François Deblois

• PhD
• McGill University

Purpose The addition of interstitial (IS) needles to intra-cavitary (IC) brachytherapy applicators is associated with improved outcomes in locally advanced cervical cancers involving parametrial tumor extensions. The purpose of this work was to validate a clinical workflow involving 3D-printed caps for a commercial IC split ring applicator that ena...

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...

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...

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...

Owing to its short computation time and simplicity, the Ray-Tracing algorithm (RAT) has long been used to calculate dose distributions for the CyberKnife system. However, it is known that RAT fails to fully account for tissue heterogeneity and is therefore inaccurate in the lung. The aim of this study is to make a dosimetric assessment of 219 non-s...

Introduction Trajectory‐based volumetric modulated arc therapy (tr‐VMAT) treatment plans enable the option for noncoplanar delivery yielding steeper dose gradients and increased sparing of critical structures compared to conventional treatment plans. The addition of translational couch motion to shorten the effective source‐to‐axis distance (SAD) m...

Introduction: Stereotactic radiosurgery (SRS) is a promising treatment option for patients with multiple brain metastases (BM). Recent technical advances have made LINAC based SRS a patient friendly technique, allowing for accurate patient positioning and a short treatment time. Since SRS is increasingly being used for patients with multiple BM, it...

Purpose: The Papillon technique using 50-kVp soft X-rays to treat rectal adenocarcinomas was developed and clinically implemented in the 1960s. We describe differences between accurate dosimetry and clinical implementation of this technique that is extending from its very inception to date. Methods and materials: A renaissance of the Papillon te...

Purpose: Current high-dose-rate brachytherapy skin treatments with the Freiburg flap (FF) applicator are planned with treatment planning systems based on the American Association of Physicists in Medicine TG-43 data sets, which assume full backscatter conditions in dose calculations. The aim of this work is to describe an experimental method based...

Objective: Dual-energy computed tomography high energy virtual monochromatic images (VMIs) can reduce artifact but suppress iodine attenuation in enhancing tumor. We investigated this trade-off to identify VMI(s) that strike the best balance between iodine detection and artifact reduction. Methods: The study was performed using an Alderson radia...

Transmission through the rounded leaf ends of Varian MLCs causes a discrepancy between the dosimetric and geometric field widths, defined as the dosimetric leaf gap (DLG). This parameter is necessary for Varian Eclipse dose calculations to accurately model field modulation. Despite the results of several studies noting the effect of incorrect DLG m...

Purpose:The goal of this study is to test the possible use of the analytical decomposition of differential uptake volume histograms (dUVHs) obtained from FDG-PET/CT data to isolate sub-volumes within a tumor known as biological target volumes (BTVs). Methods:: A retrospective study was conducted on a cohort of 20 histo-pathologically confirmed rect...

Purpose:Due to inherently non-linear dose response, measurement of relative dose distribution with radiochromic film requires measurement of absolute dose using a calibration curve following previously established reference dosimetry protocol. On the other hand, a functional form that converts the inherently non-linear dose response curve of the ra...

Purpose:Both kVp settings and geometric distribution of various materials lead to significant change of the HU values, showing the largest discrepancy for high-Z materials and for the lowest CT scanning kVp setting. On the other hand, the dose distributions around low-energy brachytherapy sources are highly dependent on the architecture and composi...

We investigated the effect of the EBT3 GafChromicTM film model absorbed dose energy response when used for percent depth dose (PDD) measurements in low-energy photon beams. We measured PDDs in water from a Xoft 50 kVp source using EBT3 film, and compared them to PDD measurements acquired with a PTW-TN34013 parallel-plate ionization chamber. For the...

In the past, film dosimetry was developed into a powerful tool for external beam radiotherapy treatment verification and quality assurance. The objective of this work was the development and clinical testing of the EBT3 model GafChromic film based brachytherapy quality assurance (QA) system. Retrospective dosimetry study was performed to test a pat...

