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Tate DF, Wade BSC, Velez CS, Bigler ED, Davenport ND, Dennis EL, Esopenko C, Hinds SR, Kean J, Kennedy E, Kenney K, Mayer AR, Newsome MR, Philippi CL, Pugh MJ, Scheibel RS, Taylor BA, Troyanskaya M, Werner JK, York GE, Walker W, Wilde EA. Persistent MRI Findings Unique to Blast and Repetitive Mild TBI: Analysis of the CENC/LIMBIC Cohort Injury Characteristics. Mil Med 2024:usae031. [PMID: 38401164 DOI: 10.1093/milmed/usae031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 08/04/2023] [Accepted: 02/02/2024] [Indexed: 02/26/2024] Open
Abstract
INTRODUCTION MRI represents one of the clinical tools at the forefront of research efforts aimed at identifying diagnostic and prognostic biomarkers following traumatic brain injury (TBI). Both volumetric and diffusion MRI findings in mild TBI (mTBI) are mixed, making the findings difficult to interpret. As such, additional research is needed to continue to elucidate the relationship between the clinical features of mTBI and quantitative MRI measurements. MATERIAL AND METHODS Volumetric and diffusion imaging data in a sample of 976 veterans and service members from the Chronic Effects of Neurotrauma Consortium and now the Long-Term Impact of Military-Relevant Brain Injury Consortium observational study of the late effects of mTBI in combat with and without a history of mTBI were examined. A series of regression models with link functions appropriate for the model outcome were used to evaluate the relationships among imaging measures and clinical features of mTBI. Each model included acquisition site, participant sex, and age as covariates. Separate regression models were fit for each region of interest where said region was a predictor. RESULTS After controlling for multiple comparisons, no significant main effect was noted for comparisons between veterans and service members with and without a history of mTBI. However, blast-related mTBI were associated with volumetric reductions of several subregions of the corpus callosum compared to non-blast-related mTBI. Several volumetric (i.e., hippocampal subfields, etc.) and diffusion (i.e., corona radiata, superior longitudinal fasciculus, etc.) MRI findings were noted to be associated with an increased number of repetitive mTBIs versus. CONCLUSIONS In deployment-related mTBI, significant findings in this cohort were only observed when considering mTBI sub-groups (blast mechanism and total number/dose). Simply comparing healthy controls and those with a positive mTBI history is likely an oversimplification that may lead to non-significant findings, even in consortium analyses.
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Affiliation(s)
- David F Tate
- Department of Neurology, Traumatic Brain Injury and Concussion Center, University of Utah, Salt Lake City, UT 84132, USA
- George E. Wahlen VA Salt Lake City Healthcare System, Salt Lake City, UT 84148, USA
- Department of Psychology, Brigham Young University, Provo, UT 84604, USA
| | - Benjamin S C Wade
- Department of Neurology, Traumatic Brain Injury and Concussion Center, University of Utah, Salt Lake City, UT 84132, USA
- Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Carmen S Velez
- Department of Neurology, Traumatic Brain Injury and Concussion Center, University of Utah, Salt Lake City, UT 84132, USA
- George E. Wahlen VA Salt Lake City Healthcare System, Salt Lake City, UT 84148, USA
| | - Erin D Bigler
- Department of Neurology, Traumatic Brain Injury and Concussion Center, University of Utah, Salt Lake City, UT 84132, USA
- Department of Psychology, Brigham Young University, Provo, UT 84604, USA
- Departments of Neuroscience, Brigham Young University, Provo, UT 84604, USA
| | - Nicholas D Davenport
- Minneapolis Veterans Affairs Health Care System, Minneapolis, MN 55417, USA
- Department of Psychiatry and Behavioral Sciences, University of Minnesota, Minneapolis, MN 55454, USA
| | - Emily L Dennis
- Department of Neurology, Traumatic Brain Injury and Concussion Center, University of Utah, Salt Lake City, UT 84132, USA
- George E. Wahlen VA Salt Lake City Healthcare System, Salt Lake City, UT 84148, USA
| | - Carrie Esopenko
- Department of Rehabilitation and Human Performance, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Sidney R Hinds
- Department of Neurology, Uniformed Services University, Bethesda, MD 20814, USA
| | - Jacob Kean
- George E. Wahlen VA Salt Lake City Healthcare System, Salt Lake City, UT 84148, USA
- Department of Population Health Sciences, University of Utah, Salt Lake City, UT 84108, USA
| | - Eamonn Kennedy
- Department of Population Health Sciences, University of Utah, Salt Lake City, UT 84108, USA
| | - Kimbra Kenney
- Department of Neurology, Uniformed Services University, Bethesda, MD 20814, USA
- National Intrepid Center of Excellence, Walter Reed National Military Medical Center, Bethesda, MD 20814, USA
| | - Andrew R Mayer
- The Mind Research Network, University of New Mexico Health Science Center, Albuquerque, NM 87106, USA
| | - Mary R Newsome
- Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030, USA
- H. Ben Taub Department of Physical Medicine & Rehabilitation, Baylor College of Medicine, Houston, TX 77030, USA
| | - Carissa L Philippi
- Department of Psychological Sciences, University of Missouri-St. Louis, St. Louis, MO 63121, St. Louis
