Guy Cloutier’s research while affiliated with University of Quebec in Montreal and other places

Purpose. To investigate the diagnostic performance of ultrasound (US)-based shear wave speed (SWS), shear wave attenuation (SWA), and combination of them as shear wave viscoelastography (SWVE) methods in patients undergoing US to characterize focal liver nodules. Materials and methods. In this prospective cross-sectional study, 70 patients with 72 nodules were enrolled. Investigational US and clinical magnetic resonance imaging (MRI) examinations were performed in all participants. The composite reference standard included MRI or histopathology to differentiate benign and malignant nodules. A linear discriminant analysis (LDA) was used to assess the combination of SWVE methods. Analyzes included Mann–Whitney U test, receiver operating characteristic analysis, and computation of sensitivity and specificity at the point that maximized the Youden index. Results. Mean SWS was significantly higher in malignant than benign nodules (2.49 ± 0.76 m s⁻¹ vs. 1.72 ± 0.70, p< 0.001), whereas SWA was lower (0.56 ± 0.30 vs. 1.10 ± 0.43 Np/m/Hz, p < 0.001). To differentiate between malignant and benign nodules, SWS with a threshold of 2.43 m s⁻¹ achieved a sensitivity of 0.54 (95% confidence interval (CI): 0.38-0.69) and a specificity of 0.88 (CI: 0.74-0.95). SWA with a threshold of 0.81 Np/m/Hz yielded a sensitivity of 0.81 (CI: 0.66-0.90) and a specificity of 0.74 (CI: 0.58-0.86). Combining these SWVE methods using a LDA resulted in a sensitivity of 0.81 (CI: 0.66-0.91) and a specificity of 0.86 (CI: 0.71-0.94). Conclusion. Malignant nodules had higher SWS and lower SWA than benign ones. The combination of SWS and SWA in a LDA classification algorithm increased the diagnostic performance.

Ultrasound is considered a key modality for the clinical assessment of hepatic steatosis (i.e., fatty liver) due to its non-invasiveness and availability. Deep learning methods have attracted considerable interest in this field, as they are capable of learning patterns in a collection of images and achieve clinically comparable levels of accuracy in steatosis grading. However, variations in patient populations, acquisition protocols, equipment, and operator expertise across clinical sites can introduce domain shifts that reduce model performance when applied outside the original training setting. In response, unsupervised domain adaptation techniques are being investigated to address these shifts, allowing models to generalize more effectively across diverse clinical environments. In this work, we propose a test-time batch normalization technique designed to handle domain shift, especially for changes in label distribution, by adapting selected features of batch normalization layers in a trained convolutional neural network model. This approach operates in an unsupervised manner, allowing robust adaptation to new distributions without access to label data. The method was evaluated on two abdominal ultrasound datasets collected at different institutions, assessing its capability in mitigating domain shift for hepatic steatosis classification. The proposed method reduced the mean absolute error in steatosis grading by 37% and improved the area under the receiver operating characteristic curve for steatosis detection from 0.78 to 0.97, compared to non-adapted models. These findings demonstrate the potential of the proposed method to address domain shift in ultrasound-based hepatic steatosis diagnosis, minimizing risks associated with deploying trained models in various clinical settings.

People with HIV (PWH) have an increased risk of developing cardiovascular disease (CVD). Our recent data demonstrated that the multi-isoform proinflammatory cytokine IL-32 is upregulated in PWH and is associated with arterial stiffness and subclinical atherosclerosis. However, the mechanisms by which IL-32 contributes to the pathogenesis of these diseases remain unclear. Here, we show that while the less expressed IL-32α isoform induces the differentiation of human classical monocytes into the calcium-resorbing osteoclast cells, the dominantly expressed isoforms IL-32β and IL-32γ suppress this function through the inhibition of TGF-β and induce the differentiation of monocytes into the calcium-depositing osteocalcin+ osteoblasts. These results aligned with the increase in plasma levels of osteoprotegerin, a biomarker of vascular calcification, and its association with the presence of coronary artery subclinical atherosclerosis and calcium score in PWH. These findings support a novel role for the proinflammatory cytokine IL-32 in the pathophysiology of CVD by increasing vascular calcification in PWH.

