Publications by authors named "Hector Rene Vega-Carrillo"

49 Publications

Feasibility of 18-MV grid therapy from radiation protection aspects: unwanted dose and fatal cancer risk caused by photoneutrons and scattered photons.

Comput Methods Programs Biomed 2022 Jan 12;213:106524. Epub 2021 Nov 12.

Department of Radiation Oncology, Advocate Lutheran General Hospital, 1700 Lutheran, Park Ridge, Illinois, USA. Electronic address:

Purpose: Photoneutron production is a common concern when using 18-MV photon beams in radiation therapy. In Spatially Fractionated Grid Radiation Therapy (SFGRT), the grid block in the collimation system modifies the neutron production, photon scattering, and electron contamination in and out of the radiation field. Such an effect was studied with grids made of different high-Z materials by Monte Carlo simulations. The results were also used to evaluate the lifetime risk of fatal cancers.

Methods: MCNPX® code (2.7.0 extensions) was employed to simulate an 18-MV LINAC (Varian 2100 C/D). Three types of grid made of brass, cerrobend, and lead were used to study the neutron and electron fluence. Output factors for each grid with different field sizes were calculated. A revised female MIRD phantom with an 8-cm spherical tumor inside the liver was used to estimate the dose to the tumor and the critical organs. A 20-Gy SFGRT plan with Anterior Posterior (AP) - Posterior Anterior (PA) grid beams was compared with a Conventional Fractionated Radiation Therapy (CFRT) plan which delivered 40-Gy to the tumor by AP-PA open beams. Neutron equivalent dose, photon equivalent dose, as well as lifetime risks of fatal cancer were calculated in the organs at risk.

Results: The grid blocks reduced the fluence of contaminant electrons inside the treatment field by more than 50%. The neutron fluences per electron-history in SFGRT plans with brass, cerrobend and lead were on average 55%, 31% and 31% less than that of the CFRT plan, respectively. However, when converting to fluences per delivered dose (Gy), the cerrobend and lead grid may incur higher neutron dose for 20 × 20 cm field size and above. The changes in neutron mean energy, as well as the correlated radiation weighting factors, were insignificant. The total risk due to the photoneutrons in the SFGRT plans was 87% or lower than that in the CFRT plans. In both SFGRT and CFRT plans, the contribution of the primary and scattered photons to the fatal cancer risk was 2 times or more than the photoneutrons. The total risks from photons in SFGRT with brass, cerrobend, and lead blocks were 1.733, 1.374, and 1.260%, respectively, which were less than 30% of the total photon-risk in CFRT (5.827%).

Conclusion: In the brass, cerrobend, and lead grids, the attenuation of photoneutrons outweighs its photoneutron production in 18-MV SFGRT. The total cancer risks from photons and photoneutrons in the SFGRT plans were 30% or less of the risks in the CFRT plans (5.911%). Using 18 MV photon beams with brass, cerrobend, and lead grid blocks is still a feasible option for SFGRT.
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http://dx.doi.org/10.1016/j.cmpb.2021.106524DOI Listing
January 2022

Beam port filters in a TRIGA MARK III nuclear reactor to produce epithermal neutrons for BNCT.

Appl Radiat Isot 2022 Jan 4;179:110018. Epub 2021 Nov 4.

Unidad Académica de Ingeniería Eléctrica, Universidad Autónoma de Zacatecas, Av. Lopez Velarde s/n. Col. Centro, 98000, Zacatecas, Zac, Mexico.

Glioblastoma multiforme is the most common and aggressive brain tumor and it is difficult to treat with conventional surgery, chemotherapy, or radiation therapy. An alternative treatment is boron neutron capture therapy which requires an energy modulated beam of neutrons and aB drug capable of adhering to the tumor. In this work, MCNP6 Monte Carlo code was used to evaluate the effect on the neutron spectrum by placing two filters along the radial beam tube of the TRIGA Mark III nuclear reactor of ININ in Mexico. Every filter was made with the same amount and type of materials: Steel and Graphite for filter 1 and Cadmium, Aluminum, and Cadmium (Cd + Al + Cd) for filter 2. Two cases were analyzed for each filter as follows: Case A for filter 1 was considering 30 cm of steel and 30 cm of graphite, while for case B, the dimensions of filter 1 were 15 cm of steel, 15 cm of graphite, 15 cm of steel and 15 cm of graphite. Cases A and B for filter 2 were analyzed considering the same dimensions and amount of materials. The work was in the aim to produce epithermal neutrons for boron neutron capture therapy. Neutron spectra were calculated at three sites along the beam tube and two sites outside the beam tube; here, the ambient dose equivalent, the personal dose equivalent, and the effective doses were also estimated. At a distance of 517 cm of core, in case B, results in an epithermal-to-thermal neutron fluence ratio of 30.39 was obtained being larger than the one recommended by the IAEA of 20.
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http://dx.doi.org/10.1016/j.apradiso.2021.110018DOI Listing
January 2022

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

Biomed Phys Eng Express 2021 Nov 11;8(1). Epub 2021 Nov 11.

Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

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 MCNPXcode 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, ranging from 0.17 to 72.11 mSv Gy, 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.
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http://dx.doi.org/10.1088/2057-1976/ac35a1DOI Listing
November 2021

Comparison of FANT results using the ENDF/B-VII.1, JEFF-3.3 and TENDL2017 nuclear data libraries.

Appl Radiat Isot 2022 Jan 25;179:109992. Epub 2021 Oct 25.