| | - Mary J Pugh
- George E. Wahlen VA Salt Lake City Healthcare System, Salt Lake City, UT 84148, USA
- Department of Population Health Sciences, University of Utah, Salt Lake City, UT 84108, USA
| | - Randall S Scheibel
- Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030, USA
- H. Ben Taub Department of Physical Medicine & Rehabilitation, Baylor College of Medicine, Houston, TX 77030, USA
| | - Brian A Taylor
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Maya Troyanskaya
- Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030, USA
- H. Ben Taub Department of Physical Medicine & Rehabilitation, Baylor College of Medicine, Houston, TX 77030, USA
| | - John K Werner
- Department of Neurology, Uniformed Services University, Bethesda, MD 20814, USA
| | - Gerald E York
- Imaging Associates of Alaska, Anchorage, AK 99508, USA
| | - William Walker
- Department of Physical Medicine and Rehabilitation, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Elisabeth A Wilde
- Department of Neurology, Traumatic Brain Injury and Concussion Center, University of Utah, Salt Lake City, UT 84132, USA
- George E. Wahlen VA Salt Lake City Healthcare System, Salt Lake City, UT 84148, USA
- Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030, USA
- H. Ben Taub Department of Physical Medicine & Rehabilitation, Baylor College of Medicine, Houston, TX 77030, USA
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Karperien AL, Jelinek HF. Morphology and Fractal-Based Classifications of Neurons and Microglia in Two and Three Dimensions. ADVANCES IN NEUROBIOLOGY 2024; 36:149-172. [PMID: 38468031 DOI: 10.1007/978-3-031-47606-8_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Microglia and neurons live physically intertwined, intimately related structurally and functionally in a dynamic relationship in which microglia change continuously over a much shorter timescale than do neurons. Although microglia may unwind and depart from the neurons they attend under certain circumstances, in general, together both contribute to the fractal topology of the brain that defines its computational capabilities. Both neuronal and microglial morphologies are well-described using fractal analysis complementary to more traditional measures. For neurons, the fractal dimension has proved valuable for classifying dendritic branching and other neuronal features relevant to pathology and development. For microglia, fractal geometry has substantially contributed to classifying functional categories, where, in general, the more pathological the biological status, the lower the fractal dimension for individual cells, with some exceptions, including hyper-ramification. This chapter provides a review of the intimate relationships between neurons and microglia, by introducing 2D and 3D fractal analysis methodology and its applications in neuron-microglia function in health and disease.
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Affiliation(s)
- Audrey L Karperien
- School of Community Health, Charles Sturt University, Albury, NSW, Australia
| | - Herbert F Jelinek
- Department of Medical Sciences and Biotechnology Center, Khalifa University, Abu Dhabi, UAE
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Verhulst MMLH, Glimmerveen AB, van Heugten CM, Helmich RCG, Hofmeijer J. MRI factors associated with cognitive functioning after acute onset brain injury: Systematic review and meta-analysis. Neuroimage Clin 2023; 38:103415. [PMID: 37119695 PMCID: PMC10165272 DOI: 10.1016/j.nicl.2023.103415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 03/22/2023] [Accepted: 04/19/2023] [Indexed: 05/01/2023]
Abstract
Impairments of memory, attention, and executive functioning are frequently reported after acute onset brain injury. MRI markers hold potential to contribute to identification of patients at risk for cognitive impairments and clarification of mechanisms. The aim of this systematic review was to summarize and value the evidence on MRI markers of memory, attention, and executive functioning after acute onset brain injury. We included ninety-eight studies, on six classes of MRI factors (location and severity of damage (n = 15), volume/atrophy (n = 36), signs of small vessel disease (n = 15), diffusion-weighted imaging measures (n = 36), resting-state functional MRI measures (n = 13), and arterial spin labeling measures (n = 1)). Three measures showed consistent results regarding their association with cognition. Smaller hippocampal volume was associated with worse memory in fourteen studies (pooled correlation 0.58 [95% CI: 0.46-0.68] for whole, 0.11 [95% CI: 0.04-0.19] for left, and 0.34 [95% CI: 0.17-0.49] for right hippocampus). Lower fractional anisotropy in cingulum and fornix was associated with worse memory in six and five studies (pooled correlation 0.20 [95% CI: 0.08-0.32] and 0.29 [95% CI: 0.20-0.37], respectively). Lower functional connectivity within the default-mode network was associated with worse cognition in four studies. In conclusion, hippocampal volume, fractional anisotropy in cingulum and fornix, and functional connectivity within the default-mode network showed consistent associations with cognitive performance in all types of acute onset brain injury. External validation and cut off values for predicting cognitive impairments are needed for clinical implementation.
