Small but visible: Predicting rare bryophyte distribution and richness patterns using remote sensing-based ensembles of small models

In Canadian boreal forests, bryophytes represent an essential component of biodiversity and play a significant role in ecosystem functioning. Despite their ecological importance and sensitivity to disturbances, bryophytes are overlooked in conservation strategies due to knowledge gaps on their distribution, which is known as the Wallacean shortfall. Rare species deserve priority attention in conservation as they are at a high risk of extinction. This study aims to elaborate predictive models of rare bryophyte species in Canadian boreal forests using remote sensing-derived predictors in an Ensemble of Small Models (ESMs) framework. We hypothesize that high ESMs-based prediction accuracy can be achieved for rare bryophyte species despite their low number of occurrences. We also assess if there is a spatial correspondence between rare and overall bryophyte richness patterns. The study area is located in western Quebec and covers 72,292 km2. We selected 52 bryophyte species with <30 occurrences from a presence-only database (214 species, 389 plots in total). ESMs were built from Random Forest and Maxent techniques using remote sensing-derived predictors related to topography and vegetation. Lee’s L statistic was used to assess and map the spatial relationship between rare and overall bryophyte richness patterns. ESMs yielded poor to excellent prediction accuracy (AUC > 0.5) for 73% of the modeled species, with AUC values > 0.8 for 19 species, which confirmed our hypothesis. In fact, ESMs provided better predictions for the rarest bryophytes. Likewise, our study revealed a spatial concordance between rare and overall bryophyte richness patterns in different regions of the study area, which have important implications for conservation planning. This study demonstrates the potential of remote sensing for assessing and making predictions on inconspicuous and rare species across the landscape and lays the basis for the eventual inclusion of bryophytes into sustainable development planning.

A Guttate Psoriasis That Tends to Spare Three Tattoos: A Macrophage Liaison

Induction of new psoriasis sites was reported in only a small amount of psoriasis patients undergoing tattooing, despite the intuitive belief that tattoo trauma might awaken the disease due to the isomorphic phenomenon of Koebner. In this case report, we discuss a patient who presented with a remarkable sparing of his three tattoo sites during a guttate psoriasis flare-up that was unrelated to tattooing. The spatial concordance of tattoo and psoriasis lesions was analyzed on clinical pictures of tattoo sites taken during the psoriasis episode. For the quantification of the spatial distribution of the psoriasis lesions, Voronoi diagrams were generated, and coefficients of variation and the two-sample t-test were employed to compare the distributions of Voronoi patch sizes in different settings. Compared to skin areas without tattoos, a tattoo introduced a higher variation in the sizes of the Voronoi patches centered around psoriasis lesions. Based on our findings, we would like to discuss the possible role of macrophages as the key cellular link in the complex pathophysiologic relationship between tattooing/tattoo and psoriasis. Taking into account the relationship of autophagy and psoriasis lesions, we propose the hypothesis that tattoos represent a “psoriasis-hostile” tissue environment pertained by a population of LAP active M2-polarized macrophages. Further clinical studies of the relationship of psoriasis lesions to the tattooed skin are needed and may provide important insights into the role of macrophages in the pathogenesis of psoriasis.

Combined amino acid PET-MRI for identifying recurrence in post-treatment gliomas: together we grow

Purpose The aim of this study is to compare the diagnostic accuracy of amino acid PET, MR perfusion and diffusion as stand-alone modalities and in combination in identifying recurrence in post-treatment gliomas and to qualitatively assess spatial concordance between the three modalities using simultaneous PET-MR acquisition. Methods A retrospective review of 48 cases of post-treatment gliomas who underwent simultaneous PET-MRI using C11 methionine as radiotracer was performed. MR perfusion and diffusion sequences were acquired during the PET study. The following parameters were obtained: TBRmax, TBRmean, SUVmax, and SUVmean from the PET images; rCBV from perfusion; and ADCmean and ADCratio from the diffusion images. The final diagnosis was based on clinical/imaging follow-up and histopathology when available. ROC curve analysis in combination with logistic regression analysis was used to compare the diagnostic performance. Spatial concordance between modalities was graded as 0, 1, and 2 representing discordance, < 50% and > 50% concordance respectively. Results There were 35 cases of recurrence and 13 cases of post-treatment changes without recurrence. The highest area under curve (AUC) was obtained for TBRmax followed by rCBV and ADCratio. The AUC increased significantly with a combination of rCBV and TBRmax. Amino acid PET showed the highest diagnostic accuracy and maximum agreement with the final diagnosis. There was discordance between ADC and PET in 22.9%, between rCBV and PET in 16.7% and between PET and contrast enhancement in 14.6% cases. Conclusion Amino acid PET had the highest diagnostic accuracy in identifying recurrence in post-treatment gliomas. Combination of PET with MRI further increased the AUC thus improving the diagnostic performance.