Unidad Académica de Estudios Nucleares, Universidad Autónoma de Zacatecas (UAZ), C. Ciprés, 10, 98060, Zacatecas, Zac, Mexico.

FANT (Fuente Ampliada de Neutrones Térmicos; in Spanish) is a thermal neutron irradiation facility with an extended and very uniform irradiation area, that has been developed by the Neutron Measurements Laboratory of the Energy Engineering Department at Universidad Politecnica de Madrid (LMN-UPM). This device is a parallelepiped box made of high-density polyethylene (HDPE), moderator material, that uses an A95241m/B49e neutron source of 111 GBq nominal activity for irradiating materials. The facility design was previously optimized, and the neutron spectra were estimated by extensive calculations with the MCNP6.1 code and carrying out experimental measurements (Bedogni et al., 2017). The facility takes advantage of the scattering reactions of neutrons with the HDPE surfaces of the chamber, where the moderation process is effective, achieving relevant thermal neutron fluence rates. The main goal of this work has been to simulate and analyse the FANT system by Monte Carlo methods using the MCNP6.1 code, employing 3 different nuclear data libraries: ENDF/B-VII.1, JEFF-3.3 and TENDL 2017. The transport of thermal neutrons in HDPE, E < 1eV, has been calculated in all the cases taking into account the thermal S (α,β) treatment. The results achieved in this work have been compared with those previously obtained in the former development of FANT, using the MCNP6.1 code with the ENDF/B-VII.1 nuclear data, and experimental measurements. These results have shown that the JEFF-3.3 nuclear data library is the nuclear data library that provides of the best matching between the MCNP computational results, and the experimental data collected at FANT. Hence, the JEFF-3.3 nuclear data library seems to be the most correct library to design and benchmark thermal neutron activation devices.
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http://dx.doi.org/10.1016/j.apradiso.2021.109992DOI Listing
January 2022

Dosimetric evaluation of radiopharmaceuticals in kidneys and uterine wall of a woman with early pregnancy using Stabin/Segars representations.

Appl Radiat Isot 2021 Oct 4;176:109888. Epub 2021 Aug 4.

Universidad Privada del Norte, Trujillo, Peru.

MIRD method with the Stabin/Segars anthropomorphic representations were used to calculate the absorbed doses in kidneys and uterine wall of an early-stage pregnant woman when Tc (DTPA), Tc (DMSA) and Tc (MAG3) are used for renal studies. Stabin and Segars anatomical representations are phantoms that are used in Monte Carlo calculations to determine the SAF, that with the pharmaceutical residence time are used to calculate the absorbed dose, from source organs, on target organs. Concerns about the impact on the absorbed dose due to the use of the three Tc-based compounds as well as the use of different phantoms were here treated for the case of a female at early pregnant state. The lowest absorbed dose in the kidneys was obtained with Tc (MAG3), and the relative difference of using Stabin and Segars anthropomorphic representations was 2.5%. For bladder and rest of organs the relative difference 14.63%. The lowest absorbed dose by uterine wall was obtained with Tc(DMSA), however the relative difference of using Stabin and Segars anthropomorphic representations was 12%.
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http://dx.doi.org/10.1016/j.apradiso.2021.109888DOI Listing
October 2021

Gamma-ray spectroscopy with anode pulses of NaI(Tl) detector using a low-cost digitizer system.

Appl Radiat Isot 2021 Oct 4;176:109854. Epub 2021 Jul 4.

Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, Cipres 10, Fracc. La Penuela, 98068, Zacatecas, Mexico.

Recently, digital gamma-ray spectroscopy employing low-cost and publicly available (Commercial off the shelf) digitizers has been frequently used in different studies worldwide. In this paper, we considered the digital methods for gamma-ray spectroscopy in which the anode pulses of the photomultiplier tube (PMT) output in a NaI(Tl) scintillation detector were immediately digitized by a PC sound card. We introduced and developed the methods for gamma-ray spectroscopy of microCurie gamma-ray sources by a sampling rate of 96 kHz. First, at low count rates, the pulse arrival time was determined directly by the raw waveform, and the gamma-ray spectrum was obtained by summing the corresponding values in the samples per pulse. In addition, the gamma-ray spectrum was obtained by an enhanced sampling rate waveform and the pulse arrival time was determined by employing the digital constant fraction discrimination (DCFD) method, where each pulse area was achievable by summing the corresponding values of pulse samples. On the other hand, fitting the appropriate model function on the pulses and obtaining the fitted pulse area were undertaken for gamma-ray spectroscopy. To this end, a non-iterative algorithm to fast fit the Gaussian model function was improved. Moreover, the pile-up correction was performed at different count rates employing the Maximum Likelihood Estimation (MLE) method and Gaussian model function. Also, an approximate method for solving the high run time challenge was identified in the MLE method for long-time waveforms. To reject the pile-up events, a method was introduced based on the calculation of the full-width at half maximum pulses. By applying the proposed rejection method, we achieved an energy resolution of 6.2% at 663 keV gamma-rays and a count rate of 5.3 kcps.
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http://dx.doi.org/10.1016/j.apradiso.2021.109854DOI Listing
October 2021

Shielding features of seven types on natural quartz.

Appl Radiat Isot 2021 Jan 6;167:109450. Epub 2020 Oct 6.