Objectives To compare thoracolumbar fascia (TLF) shear strain between individuals with and without nonspecific low back pain (NSLBP), investigate its correlation with symptoms, and assess a standardized massage technique’s impact on TLF shear strain. Methods Participants were prospectively enrolled between February 2021 and June 2022. Pre- and post-intervention TLF ultrasound and pain/disability questionnaires were conducted. Cumulated (C|ShS| L ) and maximum (Max|ShS| L ) shear strain parameters were computed from radiofrequency data, and TLF thickness was measured on reconstructed B-mode images. Statistical analysis included linear mixed-effects regression. Results Thirty-two NSLBP participants (mean age, 57 ± 9 years [standard deviation]; 21 women) and 32 controls (51 ± 10 years; 22 women) ( p = 0.02) were enrolled. The mean shear strain was higher in NSLBP participants (C|ShS| L : 327.1% ± 106.0 vs 290.2% ± 99.8, p < 0.0001; Max|ShS| L : 8.1% ± 2.8 vs 7.0% ± 2.4, p < 0.0001) than controls, while mean TLF thickness (1.6 mm ± 1.0 vs 1.5 mm ± 0.9; p = 0.43) was comparable. Elastography parameters correlated with pain [C|ShS| L estimate [β], 0.01 [95% CI: 0.002, 0.02]; p = 0.02); Max|ShS| L [β] , 0.003 [95% CI: 0.001, 0.005]; p < 0.001)] and disability [C|ShS| L [β] 0.02 [95% CI: 0.005, 0.03]; p = 0.009); Max|ShS| L [β] 0.003 [95% CI: 0.001, 0.006]; p = 0.002)] scores. Neither C|ShS| L (β, 0.13 [−0.27, 0.53]; p = 0.53) nor Max|ShS| L (β, −0.02 [−0.10, 0.05]; p = 0.59) changed post-intervention. Conclusion Individuals with NSLBP demonstrated elevated TLF shear strain compared to controls, with similar TLF thickness. The shear strain correlated with pain and disability scores, yet a brief massage did not influence shear strain. Trial registration Clinicaltrials.gov, NCT04716101. Registered 14 January 2021, https://clinicaltrials.gov/study/NCT04716101 . Critical relevance statement Ultrasound shows elevated TLF shear strain in lower back pain sufferers compared to controls. This correlates with symptoms, suggesting a role as a pain generator. Further investigation into its anatomy, mechanical characteristics, and pathophysiology is crucial for better understanding. Key Points Structural and mechanical alterations of the TLF may contribute to low back pain. Elevated TLF lateral shear strain was found in patients with NSLBP. A brief standardized massage therapy technique did not influence elastography parameters. Graphical Abstract

The ultrasound backscatter coefficient is a frequency-dependent quantity intrinsic to biological tissues that can be recovered from backscattered radiofrequency signals, granted acquisitions on a reference phantom are available under the same system’s settings. A phantom-free backscatter coefficient estimation method is proposed based on Gaussian-shaped approximation of the point spread function (electronics and piezoelectric characteristics of the scanner’s probe) and the effective medium theory combined with the structure factor model, albeit the proposed approach is amenable to other models. Meanwhile, the total attenuation due to intervening tissues is refined from its theoretical value, which is based on reported average behaviors of tissues, while allowing correction for diffraction due to the probe’s geometry. The reference phantom method adapted to a similar approach except for the Gaussian approximation is also presented. The proposed phantom-free and reference phantom methods were compared on ten COVID-19 positive patients and twelve control subjects with measures on femoral veins and arteries. In this context, red blood cells are viewed as scatterers that form aggregates increasing the backscatter under the COVID-19 inflammatory condition. The considered model comprises five parameters, including the mean aggregate size estimated according to polydispersity of aggregates’ radii, and anisotropy of their shape. The mean aggregate size over the two proposed methods presented an intraclass correlation coefficient of 0.964 for consistency. The aggregate size presented a significant difference between the two groups with either two methods, despite the confounding effect of the maximum Doppler velocity within the blood vessel and its diameter.