Localized Atrial Tachycardia and Dispersion Regions in Atrial Fibrillation: Evidence of Spatial Concordance

Introduction: During atrial fibrillation (AF) ablation, it is generally considered that atrial tachycardia (AT) episodes are a consequence of ablation. Objective: To investigate the spatial relationship between localized AT episodes and dispersion/ablation regions during persistent AF ablation procedures. Methods: We analyzed 72 consecutive patients who presented for an index persistent AF ablation procedure guided by the presence of spatiotemporal dispersion of multipolar electrograms. We characterized spontaneous or post-ablation ATs’ mechanism and location in regard to dispersion regions and ablation lesions. Results: In 72 consecutive patients admitted for persistent AF ablation, 128 ATs occurred in 62 patients (1.9 ± 1.1/patient). Seventeen ATs were recorded before any ablation. In a total of 100 ATs with elucidated mechanism, there were 58 localized sources and 42 macro-reentries. A large number of localized ATs arose from regions exhibiting dispersion during AF (n = 49, 84%). Importantly, these ATs’ locations were generally remote from the closest ablation lesion (n = 42, 72%). Conclusions: In patients undergoing a persistent AF ablation procedure guided by the presence of spatiotemporal dispersion of multipolar electrograms, localized ATs originate within dispersion regions but remotely from the closest ablation lesion. These results suggest that ATs represent a stabilized manifestation of co-existing AF drivers rather than ablation-induced arrhythmias.

Spatial and quantitative assessment of the correlation between sinus rhythm and atrial fibrillation voltage mapping to identify low voltage substrate in persistent atrial fibrillation

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft (DFG) through DO637/22-3 Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg through the Research Seed Capital (RiSC) program. Introduction Presence of left atrial (LA) fibrotic low voltage substrate (LVS) is associated with high risk for arrhythmia recurrences in patients undergoing pulmonary vein isolation (PVI) for atrial fibrillation (AF). PVI and additional ablation of LVS - as identified by mapping in sinus rhythm (SR) or AF - has been reported to improve SR maintenance rates, despite differences of the extent and distribution of LA-LVS in SR versus AF. Aims To study the relationship between SR and AF voltage maps, we sought to identify the optimal AF voltage threshold providing the highest concordance in the extent and distribution of LVS when comparing voltage maps in SR vs. AF. Methods Using the statistical shape modelling software Scalismo, the voltage information from the SR and AF maps (acquired prior to PVI) from 28 patients (66 ± 7 years, 46% male, 82% persistent AF) was projected onto a representative LA-geometry. Sensitivity and specificity of LVS identification were calculated for varying thresholds during AF and the correlation between the SR (threshold 0.5mV) and AF maps was assessed and areas of agreeing LVS classification (SR & AF) were identified for each patient. The data of all 28 patients were combined to a spatial histogram of agreement between SR and AF low voltage maps. Results The correlation between SR and AF maps was high across all patients, with agreement at 60-95% of all mapped sites (Figure A: each red triangle represents one patient and the respective agreement of LVS classification and substrate extent). The optimal AF threshold - to identify LA-LVS &lt;0.5 mV in SR - was 0.29 mV (Q1-3: 0.20-0.37 mV) and was independent of the underlying extent of LVS during SR (Figure A: each blue asterisk represents one patient and the corresponding AF threshold and substrate extent). Agreement between LVS in AF vs. SR was high across most (&gt;90) patients on the anterior LA, lateral LA and the left atrial appendage. Lower agreement (60% of patients) was observed in the posterior wall (Figure B). Conclusions SR and AF voltage maps reveal high spatial concordance in low voltage substrate at the anterior LA, lateral LA and LA appendage, however significant discordances in LVS are found in 40% of patients at the posterior LA. Further studies on an extended patient cohort should assess if regional voltage-thresholds would result in an improved substrate concordance between AF and SR substrate maps. Abstract Figure.

