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1.
Heliyon ; 9(1): e12839, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36699266

RESUMO

Objective: Nowadays, in Bulgaria there is a trend of increasing entry into the surgical field of robot-assisted surgery operations, which suggests a need for the establishment of a large number of specialists in this field in a short period. Based on these arguments, the Medical University of Varna was the first university in the country to introduce a robotic surgery training program for medical students. The study aims to investigate the medical students' satisfaction on robotic surgery training provided at Medical University of Varna with da Vinci Skills Simulator. Design: During the summer semester of the academic 2020/2021 and 2021/2022 years, a pilot training of robotic surgery was conducted with 5th year students in Medicine. Within one month, the students had the opportunity to get acquainted with the simulator of da Vinci Xi robotic system. The training was divided into two modules: a two-week theoretical module and a two-week practical module. After completing the training, students filled out a questionnaire dedicated to assess their satisfaction with the proposed training. Correlation between their responses and the objective parameters assessed on the simulator was calculated. Results: Thirty participants (16 men and 14 women) shared their opinion on easiness of use and usefulness of the robotic simulator in training of surgery activities. Students' responses highly evaluated both aspects with average five-point Likert scale scores of 4.3 and 4.5, respectively. 93% of the participants would continue their further education and training in robotic surgery field. In addition, there was no correlation between objective evaluation by the simulator and students responses. Conclusions: Training in robotic surgery proves to be a useful approach for training students to develop skills and profession in the field of surgery. The results suggest that training in this field may be accomplished even at the student level, by exploiting the robotic surgery in realistic scenario and thus, in a timely manner to find out the surgical direction they want to be further evolved.

2.
Phys Med ; 74: 133-142, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32470909

RESUMO

Virtual clinical trials (VCT) are in-silico reproductions of medical examinations, which adopt digital models of patients and simulated devices. They are intended to produce clinically equivalent outcome data avoiding long execution times, ethical issues related to radiation induced risks and huge costs related to real clinical trials with a patient population. In this work, we present a platform for VCT in 2D and 3D X-ray breast imaging. The VCT platform uses Monte Carlo simulations based on the Geant4 toolkit and patient breast models derived from a cohort of high resolution dedicated breast CT (BCT) volume data sets. Projection images of the breast and three-dimensional glandular dose maps are generated for a given breast model, by simulating both 2D full-field digital mammography (DM) and 3D BCT examinations. Uncompressed voxelized breast models were derived from segmented patient images. Compressed versions of the digital breast phantoms for DM were generated using a previously published digital compression algorithm. The Monte Carlo simulation framework has the capability of generating and tracking ~105 photons/s using a server equipped with 16-cores and 3.0 GHz clock speed. The VCT platform will provide a framework for scanner design optimization, comparison between different scanner designs and between different modalities or protocols on computational breast models, without the need for scanning actual patients as in conventional clinical trials.


Assuntos
Mama/diagnóstico por imagem , Ensaios Clínicos como Assunto , Mamografia , Método de Monte Carlo , Humanos , Imageamento Tridimensional
3.
Phys Med ; 55: 142-148, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30314732

RESUMO

PURPOSE: To provide mean glandular dose (MGD) estimates via Monte Carlo (MC) simulations as a function of the breast models and scan parameters in mammography, digital breast tomosynthesis (DBT) and dedicated breast CT (BCT). METHODS: The MC code was based on GEANT4 toolkit. The simulated compressed breast was either a cylinder with a semi-circular section or ad hoc shaped for oblique view (MLO). In DBT we studied the influence of breast models and exam parameters on the T-factors (i.e. the conversion factor for the calculation of the MGD in DBT from that for a 0-degree projection), and in BCT we investigated the influence on the MGD estimates of the ion chamber volume used for the air kerma measurements. RESULTS: In mammography, a model representative of a breast undergoing an MLO view exam did not produce substantial differences (0.4%) in MGD estimates, when compared to a conventional cranio-caudal (CC) view breast model. The beam half value layer did not present a significant influence on T-factors in DBT (<0.8%), while the skin model presented significant influence on MGD estimates (up to 3.3% at 30 degrees scan angle), increasing for larger scan angles. We derived a correction factor for taking into account the different ion chamber volume used in MGD estimates in BCT. CONCLUSIONS: A series of MC code modules for MGD estimates in 2D and 3D breast imaging have been developed in order to take into account the most recent advances in breast models.


