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INTRODUCTION: Orofacial pain and tension headache are symptoms that affect a large portion of the population, compromising productivity, social ability, and functional development. The treatment for reducing painful sensation should be chosen carefully, as pharmacological treatment may bring side effects and overload the organism of patients in pain. Low-level laser therapy has been used with local and systemic [vascular] applications for pain control. However, there is still uncertainty in the literature about the ideal dosimetric parameters for photobiomodulation treatment according to patient characteristics. METHODS: The objective of this project is to validate a dosimetry model based on the relationship between the effects of photobiomodulation with anthropometric and hemodynamic variables, both in local application and systemic application in patients with symptoms of orofacial pain and tension headache. For this purpose, 180 participants with orofacial pain post-covid eligible participants will be randomly assigned to Group 1-Local Photobiomodulation, Group 2-Vascular Photobiomodulation, Group 3-Placebo Local Photobiomodulation, or Group 4-Placebo Vascular Photobiomodulation [Therapy EC-DMC device, São Carlos, Brazil,- 660 nm, 100mW] using stratified block randomization. Before the application, sociodemographic information such as age, skin phototype [classified by the Fitzpatrick scale], weight, height, body mass index [BMI], oxygen saturation [SaO2], blood pressure [BP], heart rate [HR], and thickness of skin, fat, and facial muscles will be collected. During the application, we will collect local temperature, SaO2, BP, and HR. Before and after laser application, blood levels of lactate and hemoglobin, BP, and HR will be measured in the first and last session. In addition to demographic, anthropometric, and hemodynamic variables, the penetrated energy will be quantified using a power meter, and information from orofacial pain and headache symptom questionnaires will be analyzed. The Monte Carlo simulation technique will be used to systematically study the relationship between the light penetration profile into the target tissues and the most relevant variables, namely BMI, tissue layer thicknesses, and skin phototype. Light transmittance, measured in vivo and simulated, will be compared to validate a personalized dosimetry model. DISCUSSION: The results of this study contribute to validating a Monte Carlo Simulation model to calculate the appropriate dosimetry for photobiomodulation therapies in the control of patients with Post-Covid-19 orofacial pain. TRIAL REGISTRATION: Trial registration number: NCT06065969.
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COVID-19 , Dolor Facial , Hemodinámica , Terapia por Luz de Baja Intensidad , Humanos , Terapia por Luz de Baja Intensidad/métodos , COVID-19/complicaciones , COVID-19/radioterapia , Dolor Facial/radioterapia , Dolor Facial/fisiopatología , Masculino , Femenino , Adulto , Antropometría , Persona de Mediana Edad , Radiometría , SARS-CoV-2 , Ensayos Clínicos Controlados Aleatorios como AsuntoRESUMEN
Objectives.The aim of this work is to evaluate energy deposition in the nucleus and cytoplasm in targeted alpha therapy of metastatic castration-resistant prostate cancer by modeling two cell lines, PC3 (osteolytic) and LNCaP C4-2 (osteoblastic), for actinium-225, astatine-211, and radium-223 and their progeny, using Monte Carlo simulations with the GATE/Geant4 code.Approach.We developed single cell and cell clusters models to Monte Carlo simulations, performed on the GATE platform version 9.3, with the GEANT4-DNA physics list emstandard_opt3_mixed_dna for At-211, Ac-225 and Ra-223 progenies. We considered three radionuclide distributions as a sources: the nucleus, the cytoplasm and the whole cell.Main results.When the nucleus was considered as a target, theS-values (NâN) calculated for At-211, Ac-225 and Ra-223 progenies were significantly higher, within 60%-90%, thanS-values (NâCy), demonstrating less influence of cytoplasm only internalization. When the cytoplasm was considering as a target, theS-values (CyâCy) calculated for At-211, Ac-225 and Ra-223 progeny were significantly higher, within 30%-90%, than theS-values (CyâN). When no progeny migration occurs and for target nucleus , the cumulativeS-values (NâN) calculated for At-211, Ac-225 and Ra-223 were significantly higher, within 50%-70%, than theS-values (NâN) computed for At-211, Ac-225, and Ra-223. Comparing the cumulativeS-values, Ac-225 and Ra-223 therapies is more effective, in terms of deposited energy in a target, than that with At-211.Significance.The data presented in this research indicates that Ac-225 therapy may be the optimum choice due to the energy deposited in the nucleus, as long as the recoil effects and redistribution of progeny are understood. In contrast, At-211 is an alternative to avoid progeny migration. However, to completely analyze the efficacy of radionuclide therapy, other parameters must be considered, such as biological half-life, stability of the transport molecule, progeny migration, excretion pathways, and uptake in different organs.