Isocentre verification tests, such as the Winston-Lutz (WL) test, have gained popularity in the recent years as techniques such as stereotactic radiosurgery/radiotherapy (SRS/SRT) treatments are more commonly performed on radiotherapy linacs. These highly conformal treatments require frequent monitoring of the geometrical accuracy of the isocentre...

The TrueBeam linear accelerator platform has a developer's mode which permits the user dynamic control over many of the machine's mechanical and radiation systems. Using this research tool, synchronous couch and gantry motion can be programmed to simulate isocentric treatment with a shortened SAD, with benefits such as smaller projected M...

The purpose of the study was evaluating accuracy and reproducibility of a radiochromic film‐based protocol to measure computer tomography dose index (CTDI) as a part of annual QA on CT scanners and kV‐CBCT systems attached to linear accelerators. Energy dependence of Gafchromic XR‐QA2 ® film model was tested over imaging beam qualities (50 – 140 kV...

Current techniques to acquire patient surface data are often very expensive and lack flexibility. In this study, the use of the Microsoft Kinect to reliably acquire 3D scans of patient surface is investigated. A design is presented to make the system easily applicable to the clinic. Potential applications of the device to radiotherapy are also pres...

Purpose: The authors investigated the energy response of XR-QA2 GafChromic™ film over a broad energy range used in diagnostic radiology examinations. The authors also made an assessment of the most suitable functions for both reference and relative dose measurements. Methods: Pieces of XR-QA2 film were irradiated to nine different values of air...

Purpose With the emergence of flattening filter free (FFF) photon beams, several authors have noted many advantages to their use. One such advantage is the decrease in neutron production by photonuclear reactions in the linac head. In the present work we investigate the reduction in neutrons from a Varian TrueBeam linac using the Nested Neutron Spe...

Purpose To evaluate accuracy and reproducibility of a radiochromic film‐based protocol to measure computer tomography dose index (CTDI) as a part of annual QA on CT scanners and kV CBCT systems attached to linear accelerators. Methods Energy dependence of Gafchromic XR‐QA2(R) film model was tested over imaging beam qualities (50 – 140 kVp). Film p...

Purpose of this work is to investigate the effects of varying the active layer composition of external beam therapy (EBT) GafChromic(TM) films on the energy dependence of the film, as well as try to develop a new prototype with more uniform energy response at low photon energies (⩽100 keV). First, the overall energy response (SAD, W(Q)) of differen...

Introduction: X-ray imaging is an important part of medicine and plays a crucial role in radiotherapy. Education in this field is mostly limited to textbook teaching due to equipment restrictions. A novel simulation tool, ImaSim, for teaching the fundamentals of the x-ray imaging process based on ray-tracing is presented in this work. ImaSim is use...

Purpose: To assess the geometrical accuracy of treatment deliveries involving dynamic couch trajectories and to evaluate the accuracy of DMLC dose calculations in Eclipse at nonstandard SSDs. Methods: Eleven DMLC IMRT plans were recalculated as verification plans in Eclipse (AAA 10.0.28) using the collapsed gantry method, at SSDs between 85‐135 cm....

Purpose: To design and evaluate a patient-specific quality assurance program for HDR Brachytherapy of rectal cancer. Methods: A solid water phantom with a rectal applicator positioned in the center was designed. Dose distributions were measured with two sheets of EBT3 model GAFCHROMIC™ film placed at 2 cm above and 5 cm below the center of the a...

Purpose: We demonstrate a new method for computed tomography dose index (CTDI) measurements performed on CT scanners using XR-QA model radiochromic film dosimetry system. Method was tested by comparing measured to CT scanner listed CTDI values for fifteen different CT scanners at various locations. Methods: Reference dosimetry system was calibra...

Purpose: The scope of this study is to implement an accurate Cyberknife model on a web‐based tool (WebTPS), which uses the EGSnrc Monte Carlo dose calculation engine. WebTPS will be mostly used as a reference to evaluate clinical treatment plans in highly heterogeneous phantoms. Methods: The WebTPS dose calculation module is linked to the user code...

