130 nacimientos y 479 MFs. Tasa de MF, 8.5 por 1000 nacimientos. Se identificaron el 93.5% de las condiciones obstétricas de MF y 6.5% fueron inexplicables. Las más frecuentes fueron: infección bacteriana ascendente (IBA) 24.9%, anomalía congénita 18.0%, y patología placentaria 14.0%. La restricción del crecimiento fetal intrauterino (RCIU) se presentó en el 49.7% de los mortinatos, la mayoría 93.7%, fue secundaria a condición obstétrica primaria. La asfixia durante el parto fue el 0.8% de los mortinatos y se presentó en embarazos de término. El parto prematuro (PP) representó el 80% de los casos de MF. La condición más frecuente asociada con PP fue IBA (38.5% y 38.2% de las MF menores de 30 semanas y menores de 1000 gramos respectivamente). Conclusiones: El método clasificación de mortinatos CORM, es más eficiente que los métodos convencionales en detectar la causa de MF porque identifica la mayoría de las condiciones obstétricas responsables de la MF. Es reproducible, requiere estudio histopatológico de la placenta y no de autopsia fetal. Permite elaborar guías de prevención por causa.

SUMMARY Introduction: Stillbirth is the main contributor to perinatal mortality. Aim: To analyze the efficiency of the method for classification of fetal death (FD), "obstetric condition relevant to the death (OCRD). Methods: Retrospective cohort study of the FD that occurred in the Maternity Hospital of San Borja Arriarán for ten years. The data comes from the reports of the stillborn audits. We applied the classification method OCRD, which uses placental biopsy, clinical and laboratory data analyzed by a single obstetrician and a single pathologist. Results: 56,130 births and 479 FD occurred. FD rate, 8.5 per 1000 births. We identified 93.5% of the obstetric conditions of FD and 6.5% were unexplained. The most frequent were: ascending bacterial infection (ABI) 24.9%, congenital anomaly 18.0%, and placental pathology 14.0%. The intrauterine fetal growth restriction (IUGR) was present in 49.7% of the stillbirths, the majority 93.7%, was secondary to primary obstetric condition. Asphyxia during delivery was 0.8% of the stillbirths and occurred in term pregnancies. Preterm birth (PB) represented 80% of FD cases. The most frequent condition associated with PB was ABI (38.5% and 38.2% of the FD less than 30 weeks and less than 1000 grams respectively). Conclusions: The OCRD stillbirth classification method is more efficient than conventional methods in detecting the cause of MF because it identifies most of the obstetric conditions responsible for FD. It is reproducible, requires histopathological study of the placenta and not fetal autopsy. It allows developing guidelines of prevention for cause.

Alpha emitter NORM crystal scales in industrial pipelines: A study case.

Radioactive related pollution due to suspended particulate matter dispersion is an important workplace and health care issue. Recycling oil production ducts and contaminated production equipment, represent a health hazard to workers and public alike. Radioactive plate-out NORM scales with crystal deposit is analyzed by different techniques; results provide proper information on physico-chemical features and emitted alpha particles. Recommendations for handling and recycling procedures are included in relation to health risk and radiological hazard.