Assuntos
Mama/citologia , Mama/diagnóstico por imagem , Mamografia/métodos , Doses de Radiação , Feminino , Humanos , Mamografia/instrumentação , Método de Monte Carlo
4.
Phys Med ; 51: 56-63, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29705184

RESUMO

PURPOSE: To compare, via Monte Carlo simulations, homogeneous and non-homogenous breast models adopted for mean glandular dose (MGD) estimates in mammography vs. patient specific digital breast phantoms. METHODS: We developed a GEANT4 Monte Carlo code simulating four homogenous cylindrical breast models featured as follows: (1) semi-cylindrical section enveloped in a 5-mm adipose layer; (2) semi-elliptical section with a 4-mm thick skin; (3) semi-cylindrical section with a 1.45-mm skin layer; (4) semi-cylindrical section in a 1.45-mm skin layer and 2-mm subcutaneous adipose layer. Twenty patient specific digital breast phantoms produced from a dedicated CT scanner were assumed as reference in the comparison. We simulated two spectra produced from two anode/filter combinations. An additional digital breast phantom was produced via BreastSimulator software. RESULTS: With reference to the results for patient-specific breast phantoms and for W/Al spectra, models #1 and #3 showed higher MGD values by about 1% (ranges [-33%; +28%] and [-31%; +30%], respectively), while for model #4 it was 2% lower (range [-34%; +26%]) and for model #2 -11% (range [-39%; +14%]), on average. On the other hand, for W/Rh spectra, models #1 and #4 showed lower MGD values by 2% and 1%, while for model #2 and #3 it was 14% and 8% lower, respectively (ranges [-43%; +13%] and [-41%; +21%]). The simulation with the digital breast phantom produced with BreastSimulator showed a MGD overestimation of +33%. CONCLUSIONS: The homogeneous breast models led to maximum MGD underestimation and overestimation of 43% and 28%, respectively, when compared to patient specific breast phantoms derived from clinical CT scans.


Assuntos
Mama/diagnóstico por imagem , Mamografia/métodos , Método de Monte Carlo , Modelagem Computacional Específica para o Paciente , Doses de Radiação , Mama/citologia , Humanos , Imagens de Fantasmas , Software
5.
Phys Med ; 32(2): 353-61, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26818470

RESUMO

PURPOSE: Breast augmentation is one of the most popular cosmetic surgeries worldwide. The aim of this study is to investigate the effect of breast implant insertion on the detectability and visibility of lesions on mammography and breast tomosynthesis (BT) images. MATERIALS AND METHODS: Three software phantoms, composed of a homogeneous background with embedded silicone gel structures, and two types of breast abnormalities, microcalcifications (µCs) and masses, were generated. Two X-ray breast imaging modalities were simulated: mammography and BT with six incident monochromatic X-ray beams with energies in the interval between 20 and 30 keV. Projection images were generated using an in-house developed Monte Carlo simulator. The detectability of mammographic findings adjacent to the implant material and the influence of the incident beam energy and implant thickness on the feature detection were studied. RESULTS: It was found that implants thicker than 26 mm for the case of mammography and 14 mm for the case of BT obscured the visibility of underlying structures. Although BT demonstrated a lack of contrast, this modality was able to visualize µCs under considerable depths of implant. Increasing the incident beam energy led to better visualization of small µCs, while in the case of breast masses, their detectability was limited. CONCLUSIONS: Silicone gel implants introduce a limitation in the image quality of mammograms resulting in low detectability of features. In addition, silicone gel implants obscure partially or totally parts of the image, depending on the size and the thickness of the implant as well the energy of the X-rays used.


