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Numerous filtering methods have been proposed for estimating asymmetric orientation distribution functions (ODFs) for diffusion magnetic resonance imaging (dMRI). It can be hard to make sense of all these different methods, which share similar features and result in similar outputs. In this work, we disentangle these many filtering methods proposed in the past and combine them into a novel, unified filtering equation. We also propose a self-supervised data-driven approach for calibrating the filtering parameter values. Our equation is implemented in an open-source GPU-accelerated python software to facilitate its integration into any existing dMRI processing pipeline. Our method is applied on multi-shell multi-tissue fiber ODFs from the Human Connectome Project dataset (1.25 mm3 native resolution) and on single-shell single-tissue fiber ODFs from the Bilingualism and the Brain dataset (2.0 mm3 isotropic resolution) to evaluate the occurrence of asymmetric patterns on different spatial resolutions, representing cutting-edge and “clinical” research data. Asymmetry measures such as the asymmetric index (ASI) and our novel number of fiber directions (NuFiD) are then used to explain the behaviour of our method in these images. The contributions of this work are: (i) the disentanglement and unification of filtering methods for estimating asymmetric ODFs; (ii) a calibration method for automatically fixing the parameters governing the filtering; (iii) an open-source, efficient implementation of our unified filtering method for estimating asymmetric ODFs; (iv) a novel number of fiber directions (NuFiD) index for explaining asymmetric fiber configurations; and (v) a novel template of asymmetries, revealing that our filtering method estimates asymmetric configurations in at least 50% of the brain voxels (∼31% of the white matter and ∼63% of the gray matter). [Display omitted] •An open-source unified filtering method for estimating asymmetric ODFs on the GPU.•A data-driven calibration method for fixing the filtering parameter values.•Our novel NuFiD index gives a new insight into how asymmetries occur in the brain.•Our MNI-aligned template explains where our filtering estimates asymmetries.•Branching, fanning, bending, and ending ODFs are found in ∼50% of WM and GM.

This study aimed to preliminary test the effectiveness of 12-week virtual physical prehabilitation program followed by a maintenance phase. The main objective was to estimate the extent to which it affects exercise capacity, frailty, lower limb strength and health-related quality of life (HRQOL) in lung transplant candidates. The program offered supervised strengthening exercises, independent aerobic exercises and weekly phone calls (maintenance phase). Primary outcome was the six-minute walk distance (6MWD). Secondary outcomes: the Short Physical Performance Battery (SPPB), five-times sit-to-stand test (5STS), the St George’s Respiratory Questionnaire (SGRQ) for HRQOL. Twenty patients were included (mean age 57.9; 6 women/14 men); fourteen completed the prehabilitation program and 5 completed the maintenance phase. There was no statistically significant improvement in 6MWD, SPPB or SGRQ after the 12-week program. Most patients either maintained or improved the 6MWT and SPPB scores. There was a significant improvement in the 5STS. After the maintenance phase, most patients either improved or maintained their scores in all outcomes except for the sub-score of symptoms in the SGRQ. A 12-week virtual physical prehabilitation program with a 12-week maintenance phase can help lung transplant candidates improve or maintain their physical function while waiting for transplantation.

Severe COVID-19 appears to disproportionately affect people who are immunocompromised, although Canadian data in this context are limited. We sought to determine factors associated with severe COVID-19 outcomes among recipients of organ transplants across Canada. We performed a multicentre, prospective cohort study of all recipients of solid organ transplants from 9 transplant programs in Canada who received a diagnosis of COVID-19 from March 2020 to November 2021. Data were analyzed to determine risk factors for oxygen requirement and other metrics of disease severity. We compared outcomes by organ transplant type and examined changes in outcomes over time. We performed a multivariable analysis to determine variables associated with need for supplemental oxygen. A total of 509 patients with solid organ transplants had confirmed COVID-19 during the study period. Risk factors associated with needing (n = 190), compared with not needing (n = 319), supplemental oxygen included age (median 62.6 yr, interquartile range [IQR] 52.5–69.5 yr v. median 55.5 yr, IQR 47.5–66.5; p < 0.001) and number of comorbidities (median 3, IQR 2–3 v. median 2, IQR 1–3; p < 0.001), as well as parameters associated with immunosuppression. Recipients of lung transplants (n = 48) were more likely to have severe disease with a high mortality rate (n = 15, 31.3%) compared with recipients of other organ transplants, including kidney (n = 48, 14.8%), heart (n = 1, 4.4%), liver (n = 9, 11.4%) and kidney–pancreas (n = 3, 12.0%) transplants (p = 0.02). Protective factors against needing supplemental oxygen included having had a liver transplant and receiving azathioprine. Having had 2 doses of SARS-CoV-2 vaccine did not have an appreciable influence on oxygen requirement. Multivariable analysis showed that older age (odds ratio [OR] 1.04, 95% confidence interval [CI] 1.02–1.07) and number of comorbidities (OR 1.63, 95% CI 1.30–2.04), among other factors, were associated with the need for supplemental oxygen. Over time, disease severity did not decline significantly. Despite therapeutic advances and vaccination of recipients of solid organ transplants, evidence of increased severity of COVID-19, in particular among those with lung transplants, supports ongoing public health measures to protect these at-risk people, and early use of COVID-19 therapies for recipients of solid organ transplants.