Unidad Académica de Estudios Nucleares de La UAZ, C. Ciprés 10, Fracc. La Peñuela, 98060, Zacatecas, Zac, Mexico. Electronic address:

The shielding features of amethyst, chalcedony, crystal rock, milky, pink, flint, and jasper quartz were calculated. The seven varieties of quartz were collected within the territory of the state of Zacatecas in Mexico. Shielding characteristics include the linear attenuation coefficients, the effective atomic numbers and the mass interaction coefficients for 1 keV to 100 GeV photons. The interaction coefficients were calculated for the coherent scattering, the photoelectric absorption, the Compton scattering, and the pair production occurring in the electric field of the atomic nucleus and the electrons. The linear attenuation coefficients were compared with those of the Portland concrete widely used as radiation shielding. In the low energy region where the photoelectric absorption is dominant the mass interaction coefficients and the total linear attenuation coefficients have three resonances due to the Si, Ca and Fe concentration, these resonances are also noticed in the effective atomic number. For photons below 60 keV the shielding performance of quartz can be used to shield X-ray devices working with less than 60 kV.
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http://dx.doi.org/10.1016/j.apradiso.2020.109450DOI Listing
January 2021

Experimental characterization of FANT, a new thermal neutron source.

Appl Radiat Isot 2021 Jan 24;167:109437. Epub 2020 Sep 24.

AORTech, Research Department, Calle Purísima 227, Lomas de Cristo, 98085, Zacatecas, Mexico.

FANT is the acronym of Enhanced Thermal Neutron Source (Fuente Ampliada de Neutrones Térmicos, in Spanish). This is a parallelepiped box of high-density polyethylene moderator and an isotopic neutron source. The moderator has a cylindrical irradiation chamber where a rather uniform thermal neutron flux is obtained. The FANT design was previously optimized and the neutron spectra were estimated by Monte Carlo calculations with the MCNP6.1 code. To check the characteristics of the FANT thermal neutron field, measurements have been performed at the reference point inside the irradiation chamber with a Bonner sphere spectrometer holding a small LiI(Eu) thermal neutron detector. To unfold the neutron spectrum BUNKIUT with UTA4 response matrix and NSDann Ver 4.0 codes were used. Some issues have been found and recommendations are made about the use of large BSS inside narrow spaces, and about the capacity of NSDann code to unfold these kind of spectra. However, the results confirm that the moderation process in FANT is very effective and allows obtaining useful thermal neutron fluence rates.
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http://dx.doi.org/10.1016/j.apradiso.2020.109437DOI Listing
January 2021

Sparsity-based pulse-processor for digital α-particle spectroscopy with Si-PIN-Diode detector.

Appl Radiat Isot 2020 Sep 29;163:109245. Epub 2020 May 29.

Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas Cipres 10, Fracc. La Penuela, 98068, Zacatecas, Mexico.

Nowadays, digital methods are used in nuclear detection instruments which are more popular than conventional signal processing. In this work, a digital α-particle spectrometer, compatible with the low-cost digitizers, was designed and constructed. Similar to the analog pulse-height analyses, the digital signals must also be carefully shaped. Here, the charge pulses induced by alpha particles were measured in a silicon PIN-diode detector. Then, a digital sparsity-based pulse-processor was introduced for shaping the charge signals that were digitized by a low sampling rate digitizer. To this end, a charge-sensitive pre-amplifier was designed and fabricated for coupling to the digitizers. To perform off-line analysis, the detector pulses were stored through a combination of a fast-digital oscilloscope and the LabVIEW software. Finally, the pulse-height spectrum was obtained by a digital multi-channel analyzer block. The performance of the designed filter was examined for Ra-226 alpha spectrum by comparing its output with those of other conventional filters. Our results show the advantages of the sparsity-based filter in high-resolution measurements. The designed filter achieved an energy resolution of 12.3% at 4.78 MeV alpha particles.
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http://dx.doi.org/10.1016/j.apradiso.2020.109245DOI Listing
September 2020

CubBonner - A novel passive neutron area monitor.

Appl Radiat Isot 2020 Jul 19;161:109129. Epub 2020 Mar 19.

Unidad Académica de Ingeniería Eléctrica de la Universidad Autonoma de Zacatecas, Av. López Velarde 801 Col. Centro, 98000, Zacatecas, Zac, Mexico.

Responses of a novel passive neutron area monitor, named CubBonner, were calculated. The responses were estimated for sixty monoenergetic neutrons, from 10 to 20 MeV, with the MCNP5 code. The CubBonner is a cubic polyethylene moderator and a gold foil as thermal neutron detector. The ambient dose equivalent response was calculated for three cubes (5″, 8″ and 10" side) with the gold foil at the cube's centers. The moderator cube having the best ambient dose equivalent response was used to estimate the neutron fluence and the Au(n,γ) responses per history. The ambient dose response per unit mass of gold was compared with the response of the Berthold LB 6411 active neutron area monitor, and the response for the (n,γ) reaction in the gold foil was compared with the evaporation photo neutrons produced in linear accelerators for radiotherapy.
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http://dx.doi.org/10.1016/j.apradiso.2020.109129DOI Listing
July 2020

Grid therapy vs. conventional radiotherapy - 18 MV treatments: Photoneutron contamination along the maze of a linac bunker.

Appl Radiat Isot 2020 Apr 29;158:109064. Epub 2020 Jan 29.