Combined Amino Acid Pet-Mri for Differentiating Recurrence from Radiation Necrosis in Gliomas- Together We Grow

PURPOSE: To compare the diagnostic accuracy of amino acid PET, MR perfusion and diffusion as stand-alone modalities and in combination in differentiating recurrence from radiation necrosis in post-treatment gliomas and to qualitatively assess spatial concordance between the three modalities using simultaneous PET-MR acquisition.METHODS: A retrospective review of 48 cases of post-treatment gliomas who underwent simultaneous PET-MRI using C11 Methionine as radiotracer was performed. MR perfusion and diffusion sequences were acquired during the PET study. The following parameters were obtained: TBRmax, TBRmean, SUVmax and SUVmean from the PET images, rCBV from perfusion, ADCmean and ADCratio from the diffusion images. The final diagnosis was based on clinical/imaging follow-up and histopathology when available. ROC curve analysis in combination with logistic regression analysis was used to compare the diagnostic performance. Spatial concordance between modalities was graded as 0,1 and 2 representing discordance, <50% and >50% concordance respectively.RESULTS: There were 35 cases of recurrence and 13 cases of radiation necrosis. The highest area under curve(AUC) was obtained for TBRmax followed by rCBV and ADCratio. The AUC increased significantly with a combination of rCBV and TBRmax. Amino acid PET showed the highest diagnostic accuracy and maximum agreement with the final diagnosis. There was discordance between ADC and PET in 22.9%, between rCBV and PET in 16.7% and between PET and contrast enhancement in 14.6% cases.CONCLUSIONAmino acid PET had the highest diagnostic accuracy in differentiating radiation necrosis from recurrence. Combination of PET with MRI further increased the AUC thus improving the diagnostic performance.

Brain Metabolism and Microglia Activation in Mild Cognitive Impairment: A Combined [18F]FDG and [11C]-(R)-PK11195 PET Study

Background: Mild cognitive impairment (MCI) is a transitional condition between normal cognition and dementia. [18F]FDG-PET reveals brain hypometabolism patterns reflecting neuronal/synaptic dysfunction, already in the prodromal MCI phase. Activated microglia is part of the pathogenetic processes leading to neurodegeneration. Objective: Using [11C]-(R)-PK11195 and [18F]FDG-PET, we aimed to in vivo investigate the presence of microglial activation, and the relationship with brain glucose metabolism, in single MCI subjects. Methods: Eight MCI subjects underwent both [18F]FDG-PET and [11C]-(R)-PK11195 PET. We used validated quantification methods to obtain brain hypometabolism maps and microglia activation peaks in single subjects. We investigated both the spatial overlap and the relationship between brain glucose hypometabolism and microglia activation, by means of Dice similarity coefficient and using Pearson’s correlation at single subject level. Results: Each MCI showed a specific brain hypometabolism pattern indicative of different possible etiologies, as expected in MCI population (i.e., Alzheimer’s disease-like, frontotemporal dementia-like, hippocampal-type, normal aging type). [11C]-(R)-PK11195 PET analysis revealed a spatial concordance with regional hypometabolism in all subjects with several clusters of significant microglia activation showing an inverse correlation with the regional metabolism. This was proportional to the strength of between-signals correlation coefficient (β = –0.804; p = 0.016). Conclusion: Microglia activation is present in the prodromal MCI phase of different underlying etiologies, showing spatial concordance and inverse correlation with brain glucose metabolism at single-subject level. These findings suggest a possible contribution of activated microglia to neurodegeneration, showing important implications for local immune activity in the early neurodegenerative processes.

Exploring MEG brain fingerprints: evaluation, pitfalls and interpretations

Individual characterization of subjects based on their functional connectome (FC), termed “FC fingerprinting”, has become a highly sought-after goal in contemporary neuroscience research. Recent functional magnetic resonance imaging (fMRI) studies have demonstrated unique characterization and accurate identification of individuals as an accomplished task. However, FC fingerprinting in magnetoencephalography (MEG) data is still widely unexplored. Here, we study resting-state MEG data from the Human Connectome Project to assess the MEG FC fingerprinting and its relationship with several factors including amplitude- and phase-coupling functional connectivity measures, spatial leakage correction and frequency bands. To this end, we first employ two identification scoring methods, differential identifiability and success rate, to provide quantitative fingerprint scores for each FC measurement. Secondly, we explore the edgewise and nodal MEG fingerprinting patterns across the different frequency bands (delta, theta, alpha, beta, and gamma). Finally, we investigate the cross-modality fingerprinting patterns obtained from MEG and fMRI recordings from the same subjects. Our results suggest that fingerprinting performance is heavily dependent on the functional connectivity measure, frequency band, identification scoring method, and spatial leakage correction. We report higher MEG fingerprints in phase-coupling methods, central frequency bands (alpha and beta), and in the visual, frontoparietal, dorsal-attention and default-mode networks. Furthermore, cross-modality comparisons reveal a certain degree of spatial concordance in fingerprinting patterns between the MEG and fMRI data, especially in the visual system. This comprehensive, albeit preliminary investigation of MEG connectome test-retest identification offers a first characterization of MEG fingerprinting in relation to different methodological and electrophysiological factors and contributes to the understanding of fingerprinting cross-modal relationships. We hope that this first investigation will contribute to setting the grounds for MEG connectome identification.