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Actinio , Partículas alfa , Astato , Neoplasias Óseas , Neoplasias de la Próstata Resistentes a la Castración , Radiometría , Radio (Elemento) , Radio (Elemento)/uso terapéutico , Masculino , Neoplasias de la Próstata Resistentes a la Castración/radioterapia , Neoplasias de la Próstata Resistentes a la Castración/metabolismo , Neoplasias de la Próstata Resistentes a la Castración/patología , Humanos , Partículas alfa/uso terapéutico , Neoplasias Óseas/radioterapia , Neoplasias Óseas/secundario , Neoplasias Óseas/metabolismo , Actinio/uso terapéutico , Astato/uso terapéutico , Método de Montecarlo , Línea Celular Tumoral , Núcleo Celular/metabolismoRESUMEN
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.
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Neoplasias de Cabeza y Cuello , Máscaras , Método de Montecarlo , Dosificación Radioterapéutica , Neoplasias de Cabeza y Cuello/radioterapia , Humanos , Plásticos/química , Planificación de la Radioterapia Asistida por Computador/métodos , Radiometría/métodosRESUMEN
Some of the difficulties in numerical modeling of wireless communication devices for dosimetric evaluations arise from, e.g. incomplete documentation available for the numerical model, such as missing information on dielectric materials or the antenna matching circuitry. This study investigates the impact of these difficulties on the dosimetric results, such as the peak spatial average specific absorption rate at 900 and 1800 MHz and the peak spatial average power density at 28 GHz. The impact of dielectric losses, detuning, and mesh resolution is quantified using different generic and Computer Aided Design (CAD) based models of wireless transmitters. The findings show that the uncertainties of the numerical results due to detuning and mesh resolution can be reduced by normalization to the antenna feedpoint power instead of the feedpoint current. Uncertainties due to variations in dielectric losses can largely be compensated by normalization to the radiated power.
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Tecnología Inalámbrica , Incertidumbre , Simulación por Computador , Modelos Teóricos , Humanos , Diseño Asistido por Computadora , Radiometría/métodos , Diseño de Equipo , Ondas de RadioRESUMEN
BACKGROUND: Although standard operational procedures for pre-therapeutic dosimetry already exist for the determination of the maximum safe activity to treat differentiated thyroid cancer patients, empiric activity administration of 131I is still the most frequent way of treatment. In this way, the absorbed dose to the blood/bone marrow remains unknown. PURPOSE: In this work, we present a strategy to estimate radiation dose to the blood in an outpatient setting. METHODS: A mobile application was developed, which together with an off-the-shelf compact semiconductor radiation detector allows the determination of whole-body time-integrated activity coefficients. The methodology was tested in a cohort of 79 differentiated cancer patients who received therapeutic 131I activities. Post-therapeutic whole-body time-integrated activity coefficients were compared against pre-therapeutic estimates in a subset of 13 patients. RESULTS: The 95% limits of agreement between pre whole-body and post whole-body time integrated activity coefficients were [-14.4; 6.6] h when considering outliers and [-6.2; 3.6] h without outliers. A high dispersion in blood dose coefficients was found, with a four-fold difference between the highest and lower values. Blood doses were significantly higher for patients treated with dosimetrically guided activities than for empirical activities (median dose = 118 vs. 49 cGy, respectively). Blood dose coefficients were significantly lower for patients prepared with recombinant human thyroid stimulating hormone (rhTSH) than for patients prepared with thyroid hormone withdrawal. A low correlation between blood dose and administered activity was found in empirically treated patients (R2 = 0.26). CONCLUSIONS: We successfully implemented a post-therapeutic internal dosimetry methodology for differentiated thyroid cancer therapy with 131I, which allows to estimate dose to the blood from outpatient measurements with mobile devices. The proposed methodology avoids the need of daily visits to the nuclear medicine department, thus reducing the burden for the patient and for the staff.