The lattice Boltzmann method is used to model a horizontal axis tidal turbine. Because tidal turbines generally operate in highly turbulent flows, a synthetic eddy method is implemented to generate realistic turbulent inflow condition. The approach makes use of the open-source code Palabos. Large eddy simulation is employed. A coupling between an immersed boundary method and a wall model is realized to model the turbine. Calculations are performed at two different turbulence rates. The upstream flow condition is first set up to match with experimental results. Numerical simulations of a tidal turbine with realistic turbulent inflow conditions are then realized with the lattice Boltzmann method. The approach is found to be in good agreement with experimental data. Cases with three different inflow turbulence rates are simulated. An almost linear evolution with the turbulence rate is observed for the axial velocity deficit. An analysis of the propagation of tip-vortices in the close wake is carried out. It is found that turbulence has a great impact on the tip-vortices propagation envelope.

La forme grave de COVID-19 semble affecter de manière disproportionnée les gens immunovulnérables, même si les données canadiennes dans ce contexte sont limitées. Nous avons voulu déterminer quels facteurs sont associés aux paramètres de la forme grave de COVID-19 chez les receveurs de transplantations au Canada. Nous avons procédé à une étude de cohorte multicentrique prospective regroupant tous les receveurs d’une transplantation d’organe plein ayant reçu un diagnostic de COVID-19 suivis dans 9 programmes de transplantation au Canada entre mars 2020 et novembre 2021. Les données ont été analysées afin de dégager les facteurs de risque à l’égard du recours à l’oxygénothérapie et autres critères de la gravité de la maladie. Nous avons comparé les paramètres selon le type d’organe transplanté et suivi l’évolution des paramètres au fil du temps. Nous avons procédé à une analyse multivariée pour déterminer quelles variables sont associées au recours à l’oxygénothérapie. En tout, 509 patients ayant reçu une transplantation d’organe plein ont contracté la COVID-19 durant la période de l’étude. Les facteurs de risque associés au recours à l’oxygénothérapie (n = 190) ou non (n = 319) incluaient l’âge (âge médian 62,6 ans, intervalle interquartile [II] 52,5–69,5 ans c. âge médian 55,5 ans, II 47,5–66,5; p < 0,001) et le nombre de comorbidités (nombre médian 3, II 2–3 c. nombre médian 2, II 1–3; p < 0,001), de même que les paramètres concernant l’immunosuppression. Les receveurs d’une transplantation pulmonaire (n = 48) étaient plus susceptibles de souffrir d’une forme grave de la maladie, avec un taux de mortalité élevé (n = 15, 31,3 %) comparativement aux receveurs d’autres organes, y compris le rein (n = 48, 14,8 %), le cœur (n = 1, 4,4 %), le foie (n = 9, 11,4 %) et le rein–pancréas (n = 3, 12,0 %) (p = 0,02). Les facteurs protecteurs contre le recours à l’oxygénothérapie incluaient le fait d’avoir subi une transplantation hépatique et de recevoir de l’azathioprine. Le fait d’avoir reçu 2 doses de vaccin anti-SRAS-CoV-2 n’a pas eu d’influence appréciable sur le recours à l’oxygénothérapie. L’analyse multivariée a montré que l’âge avancé (rapport des cotes [RC] 1,04, intervalle de confiance [IC] de 95 % 1,02–1,07) et le nombre de comorbidités (RC 1,63, IC de 95 % 1,30–2,04), entre autres facteurs, étaient associés au recours à l’oxygénothérapie. La gravité de la maladie n’a pas considérablement diminué au fil du temps. Malgré les progrès thérapeutiques et la vaccination des receveurs d’une transplantation d’organe plein, les signes de gravité accrue de la COVID-19, en particulier chez les receveurs d’une transplantation pulmonaire, justifient le maintien des mesures de santé publique pour protéger ces personnes à risque, et l’utilisation hâtive de traitements contre la COVID-19 chez les receveurs d’une transplantation d’organe plein.