Assuntos
Artefatos , Implantes de Mama , Mama , Mamografia/métodos , Método de Monte Carlo , Silicones , Imagens de Fantasmas
6.
Phys Med Biol ; 59(16): 4681-96, 2014 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-25082791

RESUMO

The aim of this study is to investigate the impact on image quality of using monochromatic beams for lower dose breast tomosynthesis (BT). For this purpose, modeling and simulation of BT and mammography imaging processes have been performed using two x-ray beams: one at 28 kVp and a monochromatic one at 19 keV at different entrance surface air kerma ranging between 0.16 and 5.5 mGy. Two 4 cm thick computational breast models, in a compressed state, were used: one simple homogeneous and one heterogeneous based on CT breast images, with compositions of 50% glandular-50% adipose and 40% glandular-60% adipose tissues by weight, respectively. Modeled lesions, representing masses and calcifications, were inserted within these breast phantoms. X-ray transport in the breast models was simulated with previously developed and validated Monte Carlo application. Results showed that, for the same incident photon fluence, the use of the monochromatic beam in BT resulted in higher image quality compared to the one using polychromatic acquisition, especially in terms of contrast. For the homogenous phantom, the improvement ranged between 15% and 22% for calcifications and masses, respectively, while for the heterogeneous one this improvement was in the order of 33% for the masses and 17% for the calcifications. For different exposures, comparable image quality in terms of signal-difference-to-noise ratio and higher contrast for all features was obtained when using a monochromatic 19 keV beam at a lower mean glandular dose, compared to the polychromatic one. Monochromatic images also provide better detail and, in combination with BT, can lead to substantial improvement in visualization of features, and particularly better edge detection of low-contrast masses.


Assuntos
Mama , Mamografia/métodos , Método de Monte Carlo , Mama/citologia , Estudos de Viabilidade , Feminino , Humanos , Imagens de Fantasmas , Doses de Radiação , Razão Sinal-Ruído
7.
Med Phys ; 39(11): 6638-51, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23127058

RESUMO

PURPOSE: In x-ray mammography, some of the components that play significant role to early diagnosis are the x-ray source, the breast composition as well as the composition of the x-ray converter. Various studies have previously investigated separately the influence of breast characteristics and detector configuration on the optimization of mammographic imaging systems. However, it is important to examine the combined effect of both components in improving the signal transfer properties in mammography systems of the mammograms. In the present study, the authors compared and evaluated x-ray converters using software breast models and realistic mammographic spectra in terms of: (a) zero-frequency detective quantum efficiency (DQE) and (b) sensitivity. The impact of x-ray converter thickness on contrast threshold (C(TH)) for observer assessment, based on the Rose model, was demonstrated as well. METHODS: Monte Carlo techniques were applied to simulate the x-ray interactions within the software breast phantoms and thereafter within the detective medium. Simulations involved: (a) two mammographic x-ray spectra: 28 kV Mo, 0.030 mm Mo, and 32 kV W, 0.050 mm Rh of different entrance surface air kerma (ESAK: 3-7 mGy), (b) realistic breast models (dense and fatty) and (c) x-ray converter materials most frequently considered in investigations on energy integrating digital mammography detectors: the Gd(2)O(2)S:Tb granular phosphor, the CsI:Tl structured phosphor, and the a-Se photoconductive layer. Detector material thickness was considered to vary in the range from 50 mg∕cm(2) up to 150 mg∕cm(2). RESULTS: The Monte Carlo study showed that: (a) the x-ray beam becomes less penetrating after passing through dense breasts leading to higher values of zero-frequency DQE of the x-ray imaging converters and improved C(TH) values in all cases considered, (b) W∕Rh target∕filter combination results in improved C(TH) values at higher ESAK values, and (c) a-Se shows higher zero-frequency DQE values than the phosphor-based converters, Gd(2)O(2)S:Tb and CsI:Tl. However, thicker layers of CsI:Tl could be comparable to a-Se layers achieving approximately 27.6% C(TH) improvement at a thickness of 150 mg∕cm(2). CONCLUSIONS: The present Monte Carlo investigation indicates that in the energy range employed in mammography, an upper limit, approximately 100 mg∕cm(2), should be considered in the development of thicker a-Se converters. On the other hand, above this thickness value, CsI:Tl converter could improve its imaging performance.


