Stephane Bedwani

Stephane Bedwani
Centre hospitalier de l'Université de Montréal (CHUM) | CHUM · Département Radio-oncologie

PhD

About

47
Publications
2,142
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365
Citations
Citations since 2017
20 Research Items
244 Citations
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2017201820192020202120222023010203040

Publications

Publications (47)
Article
Full-text available
3D-printed alternatives to standard flocked swabs were rapidly developed to provide a response to the unprecedented and sudden need for an exponentially growing amount of diagnostic tools to fight the COVID-19 pandemic. In light of the anticipated shortage, a hospital-based 3D-printing platform was implemented in our institution for the production...
Preprint
Full-text available
3D printed alternatives to standard flocked swabs were rapidly developed to provide a response to the unprecedented and sudden need for an exponentially growing amounts of diagnostic tools to fight the pandemics of COVID-19. In light of the anticipated shortage, an hospital-based 3D printing platform was implemented in our institution for the produ...
Article
Full-text available
Purpose: The geometry of an immobilization device such as a headrest can cause undesired computed tomography (CT) artifacts that may affect both volume definition and dosimetry in radiotherapy of the brain. The purpose of this work was to reduce CT artifacts caused by a standard hard plastic hollow radiotherapy headrest. This was to be achieved th...
Article
Purpose To compare cardiac doses of different whole-breast optimization schemes including free-breathing (FB) tangential radiotherapy (TRT), deep-inspiration breath-hold (DIBH) TRT, and FB helical tomotherapy (HT). Methods Early-stage left-sided breast cancer patients who underwent breast-conserving surgery followed by adjuvant radiotherapy were in...
Article
Purpose To investigate the role of quantitative pre-treatment dual-energy computed tomography (DECT) for prediction of loco-regional recurrence (LRR) in patients with larynx/hypopharynx squamous cell cancer (L/H SCC). Methods Patients with L/H SCC treated with curative intent loco-regional radiotherapy and that underwent treatment planning with co...
Article
Objectif de l’étude L’objectif de cette étude était de quantifier les avantages dosimétriques de préservation cardiovasculaire de la tomothérapie hélicoïdale comparativement à des radiothérapies conformationnelle avec modulation d’intensité (RCMI) tangentielles. Matériel et méthode Des patientes atteintes d’un cancer du sein gauche ayant été pris...
Article
Purpose: We present a concise description of an in-house decision aid software called "Central3D" that allows a quick and robust lung tumor classification between central and peripheral as defined by the Radiation Therapy Oncology Group (RTOG) 0813. Methods and materials: Twenty cases of lung tumors were selected for this study and four radiatio...
Article
Purpose: The purpose of this study is to develop and validate accurate methods for determining iodine content and virtual non contrast maps of physical parameters, such as electron density, in the context of radiotherapy. Methods: A simulation environment is developed to compare three methods allowing extracting iodine content and virtual non-co...
Article
Purpose: The aim of this study was to compare early prostate-specific antigen (PSA) decline patterns and PSA nadirs between low-dose-rate seed prostate brachytherapy (LDR-PB) and different fractionations of external beam radiotherapy (EBRT) and their predictive importance for biochemical failure (bF). Methods and materials: Patients with D'Amico...
Article
Purpose: To assess overall robustness and accuracy of a modified particle filter-based tracking algorithm for magnetic resonance (MR)-guided radiation therapy treatments. Methods and materials: An improved particle filter-based tracking algorithm was implemented, which used a normalized cross-correlation function as the likelihood calculation. W...
Article
Full-text available
Purpose: There is an increasing interest in the evaluation of lung function from physiological images in radiation therapy treatment planning to reduce the extent of post-radiation toxicities. The purpose of this work is to retrieve reliable functional information from contrast-enhanced dualenergy computed tomography (DECT) for new applications in...
Article
Purpose To quantify lung function based on a dual energy computed tomography (DECT)-derived iodine map in patients treated with radiotherapy for lung cancer, and to assess the dosimetric impact of its integration in radiotherapy planning. Methods Patients treated with stereotactic ablative radiotherapy (SABR) for early stage or intensity-modulated...
Article
This work introduces a 2D motion prediction algorithm for lung tumors applied to dynamic MR images that combines intrafractional tumor deformations. It is developed in the context of MR-linac treatments and evaluates uniform and patient-specific margins about the gross tumor volume to optimize the tumor coverage. Seven early stage non-small cell lu...
Article
Introduction: The purpose of this study is quantify intrafraction motion (IFM) during lung volumetric-modulated arc therapy (VMAT) and evaluate the impact of mid-treatment cone beam computed tomography (CBCT)-guided patient repositioning on target coverage. Method: This analysis included lung tumours treated with VMAT to 50-60 Gy in 3-5 fraction...
Article
Purpose:This study introduces a novel autocontouring algorithm based on particle filter for lung tumors. It is validated on dynamic magnetic resonance (MR) images and is developed in the context of MR-linac treatments. Methods:A sequential Monte Carlo method called particle filter is used as the main structure of the algorithm and is combined with...
Article
Purpose:This study proposes a novel autocontouring algorithm for lung tumors based on particle filter. It is developed in the context of MR-linac treatments and is validated on in-vivo dynamic magnetic resonance images. Methods:A sequential Monte Carlo method called particle filter is combined with Otsu’s thresholding technique to contour lung tumo...