Unidad Academica de Estudios Nucleares de la Universidad Autonoma de Zacatecas C. Cipres 10, Fracc, La Peñuela, 98068, Zacatecas, Zac, Mexico. Electronic address:

The present Monte Carlo study was devoted to the comparison of photoneutron contamination (per 1 Gy photon dose), along the maze of a radiotherapy bunker, between two 18-MV modalities: grid therapy (with grids made of brass, cerrobend, and lead) and conventional radiotherapy. It was turned out that both in grid therapy and in conventional radiotherapy, with increasing distance from the entrance of treatment hall (toward the maze entrance), fluence and ambient dose equivalent of neutrons decrease. Evidence also shows that in grid therapy, independent of materials used in the grid construction, photoneutron contamination along the maze is 45±6 % larger than conventional radiotherapy.
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http://dx.doi.org/10.1016/j.apradiso.2020.109064DOI Listing
April 2020

ESTIMATION OF THE ANISOTROPY EMISSION OF LPN/CIEMAT NEUTRON SOURCES: EFFECT OF HEAVY CAPSULE HOLDERS.

Radiat Prot Dosimetry 2019 Dec;186(4):452-461

Unidad Académica de Estudios Nucleares, Universidad Autónoma de Zacatecas, C. Ciprés 10, Fracc. La Peñuela, 98068 Zacatecas, Zac, Mexico.

In order to estimate the anisotropy emission of 241Am-Be and 252Cf neutron sources from the Spanish Neutron Standards Laboratory (LPN/CIEMAT) detailed models of sources capsules and capsule holders were designed with the MCNPX code. Simulations of the sources inside the capsules without the capsule holders were done to validate the MC model by comparison with experimental results provided by other authors. After that, the capsule holders were incorporated to the simulation. In general, a good agreement has been found between measurements and our calculations. Results show the additional encapsulations have significant influence on anisotropy factors, energy spectra and dose rates.
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http://dx.doi.org/10.1093/rpd/ncz050DOI Listing
December 2019

Design by Monte Carlo method of a thermal neutron device using a Am/Be source and high-density polyethylene moderator.

Appl Radiat Isot 2019 Sep 31;151:150-156. Epub 2019 May 31.

Departamento de Ingeniería Energética, ETSI Industriales, Universidad Politécnica de Madrid, José Gutiérrez Abascal 2, 28006, Madrid, Spain.

A thermal neutron system intended to be used in neutron activation analysis has been designed by Monte Carlo methods. The device is based on aAm/Be neutron source of 111 GBq, placed inside a cylindrical cavity open inside a parallelepiped of moderator material. Three different moderator materials, water, graphite and high-density polyethylene (HDPE), were simulated to check what is the most suitable for the detection system, concluding that HDPE reach the better performance. The device achieves an increased thermal neutron flux by taking advantage of neutron moderation in the polyethylene and the neutron scattering in the irradiation chamber walls. The thermal fluence rates obtained were 904 cm  s, i.e. 8.144 cm s GBq, with a fraction of thermal neutrons at the best point of 83% of pristine fast neutrons emitted by the source. The device has been designed by Monte Carlo techniques using the MCNP6 code, and the main tasks developed were to select the moderator material and to maximize the thermal neutrons flux in the irradiation chamber.
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http://dx.doi.org/10.1016/j.apradiso.2019.05.040DOI Listing
September 2019

Analysis by Monte Carlo of thermal neutron flux from a Am/Be source for a system of trace analysis in materials.

Appl Radiat Isot 2019 Sep 1;151:19-24. Epub 2019 May 1.

Departamento de Ingeniería Energética, ETSI Industriales, Universidad Politécnica de Madrid, José Gutiérrez Abascal 2, 28006, Madrid, Spain.

Neutron techniques to characterize materials have a wide range of applications, one of the major developments being the identification of terrorist threats with chemical, biological, radiological, nuclear and explosives (CBRNE) materials. In this work, a thermal neutron irradiation system, using aAm/Be source of 111 GBq inside polyethylene cylindrical moderators, has been designed, built and tested. The geometry of moderator and the neutron source position were fixed trying to maximize the thermal neutrons flux emitted from the system. Therefore, the system is in fact a thermalized neutron source taking advantage of the backscattered neutrons, achieving thermal fluence rates of up to 5.3x10 cm s, with dominantly thermal spectra. Samples can be placed there for several hours and thereafter be measured to identify their component elements by NAA (Neutron Activation Analysis). Through Monte Carlo techniques employing the MCNP6 code (Pelowitz et al., 2014), four different configurations with polyethylene cylinders were simulated to choose the most adequate geometry. The theoretical model was then replicated in the neutronics hall of the Neutron Measurements Laboratory of the Energy Engineering Department of Universidad Politécnica de Madrid (LMN-UPM), carrying out experimental measurements using a BF neutron detector. A high agreement between MCNP6 results and the experimental values measured was observed. Consequently, the system developed could be employed in future laboratory experiments, both for the identification of trace substances by NAA and for the calibration of neutron detection equipment.
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http://dx.doi.org/10.1016/j.apradiso.2019.04.041DOI Listing
September 2019

Synthesis and thermoluminescent response to γ-rays and neutrons of MgBO:Dy and MgBO:Dy,Na.

Appl Radiat Isot 2019 May 6;147:159-164. Epub 2019 Mar 6.

Unidad Académica de Física de la Universidad Autónoma de Zacatecas, C. Solidaridad, Col. Hidráulica, 98068, Zacatecas, Zac, Mexico.