Background Intrinsic activation MR elastography (iMRE) uses cardiovascular pulsations to assess tissue viscoelastic properties. Applying it to focal liver lesions extends its capabilities. Purpose To assess the viscoelastic parameters of focal liver lesions measured by iMRE and compare its diagnostic performance with extrinsic MRE (eMRE) for differentiating malignant and benign lesions. Study type Prospective. Population A total of 55 participants underwent MRI with research MRE sequences; 32 participants with 17 malignant and 15 benign lesions underwent both iMRE and eMRE. Field Strength/Sequence iMRE at ~1 Hz heart rate used a 3 T scanner with a modified four‐dimensional (4D)‐quantitative flow gradient‐echo phase contrast and low‐velocity encoding cardiac‐triggered technique. eMRE employed a gradient‐echo sequence at 30, 40, and 60 Hz. Assessment Liver displacements were measured using 4D‐phase contrast and reconstructed via a nonlinear inversion algorithm to determine shear stiffness (SS) and damping ratio (DR). iMRE parameters were normalized to the corresponding values from the spleen. Lesions were manually segmented, and image quality was reviewed. Statistical Tests Kruskal–Wallis, Mann–Whitney, Dunn's test, and areas under receiver operating characteristic curves (AUC) were assessed. Results SS was significantly higher in malignant than benign lesions with iMRE at 1 Hz (3.69 ± 1.31 vs. 1.63 ± 0.45) and eMRE at 30 Hz (3.76 ± 1.12 vs. 2.60 ± 1.26 kPa), 40 Hz (3.76 ± 1.12 vs. 2.60 ± 1.26 kPa), and 60 Hz (7.32 ± 2.87 vs. 2.48 ± 1.12 kPa). DR was also significantly higher in malignant than benign lesions at 40 Hz (0.36 ± 0.11 vs. 0.21 ± 0.01) and 60 Hz (0.89 ± 0.86 vs. 0.22 ± 0.09). The AUC were 0.86 for iMRE SS, 0.87–0.98 for eMRE SS, 0.47 for iMRE DR, and 0.62–0.86 for eMRE DR. Data Conclusion Cardiac‐activated iMRE can characterize liver lesions and differentiate malignant from benign lesions through normalized SS maps. Level of Evidence 2 Technical Efficacy Stage 2

Quantitative ultrasound (QUS) and ultrasound-based elastography techniques are emerging as non-invasive effective methods for assessing chronic liver disease. They are more accurate than B-mode imaging alone and more accessible than MRI as alternatives to liver biopsy. Early detection and monitoring of diffuse liver processes such as steatosis, inflammation, and fibrosis play an important role in guiding patient management. The most widely available and validated techniques are attenuation-based QUS techniques and shear-wave elastography techniques that measure shear-wave speed. Other techniques are supported by a growing body of evidence and are increasingly commercialized. This review explains general physical concepts of QUS and ultrasound-based elastography techniques for evaluating chronic liver disease. The first section describes QUS techniques relying on attenuation, backscatter, and speed of sound. The second section discusses ultrasound-based elastography techniques analyzing shear-wave speed, shear-wave dispersion, and shear-wave attenuation. With an emphasis on clinical implementation, each technique's diagnostic performance along with thresholds for various clinical applications are summarized, to provide guidance on analysis and reporting for radiologists. Measurement methods, advantages, and limitations are also discussed. The third section explores developments in quantitative contrast-enhanced and vascular ultrasound that are relevant to chronic liver disease evaluation.