In primates, the putamen and the caudate nucleus are connected by ~1 mm‐thick caudolenticular gray matter bridges (CLGBs) interspersed between the white matter bundles of the internal capsule. Little is understood about the functional or microstructural properties of the CLGBs. In studies proposing high resolution diffusion magnetic resonance imaging (dMRI) techniques, CLGBs have been qualitatively identified as an example of superior imaging quality; however, the microstructural properties of these structures have yet to be examined. In this study, it is demonstrated for the first time that dMRI is sensitive to an organized anisotropic signal oriented in the direction parallel to the CLGBs, suggesting that dMRI could be a useful imaging method for probing the microstructure of the CLGBs. To demonstrate the anisotropic diffusion signal is coherently organized along the extent of the CLGBs and to enable a subsequent CLGB microstructural measurement, a customized tractography seeding and filtering method is proposed that utilizes the shape of the human striatum (putamen + caudate nucleus) to reconstruct the CLGBs in 3D. The proposed seeding strategy seeds tractography streamlines outward and normal to the surface of a 3D model of the striatum such that reconstructed streamlines are more likely to follow the diffusion signal peaks aligned parallel to the CLGBs. The method is applied to three different diffusion datasets, namely a high resolution 760 μm isotropic diffusion dataset acquired on a single subject, the test–retest cohort included as part of the human connectome project (N = 44) with diffusion data acquired at 1.25 mm isotropic, and a locally acquired “clinical” test–retest dataset acquired at 2.0 mm isotropic (N = 24). Reconstructed CLGBs directly overlap expected gray matter regions in the human brain for all three datasets. In addition, the method is shown to accurately reconstruct CLGBs repeatedly across multiple test–retest cohorts. The tractography CLGB reconstructions are then used to extract a quantitative measurement of microstructure from a local model of the diffusion signal along the CLGBs themselves. This is the first work to comprehensively study the CLGBs in vivo using dMRI and presents techniques suitable for future human neuroscience studies targeting these structures. This work demonstrates that diffusion MRI is sensitive to an anisotropic signal oriented along the caudolenticular gray matter bridges (CLGBs) of the striatum. A tractography approach was developed to track this signal, reconstructing the CLGBs and demonstrating that the signal is present across the entirety of these gray matter structures.

The segmentation of brain structures is a key component of many neuroimaging studies. Consistent anatomical definitions are crucial to ensure consensus on the position and shape of brain structures, but segmentations are prone to variation in their interpretation and execution. White‐matter (WM) pathways are global structures of the brain defined by local landmarks, which leads to anatomical definitions being difficult to convey, learn, or teach. Moreover, the complex shape of WM pathways and their representation using tractography (streamlines) make the design and evaluation of dissection protocols difficult and time‐consuming. The first iteration of Tractostorm quantified the variability of a pyramidal tract dissection protocol and compared results between experts in neuroanatomy and nonexperts. Despite virtual dissection being used for decades, in‐depth investigations of how learning or practicing such protocols impact dissection results are nonexistent. To begin to fill the gap, we evaluate an online educational tractography course and investigate the impact learning and practicing a dissection protocol has on interrater (groupwise) reproducibility. To generate the required data to quantify reproducibility across raters and time, 20 independent raters performed dissections of three bundles of interest on five Human Connectome Project subjects, each with four timepoints. Our investigation shows that the dissection protocol in conjunction with an online course achieves a high level of reproducibility (between 0.85 and 0.90 for the voxel‐based Dice score) for the three bundles of interest and remains stable over time (repetition of the protocol). Suggesting that once raters are familiar with the software and tasks at hand, their interpretation and execution at the group level do not drastically vary. When compared to previous work that used a different method of communication for the protocol, our results show that incorporating a virtual educational session increased reproducibility. Insights from this work may be used to improve the future design of WM pathway dissection protocols and to further inform neuroanatomical definitions. Structural connectivity reconstructed using diffusion magnetic resonance imaging tractography can isolate white‐matter pathways using a technique called virtual dissection. Human variability in the interpretation and execution of the virtual dissection causes a measurement error in the digital reconstruction of pathways. This work quantifies the variability of a specific protocol taught using an online course and the impact of repeating the procedures (practices) on variability.