MgBO doped with rare earths and alkaline elements has been reported as a good TLD because of its high sensitivity, effective atomic number close to that of biological tissue and low fading. In this work, thermoluminescent matrices were synthesized of MgBO:Dy and MgBO:Dy, Na to evaluate their thermoluminescent response (TL) when exposed to γ-rays and neutrons. The amount of Dy was studied in a concentration range of 0.01-1.5 mol% of total doping, while for Na the concentration of 0.5 mol% was established to determine the TL response as a function of doping. The synthesis of the powders was carried out by the method of wet reaction assisted by heat treatment and the samples were characterized by techniques of scanning electron microscopy and X-ray diffraction to determine the size of grain and crystallographic phase. For the dosimetric study, thermoluminescent phosphors were irradiated with a source of Cs at an estimated dose 6.8 ± 0.4 mGy to evaluate their response to γ-rays exposure, while for neutrons a source of AmBe was used (estimated dose of 3.1 ± 0.1 mGy). The thermoluminescent responses are similar for all materials exposed to γ-rays as for neutrons, the differences are shown to 280 °C, where a peak of high temperature is observed in materials exposed to neutrons.
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http://dx.doi.org/10.1016/j.apradiso.2019.03.001DOI Listing
May 2019

Nuclear pulse generator embedded in FPGA.

Appl Radiat Isot 2019 May 6;147:129-135. Epub 2019 Mar 6.

Unidad Académica de Estudios Nucleares de la Universidad Autonomía de Zacatecas, Ciprés 10; Frac. La Peñuela. 98060 Zacatecas, Zac. Mexico.

This manuscript presents the design and implementation of an intellectual property core, which acts as a generator of nuclear pulses. The design is embedded in a Field programmable gate array. It is capable of forming pulses with an exponential shape such as those from a radiation detector or Gaussian-shaped pulses such as those provided by a spectroscopy amplifier. Its characteristic is that the amplitude and period of these pulses can be configured by the user through a Virtual instrument generated in graphic language through the LabVIEW development platform. This can greatly reduce the volume, cost and energy consumption in relation to commercial analog nuclear electronics pulse generators.
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http://dx.doi.org/10.1016/j.apradiso.2019.03.003DOI Listing
May 2019

Characterization of six types of Mexican Onyx.

Appl Radiat Isot 2019 Apr 26;146:139-144. Epub 2019 Jan 26.

Unidad Académica de Estudios Nucleares de la Universidad Autónoma de Zacatecas, Cipres 10, Fracc. La Peñuela, 98060, Zacatecas, Zac, Mexico.

Optical, chemical, and radiation shielding characteristics of 6 types of Mexican onyx from the semi-desert of Zacatecas have been determined. Onyx samples are Yellow, Blue, Brown, Orange, Red and Green. Characterization was carried out using Energy dispersed X-Ray fluorescence, Visible Ultraviolet Spectrometry and Infrared Spectroscopy. With these techniques it was possible to study the chemical, physical and optical characteristics of the Mexican Onyx; from where the elemental composition was obtained, the absorption peaks, the vibrational modes and the optical band gap. As well as the interactions of these materials with radiation was studied. From this last study we obtained the Mass interaction coefficient for the coherent and incoherent dispersion, the photoelectric effect, the Compton scattering and the pair production, in the atomic nucleus and the electron field. For all types of onyx the total mass attenuation coefficients are alike showing a resonance due to K-shell of Ca. Mexican onyx has a good shielding features to photons of energy less than 100 keV because the most probable event is the photoelectric effect.
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http://dx.doi.org/10.1016/j.apradiso.2019.01.012DOI Listing
April 2019

Doses in eye lens, thyroid, and gonads, due to scattered radiation, during a CT radiodiagnosis study.

Appl Radiat Isot 2019 May 15;147:31-34. Epub 2019 Feb 15.

Unidad Académica de Estudios Nucleares, Universidad Autónoma de Zacatecas, C. Ciprés 10, Fracc. La Peñuela, 98068, Zacatecas, Zac., Mexico; Programa de Doctorado en Ingeniería y Tecnología Aplicada, Unidad Académica de Ingeniería Eléctrica, Universidad Autonomía de Zacatecas, Av. López Velarde 801, Col. Centro, 98000, Zacatecas, Zac., Mexico. Electronic address:

X-ray images used for radio-diagnosis are very useful to evaluate the progress of a treatment or to have a better diagnosis. However, during the interaction between the incoming X-ray beam and the body surface, part of the radiation is scattered out reaching other parts of the body delivering an undesirable dose. In this work the dose in eye lenses, thyroid, and gonads of a solid water phantom was measured using thermoluminescent dosimeters, while a Computer Tomography of the torso was obtained. With the measured absorbed dose the effective dose was calculated. Thus, the effective dose in the eye lens, thyroid, and gonads is approximately 57, 214 and 9 μSv respectively. The largest effective dose was on that area located nearest to the region where the radiation is scattered.
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http://dx.doi.org/10.1016/j.apradiso.2019.02.012DOI Listing
May 2019

Doses in eye lens, thyroid, salivary glands, mammary glands, and gonads, due to radiation scattered in dental orthopantomography.

Appl Radiat Isot 2019 Apr 28;146:57-60. Epub 2019 Jan 28.

Unidad Académica de Estudios Nucleares de la Universidad Autónoma de Zacatecas, C. Cipres 10, Fracc. La Peñuela, 98060, Zacatecas, Zac, Mexico. Electronic address:

In the aim to support treatments and diagnostics in Dentistry the most common radiographies are the periapical radiography and the dental panoramic. In the dental panoramic the X-ray beam is addressed into a large zone of the face obtaining the image of the upper and lower jaw. In this procedure part of the X-rays are scattered reaching some other parts of the patient body. In this work the absorbed dose in the eye lens, thyroid, salivary glands, mammary glands, and gonads, was measured in patients undergoing a dental orthopantomography. Measurements were carried out with thermolmuminiscent dosimeters. With the absorbed doses the Effective dose were calculated. The highest dose was obtained in the salivary glands (30.4 μSv) and the lowest dose was obtained in thyroid (3.8 μSv).
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http://dx.doi.org/10.1016/j.apradiso.2019.01.022DOI Listing
April 2019

FPGA embedded multichannel analyzer.

