Publications by authors named "Nachev P"

Pituitary neuroendocrine tumors remain one of the most common intracranial tumors. While radiomic research related to pituitary tumors is progressing, public data sets for external validation remain scarce. We introduce an open dataset comprising high-resolution T1 contrast-enhanced MR scans of 136 patients with pituitary tumors, annotated for tumor segmentation and accompanied by clinical, radiological and pathological metadata.

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  • The review highlights the complexity of stroke, driven by disruptions in blood supply and complicated by the neural and vascular systems' interactions.
  • Advances in machine vision and deep learning are improving predictive tools for stroke, but their clinical impact is limited by real-world data challenges.
  • Although AI's potential benefits for stroke care are clear, the best approaches for practical application are still being explored, with deep generative models seen as a promising avenue for innovation.
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Influential theories of complex behaviour invoke the notion of cognitive control modulated by conflict between counterfactual actions. Medial frontal cortex, notably the anterior cingulate cortex, has been variously posited as critical to such conflict detection, resolution, or monitoring, largely based on correlative data from functional imaging. Examining performance on the most widely used "conflict" task-Stroop-in a large cohort of patients with focal brain injury (N = 176), we compare anatomical patterns of lesion-inferred neural substrate dependence to those derived from functional imaging, meta-analytically summarised.

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  • The study examined the management of cerebrospinal fluid (CSF) drainage in patients with acute hydrocephalus, focusing on the effects of different weaning methods and timing on outcomes.
  • It included 69 adult patients, predominantly with conditions like aneurysmal subarachnoid hemorrhage, and found that delaying the initiation of drain weaning led to longer hospital stays and increased risk of complications.
  • The results suggest that an early rapid wean could improve patient outcomes by shortening hospital stays and reducing mechanical issues, but emphasizes the need for better quality evidence in future research.
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  • This study evaluates how effective deep-learning models, specifically a 3D U-Net network, are at quickly generating disconnectomes to predict neuropsychological outcomes in stroke patients one year post-stroke.
  • The model was trained on 1333 synthetic lesions and then applied to 1333 actual stroke lesions, leading to the creation of deep-disconnectomes much faster than existing methods—approximately 720 times quicker.
  • The findings show that these deep-disconnectomes have an impressive predictive accuracy of 85.2% for neuropsychological scores, marking a significant improvement over traditional disconnectome approaches and potentially enhancing stroke survivors' prognostic assessments.
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Intracranial pressure (ICP) is a physiological parameter that conventionally requires invasive monitoring for accurate measurement. Utilising multivariate predictive models, we sought to evaluate the utility of non-invasive, widely accessible MRI biomarkers in predicting ICP and their reversibility following cerebrospinal fluid (CSF) diversion. The retrospective study included 325 adult patients with suspected CSF dynamic disorders who underwent brain MRI scans within three months of elective 24-h ICP monitoring.

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Lesion analysis aims to reveal the causal contributions of brain regions to brain functions. Various strategies have been used for such lesion inferences. These approaches can be broadly categorized as univariate or multivariate methods.

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The VASARI MRI feature set is a quantitative system designed to standardise glioma imaging descriptions. Though effective, deriving VASARI is time-consuming and seldom used clinically. We sought to resolve this problem with software automation and machine learning.

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Background: The presence of bias in artificial intelligence has garnered increased attention, with inequities in algorithmic performance being exposed across the fields of criminal justice, education, and welfare services. In health care, the inequitable performance of algorithms across demographic groups may widen health inequalities.

Objective: Here, we identify and characterize bias in cardiology algorithms, looking specifically at algorithms used in the management of heart failure.

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The quantification of cognitive powers rests on identifying a behavioural task that depends on them. Such dependence cannot be assured, for the powers a task invokes cannot be experimentally controlled or constrained a priori, resulting in unknown vulnerability to failure of specificity and generalisability. Evaluating a compact version of Raven's Advanced Progressive Matrices (RAPM), a widely used clinical test of fluid intelligence, we show that LaMa, a self-supervised artificial neural network trained solely on the completion of partially masked images of natural environmental scenes, achieves representative human-level test scores a prima vista, without any task-specific inductive bias or training.

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Background And Methods: In this narrative review, we introduce key artificial intelligence (AI) and machine learning (ML) concepts, aimed at headache clinicians and researchers. Thereafter, we thoroughly review the use of AI in headache, based on a comprehensive literature search across PubMed, Embase and IEEExplore. Finally, we discuss limitations, as well as ethical and political perspectives.

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-Business reliance on algorithms is becoming ubiquitous, and companies are increasingly concerned about their algorithms causing major financial or reputational damage. High-profile cases include Google's AI algorithm for photo classification mistakenly labelling a black couple as gorillas in 2015 (Gebru 2020 In , pp. 251-269), Microsoft's AI chatbot Tay that spread racist, sexist and antisemitic speech on Twitter (now X) (Wolf .

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Introduction: Altered neurometabolism, detectable via proton magnetic resonance spectroscopic imaging (H-MRSI), is spatially heterogeneous and underpins cognitive impairments in Alzheimer's disease (AD). However, the spatial relationships between neurometabolic topography and cognitive impairment in AD remain unexplored due to technical limitations.