Disclosure: F. Perreault: None. S. Parisien-Lasalle: None. J. Morisset: None. C. Poirier: None. C. Beauregard: None. R. Agnès: None. P. Ferraro: None. I. Bourdeau: None. Background: Pheochromocytomas (PHEOs) and paragangliomas (PGLs) (PPGLs) are rare tumors arising from the chromaffin cells. Approximately 40% of PPGL patients carry germline mutations in susceptibility genes, including pseudohypoxic related SDHx and VHL genes. An association was described between hypoxemia and PPGLs, notably in higher altitude exposition and cyanotic congenital heart disease. In the latter, a chronic hypoxemic state can lead to gain of function somatic mutations in the EPAS1 gene that encodes for hypoxia-inducible factor 2-alpha (HIF-2) (1). Objective: To describe a rare case of PHEO in a pulmonary transplant patient and characterize the genetic background of the tumor. Clinical Case: A 66 year-old man underwent an unilateral lung transplant at the age of 47 for chronic obstructive pulmonary disease associated with alpha-1 antitrypsin deficiency. He required home oxygen therapy for 3 years prior to transplant and was known for new onset diabetes after transplant, chronic kidney disease, hypertension and paroxysmal atrial tachycardia. His family history was non-contributing. Nineteen years after transplant, a thoracic CT-scan showed a 6.1 cm x 3.9 cm right adrenal mass (HU of 7). Retrospectively, the mass had been present for the last seven years, and increased progressively in size. Diagnosis of PHEO was confirmed by the 24-h urinary catecholamines (norepinephrine 713 nmol/d (N< 650), epinephrine 588 nmol/d (N < 145), normetanephrines 900 nmol/d (N < 600) and metanephrines 1191 nmol/d (N < 370)). Chromogranin A was elevated (3297 ng/mL (N < 104)). The adrenal mass showed no uptake at 18F-FDG PET/CT imaging but fixation at MIBG scintigraphy. The patient received alpha blockers and underwent a laparoscopic right adrenalectomy. The pathology report confirmed a PHEO with a PASS score of 8 to 10. Eighteen months following the surgery, the patient showed no signs of biochemical or radiological recurrence. Genetic studies: 1) Germline PPGL multigene panel: After consent, the patient underwent a panel of 14 susceptibility genes for PPGLs (INVITAE, CA, USA) that revealed no pathogenic variants. 2) Somatic genetic analysis for EPAS1 gene: PHEO DNA was extracted and exons 9, 12 and 16 of the EPAS1 gene were studied by Sanger Sequencing. No pathogenic variants were identified.Conclusion: We report a rare case of PHEO in a pulmonary transplant patient. Our genetic analyses demonstrated the absence of a pathogenic germline variant in known susceptibility PPGL genes and no somatic mutations in the EPAS1 gene. Further work is needed to better understand the genetic and molecular events leading to PHEO in this specific case and determine its possible relationship with hypoxemia. (1) Vaidya A, Flores SK, Cheng Z-M, Nicolas M, Deng Y, Opotowsky AR, et al. EPAS1 Mutations and Paragangliomas in Cyanotic Congenital Heart Disease. New England Journal of Medicine. 2018;378(13):1259-61. Presentation: Saturday, June 17, 2023

To study the prevalence and impact of pain on the quality of life (QOL) of lung transplant recipients. Prospective, observational, cross-sectional study. Ninety-six lung transplant recipients (> 3 months after transplantation) completed questionnaires measuring the severity and impact of pain (Brief Pain Inventory), anxiety (State Trait Anxiety Inventory), QOL (Short Form-36 version 2 [SF-36v2]), and depression (Beck Depression Inventory [BDI]). University medical center lung transplant outpatient clinic. The prevalence of pain in lung transplant recipients was 49%. Patients with pain were older, more likely to have undergone unilateral lung transplantation (64% vs 40%, p = 0.03), and were more likely to have lung emphysema (55% vs 38%, p = 0.004). Only a pulmonary diagnosis of lung emphysema remained an independent predictor for postoperative pain in a logistic regression model. Average (± SD) score of the BDI was 9.6 ± 7.8 and 5.8 ± 5.8 (p = 0.005) for patients with and without pain, respectively. Patients with and without pain did not significantly differ in terms of anxiety. Pain-free patients had a significantly higher physical component score than patients with pain in the SF-36v2 (mean, 48.7 ± 8.6 vs 38.6 ± 9.8, p < 0.0001, respectively), while the mental component scores were not statistically different between the two groups. Lung transplant recipients have a high prevalence of pain. Patients with lung emphysema as their preoperative diagnosis are more likely to have pain. The occurrence of pain is associated with a decreased QOL in lung transplant recipients.