Appl Radiat Isot 2018 Nov 17;141:282-287. Epub 2018 Jul 17.

Unidad Academica de Ingenieria Electrica de la Universidad Autonoma de Zacatecas, Av. López Velarde 801, Col. Centro, 98000 Zacatecas, Zac., Mexico.

An multichannel analyzer has been designed, and its performance has been evaluated. The multichannel analyzer is embedded into a Field programmable gate array. The design incudes the virtual instrument in order to hand and to visualize the pulse height spectrum. Two commercially available multichannel analyzers using a NaI(Tl) and HPGe detectors were used to obtain the pulse height spectra of Cs, Co and Eu sources and were compared with the pulse height spectra obtained with the embedded multichannel analyzer, being alike the spectra obtained with the commercial multichannel analyzer. Our design is smaller, low cost and it has options to add other features.
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http://dx.doi.org/10.1016/j.apradiso.2018.07.017DOI Listing
November 2018

Thermoluminescence from Cu Doped Lithium Tetraborate Irradiated with X-ray and Using Cs Radioactive Source.

J Nanosci Nanotechnol 2018 10;18(10):6919-6927

Lithium tetraborate (Li2B4O7) pellets prepared by using water/solution assisted method were synthesized and characterized. Copper was used as doping material in order to enhance the Li2B4O7 thermoluminescent properties. For synthesis heating temperature parameters were defined at 750 °C for 2 hr, followed by 150 °C for another 2 hr. The materials were produced at five different Cu concentrations: 0.02, 0.04, 0.06, 0.08, and 0.1 wt%. The luminescent and morphological characterizations were performed by X-ray diffraction (XRD), Scanning electron microscope (SEM), Photoluminescence (PL), and Ultraviolet-visible spectroscopy (UV-Vis). XRD and SEM analysis of intrinsic and doped materials confirmed the obtained Li2B4O7 structure and show its morphology. XRD patterns of the Li2B4O7 matched a tetragonal crystal structure. Crystals of Li2B4O7 of an average size of 50 nm were obtained. The presence of the copper dopant was confirmed in crystals of Li2B4O7:Cu by SEM-EDS (energy dispersive spectroscopy X-ray). The emission spectrum of Cu doped Li2B4O7 showed a prominent peak at 367 nm, while the main UV-Vis absorption was observed from 240 nm to 300 nm due to Cu+ ion 3d10 → 3d9 4s transitions. The thermoluminescent (TL) response was studied for both γ radiation and X-ray. A 661.7 keV γ radiation using a 137Cs source at doses of 50, 100, 200, 300, 400 and 500 mGy was applied to Li2B4O7:Cu (0.1 wt%) pellets. An X-ray source was used at doses of 600, 800 and 1000 mGy to irradiate pellets of Li2B4O7:Cu (0.02, 0.04, 0.06, 0.08 and 0.1 wt%). A linear TL response was observed for both X-ray and γ radiation. The kinetic parameters were calculated using the peak shape method for the Li2B4O7:Cu (0.1 wt%).
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http://dx.doi.org/10.1166/jnn.2018.15532DOI Listing
October 2018

Determination of spatial dose distribution in UCC treatments with LDR brachytherapy using Monte Carlo methods.

Appl Radiat Isot 2018 Nov 19;141:224-227. Epub 2018 May 19.

Unidad Academica de Estudios Nucleares de la Universidad Autonoma de Zacatecas, C. Cipres 10, Fracc, La Peñuela, 98068 Zacatecas, Zac, Mexico. Electronic address:

Using Monte Carlos methods, with the MCNP5 code, a gynecological phantom and a vaginal cylinder were modeled. The spatial distribution of absorbed dose rates in Uterine Cervical Cancer treatment through low dose rate brachytherapy was determined. A liquid water gynecology computational phantom, including a vaginal cylinder applicator made of Lucite, was designed. The applicator has a linear array of four radioactive sources of Cesium 137. Around the vaginal cylinder, 13 water spherical cells of 0.5 cm-diameter were modeled to calculate absorbed dose emulating the procedure made by the treatment planning system. The gamma-ray fluence distribution was estimated, as well as the absorbed doses resulting approximately symmetrical for cells located at upper and lower of vaginal cylinder. Obtained results allow the use of the radioactive decay law to determine dose rate for Uterine Cervical Cancer using low dose rate brachytherapy.
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http://dx.doi.org/10.1016/j.apradiso.2018.04.034DOI Listing
November 2018

Neutron production in the interaction of 12 and 18 MeV electrons with a scattering foil inside a simple LINAC head.

Appl Radiat Isot 2018 Sep 18;139:46-52. Epub 2018 Apr 18.

Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, C. Cipres 10, Fracc. La Peñuela, 98060 Zacatecas, Zac, Mexico.

The characteristics of photons and neutrons produced during the interaction between a monoenergetic (12 and 18 MeV) electron beam and a tungsten scattering foil enclosed into a 10 cm-thick tungsten shell have been determined using Monte Carlo methods. This model was used aiming to represent a linac head working in electron-mode for cancer treatment. Photon and neutron spectra were determined around the scattering foil and to 50 and 100 cm below the electron source. Induced photons are mainly produced along the direction of the incoming electron beam. On the other hand, neutrons are produced in two sites, mainly in the inner surface of the linac head and in less extent in the scattering foil. The neutron spectra are evaporation neutrons which are emitted isotropically from the site where are produced leaking out from the linac head, reaching locations were the patient is allocated.
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http://dx.doi.org/10.1016/j.apradiso.2018.04.024DOI Listing
September 2018

H*(10) due to scattered radiation on the cancer-patient bodies treated with Tomotherapy.