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Radioisótopos de Yodo , Pacientes Ambulatorios , Neoplasias de la Tiroides , Humanos , Radioisótopos de Yodo/uso terapéutico , Neoplasias de la Tiroides/radioterapia , Neoplasias de la Tiroides/sangre , Dosis de Radiación , Masculino , Radiometría , Femenino , Persona de Mediana Edad , Adulto , Aplicaciones Móviles , Dosificación Radioterapéutica , AncianoRESUMEN
Whole-body counters (WBC) are used in internal dosimetry forin vivomonitoring in radiation protection. The calibration processes of a WBC set-up include the measurement of a physical phantom filled with a certificate radioactive source that usually is referred to a standard set of individuals determined by the International Commission on Radiological Protection (ICRP). The aim of this study was to develop an anthropomorphic and anthropometric female physical phantom for the calibration of the WBC systems. The reference female computational phantom of the ICRP, now called RFPID (Reference Female Phantom for Internal Dosimetry) was printed using PLA filament and with an empty interior. The goal is to use the RFPID to reduce the uncertainties associated within vivomonitoring system. The images which generated the phantom were manipulated using ImageJ®, Amide®, GIMP®and the 3D Slicer®software. RFPID was split into several parts and printed using a 3D printer in order to print the whole-body phantom. The newly printed physical phantom RFPID was successfully fabricated, and it is suitable to mimic human tissue, anatomically similar to a human body i.e., size, shape, material composition, and density.
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Fantasmas de Imagen , Impresión Tridimensional , Recuento Corporal Total , Humanos , Femenino , Recuento Corporal Total/métodos , Calibración , Protección Radiológica/métodos , Protección Radiológica/instrumentación , Radiometría/métodos , Radiometría/instrumentación , AntropometríaRESUMEN
PURPOSE: To analyze the effects of extending lymphocyte cultivation time on the Mitotic Index, frequency of first-division cells, and dose estimation after irradiating blood samples with different doses of radiation. MATERIALS AND METHODS: Blood samples from two healthy male volunteers were separately irradiated with three doses (3, 5, and 6 Gy) using a 60Co gamma source (average dose rate: 1.48 kGy.h-1) and cultivated in vitro for conventional (48 h) and extended (56, 68, and 72 h) amounts of time. Colcemid (0.01 µg.mL-1) was added at the beginning of the culture period. Cells were fixed, stained with fluorescence plus Giemsa (FPG), and analyzed under a light microscope. The effects of prolonged culture duration on the Mitotic Index (MI), frequency of first-division cells (M1 cells), and the First-Division Mitotic Index (FDMI) were investigated. The estimation of delivered doses was conducted using a conventional 48h-culture calibration curve. RESULTS: Overall, cells presented higher MI (up to 12-fold) with the extension of culture, while higher radiation doses led to lower MI values (up to 80% reduction at 48 h). Cells irradiated with higher doses (5 and 6 Gy) had the most significant increase (5- to 12-fold) of MI as the cultivation was prolonged. The frequency of M1 cells decreased with the prolongation of culture for all doses (up to 75% reduction), while irradiated cells presented higher frequencies of M1 cells than non-irradiated ones. FDMI increased for all irradiated cultures but most markedly in those irradiated with higher doses (up to 10-fold). The conventional 48h-culture calibration curve proved adequate for assessing the delivered dose based on dicentric frequency following a 72-hour culture. CONCLUSION: Compared to the conventional 48-hour protocol, extending the culture length to 72 hours significantly increased the Mitotic Index and the number of first-division metaphases of irradiated lymphocytes, providing slides with a better scorable metaphase density. Extending the culture time to 72 hours, combined with FPG staining to score exclusively first-division metaphases, improved the counting of dicentric chromosomes. The methodology presented and discussed in this study can be a powerful tool for dicentric-based biodosimetry, especially when exposure to high radiation doses is involved.