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Affiliation(s)
- Marlous M L H Verhulst
- Clinical Neurophysiology, University of Twente, Enschede, The Netherlands; Department of Neurology, Rijnstate Hospital, Arnhem, The Netherlands.
| | - Astrid B Glimmerveen
- Clinical Neurophysiology, University of Twente, Enschede, The Netherlands; Department of Neurology, Rijnstate Hospital, Arnhem, The Netherlands
| | - Caroline M van Heugten
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands; Limburg Brain Injury Center, Maastricht University, Maastricht, The Netherlands; Department of Neuropsychology and Psychopharmacology, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Rick C G Helmich
- Donders Institute for Brain, Cognition, and Behavior, Centre for Cognitive Neuroimaging, Radboud University Nijmegen, Nijmegen, The Netherlands; Department of Neurology, Centre of Expertise for Parkinson & Movement Disorders, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Jeannette Hofmeijer
- Clinical Neurophysiology, University of Twente, Enschede, The Netherlands; Department of Neurology, Rijnstate Hospital, Arnhem, The Netherlands
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Zhou J, Chen W, Wu Q, Chen L, Chen HH, Liu H, Xu XQ, Wu FY, Hu H. Reduced cortical complexity in patients with thyroid-associated ophthalmopathy. Brain Imaging Behav 2022; 16:2133-2140. [PMID: 35821157 DOI: 10.1007/s11682-022-00683-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/29/2022] [Indexed: 11/02/2022]
Abstract
Psychical and functional disturbances of thyroid-associated ophthalmopathy (TAO) patients are drawing increasingly attention, despite the characterized ophthalmic symptoms. We aimed to investigate the alterations of structural complexity using fractal dimension (FD) analysis in patients with TAO. Thirty-nine TAO patients and 25 healthy controls underwent high-resolution 3.0 T structural brain magnetic resonance imaging (MRI). FD values of brain regions were calculated by Computational Anatomy Toolbox (CAT12) and compared between groups. The associations between clinical variables and FD values were further estimated. We found that TAO patients exhibited significantly decreased FD values in right caudal anterior cingulate cortex, right lingual gyrus, right pars orbitalis and right cuneus cortex (FDR corrected p < 0.05). FD values of right cuneus cortex were positively correlated with visual acuity, and FD values of right caudal anterior cingulate cortex were also positively correlated with cognitive performance. Meanwhile, FD values of right lingual gyrus were found to be negatively correlated with emotional function. Our study indicated disturbed cortical complexity in brain regions corresponding to known functional deficits of vision, emotion and cognition in TAO. FD might be a potential marker for reflecting the underlying neurobiological basis of TAO.
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Affiliation(s)
- Jiang Zhou
- Department of Radiology, The First Affiliated Hospital of Nanjing Medical University, No. 300, Guangzhou Rd., Nanjing, 210029, China
| | - Wen Chen
- Department of Radiology, The First Affiliated Hospital of Nanjing Medical University, No. 300, Guangzhou Rd., Nanjing, 210029, China
| | - Qian Wu
- Department of Radiology, The First Affiliated Hospital of Nanjing Medical University, No. 300, Guangzhou Rd., Nanjing, 210029, China
| | - Lu Chen
- Department of Radiology, The First Affiliated Hospital of Nanjing Medical University, No. 300, Guangzhou Rd., Nanjing, 210029, China
| | - Huan-Huan Chen
- Department of Endocrinology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Hu Liu
- Department of Ophthalmology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Xiao-Quan Xu
- Department of Radiology, The First Affiliated Hospital of Nanjing Medical University, No. 300, Guangzhou Rd., Nanjing, 210029, China
| | - Fei-Yun Wu
- Department of Radiology, The First Affiliated Hospital of Nanjing Medical University, No. 300, Guangzhou Rd., Nanjing, 210029, China.
| | - Hao Hu
- Department of Radiology, The First Affiliated Hospital of Nanjing Medical University, No. 300, Guangzhou Rd., Nanjing, 210029, China.