Appl Radiat Isot 2018 Nov 6;141:206-209. Epub 2018 Apr 6.

CICATA-IPN Unidad Legaria, Ciudad de Mexico, Mexico.

The ambient dose equivalent has been measured on the walls of a bunker with a 6 MV TomoLINAC, which was designed to have a conventional 18 MV LINAC. The ambient dose equivalent is due to scattered photons on patient bodies during cancer treatment. Measurements were carried out with thermoluminescent dosimeters that were fixed, at the isocentre plane, on the primary and secondary barriers, the maze, and on the TomoLINAC surface. Measurements were repeated three times, in each time dosimeters were on place during seven working days, where approximately 50 patients were treated per day. Ambient dose equivalent at each location was normalized to the total dose applied during the measuring time. The primary and secondary concrete barriers are thick enough to reduce the dose to safe values.
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http://dx.doi.org/10.1016/j.apradiso.2018.04.015DOI Listing
November 2018

Study by Monte Carlo methods of an explosives detection system made up with a D-D neutron generator and NaI(Tl) gamma detectors.

Appl Radiat Isot 2018 Nov 17;141:167-175. Epub 2018 Feb 17.

Unidad Académica de Estudios Nucleares, Universidad Autónoma de Zacatecas, C. Ciprés, 10, 98060 Zacatecas, Zac., Mexico.

Detection of hidden explosives is of utmost importance for homeland security. Several configurations of an Explosives Detection System (EDS) to intercept hidden threats, made up with a Deuterium-Deuterium (D-D) compact neutron generator and NaI (Tl) scintillation detectors, have been evaluated using MCNP6 code. The system's response to various samples of explosives, such as RDX and Ammonium Nitrate, is analysed. The D-D generator is able to produce fast neutrons with 2.5 MeV energy in a maximum yield of 10 n/s. It is surrounded by high-density polyethylene to thermalize the fast neutrons and to optimize interactions with the sample inspected, whose emission of gamma rays gives a characteristic spectrum of the elements that constitute it. This procedure allows to determine its chemical composition and to identify the type of substance. The necessary shielding is evaluated to estimate its thicknesses depending on the admissible dose of operation, using lead and polyethylene. The results show that its functionality is promising in the field of national security for explosives inspection.
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http://dx.doi.org/10.1016/j.apradiso.2018.02.018DOI Listing
November 2018

Induced accumulation of Au, Ag and Cu in Brassica napus grown in a mine tailings with the inoculation of Aspergillus niger and the application of two chemical compounds.

Ecotoxicol Environ Saf 2018 Jun 22;154:180-186. Epub 2018 Feb 22.

Unidad de Servicios de Apoyo en Resolución Analítica, Universidad Veracruzana, Veracruz, Mexico. Electronic address:

This study evaluated the ability of Brassica napus for extracting gold (Au), silver (Ag) and copper (Cu) from a mine tailings, with the inoculation of two Aspergillus niger strains, and the application of ammonium thiocyanate (NHSCN) or ammonium thiosulfate [(NH)SO]. After seven weeks of growth inoculated or non-inoculated plants were applied with 1 or 2 g kg of either NHSCN or (NH)SO, respectively. Eight days after the application of the chemical compounds, plants were harvested for determining the total dry biomass, and the content of Au, Ag, and Cu in plant organs. Application of (NH)SO or NHSCN resulted in enhanced Au-accumulation in stems (447% and 507%, respectively), while either (NH)SO+Aspergillus, or NHSCN increased the Au-accumulation in roots (198.5% and 404%, respectively) when compared to the control. Treatments with (NH)SO or (NH)SO+Aspergillus significantly increased (P ≤ 0.001) the accumulation of Ag in leaves (677% and 1376%, respectively), while NHSCN + Aspergillus, and (NH)SO enhanced the accumulation in stems (7153% and 6717.5%). The Ag-accumulation in roots was stimulated by NHSCN+ Aspergillus, and (NH)SO+ Aspergillus (132.5% and 178%, respectively), when compared to the control. The combination of NHSCN+Aspergillus significantly enhanced the Cu-accumulation in leaves (228%); whereas NHSCN+ Aspergillus, or (NH)SO+ Aspergillus resulted in greater accumulation of Cu in stems (1233.5% and 1580%, respectively) than the control. Results suggest that either NHSCN or (NH)SO (with or without Aspergillus) improved the accumulation of Au and Ag by B. napus. Accumulation of Au and Ag in plant organs overpassed the hyperaccumulation criterion (> 1 mg kg of plant biomass); whereas Cu-accumulation in stems and roots also overpassed such criterion (> 1000 mg kg) by applying either NHSCN or (NH)SO + A. niger.
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http://dx.doi.org/10.1016/j.ecoenv.2018.02.055DOI Listing
June 2018

Neutron H*(10) estimation and measurements around 18MV linac.

Appl Radiat Isot 2016 11 11;117:2-7. Epub 2016 May 11.

Universidad Autónoma de Zacatecas Unidad Académica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas, México.

