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Magalie Viallon

Publications and source records attributed to Magalie Viallon.

7 recordsLinked to original sources
arXiv2026

The MYOSAIQ Challenge: Myocardial Segmentation with Automated Infarct Quantification

Late gadolinium enhancement (LGE) cardiac magnetic resonance (MR) imaging is the modality of choice to assess myocardial infarction (MI) lesions. Nowadays MI volume quantification is not performed routinely in clinical practice. Numerous deep learning (DL) methods have been developed to automate the segmentation of the myocardium and infarct regions. However, most studies rely on relatively small datasets which typically undergo pre-processing steps to standardize images and focus on a specific phase of myocardial infarction following reperfusion therapy. These limitations have impeded the development of models that are generalizable across diverse conditions and thus suitable for routine clinical use. To advance research and establish benchmarks in generalizable learning for myocardial infarct quantification, this paper presents findings from the Myocardial Segmentation with Automated Infarct Quantification (MYOSAIQ) challenge. The dataset set up for the challenge combines 439 CMR volumes from two multicenter clinical trials, with representative data acquired in acute and chronic phases after acute MI. Data were acquired in 16 centers using MRI scanners from three different vendors. Six teams participated until the end of the challenge, employing various baseline models, data augmentation techniques, and confidence strategies. To enhance the significance of this study, we compare the challengers' results with those of fine-tuned foundation models. Our results indicate that well-designed UNet-based techniques outperform fully automatic foundation models for LGE MR segmentation. While the best methods achieve high-quality and stable delineations of the left ventricle and myocardium under various conditions, they remain improvable in accurately segmenting infarct regions.

eess.IV↗
arXiv2026

Temporal interleaving artifacts in spiral MRSI: characterization and retrospective correction

Purpose: In Spiral Magnetic Resonance Spectroscopic Imaging (MRSI), achieving suitable spatio-temporal resolutions requires interleaving. Sampling inconsistencies occurring between temporally interleaved signals, -whether due to time-interleaved ADCs or phase/frequency mismatches in the excitation and demodulation stages-, result in artifacts in the recombined data. This paper proposes a mathematical description of these unavoidable artifacts and a postprocessing solution to circumvent the issues and mitigate them. Methods: The study proposed a detailed description and explanation of these artifacts using data acquired with MRSI interleaved sequence with gradients off, as well as standard interleaved FID sequence. The random signal mismatch between the interleaves was described as additional artifactual signals $ψ$(t) at each temporal interleave. A model was further proposed to match the acquired signal in relation to the ideal, artifact-free signal. Considering M interleaves, a correction method was derived relying on estimating 4 parameters in the $ψ$(t) model for each interleave by minimizing a multivariable cost function. This correction method was evaluated on spectra acquired from phantoms and in vivo acquisitions obtained in healthy volunteers. Results: The proposed correction method significantly reduced artifacts by a factor of 4 in the phantom and 1.8 in the healthy volunteers. This correction ensured accurate spectral quantification in regions where artifacts overlapped with the content of interest, such as lipids in subcutaneous fat. Additionally, it was demonstrated that appropriately selecting the number of temporal interleaves can shift the artifact away from the frequency of interest, leveraging the periodic and limited frequency span of the observed artifacts. Conclusion: In spiral-MRSI, temporal interleaves, while enhancing spectral bandwidth, introduced spurious content characterized by distinctive resonance frequencies and nonreproducible amplitudes and phases. The study proposes two solutions: manipulating the number of interleaves to control artifact frequency localization or using a retrospective correction method to approximate and attenuate artifacts.

eess.SP↗
arXiv2023

Alteration of skeletal muscle energy metabolism assessed by 31P MRS in clinical routine, part 1: Advanced Quality Control pipeline

Background: Implementing a standardized 31P-MRS dynamic acquisition protocol to evaluate skeletal muscle energy metabolism and monitor muscle fatigability1,2, while being compatible with various longitudinal clinical studies on diversified patient cohorts, requires a high level of technicality and expertise. Furthermore, processing data to obtain reliable results also demands a great degree of expertise from the operator. In this two-part article, we present an advanced quality control approach for data acquired using a dynamic 31P-MRS protocol. The aim is to provide decision support to the operator in order to assist in data processing and obtain reliable results based on objective criteria. We present first in part one, an advanced data quality control (QC) approach of a dynamic 31P-MRS protocol. Part two is an impact study demonstrating the added value of the QC approach to explore clinical results derived from two patient populations with significant fatigue: COVID19 and multiple sclerosis (MS). Experimental: 31P-MRS was performed on a 3T clinical MRI in 175 subjects from clinical and healthy control populations conducted in a University Hospital. An advanced data QC Score (QCS) was developed using multiple objective criteria. The criteria were based on current recommendations from the literature enriched by new proposals based on clinical experience. The QCS was designed to indicate valid and corrupt data and guide necessary objective data editing to extract as much valid physiological data as possible. Dynamic acquisitions using an MR-compatible ergometer ran over a rest(40s), exercise(2min), and a recovery phase(6min). Results: Using QCS enabled rapid identification of subjects with data anomalies allowing the user to correct the data series or reject them partially or entirely as well as identify fully valid datasets. Overall, the use of the QCS resulted in the automatic classification of 45% of the subjects including 58 participants that had data with no criterion violation and 21 participants with violations that resulted in the rejection of all dynamic data. The remaining datasets were inspected manually with guidance allowing acceptance of full datasets from an additional 80 participants and recovery phase data from an additional 16 subjects. Overall, more anomalies occurred with patient data (35% of datasets) compared to healthy controls (15% of datasets). Conclusion: This paper describes typical difficulties encountered during the dynamic acquisition of 31P-MRS. Based on these observations, a standardized data quality control pipeline was created and implemented in both healthy and patient populations. The QC scoring ensures a standardized data rejection procedure and rigorous objective analysis of dynamic 31P-MRS data obtained from patients. The contribution of this methodology contributes to efforts made to standardize the practices of the 31P-MRS that has been underway for a decade, with the ultimate goal of making it an empowered tool for clinical research.

