Philippe Després

Université Laval | ULAVAL

During the last decade, studies have shown that 3D list-mode ordered-subset expectation-maximization (LM-OSEM) algorithms for positron emission tomography (PET) reconstruction could be effectively computed and considerably accelerated by graphics processing unit (GPU) devices. However, most of these studies rely on pre-calculated sensitivity matric...

A new hybrid imaging-treatment modality, the MRI-Linac, involves the irradiation of the patient in the presence of a strong magnetic field. This field acts on the charged particles, responsible for depositing dose, through the Lorentz force. These conditions require a dose calculation engine capable of taking into consideration the effect of the ma...

Monte Carlo methods are considered as the gold standard for dosimetric computations in radiotherapy. Their execution time is, however, still an obstacle to the routine use of Monte Carlo packages in a clinical setting. To address this problem, a completely new, and designed from the ground up for the GPU, Monte Carlo dose calculation package for vo...

Deep learning (DL) methods have demonstrated remarkable effectiveness in assisting with lung cancer risk prediction tasks using computed tomography (CT) scans. However, the lack of comprehensive comparison and validation of state-of-the-art (SOTA) models in practical settings limits their clinical application. This study aims to review and analyze...

Objective Lung cancer remains the leading cause of cancer‐related mortality worldwide, with most cases diagnosed at advanced stages. Hence, there is a need to develop effective predictive models for early detection. This study aims to investigate the impact of imaging parameters and delta radiomic features from temporal scans on lung cancer risk pr...

Objective The influence of radiomics pipeline and the grey-level discretization on the discovery of immunotherapy biomarkers is still a poorly understood topic. This study is aimed at identifying robust features by comparing two radiomics libraries and their association with clinical outcomes in non-small cell lung cancer (NSCLC) patients treated w...

Risk-stratified breast screening has been proposed as a strategy to overcome the limitations of age-based screening. A prospective cohort study was undertaken within the PERSPECTIVE I&I project, which will generate the first Canadian evidence on multifactorial breast cancer risk assessment in the population setting to inform the implementation of r...

BACKGROUND Artificial intelligence (AI) predictive models in primary healthcare can potentially lead to benefits for population health. Algorithms can identify more rapidly and accurately who should receive care and health services, but they could also perpetuate or exacerbate existing biases toward diverse groups. We noticed a gap in actual knowle...

Background Artificial intelligence (AI) predictive models in primary health care have the potential to enhance population health by rapidly and accurately identifying individuals who should receive care and health services. However, these models also carry the risk of perpetuating or amplifying existing biases toward diverse groups. We identified a...

Purpose We report outcomes of high-risk prostate cancer (PCa) patients, initially classified according to a 3-tier NCCN classification system, treated with external beam radiation therapy (EBRT) and high-dose-rate brachytherapy boost (HDR-BT). Patients were analyzed based on a re-stratification of their risk grouping using CAPRA score and a newer 5...

Dual‐energy X‐ray computed tomography consists of imaging objects using two incident X‐ray beams of different energy to distinguish the different compounds within a sample based on their density (electron density, ρ e ) and elemental composition (effective atomic number, Z eff ). The stoichiometric calibration for dual‐energy X‐ray computed tomogra...

Background: Recent advances in cancer biomarker development have led to a surge of distinct data modalities, such as medical imaging and histopathology. To develop predictive immunotherapy biomarkers, these modalities are leveraged independently, despite their orthogonality. This study aims to explore the cross-scale association between radiologica...

In this work, a framework was developed to access and process raw data from a commercial X-ray Computed Tomography (CT) scanner for research purposes. Our method requires vendor-provided binaries to convert the data to a readable format and also to remove the effect of proprietary beam hardening preprocessing. As a result, custom reconstruction tec...

Monte Carlo (MC) dose datasets are valuable for large-scale dosimetric studies. This work aims to build and validate a DICOM-compliant automated Monte Carlo dose recalculation pipeline with an application to the production of I-125 LDR prostate brachytherapy MC datasets. Built as a self-contained application, the recalculation pipeline ingested cli...