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Relación Dosis-Respuesta en la Radiación , Linfocitos , Índice Mitótico , Radiometría , Humanos , Masculino , Linfocitos/efectos de la radiación , Linfocitos/citología , Análisis Citogenético , Adulto , Factores de Tiempo , Dosis de Radiación , Células Cultivadas , Técnicas de Cultivo de Célula/métodosRESUMEN
PURPOSE: This interlaboratory comparison was conducted to evaluate the performance of the Latin-American Biodosimetry Network (LBDNet) in analyzing digitized images for scoring dicentric chromosomes from in vitro irradiated blood samples. The exercise also assessed the use of weighted robust algorithms to compensate the uneven expertise among the participating laboratories. METHODS: Three sets of coded images obtained through the dicentric chromosome assay from blood samples irradiated at 1.5 Gy (sample A) and 4 Gy (sample B), as well as a non-irradiated whole blood sample (sample C), were shared among LBDNet laboratories. The images were captured using the Metafer4 platform coupled with the AutoCapt module. The laboratories were requested to perform triage scoring, conventional scoring, and dose estimation. The dose estimation was carried out using either their laboratory calibration curve or a common calibration curve. A comparative statistical analysis was conducted using a weighted robust Hampel algorithm and z score to compensate for uneven expertise in dicentric analysis and dose assessment among all laboratories. RESULTS: Out of twelve laboratories, one had unsatisfactory estimated doses at 0 Gy, and two had unsatisfactory estimated doses at 1.5 Gy when using their own calibration curve and triage scoring mode. However, all doses were satisfactory at 4 Gy. Six laboratories had estimated doses within 95% uncertainty limits at 0 Gy, seven at 1.5 Gy, and four at 4 Gy. While the mean dose for sample C was significantly biased using robust algorithms, applying weights to compensate for the laboratory's analysis expertise reduced the bias by half. The bias from delivered doses was only notable for sample C. Using the common calibration curve for dose estimation reduced the standard deviation (s*) estimated by robust methods for all three samples. CONCLUSIONS: The results underscore the significance of performing interlaboratory comparison exercises that involve digitized and electronically transmitted images, even when analyzing non-irradiated samples. In situations where the participating laboratories possess different levels of proficiency, it may prove essential to employ weighted robust algorithms to achieve precise outcomes.
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Aberraciones Cromosómicas , Humanos , Aberraciones Cromosómicas/efectos de la radiación , Algoritmos , Laboratorios/normas , Radiometría/métodos , Procesamiento de Imagen Asistido por Computador/métodosRESUMEN
Introduction. The currently available dosimetry techniques in computed tomography can be inaccurate which overestimate the absorbed dose. Therefore, we aimed to provide an automated and fast methodology to more accurately calculate the SSDE usingDwobtained by using CNN from thorax and abdominal CT study images.Methods. The SSDE was determined from the 200 records files. For that purpose, patients' size was measured in two ways: (a) by developing an algorithm following the AAPM Report No. 204 methodology; and (b) using a CNN according to AAPM Report No. 220.Results. The patient's size measured by the in-house software in the region of thorax and abdomen was 27.63 ± 3.23 cm and 28.66 ± 3.37 cm, while CNN was 18.90 ± 2.6 cm and 21.77 ± 2.45 cm. The SSDE in thorax according to 204 and 220 reports were 17.26 ± 2.81 mGy and 23.70 ± 2.96 mGy for women and 17.08 ± 2.09 mGy and 23.47 ± 2.34 mGy for men. In abdomen was 18.54 ± 2.25 mGy and 23.40 ± 1.88 mGy in women and 18.37 ± 2.31 mGy and 23.84 ± 2.36 mGy in men.Conclusions. Implementing CNN-based automated methodologies can contribute to fast and accurate dose calculations, thereby improving patient-specific radiation safety in clinical practice.
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Algoritmos , Dosis de Radiación , Tomografía Computarizada por Rayos X , Humanos , Tomografía Computarizada por Rayos X/métodos , Masculino , Femenino , Tamaño Corporal , Redes Neurales de la Computación , Programas Informáticos , Automatización , Tórax/diagnóstico por imagen , Adulto , Abdomen/diagnóstico por imagen , Radiometría/métodos , Radiografía Torácica/métodos , Persona de Mediana Edad , Procesamiento de Imagen Asistido por Computador/métodos , Radiografía Abdominal/métodos , AncianoRESUMEN
The aim of this study was to use computer simulation to analyze the impact of the aluminum fixing support on the Reference Air Kerma (RAK), a physical quantity obtained in a calibration system that was experimentally developed in the Laboratory of Radiological Sciences of the University of the State of Rio de Janeiro (LCR-UERJ). Correction factors due to scattered radiation and the geometry of the192Ir sources were also sought to be determined. The computational simulation was validated by comparing some parameters of the experimental results with the computational results. These parameters were: verification of the inverse square law of distance, determination of (RAKR), analysis of the source spectrum with and without encapsulation, and the sensitivity curve of the Sourcecheck 4PI ionization chamber response, as a function of the distance from the source along the axial axis, using the microSelectron-v2 (mSv2) and GammaMedplus (GMp) sources. Kerma was determined by activity in the Reference air, with calculated values of 1.725 × 10-3U. Bq-1and 1.710 × 10-3U. Bq-1for the ionization chamber NE 2571 and TN 30001, respectively. The expanded uncertainty for these values was 0.932% and 0.919%, respectively, for a coverage factor (k = 2). The correction factor due to the influence of the aluminum fixing support for measurements at 1 cm and 10 cm from the source was 0.978 and 0.969, respectively. The geometric correction factor of the sources was ksg= 1.005 with an expanded uncertainty of 0.7% for a coverage factor (k = 2). This value has a difference of approximately 0.2% compared to the experimental values.