eess.SP↗
arXiv2023

Alteration of skeletal muscle energy metabolism assessed by 31P MRS in clinical routine, part 2: Clinical application

Background: In this second part of a two-part paper, we intend to demonstrate the impact of the previously proposed advanced quality control pipeline. To understand its benefit and challenge the proposed methodology in a real scenario, we chose to compare the outcome when applying it to the analysis of two patient populations with a significant but highly different types of fatigue: COVID19 and multiple sclerosis (MS). Experimental: 31P-MRS was performed on a 3T clinical MRI, in 19 COVID19 patients, 38 MS patients, and 40 matched healthy controls. Dynamic acquisitions using an MR-compatible ergometer ran over a rest(40s), exercise(2min), and a recovery phase(6min). Long and short TR acquisitions were also made at rest for T1 correction. The advanced data quality control pipeline presented in part 1 is applied to the selected patient cohorts to investigate its impact on clinical outcomes. We first used power and sample size analysis to estimate objectively the impact of adding QCS. Then, comparisons between patients and healthy control groups using validated QCS were performed using unpaired T-tests or Mann-Whitney tests (p<0.05).Results: The application of the QCS resulted in increased statistical power, changed the values of several outcome measures, and reduced variability (SD). A significant difference was found between the T1PCr and T1Pi of MS patients and healthy controls. Furthermore, the use of a fixed correction factor led to systematically higher estimated concentrations of PCr and Pi than when using individually corrected factors. We observed significant differences between the two patient populations and healthy controls for resting [PCr] -- MS only, [Pi], [ADP], [H2PO4-] and pH -- COVID19 only, and post-exercise [PCr],[Pi] and [H2PO4-] - MS only. The dynamic indicators $τ$PCr, $τ$Pi, ViPCr and Vmax were reduced for COVID19 and MS patients compared to controls. Conclusion: Our results show that QCS in dynamic 31P-MRS studies results in smaller data variability and therefore impacts study sample size and power. Although QCS resulted in discarded data and therefore reduced the acceptable data and subject numbers, this rigorous and unbiased approach allowed for proper assessment of muscle metabolites and metabolism in patient populations. The outcomes include an increased metabolite T1, which directly affect the T1 correction factor applied to the amplitudes of the metabolite, and a prolonged $τ$PCr indicating reduced muscle oxidative capacity for patients with MS and COVID19.

eess.SP↗
arXiv2019

Robustly segmenting quadriceps muscles of ultra-endurance athletes with weakly supervised U-Net

In this study, segmentation of quadriceps muscle heads of ultra-endurance athletes was done using a multi-atlas segmentation and corrective leaning framework where the registration based multi-atlas segmentation step was replaced with weakly supervised U-Net. For the case with remarkably different morphology, our method produced improved accuracy, while reduced significantly the computation time.

eess.IV↗
arXiv2019

Evaluation of Peak Wall Stress in an Ascending Thoracic Aortic Aneurysm Using FSI Simulations: Effects of Aortic Stiffness and Peripheral Resistance

Purpose. It has been reported clinically that rupture or dissections in thoracic aortic aneurysms (TAA) often occur due to hypertension which may be modelled with sudden increase of peripheral resistance, inducing acute changes of blood volumes in the aorta. There is clinical evidence that more compliant aneurysms are less prone to rupture as they can sustain such changes of volume. The aim of the current paper is to verify this paradigm by evaluating computationally the role played by the variation of peripheral resistance and the impact of aortic stiffness onto peak wall stress in ascending TAA. Methods. Fluid-Structure Interaction (FSI) analyses were performed using patient-specific geometries and boundary conditions derived from 4D MRI datasets acquired on a patient. Blood was assumed incompressible and was treated as a non-Newtonian fluid using the Carreau model while the wall mechanical properties were obtained from the bulge inflation tests carried out in vitro after surgical repair. The Navier Stokes equations were solved in ANSYS Fluent. The Arbitrary Lagrangian Eulerian formulation was used to account for the wall deformations. At the interface between the solid domain and the fluid domain, the fluid pressure was transferred to the wall and the displacement of the wall was transferred to the fluid. The two systems were connected by the System Coupling component which controls the solver execution of fluid and solid simulations in ANSYS. Fluid and solid domains were solved sequentially starting from the fluid simulations. Results. Distributions of blood flow, wall shear stress and wall stress were evaluated in the ascending thoracic aorta using the FSI analyses. We always observed a significant flow eccentricity in the simulations, in very good agreement with velocity profiles measured using 4D MRI. The results also showed significant increase of peak wall stress due to the increase of peripheral resistance and aortic stiffness. In the worst case scenario, the largest peripheral resistance (10 10 kg.s.m-4) and stiffness (10 MPa) resulted in a maximal principal stress equal to 702 kPa, whereas it was only 77 kPa in normal conditions. Conclusions. This is the first time that the risk of rupture of an aTAA is quantified in case of the combined effects of hypertension and aortic stiffness increase. Our findings suggest that a stiffer TAA may have the most altered distribution of wall stress and an acute change of peripheral vascular resistance could significantly increase the risk of rupture for a stiffer aneurysm.

physics.med-ph↗