Assuntos
Mama , Mamografia/instrumentação , Método de Monte Carlo , Imagens de Fantasmas , Intensificação de Imagem Radiográfica/instrumentação , Software , Raios X
8.
Comput Methods Programs Biomed ; 107(1): 90-6, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22024418

RESUMO

End stage renal disease (ESRD) treatment methods are considered to be among the most expensive procedures for chronic conditions worldwide which also have severe impact on patients' quality of life. During the last decade, Greece has been among the countries with the highest incidence and prevalence, while at the same time with the lowest kidney transplantation rates. Predicting future patients' number on Renal Replacement Therapy (RRT) is essential for health care providers in order to achieve more effective resource management. In this study a Markov Chain Monte Carlo (MCMC) simulation is presented for predicting the future number of ESRD patients for the period 2009-2020 in Greece. The MCMC model comprises Monte Carlo sampling techniques applied on probability distributions of the constructed Markov Chain. The model predicts that there will be 15,147 prevalent patients on RRT in Greece by 2020. Additionally, a cost-effectiveness analysis was performed on a scenario of gradually reducing the hemodialysis patients in favor of increasing the transplantation number by 2020. The proposed scenario showed net savings of 86.54 million Euros for the period 2009-2020 compared to the base-case prediction.


Assuntos
Simulação por Computador , Falência Renal Crônica/epidemiologia , Adulto , Idoso , Algoritmos , Análise Custo-Benefício , Grécia/epidemiologia , Humanos , Falência Renal Crônica/economia , Falência Renal Crônica/terapia , Transplante de Rim/economia , Transplante de Rim/estatística & dados numéricos , Cadeias de Markov , Pessoa de Meia-Idade , Modelos Econômicos , Método de Monte Carlo , Diálise Renal/economia , Diálise Renal/estatística & dados numéricos
9.
Comput Biol Med ; 40(2): 208-14, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20056197

RESUMO

Computer models and simulations of X-ray imaging systems are becoming a very precious tool during the development and evaluation of new X-ray imaging techniques. To provide, however, a faithful simulation of a system, all components must be accurately modelled and tested, followed by verification through experimental measurements. This paper presents a validation study of the XRayImagingSimulator, an in-house developed X-ray imaging simulator, which is extensively used as a basic tool in carrying out complex breast imaging simulations. The approach followed compares results obtained via an experimental setup for breast phantom (CIRS 011A) imaging, using synchrotron radiation (SYRMEP beamline at ELETTRA), with those from its simulated setup under the same conditions. The study demonstrated a very good agreement between experimental and simulated images compared both in terms of subjective and objective criteria. The combination of the XRayImagingSimulator with our BreastSimulator provides a powerful tool for in silico testing of new X-ray breast imaging approaches.