Objectives To report the current elastography methods used to quantify back muscles’ biomechanical characteristics in patients with musculoskeletal disorders (MSKd) and inform on their reliability, validity, and responsiveness. Methods MEDLINE, Embase, CINAHL, Cochrane library and grey literature were consulted. Predefined criteria allowed for study selection and data extraction. The quality of evidence was rated using the COSMIN tool. Data were meta-analyzed in terms of pooled intraclass correlation coefficient (pICC) for reliability and pooled standardized mean difference (pSMD) for validity and responsiveness. Heterogeneity was assessed. Results Seventy-nine studies were included in the meta-analysis (total number of participants N = 3178). Three elastography methods were identified: strain imaging (SI; number of cohorts M = 26), shear wave imaging (SWI; M = 50), and vibration sonoelastography (VSE; M = 3). Strain imaging and SWI studies reported good reliability measurement properties (pICC > 0.70) and a medium pSMD (0.58 for SI and 0.60 for SWI; p ≤ 0.020) in discriminating MSKd from controls’ condition (validity). Strain imaging studies reported a medium pSMD (0.64; p = 0.005) in detecting within-group changes over time, whereas SWI pSMD was very high (1.24; p = 0.005). Only SWI reported significant but small pSMD (0.30; p = 0.003) in detecting between-group changes over time. The small number of VSE studies could not be meta-analyzed. Heterogeneity was high (I-squared > 90%; p < 0.001). Conclusions Elastography presents good reliability results and a medium pSMD in discriminating MSKd from control conditions. Responsiveness data suggest detectable changes within groups over time using SI and SWI, calling for long-term longitudinal studies. Assessing changes between groups over time using elastography still needs to be proven. Highly significant heterogeneity limits meta-analytic results. Critical relevance statement While still in its early-stage exploration phase, musculoskeletal ultrasound elastography may reliably quantify back muscles’ biomechanics in asymptomatic individuals, moderately discriminate back musculoskeletal disorders and detect biomechanical changes over time in these conditions, calling for long-term longitudinal studies. Key Points Ultrasound elastography is reviewed for back pain and related musculoskeletal disorder assessments. Growing literature supports good reproducibility, some validity and responsiveness. Back muscle elastography considers assumptions calling for standardized protocols. Graphical Abstract

Objective To assess the reproducibility of six ultrasound (US)‐determined shear wave (SW) viscoelastography parameters for assessment of mechanical properties of the liver in volunteers and patients with biopsy‐proven metabolic dysfunction‐associated steatotic liver disease (MASLD) or metabolic dysfunction‐associated steatohepatitis (MASH). Methods This prospective, cross‐sectional, institutional review board‐approved study included 10 volunteers and 20 patients with MASLD or MASH who underwent liver US elastography twice, at least 2 weeks apart. SW speed (SWS), Young's modulus ( E ), shear modulus ( G ), SW attenuation (SWA), SW dispersion (SWD), and viscosity were computed from radiofrequency data recorded on a research US scanner. Linear mixed models were used to consider the sonographer on duty as a confounder. The reproducibility of measurements was assessed by intraclass correlation coefficient (ICC), coefficient of variation (CV), reproducibility coefficient (RDC), and Bland‐Altman analyses. Results The sonographer performing the exam had no impact on viscoelastic parameters ( P > .05). ICCs of SWS, E , G , SWA, SWD, and viscosity were, respectively, 0.89 (95% confidence intervals [CI]: 0.79‐0.95), 0.81 (95% CI: 0.79‐0.95), 0.90 (95% CI: 0.80‐0.95), 0.96 (95% CI: 0.93‐0.98), 0.78 (95% CI: 0.60‐0.89), and 0.90 (95% CI: 0.80‐0.95); CVs were 11.9, 23.3, 24.2, 10.1, 29.0, and 32.2%; RDCs were 33.0, 64.5, 66.9, 27.7, 80.3, and 89.2%, and Bland‐Altman mean biases and 95% limits of agreement were −0.05 (−0.45, 0.35) m/s, −0.61 (−5.33, 4.10) kPa, −0.25 (−2.06, 1.56) kPa, −0.01 (−0.27, 0.26) Np/m/Hz, −0.09 (−7.09, 6.91) m/s/kHz, and −0.33 (−2.60, 1.94) Pa/s, between the two visits. Conclusion US‐determined viscoelastography parameters can be measured with high reproducibility and consistency between two visits 2 weeks apart on the same ultrasound machine.