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Simulación por Computador , Radioisótopos de Iridio , Radiometría , Calibración , Radiometría/métodos , Radioisótopos de Iridio/uso terapéutico , Humanos , Aire , Aluminio , Método de Montecarlo , Dosis de Radiación , Braquiterapia/métodos , Braquiterapia/normas , Dosificación Radioterapéutica , Dispersión de RadiaciónRESUMEN
BACKGROUND: Non-melanoma skin cancer is one of the most common types of cancer and one of the main approaches is brachytherapy. For small lesions, the treatment of this cancer with brachytherapy can be done with two commercial applicators, one of these is the Large Field Valencia Applicators (LFVA). PURPOSE: The aim of this study is to test the capabilities of the LFVA to use clinically 60Co sources instead of the 192Ir ones. This study was designed for the same dwell positions and weights for both sources. METHODS: The Penelope Monte Carlo code was used to evaluate dose distribution in a water phantom when a 60Co source is considered. The LFVA design and the optimized dwell weights reported for the case of 192Ir are maintained with the only exception of the dwell weight of the central position, that was increased. 2D dose distributions, field flatness, symmetry and the leakage dose distribution around the applicator were calculated. RESULTS: When comparing the dose distributions of both sources, field flatness and symmetry remain unchanged. The only evident difference is an increase of the penumbra regions for all depths when using the 60Co source. Regarding leakage, the maximum dose within the air volume surrounding the applicator is in the order of 20% of the prescription dose for the 60Co source, but it decreases to less than 5% at about 1 cm distance. CONCLUSIONS: Flatness and symmetry remains unaltered as compared with 192Ir sources, while an increase in leakage has been observed. This proves the feasibility of using the LFVA in a larger range of clinical applications.
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Braquiterapia , Radioisótopos de Cobalto , Método de Montecarlo , Radiometría , Dosificación Radioterapéutica , Braquiterapia/instrumentación , Radioisótopos de Cobalto/uso terapéutico , Radiometría/instrumentación , Fantasmas de Imagen , Radioisótopos de Iridio/uso terapéutico , HumanosRESUMEN
Radiometric surveys in radiotherapy bunkers have been carried out in Brazil for many years, both by the same radiotherapy facility for verification of shielding as by the regulatory agency for licensing and control purposes. In recent years, the Intensity Modulated Radiation Therapy (IMRT) technique has been gradually incorporated into many facilities. Therefore, it has been necessary to consider the increased leakage component that has an important impact on the secondary walls. For that, a radiometric survey method has been used that considers an increased 'time of beam-on' for the secondary walls. In this work we discuss two methods of doing this: the first considers that this 'time of beam-on' affects the sum of the two components, leakage and scattered. In another method it is considered that only the leakage component is affected by this extended 'time of beam-on'. We compare the methods and show that for secondary walls withU= 1 the first method overestimates dose rates by important percentages and for secondary walls withU< 1 it can both overestimate or underestimate the dose rates, depending on the parameters of the project. An optimized procedure is proposed, according to the use factor (U) of the secondary wall to be measured.