Thermoluminescent dosimetry, analytical techniques and Monte Carlo calculations were used to estimate the dose of neutron radiation in a treatment room with a linear electron accelerator of 18MV. Measurements were carried out through neutron ambient dose monitors which include pairs of thermoluminescent dosimeters TLD 600 (LiF: Mg, Ti) and TLD 700 (LiF: Mg, Ti), which were placed inside a paraffin spheres. The measurements has allowed to use NCRP 151 equations, these expressions are useful to find relevant dosimetric quantities. In addition, photoneutrons produced by linac head were calculated through MCNPX code taking into account the geometry and composition of the linac head principal parts.
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http://dx.doi.org/10.1016/j.apradiso.2016.05.006DOI Listing
November 2016

A neutron spectrum unfolding code based on generalized regression artificial neural networks.

Appl Radiat Isot 2016 11 30;117:8-14. Epub 2016 Apr 30.

Laboratorio Nacional en Investigación, Desarrollo Tecnológico e Innovación en Sistemas Embebidos, Diseño Electrónico Avanzado y Microsistemas, Universidad Autónoma de Zacatecas, Av. Ramón López Velarde, 801, Col. Centro, 98000, Zacatecas, Mexico; Centro de Investigación e Innovación Tecnológica Industrial (CIITI), Universidad Autónoma de Zacatecas, Av. Ramón López Velarde, 801, Col. Centro, 98000, Zacatecas, Mexico; Grupo de Investigación Regional Emergente (GIRE), Universidad Autónoma de Zacatecas, Av. Ramón López Velarde, 801, Col. Centro, 98000, Zacatecas, Mexico; Laboratorio de Innovación y Desarrollo Tecnológico en Inteligencia Artificial (LIDTIA), Universidad Autónoma de Zacatecas, Av. Ramón López Velarde, 801, Col. Centro, 98000, Zacatecas, Mexico; Laboratorio de Medicina Molecular, Unidad Académica de Medicina Humana y Ciencias de la Salud, Universidad Autónoma de Zacatecas, Campus UAZ siglo XXI, Edificio L1, 3er Piso,Carretera Zacatecas-Guadalajara Km 6 Ejido la Escondida, 98160, Zacatecas, Mexico. Electronic address:

The most delicate part of neutron spectrometry, is the unfolding process. The derivation of the spectral information is not simple because the unknown is not given directly as a result of the measurements. Novel methods based on Artificial Neural Networks have been widely investigated. In prior works, back propagation neural networks (BPNN) have been used to solve the neutron spectrometry problem, however, some drawbacks still exist using this kind of neural nets, i.e. the optimum selection of the network topology and the long training time. Compared to BPNN, it's usually much faster to train a generalized regression neural network (GRNN). That's mainly because spread constant is the only parameter used in GRNN. Another feature is that the network will converge to a global minimum, provided that the optimal values of spread has been determined and that the dataset adequately represents the problem space. In addition, GRNN are often more accurate than BPNN in the prediction. These characteristics make GRNNs to be of great interest in the neutron spectrometry domain. This work presents a computational tool based on GRNN capable to solve the neutron spectrometry problem. This computational code, automates the pre-processing, training and testing stages using a k-fold cross validation of 3 folds, the statistical analysis and the post-processing of the information, using 7 Bonner spheres rate counts as only entrance data. The code was designed for a Bonner Spheres System based on a LiI(Eu) neutron detector and a response matrix expressed in 60 energy bins taken from an International Atomic Energy Agency compilation.
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http://dx.doi.org/10.1016/j.apradiso.2016.04.029DOI Listing
November 2016

A comparison of back propagation and Generalized Regression Neural Networks performance in neutron spectrometry.

Appl Radiat Isot 2016 Nov 19;117:20-26. Epub 2016 Apr 19.

Universidad Autónoma de Zacatecas, Centro de Investigación e Innovación Tecnológica Industrial (CIITI), Av. Ramón López Velarde, 801, Col. Centro, 98000 Zacatecas, México; Universidad Autónoma de Zacatecas, Grupo de Investigación Regional Emergente (GIRE), Av. Ramón López Velarde, 801, Col. Centro, 98000 Zacatecas, México; Universidad Autónoma de Zacatecas, Laboratorio de Innovación y Desarrollo Tecnológico en Inteligencia Artificial (LIDTIA), Av. Ramón López Velarde, 801, Col. Centro, 98000 Zacatecas, México; Universidad Autónoma de Zacatecas, Unidad Académica de Ingeniería Eléctrica (UAIE), Av. Ramón López Velarde, 801, Col. Centro, 98000 Zacatecas, México. Electronic address:

The process of unfolding the neutron energy spectrum has been subject of research for many years. Monte Carlo, iterative methods, the bayesian theory, the principle of maximum entropy are some of the methods used. The drawbacks associated with traditional unfolding procedures have motivated the research of complementary approaches. Back Propagation Neural Networks (BPNN), have been applied with success in neutron spectrometry and dosimetry domains, however, the structure and learning parameters are factors that highly impact in the networks performance. In ANN domain, Generalized Regression Neural Network (GRNN) is one of the simplest neural networks in term of network architecture and learning algorithm. The learning is instantaneous, requiring no time for training. Opposite to BPNN, a GRNN would be formed instantly with just a 1-pass training on the development data. In the network development phase, the only hurdle is to optimize the hyper-parameter, which is known as sigma, governing the smoothness of the network. The aim of this work was to compare the performance of BPNN and GRNN in the solution of the neutron spectrometry problem. From results obtained it can be observed that despite the very similar results, GRNN performs better than BPNN.
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http://dx.doi.org/10.1016/j.apradiso.2016.04.011DOI Listing
November 2016
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