The objective of this study is to find reproducible and predictive radiomic features from Computed Tomography (CT) images that are correlated to clinical endpoints and immunohistochemistry (IHC) biomarkers in an immunotherapy treated non-small cell lung cancer (NSCLC) cohort. • Materials and Methods A retrospective study of NSCLC patients receiving...

Purpose: This study aims to identify robust and reproducible radiomic features from two IBSI-compliant pipelines to predict clinical outcomes and their association with immunohistochemistry markers in non-small cell lung cancer (NSCLC) patients who received immunotherapy. Methods: We analyzed data from 164 NSCLC of whom 34 also had IHC data. We ext...

The 2023 edition of the QBIN Scientific Day took place on May 25th in University of Laval, Québec city.

BACKGROUND Current literature identifies several potential benefits of artificial intelligence (AI) in community-based primary health care (CBPHC). However, there is a lack of understanding on how the risk of bias is considered in the development of CBPHC AI-based algorithms and to what extend they perpetuate or introduce potential biases toward gr...

Background: The current literature identifies several potential benefits of artificial intelligence models for populations' health and health care systems' efficiency. However, there is a lack of understanding on how the risk of bias is considered in the development of primary health care and community health service artificial intelligence algori...

Dual-energy CT (DECT) consists in imaging objects using two X-ray incident beams with different energies to discriminate and identify the phases within a sample based on its density (electron density, ρe) and elemental composition (effective atomic number, Zeff). Here, a stoichiometric calibration method, originally developed for medical purposes a...

Purpose/Objective(s) To report and compare PROs of an HDR brachytherapy (BB) combined to an ultra-hypo fractionated (UHF) prostate radiation therapy regimen as opposed to a moderate hypo fractionated (MHF). Materials/Methods This interim analysis of a prospective mono-centric phase 2 study includes 75 prostate cancer patients, mostly intermediate...

Purpose This study aims to report prognostic factors of clinical outcomes of prostate cancer (PCa) patients treated with permanent implant prostate brachytherapy (PIPB) at our institution. Materials and Methods The study sample consists of 2364 PCa patients treated with PIPB with or without cytoreductive antiandrogen therapy (ADT) between 1994 and...

Purpose The study aimed to report clinical outcomes of high-risk prostate cancer (PCa) patients treated with external beam radiation therapy (EBRT) and high dose-rate boost (HDRB) according to CAPRA score. Material and Methods The study sample consisted of 361 high-risk PCa patients stratified according to D'Amico classification and treated with E...

This paper reports a new experimental method applying medical X-ray computed tomography (CT) to estimate the bedload in sand transport. A set of current-generated sand ripple experiments were conducted in a small hydraulic flume inserted in the CT scanner. The methodology is based on the measurements of height, velocity and density of bedforms to e...

Dual-energy CT (DECT) consists in imaging objects using two X-ray incident beams with different energies in order to discriminate and identify the different phases within a sample based on their density (specifically electron density, ρe) and elemental composition (effective atomic number, Zeff). Here, a stoichiometric calibration method, originall...

Background: Dead-time correction is required for accurate quantitative SPECT-based dosimetry in the context of personalised 177Lu radiopharmaceutical therapy. We aimed to evaluate the impact of applying dead-time correction on the reconstructed SPECT image versus on the acquisition projections before reconstruction. Methods: Data from 16 SPECT/C...

1. Introduction The dual-energy CT (DECT) scanning consists in imaging objects with two different X-ray spectra and in combining the results to achieve the discrimination and the identification of materials based on their density and elemental composition [1]. Here, a stoichiometric calibration method, originally developed for medical purposes [2]...

Background: Dead-time correction is required for accurate quantitative SPECT-based dosimetry in the context of personalised ¹⁷⁷Lu radiopharmaceutical therapy. We aimed to evaluate the impact of applying dead-time correction on the reconstructed SPECT image vs. on the acquisition projections before reconstruction. Methods: Data from 16 SPECT/CT acq...

Medical CT-scanners measure the X-rays attenuation that go through a sample allowing the non-destructive 3D internal structure visualization of a wide range of objects. The attenuation depends on the interaction between incident beam and sample density and chemical composition. By scanning specimens using two different energies (low and high), the...