Purpose: To develop a novel web-based tool for VMAT/IMRT treatment plan evaluation and to design a unique plan Quality Index (QI) quantifier to aid in decision-making for SRS, SBRT, and ENT treatment planning and evaluationMethods: A high level Python web-framework, Django, is used to develop the web application. Django uses an SQL-like database f...

PURPOSE Daily kV cone-beam computed tomography (CBCT) can provide accurate volumetric information about patient’s anatomy prior to every treatment fraction and it is suitable for adaptive corrections of treatment positioning variations. We report on in vivo measurements of radiation skin doses to prostate and rectal cancer patients from CBCT acquis...

Purpose Despite numerous advantages of radiochromic film dosimeter (high spatial resolution, near tissue equivalence, low energy dependence) to measure a relative dose distribution with film, one needs to first measure an absolute dose (following previously established reference dosimetry protocol) and then convert measured absolute dose values int...

Purpose: In order to measure relative dose distribution with radiochromic film, one need to first measure an absolute dose (following previously established reference dosimetry protocol) and then convert measured absolute dose into relative dose. We present here result of our efforts to establish a functional form that converts the inherently non-l...

High expression of vascular endothelial growth factor (VEGF) in patients with breast cancer has been associated with a poor prognosis, indicating that VEGF could be linked to the efficacy of chemotherapy and radiotherapy. It has also been suggested that radiation resistance is partly due to tumour cell production of angiogenic cytokines, particular...

PURPOSE Most of contemporary efforts in implementing functional information into radiotherapy treatment planning process are based on an attempt to replace CT/MRI based GTV with PET based GTV. However, the fact is that such approach did not lead to widespread clinical implementations of PET based GTV in patient treatments. Exploring a new venue of...

A radiochromic film based dosimetry system for high dose rate (HDR) Iridium-192 brachytherapy source was described. A comparison between calibration curves established in water and Solid Water™ was provided. Pieces of EBT-2 model GAFCHROMIC™ film were irradiated in both water and Solid Water™ with HDR (192)Ir brachytherapy source in a dose range fr...

The authors applied 2D reference dosimetry protocol for dose measurements using XR-QA radiochromic film model during diagnostic computed tomography (CT) examinations carried out on patients and humanoid Rando phantom. Response of XR-QA model GAFCHROMIC™ film reference dosimetry system was calibrated in terms of Air-Kerma in air. Four most commonly...

Sorafenib tosylate (Bay 54-9085) is an oral, small molecule multikinase inhibitor of several targets including RAF/MEK/ERK signaling, vascular endothelial growth factor receptor-2 (VEGFR-2), VEGFR-3, and platelet derived growth factor receptor-beta (PDGFR-b). Sorafenib has shown clinical efficacy in solid tumors such as renal cell and hepatocellula...

Purpose: This work explains the development of an advanced treatment planning system for the generation of intensity and energy modulated electron radiotherapy (MERT) plans. The quality of MERT plans for the treatment of tumour bed boost in breast cancer is compared to direct electrons (DE) and volumetric modulated photon arc therapy (MAT). Method...

Purpose: Comparison between radiochromic film reference dosimetry system calibration curves established in water and Solid Water(TM) for high dose rate (HDR) 192‐Iridium brachytherapy source is described and assessed. Accordingly, a new reference dosimetry system protocol for HDR 192‐Iridium using the latest EBT‐2 model GAFCHROMIC(TM) film is sugge...

To report our experience with linear accelerator-based stereotactic fractionated radiotherapy in the treatment of juxtapapillary choroidal melanoma. We performed a retrospective review of 50 consecutive patients diagnosed with juxtapapillary choroidal melanoma and treated with linear accelerator-based stereotactic fractionated radiotherapy between...

Purpose: Electron radiotherapy (RT) offers a number of advantages over photons. The high surface dose, combined with a rapid dose fall?off beyond the target volume presents a net increase in tumorcontrol probability and decreases the normal tissue complication for superficial tumors. The current techniques involving electron RT are more seldom used...