Article
Purpose:To propose an alternate treatment plan that minimizes the dose to the functional lung tissues. In clinical situation, the evaluation of the lung functionality is typically derived from perfusion scintigraphy. However, such technique has spatial and temporal resolutions generally inferior to those of a CT scan. Alternatively, it is possible...
Article
Purpose: An improvement in tissue assignment for low-dose rate brachytherapy (LDRB) patients using more accurate Monte Carlo(MC)dose calculation was accomplished with a metallic artifact reduction (MAR) method specific to dual-energy computed tomography (DECT).
Article
Purpose: To evaluate the reliability of common sinogram-based DECT reconstruction methods for radiotherapy tissue characterization and to evaluate the advantage of combining them with a stoichiometric calibration. Methods: The sinogram-based DECT method defined byAlvarez and Macovski ["Energy-selective reconstructions in x-ray computerized tomog...
Article
Purpose: To investigate an automatic bronchial and vessel bifurcations detection algorithm for deformable image registration (DIR) assessment to improve lung cancer radiation treatment.
Conference Paper
Purpose: To improve Monte Carlo dose calculation accuracy through a new tissue segmentation technique with dual energy CT (DECT).
Conference Paper
Purpose: Dual energy computed tomography (DECT) pre-reconstruction methods require the prior knowledge of the X-ray source spectrum to allow extracting physical parameters needed for radiation therapy dose calculation, such as electron density (ED) and the effective atomic number (EAN). While DECT stoichiometric calibration may provide reliable per...
Article
Purpose: To develop a new segmentation technique using dual energy CT (DECT) to overcome limitations related to segmentation from a standard Hounsfield unit (HU) to electron density (ED) calibration curve. Both methods are compared with a Monte Carlo analysis of dose distribution. Methods: DECT allows a direct calculation of both ED and effective a...
Article
Purpose To allow a reliable deformable image registration (DIR) method for dose calculation in radiation therapy. This work proposes a performance assessment of a morphological segmentation algorithm that generates a deformation field from lung surface displacements with 4DCT datasets. Methods From the 4DCT scans of 15 selected patients, the deep...
Conference Paper
Purpose: To establish the reliability of electron density (ED) mapping and tissue segmentation techniques using CT images for brachytherapy, considering stochastic and systematic Hounsfield unit (HU) variations. Methods: Most common artifacts are simulated within a Monte Carlo theoretical framework. A set of CT data is first generated with the EGSn...
Article
To assess the importance of charge-transfer on the interface properties, we studied the interaction of the tetracyanoethylene (TCNE) molecule with various copper surfaces. TCNE, a highly electrophilic molecule, appears as an ideal candidate to study the influence of high charge-transfer on the electronic and structural properties of molecule-surfac...
Article
The influence of π-interactions in thin layers of stacked polymers has been studied with first-principles DFT calculations and STM simulations. Improving π–π coupling between polymeric layers in the stack contributes to enlarging the size of STM contrasts and to attenuating the fine atomic structure features in the topmost superficial polymer layer...
Article
Single tetracyanoethyelene (TCNE) molecules on Cu(111) are reversibly switched among five states by applying voltage pulses with the tip of a scanning tunneling microscope. A pronounced Kondo resonance in tunneling spectroscopy indicates that one of the states is magnetic. Side bands of the Kondo resonance appear at energies which correspond to int...
Article
Full-text available
The interaction of the strong electron-acceptor tetracyanoethylene with the Cu(100) surface is studied with scanning tunneling microscopy experiments and first-principles density functional theory calculations. We compare two different adsorption models with the experimental results and show that the molecular self-assembly is caused by a strong st...
Article
We report a detailed investigation of the self-assembly of the organic semiconductor rubrene on low-index (100) and (110) facets of copper by scanning tunneling microscopy (STM) and supported by density functional theory (DFT) calculations. Rubrene adsorbs in orientations depending on substrate symmetry, resulting in different self-assembled motifs...
Article
We describe a multilevel multiscale mimetic (M^3) method for solving two-phase flow (water and oil) in a heterogeneous reservoir. The governing equations are the elliptic equation for the reservoir pressure and the hyperbolic equation for the water saturation. ...
Article
Full-text available
Within the framework of atomic resolution STM images, the understanding of relations between the surface, the tip, the adsorbate (if present) and the bulk materials is not always straightforward. Depending on the inherent quality of an experimental STM image, the nature of component within the entire system can be determined with a very limited cer...
Article
Full-text available
A new computational tool named SPAGS-STM has been developed to produce STM images in a very short time. Major improvement over standard STM software was made possible through the development of a strongly parallel computational approach, and by introducing new iterative algorithms for space discretization steps. This powerful technique has been use...
Article
Full-text available
The formation of self-assembled nanostructure on a surface results from a subtle equilibrium between the attractive intermolecular forces and the forces that drive molecules to the substrate. In the case of strong molecule-substrate interactions, molecules can even induce nanoscale surface reshaping, which is now a promising field in materials engi...

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Projects (5)