Background Accurate QSPECT is crucial in dosimetry-based, personalized radiopharmaceutical therapy with ¹⁷⁷ Lu and other radionuclides. We compared the quantitative performance of three NaI(Tl)-crystal SPECT/CT systems equipped with low-energy high-resolution collimators from two vendors (Siemens Symbia T6; GE Discovery 670 and NM/CT 870 DR). Meth...

In this work, a novel physics-rich beam-hardening correction algorithm was developed for X-ray Computed Tomography. This method uses the spectrum information, the detector response, the filter geometry and a calibration curve. The correction, which does not require prior material knowledge, was embedded in an iterative reconstruction algorithm, and...

Medical X-ray computed tomography (CT) can be used to rapidly and non-destructively characterize structure and density variations of geological specimens. More information about the nature of samples (electron density and elemental composition) can be retrieved using multi-spectral approaches. This paper explores one of them, a stoichiometric calib...

Purpose/Objective(s) To analyze the long term efficacity and safety of an UHF IGRT prostate treatment regimen with HDR BB. Materials/Methods In this single arm, prospective monocentric study, 28 patients with median age 69 years and D'Amico's intermediate risk prostate cancer (T1c, T2a-b), were recruited between the years 2015 and 2016 to an exper...

We sought to evaluate the feasibility of using machine learning (ML) algorithms for multipoint plastic scintillator detector (mPSD) calibration in high-dose-rate (HDR) brachytherapy. Dose measurements were conducted under HDR brachytherapy conditions. The dosimetry system consisted of an optimized 1-mm-core mPSD and a compact assembly of photomulti...

Background Polypharmacy is common among older adults and it represents a public health concern, due to the negative health impacts potentially associated with the use of several medications. However, the large number of medication combinations and sequences of use makes it complicated for traditional statistical methods to predict which therapy is...

Early detection of breast cancer through screening reduces breast cancer mortality. The benefits of screening must also be considered within the context of potential harms (e.g., false positives, overdiagnosis). Furthermore, while breast cancer risk is highly variable within the population, most screening programs use age to determine eligibility....

This paper describes the development and evaluation of a Canadian drug ontology (OCRx), built to provide a normalized and standardized description of drugs that are authorized to be marketed in Canada. OCRx aims to improve the usability and interoperability of drugs terminologies for a non-ambiguous access to drugs information that is available in...

Background: Dead time may affect the accuracy of quantitative SPECT (QPSECT), and thus of dosimetry. The aim of this study was to quantify the effect of dead time on 177Lu-QSPECT and renal dosimetry following peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumours. Methods: QSPECT/CT was performed on days 1 and 3 during 564 person...

Iterative reconstruction has been proven to be an effective tool for low-dose computed tomography imaging. However, this technology is currently not available in commercial diagnostic maxillofacial cone beam CT. For this technical note, an iterative reconstruction technique was applied to cone beam CT raw data of two maxillofacial clinical cases to...

Purpose: The purpose of this study was to evaluate whether the dose to bladder neck (BN) is a predictor of acute and late urinary toxicity after high-dose-rate brachytherapy (HDRB) boost for prostate cancer. Methods and materials: Between 2014 and 2016, patients with prostate cancer treated at our institution with external beam radiation therapy...

Purpose Currently in high-dose-rate (HDR) brachytherapy planning, manual fine-tuning of an objective function is a common practice. Furthermore, automated planning approaches such as multicriteria optimization (MCO) are still limited to the automatic generation of a single treatment plan. This study aims to quantify planning efficiency gains when u...

Purpose Monte Carlo (MC) simulations are highly desirable for dose treatment planning and evaluation in radiation oncology. This is true also in emerging nuclear medicine applications such as internal radiotherapy with radionuclides. The purpose of this study is the validation of irtGPUMCD, a GPU-based MC code for dose calculations in internal radi...

Purpose: We sought to evaluate the feasibility of using machine learning algorithms for multipoint plastic scintillator detector calibration in high-dose-rate brachytherapy. Methods: The dosimetry system consisted of an optimized 1-mm-core mPSD and a compact assembly of photomultiplier tubes coupled with dichroic mirrors and filters. An $^{192}$Ir...