Purpose: To develop a new generation energy?independent radiochromic film over a wide energy range of 50 kVp to 18 MV. The films are preferably symmetric in structure and can be used for measurements in complex spectral distributions. Methods: The overall energy dependence and intrinsic energy dependence were measured for EBT2 and several prototype...

Purpose: In this study, we evaluate feasibility of using EBT‐2 model GafchromicTM film to measure patient specific cutout output factors on an ortho‐voltage treatment machine. Methods: A Gulmay Orthovoltage D3225 unit was used to produce clinical beams in kV range from 50 kVp to 220 kVp. Previously established air kerma based radiochromic film dosi...

Purpose: IMRT is driven by volumetric segmentation, thus greater care and accuracy are necessary when contouring structures. The contouring process requires staff experience and ample time. We have evaluated the performance of two commercial atlas‐based segmentation algorithms. Methods: VelocityAI and MIMvista were compared. Twenty‐one IMRT head an...

Purpose: To investigate the feasibility of decomposition of differential uptake volume histograms (UVH) derived from FDG‐PET and CT data for uncovering tumor sub‐volumes as a novel approach for defining biological target volumes (BTV) for use in radiotherapytreatment planning. Methods: For a cohort of 27 histopathologically proven non‐small cell lu...

Purpose: Deformable contour propagation, when performed accurately, can potentially reduce the workload associated with manual contouring and minimize inter‐observer variability. In this work, we have compared propagated contours to physician‐drawn ones for gynecologic brachytherapy (GYN) and head and neck (HN) external beam radiotherapy cases.Meth...

Purpose: We applied 2D reference dosimetry protocol for dose measurements using XR-QA radiochromic film model during diagnostic computed tomography (CT) examinations carried out on patients and humanoid Rando phantom. Methods: Response of XR-QA model GAFCHROMIC™ film reference dosimetry system was calibrated in terms of Air-Kerma in air. Four most...

Modulated electron radiotherapy (MERT) has been proven to produce optimal plans for shallow tumors. This study investigates automated approaches to the field determination process in generating optimal MERT plans for few-leaf electron collimator (FLEC)-based MERT, by generating a large database of pre-calculated beamlets stored as phase-space files...

Shielding design calculations used in megavoltage radiation therapy essentially reduce to determination of barrier thicknesses. A shielding barrier serves to attenuate the radiation dose from a high level produced inside a therapy room to a lower “design goal” level at a point‐of‐interest outside. The calculation must account for both radiation phy...

The advantage of modulated electron radiation therapy (MERT) comes from the defined electron range and sharp fall‐off offered with electron beams, combined with complex inverse planning techniques to conform dose to the target and reduce dose to organs at risk (OAR) beyond the target. Recent studies have evaluated the feasibility of various electro...

Purpose: To evaluate a convolution and Monte Carlo based non?transmission portal dosimetry method used to reconstruct a 3D dose distribution. Methods:Images acquired by an amorphous siliconelectronic portal imaging device(EPID) were deconvolved with a scatter kernel to determine a 2D primary energy fluence (PEF) distribution. The scatter kernel was...

Purpose The authors present results of the measurements on the impact of radiochromic film immersion in water. The impact of film piece size, initial optical density, postimmersion waiting time prior to scanning, and the time film was kept in water has been investigated. The authors also investigated the pathways of water penetration into the film...

Purpose: Accurate dosimetry of the additional dose from kV cone‐beam CT(CBCT)image‐guidedradiation therapy(IGRT) is becoming increasingly important for radiationoncologists to make decisions on IGRT frequency in regards to the additional dose to radiosensitive organs, especially skin. In this study, the skindoses and dose profiles during CBCT scans...

Purpose: We present results of a pilot study established to investigate protocol to access inter‐fraction setup errors for patients with rectal and prostate cancer receiving CBCT based IGRT. We also report on radiationskindoses to patients from a typical CBCT acquisition for daily patient positioning using previously established 2D reference radioc...