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Protección Radiológica , Radioterapia de Intensidad Modulada , Protección Radiológica/métodos , Radiometría/métodos , Radioterapia de Intensidad Modulada/métodos , Planificación de la Radioterapia Asistida por Computador/métodosRESUMEN
BACKGROUND: Although the benefits of breast screening and early diagnosis are known for reducing breast cancer mortality rates, the effects and risks of low radiation doses to the cells in the breast are still ongoing topics of study. PURPOSE: To study specific energy distributions ( f ( z , D g ) $f(z,D_{g})$ ) in cytoplasm and nuclei of cells corresponding to glandular tissue for different x-ray breast imaging modalities. METHODS: A cubic lattice (500 µm length side) containing 4064 spherical cells was irradiated with photons loaded from phase space files with varying glandular voxel doses ( D g $D_{g}$ ). Specific energy distributions were scored for nucleus and cytoplasm compartments using the PENELOPE (v. 2018) + penEasy (v. 2020) Monte Carlo (MC) code. The phase space files, generated in part I of this work, were obtained from MC simulations in a voxelized anthropomorphic phantom corresponding to glandular voxels for different breast imaging modalities, including digital mammography (DM), digital breast tomosynthesis (DBT), contrast enhanced digital mammography (CEDM) and breast CT (BCT). RESULTS: In general, the average specific energy in nuclei is higher than the respective glandular dose scored in the same region, by up to 10%. The specific energy distributions for nucleus and cytoplasm are directly related to the magnitude of the glandular dose in the voxel ( D g $D_{g}$ ), with little dependence on the spatial location. For similar D g $D_{g}$ values, f ( z , D g ) $f(z,D_{g})$ for nuclei is different between DM/DBT and CEDM/BCT, indicating that distinct x-ray spectra play significant roles in f ( z , D g ) $f(z,D_{g})$ . In addition, this behavior is also present when the specific energy distribution ( F g ( z ) $F_{g}(z)$ ) is considered taking into account the GDD in the breast. CONCLUSIONS: Microdosimetry studies are complementary to the traditional macroscopic breast dosimetry based on the mean glandular dose (MGD). For the same MGD, the specific energy distribution in glandular tissue varies between breast imaging modalities, indicating that this effect could be considered for studying the risks of exposing the breast to ionizing radiation.
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Mamografía , Radiometría , Rayos X , Método de Montecarlo , Radiometría/métodos , Mamografía/métodos , Fantasmas de Imagen , Dosis de RadiaciónRESUMEN
BACKGROUND: X-ray breast imaging modalities are commonly employed for breast cancer detection, from screening programs to diagnosis. Thus, dosimetry studies are important for quality control and risk estimation since ionizing radiation is used. PURPOSE: To perform multiscale dosimetry assessments for different breast imaging modalities and for a variety of breast sizes and compositions. The first part of our study is focused on macroscopic scales (down to millimeters). METHODS: Nine anthropomorphic breast phantoms with a voxel resolution of 0.5 mm were computationally generated using the BreastPhantom software, representing three breast sizes with three distinct values of volume glandular fraction (VGF) for each size. Four breast imaging modalities were studied: digital mammography (DM), contrast-enhanced digital mammography (CEDM), digital breast tomosynthesis (DBT) and dedicated breast computed tomography (BCT). Additionally, the impact of tissue elemental compositions from two databases were compared. Monte Carlo (MC) simulations were performed with the MC-GPU code to obtain the 3D glandular dose distribution (GDD) for each case considered with the mean glandular dose (MGD) fixed at 4 mGy (to facilitate comparisons). RESULTS: The GDD within the breast is more uniform for CEDM and BCT compared to DM and DBT. For large breasts and high VGF, the ratio between the minimum/maximum glandular dose to MGD is 0.12/4.02 for DM and 0.46/1.77 for BCT; the corresponding results for a small breast and low VGF are 0.35/1.98 (DM) and 0.63/1.42 (BCT). The elemental compositions of skin, adipose and glandular tissue have a considerable impact on the MGD, with variations up to 30% compared to the baseline. The inclusion of tissues other than glandular and adipose within the breast has a minor impact on MGD, with differences below 2%. Variations in the final compressed breast thickness alter the shape of the GDD, with a higher compression resulting in a more uniform GDD. CONCLUSIONS: For a constant MGD, the GDD varies with imaging modality and breast compression. Elemental tissue compositions are an important factor for obtaining MGD values, being a source of systematic uncertainties in MC simulations and, consequently, in breast dosimetry.
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Mamografía , Radiometría , Rayos X , Método de Montecarlo , Radiometría/métodos , Mamografía/métodos , Fantasmas de Imagen , Dosis de RadiaciónRESUMEN
In modern radiotherapy with photons, the absorbed dose outside the radiation field is generally investigated. But it is well known that the biological damage depends not only on the absorbed dose but also on LET. This work investigated the dose-average LET (LΔ,D) outside several small radiotherapy fields to provide information that can help for better evaluating the biological effect in organs at risk close to the tumour volume. The electron fluences produced in liquid water by a 6 MV X-rays Varian iX linac were calculated using the EGSnrc Monte Carlo code. With the electron spectra, LΔ,D calculations were made for eight open small square fields and the reference field at water depths of 0.15 cm, 1.35 cm, 9.85 cm and 19.85 cm and several off-axis distances. The variation of LΔ,D from the centre of the beam to 2 cm outside the field's edge depends on the field size and water depth. Using radiobiological data reported in the literature for chromosomal aberrations as an endpoint for the induction of dicentrics determined in Human Lymphocytes, we estimated the maximum low-dose relative biological effectiveness, (RBEM) finding an increase of up to 100% from the centre of the beam to 2 cm from the field's edge.