Methods: We used a novel whole-brain high-resolution H-MRSI technique, with simultaneously acquired F-florbetapir positron emission tomography (PET) imaging, to investigate the relationship between neurometabolic topography and cognitive functions in 117 participants, including 22 prodromal AD, 51 AD dementia, and 44 controls.

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Medical imaging research is often limited by data scarcity and availability. Governance, privacy concerns and the cost of acquisition all restrict access to medical imaging data, which, compounded by the data-hungry nature of deep learning algorithms, limits progress in the field of healthcare AI. Generative models have recently been used to synthesize photorealistic natural images, presenting a potential solution to the data scarcity problem.

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The architecture of the brain is too complex to be intuitively surveyable without the use of compressed representations that project its variation into a compact, navigable space. The task is especially challenging with high-dimensional data, such as gene expression, where the joint complexity of anatomical and transcriptional patterns demands maximum compression. The established practice is to use standard principal component analysis (PCA), whose computational felicity is offset by limited expressivity, especially at great compression ratios.

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Within the past decade, the term "phantasia" has been increasingly used to describe the human capacity, faculty, or power of visual mental imagery, with extremes of imagery vividness characterised as "aphantasia" and "hyperphantasia". A substantial volume of empirical research addressing these constructs has now been published, including attempts to find inductive correlates of behaviourally defined aphantasia, for example using research questionnaires and functional magnetic resonance imaging. Mental imagery has long been noted as a source of conceptual confusions but no specific conceptual analysis of the new formulation of phantasia, aphantasia, and hyperphantasia has been undertaken hitherto.

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  • Researchers developed machine learning models to predict citation counts and the translational impact of headache research, focusing on their inclusion in guidelines or policy documents.
  • They analyzed data from 8,600 publications across three headache journals, using various machine learning techniques to classify citation count intervals and assess translational impact.
  • The best model achieved an impressive predictive accuracy with bibliometric data being key for citation counts, while a combination of bibliometric data and publication content was most effective for predicting translational impact.
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Our knowledge of the organisation of the human brain at the population-level is yet to translate into power to predict functional differences at the individual-level, limiting clinical applications and casting doubt on the generalisability of inferred mechanisms. It remains unknown whether the difficulty arises from the absence of individuating biological patterns within the brain, or from limited power to access them with the models and compute at our disposal. Here we comprehensively investigate the resolvability of such patterns with data and compute at unprecedented scale.

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This scientific commentary refers to ‘Integrating direct electrical brain stimulation with the human connectome’ by Coletta . (https://doi.org/10.

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  • Alzheimer's disease is a significant health issue for older adults with Down syndrome, and typical diagnostic methods, like MRI, are often not suitable due to difficulties with prolonged scan times.
  • This study used automated analysis of CT scans from 98 individuals with Down syndrome to identify correlations between brain structure changes and the severity of dementia stages, alongside specific Alzheimer’s biomarkers.
  • The findings indicated that increased dementia severity was linked to reduced gray and white matter volumes in the temporal lobe, suggesting a promising new method for assessing Alzheimer’s in populations that struggle with traditional imaging techniques.
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Though phonemic fluency tasks are traditionally indexed by the number of correct responses, the underlying disorder may shape the specific choice of words-both correct and erroneous. We report the first comprehensive qualitative analysis of incorrect and correct words generated on the phonemic ('S') fluency test, in a large sample of patients ( = 239) with focal, unilateral frontal or posterior lesions and healthy controls ( = 136). We conducted detailed qualitative analyses of the single words generated in the phonemic fluency task using categorical descriptions for different types of errors, low-frequency words and clustering/switching.

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Federated learning (FL) is gaining wide acceptance across the medical AI domains. FL promises to provide a fairly acceptable clinical-grade accuracy, privacy, and generalisability of machine learning models across multiple institutions. However, the research on FL for medical imaging AI is still in its early stages.

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Healthcare policy, clinical practice and clinical research all declare patient benefit as their avowed aim. Yet, the conceptual question of what exactly constitutes patient benefit has received much less attention than the practical means of realising it. Currently, three key areas of conceptual unclarity make the achieved, real-world impact hard to quantify and disconnect it from the magnitude of the practical endeavour: (1) the distinction between objective and subjective benefit, (2) the relation between individual and population measures of benefit, and (3) the optimal measurement of benefit in research studies.

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Any clinically-deployed image-processing pipeline must be robust to the full range of inputs it may be presented with. One popular approach to this challenge is to develop predictive models that can provide a measure of their uncertainty. Another approach is to use generative modelling to quantify the likelihood of inputs.

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Tumour heterogeneity is increasingly recognized as a major obstacle to therapeutic success across neuro-oncology. Gliomas are characterized by distinct combinations of genetic and epigenetic alterations, resulting in complex interactions across multiple molecular pathways. Predicting disease evolution and prescribing individually optimal treatment requires statistical models complex enough to capture the intricate (epi)genetic structure underpinning oncogenesis.

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