Assuntos
Simulação por Computador , Mamografia/métodos , Imagens de Fantasmas , Algoritmos , Mama/anatomia & histologia , Feminino , Humanos , Mamografia/instrumentação , Método de Monte Carlo , Processamento de Sinais Assistido por Computador , Software , Síncrotrons
10.
Phys Med ; 25(4): 172-80, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19186088

RESUMO

The effect of cylindrical protector dimensions, material and distance from the source on the dose distribution in rotational radiotherapy was studied to assess the potential protection possibilities of small-sized radiosensitive structures, such as spinal cord. The dose distributions were evaluated in terms of dose at the protected region and surface dose, ratio of the dose at the protected region to the maximum dose, and dose gradient. High-density materials, such as lead, tungsten, gold and cerrobend, along with new polymer-metal composite ones were used in simulation studies, performed by an in-house developed Monte Carlo Radiotherapy Simulator. To ensure correct modeling of the composite materials, simulated attenuation data were verified against experimentally measured data. The dependence of the dose at the protected region from the protector diameter and the field size was established. Protectors of higher density and larger diameter provide not only lower dose at the protected region, but also steeper dose gradient and lower ratio of the dose at the protected region to the treatment dose. For the protection of small structures, high-density protectors placed further from the source allow thicker protectors to be used. The surface dose increases insignificantly for the studied protector-surface distances. The results have shown that shielding properties of composite materials are close to those of lead.


Assuntos
Simulação por Computador , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia/métodos , Humanos , Método de Monte Carlo , Imagens de Fantasmas , Equipamentos de Proteção , Dosagem Radioterapêutica , Rotação
11.
Med Phys ; 33(11): 4289-98, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17153407

RESUMO

This article presents simulation studies of field shaping in rotational radiation therapy by means of two categories of beam modifying devices: protectors and shapers. The protectors used are diminished copies of the organs at risk (OARs) and stay parallel to them during gantry rotation. Thus, each protector always keeps the corresponding OAR in its shadow, significantly reducing the irradiation. The shapers are used in order to obtain a more uniform dose distribution in the planning target volume (PTV) while preserving their initial orientation during gantry rotation. Thus, the use of beam modifying devices allows modulation of the beam intensity, to better fit irradiation requirements, at every gantry position. A software tool for calculations of geometrical position and dimensions of the beam modifying devices, using information about the shape, size, and position of the protected organ or area at risk as input, was developed. This tool was integrated into the in-house-developed Monte Carlo radiation therapy simulator (MCRTS), used to simulate the particle transport through the designed system. The verification of the software tool showed good agreement between experimental and simulation data, with discrepancies of less than 3%. Dose distributions in solid-geometry and voxel-based neck models were evaluated. Furthermore, the effectiveness of the shapers to modify the dose distribution outside the protected area was studied. Results demonstrated that the use of the shapers effectively improves dose uniformity. Studies using shapers of different materials were also carried out and resulted in similar dose distributions. The results of the simulation studies with a voxel-based model showed that rotational therapy with beam modifying devices offers adequate protection of the OAR and a uniform dose distribution outside the protected region.


Assuntos
Algoritmos , Modelos Biológicos , Radiometria/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional/métodos , Carga Corporal (Radioterapia) , Simulação por Computador , Humanos , Modelos Estatísticos , Método de Monte Carlo , Dosagem Radioterapêutica , Eficiência Biológica Relativa , Reprodutibilidade dos Testes , Rotação , Sensibilidade e Especificidade
12.
Comput Methods Programs Biomed ; 70(3): 241-51, 2003 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-12581556

RESUMO

This paper presents a software simulation package of the entire X-ray projection radiography process including beam generation, absorber structure and composition, irradiation set up, radiation transport through the absorbing medium, image formation and dose calculation. Phantoms are created as composite objects from geometrical or voxelized primitives and can be subjected to simulated irradiation process. The acquired projection images represent the two-dimensional spatial distribution of the energy absorbed in the detector and are formed at any geometry, taking into account energy spectrum, beam geometry and detector response. This software tool is the evolution of a previously presented system, with new functionalities, user interface and an expanded range of applications. This has been achieved mainly by the use of combinatorial geometry for phantom design and the implementation of a Monte Carlo code for the simulation of the radiation interaction at the absorber and the detector.


Assuntos
Intensificação de Imagem Radiográfica/métodos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Simulação por Computador , Humanos , Computação Matemática , Método de Monte Carlo , Imagens de Fantasmas , Software
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