Background Radiotherapy and brachytherapy are common treatments for localized prostate cancer (PCa). However, very few studies evaluated the association of variations in DNA damage response genes and treatment outcomes and toxicity in brachytherapy‐treated patients. Purpose To evaluate the association of inherited germline variations in DNA repair...

X-ray computed tomography (CT) is a powerful and non-destructive technique that allows visualization of objects internal structure (Mees et al., 2003). The resulting cross section is a single grayscale image corresponding to a generic attenuation of the material (μ), without having the possibility of separating the two influencing properties (densi...

Background: Personalization of 177Lu-based radionuclide therapy requires implementation of dosimetry methods that are both accurate and practical enough for routine clinical use. Quantitative single-photon emission computed tomography/computed tomography (QSPECT/CT) is the preferred scanning modality to achieve this and necessitates characterizing...

Background: Iterative reconstruction is well-established in diagnostic multidetector computed tomography (MDCT) for dose reduction and image quality enhancement. Its application to diagnostic cone beam computed tomography (CBCT) is only emerging and warrants a quantitative evaluation. Methods: Several phantoms and a canine head specimen were ima...

Currently in HDR brachytherapy planning, a manual fine-tuning of an objective function is necessary to obtain case-specific valid plans. This study intends to facilitate this process by proposing a patient-specific inverse planning algorithm for HDR prostate brachytherapy: GPU-based multi-criteria optimization (gMCO). Two GPU-based optimization eng...

In proton therapy, Monte Carlo simulations are desirable to accurately predict the delivered dose. This paper introduces and benchmarks pGPUMCD, a GPU-based Monte Carlo code implementing the physical processes required for proton therapy applications. In pGPUMCD, the proton transport is carried out in a voxelized geometry with a class II condensed...

Currently in HDR brachytherapy planning, a manual fine-tuning of an objective function is necessary to obtain case-specific valid plans. This study intends to facilitate this process by proposing a patient-specific inverse planning algorithm for HDR prostate brachytherapy: GPU-based multi-criteria optimization (gMCO). Two GPU-based optimization eng...

Purpose: To compare health-related quality of life (HRQOL) of high-dose-rate brachytherapy (HDRB) versus low dose-rate brachytherapy (LDRB) for localized prostate cancer in a multi-institutional phase 2 randomized trial. Methods and materials: Men with favorable-risk prostate cancer were randomized between monotherapy brachytherapy with either I...

AAPM poster for the GPU implementation of the Raystretch algorithm for dosimetry in low dose-rate brachytherapy

The current iterative approach to inverse planning of high dose rate (HDR) treatment planning can be time consuming. The purpose of this two-part study is to streamline the planning process while maintaining plan quality. In this second part, a multi-criteria optimization (MCO) planning algorithm is proposed and benchmarked against a standard plann...

High dose rate (HDR) brachytherapy planning usually involves an iterative process of refining planning objectives until a clinically acceptable plan is produced. The purpose of this two-part study is to improve current planning practice by designing a novel inverse planning algorithm based on multi-criteria optimization (MCO). In the first part, co...

Background: Four-dimensional cone beam computed tomography allows for temporally resolved imaging with useful applications in radiotherapy, but raises particular challenges in terms of image quality and computation time. Objective: The purpose of this work is to develop a fast and accurate 4D algorithm by adapting a GPU-accelerated ordered subse...

Purpose Iterative reconstruction algorithms in computed tomography (CT) require a fast method for computing the intersection distances between the trajectories of photons and the object, also called ray tracing or system matrix computation. This work focused on the thin‐ray model is aimed at comparing different system matrix handling strategies usi...

The equivalent restricted stopping power formalism is introduced for proton mean energy loss calculations under the continuous slowing down approximation. The objective is the acceleration of Monte Carlo dose calculations by allowing larger steps while preserving accuracy. The fractional energy loss per step length epsilon was obtained with a secan...

Purpose: To evaluate the risk of second malignancies after migration of seeds (MS) in prostate cancer patients treated with I-125 loose seeds brachytherapy. Materials and methods: Data from 2802 prostate cancer patients treated with I-125 loose seeds brachytherapy in three Canadian centres were reviewed. After seeds implant, all patients underwent...