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Transferencia Lineal de Energía , Radiometría , Humanos , Rayos X , Fotones/uso terapéutico , Método de Montecarlo , Aceleradores de Partículas , Agua , Dosificación RadioterapéuticaRESUMEN
OBJECTIVE: To compare the dosimetry between convex triangular fields of view (FOV) and similar dimension cylindrical FOVs of two cone-beam computed tomography (CBCT) models. METHODS: Optically stimulated luminescence dosimeters (OSLDs) were placed in fiducial anatomical locations in an anthropomorphic phantom representing an adult head male for dosimetry scans. Convex triangular FOVs (100 × 80 mm/maxilla-mandible; 100 × 50 mm mandible; 100 × 50 mm/maxilla) from Veraviewepocs 3D R100 (J. Morita, Kyoto, Japan) (R100) and Veraview® X800 (J. Morita, Kyoto, Japan) (X800) and cylindrical FOVs from R100 and X800 (80 × 80 mm/maxilla-mandible; 80 × 50 mm/mandible; 80 × 50 mm/maxilla) were obtained, resulting in 12 different scan protocols. Equivalent doses for each relevant organ/tissue and the effective dose for each protocol were calculated. Mean effective doses were compared by the two-way analysis of variance (ANOVA) with Tukey's post hoc test to evaluate the effect of the FOV and device (α = 0.05). RESULTS: The effective doses ranged between 69 and 324 µSv for the convex triangular FOVs and 76 and 332 µSv for the cylindrical FOVs. Convex triangular FOVs from the R100 device had effective doses 2.3 to 15.3% lower than their corresponding cylindrical FOVs with similar height (p < 0.05), and that difference ranged between 8.8 and 11.8% for the X800 device (p < 0.05). CONCLUSION: Convex triangular fields of view delivered slightly lower effective doses than the cylindrical fields of view of similar dimensions in the R100 and X800 CBCT devices. CLINICAL RELEVANCE: Understanding the influence of the image geometry formation in effective dose allows optimization to reduce patient dose.
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Tomografía Computarizada de Haz Cónico , Radiometría , Adulto , Masculino , Humanos , Dosis de Radiación , Tomografía Computarizada de Haz Cónico/métodos , Mandíbula/diagnóstico por imagen , Maxilar , Fantasmas de ImagenRESUMEN
The 'Inverse Square Law' (ISL)( 1) requires the existence of a point radiation source to be validated, but in some cases where there is more than one source, its use is possible as long as a point is determined where a virtual source can be positioned and from this point the points correspond to the ISL. Ambient dose equivalent rate values were obtained by simulation and measurements at various points along the LNMRI Thermal Neutron Flux 2 (TNF2) central axis front face, determining a function corresponding to the inverse square of the distance and the font position at the virtual point 'y0', so that the ISL is respected. This function will help in the neutron monitors calibration, previously estimating the ambient dose equivalent at a certain distance from the face.
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Neutrones , Radiometría , Simulación por Computador , Calibración , Dosis de RadiaciónRESUMEN
Metallic nanoparticles, such as gold (Au, Z = 79) and silver (Ag, Z = 47) nanoparticles (AuNPs and AgNPs, respectively), possess strong surface plasmonic resonance (SPR) and high atomic number, which makes them ideal candidates for enhancing dosimeter sensitivity. In this study, we have inserted different mass percentages (from 0 to 0.015 wt%) of AuNPs into a gelatinous Fricke-xylenol-orange (FXO-f) gel matrix and irradiated it with doses ranging from 2 to 32 Gy, using a source of x-ray of low energy with an effective energy of 42 keV. Optical absorption increased significantly; sensitivity gains of up to 50% were achieved for the FXO-f gel matrix containing 0.011 wt% AuNPs. To elucidate the mechanism underlying this increased sensitivity, we also evaluated FXO-f gel matrixes containing AgNPs. AgNPs insertion into the FXO-f gel matrix did not enhance sensitivity, which suggested that the AgNPs plasmonic absorption band and the FXO-f gel matrix absorption band at 441 nm overlapped, to increase absorption even after the gel matrix was irradiated. To visualize the dose distribution, we recorded optical tomography and acquired 3D reconstruction maps. In addition, we analyzed the dose enhancement factor (DEF) by using magnetic resonance images. AuNPs insertion into the FXO-f gel matrix resulted in a DEF gain of 1.37, associated with the photoelectric effect originating from the increased number of free radicals.