Purpose: A new EBT‐2 GAFCHROMIC™ model radiochromic film has been released recently with addition of a yellow marker dye within sensitive layer that enables correction of non‐uniformity of the active layer of the film. Performance of the EBT‐2 was compared with former EBT model in terms of absorption spectra. Since one of the major drawbacks of the...

Purpose: To evaluate a convolution and Monte Carlo based non‐transmission portal dosimetry method used to reconstruct a 3D dose distribution. Method and Materials: Raw images acquired by an amorphous siliconelectronic portal imaging device(EPID) were deconvolved with a scatter kernel to determine a 2D primary energy fluence distribution. The scatte...

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One of the major drawbacks of the current radiochromic film dosimetry protocols is the postirradiation waiting time. In this article, the authors study the postirradiation time evolution of the absorption spectrum of radiochromic EBT-2 GAFCHROMIC film model. Postirradiation scanning times range from 3 min to 5 days and a dose range extends from 0 t...

Purpose: A common approach for dose assessment during cone beam computed tomography (CBCT) acquisition is to use thermoluminescent detectors for skin dose measurements (on patients or phantoms) or ionization chamber (in phantoms) for body dose measurements. However, the benefits of a daily CBCT image acquisition such as margin reduction in plannin...

Results: The 3-year overall survival rate was 70%. The cause-specific survival rates at 3 years were as follows: Stage I–II, 96%; Stage III, 75%; Stage IVA, 69%; and Stage IVB, 53%. All of loco-regional recurrences occurred within 2 years after radiotherapy. Twelve patients (2 with T1 disease and 10 with T2 disease) developed local recurrence and 6...

A software program, SpekCalc, is presented for the calculation of x-ray spectra from tungsten anode x-ray tubes. SpekCalc was designed primarily for use in a medical physics context, for both research and education purposes, but may also be of interest to those working with x-ray tubes in industry. Noteworthy is the particularly wide range of tube...

We describe a 2D reference dosimetry system for dose measurements during cone?beam computed tomograpfy (CBCT) scans using on?board imager (OBI) on Varian Clinac?iX linear accelerator that employs XR?QA radiochromic film model, specifically designed for measurements at low energy photons. We report on surface doses and percent depth dose (PDDs) meas...

Method for quality assurance (QA) of conformal CT?based high dose rate (HDR) brachytherapy is described, based on comparing dose distributions generated by treatment planning system and measured by EBT model GAFCHROMIC film within dedicated brachy?therapy QA phantom. Phantom consists of 3 catheters embedded in surface plane of 2 cm thick slab of so...

Purpose: We describe a method for quality assurance (QA) test that assesses all steps of conformal CT‐based high dose rate (HDR) brachytherapy. A procedure was developed to compare dose distribution generated by the treatment planning system and measured by the EBT model GAFCHROMIC™ film within a dedicated brachytherapy QA phantom. Method and Mater...

Purpose: To develop a free and easy‐to‐use software program to model the x‐ray spectra emitted from x‐ray tubes. Such a program is useful for the education of physicists, technicians and technologists working in radiation physics but also as a research tool. Method and Materials: A Graphical User Interface (GUI) was created using REALbasic (REAL so...

Purpose: Numerous Monte Carlo (MC) models of therapeuticelectron beams are presented in the literature. However, beam models built solely with manufacturer specifications of the accelerator do not systematically provide acceptable agreements with measurements. Clinically, accurate beam models are crucial to MCtreatment planning as electron dose cal...

Purpose: We describe a 2D reference dosimetry technique for measuring dose from cone‐beam computed tomography(CBCT) scans using on‐board imager (OBI) on Varian Clinac‐iX linear accelerator that employs XR‐QA radiochromic film model, specifically designed for dose measurements at low energy photons. We report on surface dose and percent depth dose (...

Introduction: X-ray imaging is an important part of medicine and plays a crucial role in radiotherapy. Education in this field is mostly limited to textbook teaching due to equipment restrictions. A novel simulation tool, ImaSim, for teaching the fundamentals of the x-ray imaging process based on ray-tracing is presented in this work. ImaSim is use...