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Oro , Nanopartículas del Metal , Radiometría/métodos , Imagen por Resonancia MagnéticaRESUMEN
OBJECTIVE: To evaluate the accuracy of five brands of radiometers in reporting the irradiance (mW/cm2 ) from twelve brands of LCUs compared to a 'Gold Standard' (GS) reference obtained from a hand-held laboratory-grade radiometer. MATERIALS AND METHODS: The irradiance was measured from two examples of twelve brands of previously used LCUs on two examples of five brands of dental radiometers. The emission spectrum was also obtained. Irradiance data from each brand of LCU against each meter was analyzed using the Shapiro-Wilk test for normality. The irradiance values were subjected to a two-way ANOVA followed by Bonferroni tests for each LCU brand. Finally, a descriptive analysis was made using a 95% confidence interval around the mean irradiance. RESULTS: The power output from the LCUs ranged from 271 mW to 1005 mW. Among the tested radiometers, only the Bluephase Meter II could accurately report the irradiance from 11 out of the 12 brands of LCU evaluated in this study. When measured using the "GS" system, the mean irradiance values from the two examples of nine brands of previously used LCU were not always within ±10% of the irradiance values stated by the manufacturer. CONCLUSIONS: The mean irradiance values from 9 of the 12 brands of used LCUs were beyond ±10% of the irradiance values stated by the manufacturer. Only the Bluephase Meter II could accurately report the irradiance from 11 out of the 12 brands of LCU evaluated in this study. CLINICAL SIGNIFICANCE: There was a wide range in the power output from the LCUs tested. It was impossible to accurately measure the irradiance from all the LCUs using the dental radiometers examined. However, dental radiometers should still be used in dental offices to monitor the light output from LCUs and verify that they are working correctly before they are used on patients.
Asunto(s)
Resinas Compuestas , Luces de Curación Dental , Humanos , Curación por Luz de Adhesivos Dentales , Radiometría , Ensayo de MaterialesRESUMEN
The development of rHDL-radionuclide theragnostic systems requires evaluation of the absorbed doses that would be produced in healthy tissues and organs at risk. Technetium-99m is the most widely used radionuclide for diagnostic imaging, therefore, the design of theragnostic reconstituted high density-lipoprotein (rHDL) nanosystems labeled with Technetium-99m offers multiple possibilities. OBJECTIVE: To determine the biokinetics, radiopharmacokinetics and estimate the absorbed doses induced in healthy organs by Technetium-99m transported in the core and on the surface of rHDL. METHODS: Biokinetic and radiopharmacokinetic models of rHDL/[99mTc]Tc-HYNIC-DA (Technetium-99m in the core) and [99mTc]Tc-HYNIC-rHDL (Technetium-99m on the surface) were calculated from their ex vivo biodistribution in healthy mice. Absorbed doses were estimated by the MIRD formalism using OLINDA/EXM and LMFIT softwares. RESULTS: rHDL/[99mTc]Tc-HYNIC-DA and [99mTc]Tc-HYNIC-rHDL show instantaneous absorption in kidney, lung, heart and pancreas, with slower absorption in spleen. rHDL/[99mTc]Tc-HYNIC-DA is absorbed more slowly in the intestine, while [99mTc]Tc-HYNIC-rHDL is absorbed more slowly in the liver. The main target organ for rHDL/[99mTc]Tc-HYNIC-DA, which is hydrophobic in nature, is the liver, whereas the kidney is for the more hydrophilic [99mTc]Tc-HYNIC-rHDL. Assuming that 925 MBq (25 mCi) of Technetium-99m, carried in the core or on the surface of rHDL, are administered, the maximum tolerated doses for the organs of greatest accumulation are not exceeded. CONCLUSION: Theragnostic systems based on 99mTc-labeled rHDL are safe from the dosimetric point of view. The dose estimates obtained can be used to adjust the 99mTc-activity to be administered in future clinical trials.