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Zhou X, Tan Y, Yu H, Liu J, Lan X, Deng Y, Yu F, Wang C, Chen J, Zeng X, Liu D, Zhang J. Early alterations in cortical morphology after neoadjuvant chemotherapy in breast cancer patients: A longitudinal magnetic resonance imaging study. Hum Brain Mapp 2022; 43:4513-4528. [PMID: 35665982 PMCID: PMC9491291 DOI: 10.1002/hbm.25969] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 05/18/2022] [Accepted: 05/22/2022] [Indexed: 11/13/2022] Open
Abstract
There is growing evidence that chemotherapy may have a significant impact on the brains of breast cancer patients, causing changes in cortical morphology. However, early morphological alterations induced by chemotherapy in breast cancer patients are unclear. To investigate the patterns of those alterations, we compared female breast cancer patients (n = 45) longitudinally before (time point 0, TP0) and after (time point 1, TP1) the first cycle of neoadjuvant chemotherapy, using voxel‐based morphometry (VBM) and surface‐based morphometry (SBM). VBM and SBM alteration data underwent correlation analysis. We also compared cognition‐related neuropsychological tests in the breast cancer patients between TP0 and TP1. Reductions in gray matter volume, cortical thickness, sulcal depth, and gyrification index were found in most brain areas, while increments were found to be mainly concentrated in and around the hippocampus. Reductions of fractal dimension mainly occurred in the limbic and occipital lobes, while increments mainly occurred in the anterior and posterior central gyrus. Significant correlations were found between altered VBM and altered SBM mainly in the bilateral superior frontal gyrus. We found no significant differences in the cognition‐related neuropsychological tests before and after chemotherapy. The altered brain regions are in line with those associated with impaired cognitive domains in previous studies. We conclude that breast cancer patients showed widespread morphological alterations soon after neoadjuvant chemotherapy, despite an absence of cognitive impairments. The affected brain regions may indicate major targets of early brain damage after chemotherapy.
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Affiliation(s)
- Xiaoyu Zhou
- Department of Radiology, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Yong Tan
- Department of Radiology, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Hong Yu
- Department of Radiology, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Jiang Liu
- Department of Radiology, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Xiaosong Lan
- Department of Radiology, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Yongchun Deng
- Breast Center, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Feng Yu
- Breast Center, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Chengfang Wang
- Department of Radiology, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Jiao Chen
- Department of Radiology, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Xiaohua Zeng
- Breast Center, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Daihong Liu
- Department of Radiology, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Jiuquan Zhang
- Department of Radiology, Chongqing University Cancer Hospital, School of Medicine, Chongqing University, Chongqing, China
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Fractal dimension of the brain in neurodegenerative disease and dementia: A systematic review. Ageing Res Rev 2022; 79:101651. [PMID: 35643264 DOI: 10.1016/j.arr.2022.101651] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 04/26/2022] [Accepted: 05/23/2022] [Indexed: 12/25/2022]
Abstract
Sensitive and specific antemortem biomarkers of neurodegenerative disease and dementia are crucial to the pursuit of effective treatments, required both to reliably identify disease and to track its progression. Atrophy is the structural magnetic resonance imaging (MRI) hallmark of neurodegeneration. However in most cases it likely indicates a relatively advanced stage of disease less susceptible to treatment as some disease processes begin decades prior to clinical onset. Among emerging metrics that characterise brain shape rather than volume, fractal dimension (FD) quantifies shape complexity. FD has been applied in diverse fields of science to measure subtle changes in elaborate structures. We review its application thus far to structural MRI of the brain in neurodegenerative disease and dementia. We identified studies involving subjects who met criteria for mild cognitive impairment, Alzheimer's Disease, Vascular Dementia, Lewy Body Dementia, Frontotemporal Dementia, Amyotrophic Lateral Sclerosis, Parkinson's Disease, Huntington's Disease, Multiple Systems Atrophy, Spinocerebellar Ataxia and Multiple Sclerosis. The early literature suggests that neurodegenerative disease processes are usually associated with a decline in FD of the brain. The literature includes examples of disease-related change in FD occurring independently of atrophy, which if substantiated would represent a valuable advantage over other structural imaging metrics. However, it is likely to be non-specific and to exhibit complex spatial and temporal patterns. A more harmonious methodological approach across a larger number of studies as well as careful attention to technical factors associated with image processing and FD measurement will help to better elucidate the metric's utility.
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Quantitative multimodal imaging in traumatic brain injuries producing impaired cognition. Curr Opin Neurol 2021; 33:691-698. [PMID: 33027143 DOI: 10.1097/wco.0000000000000872] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW Cognitive impairments are a devastating long-term consequence following traumatic brain injury (TBI). This review provides an update on the quantitative mutimodal neuroimaging studies that attempt to elucidate the mechanism(s) underlying cognitive impairments and their recovery following TBI. RECENT FINDINGS Recent studies have linked individual specific behavioural impairments and their changes over time to physiological activity and structural changes using EEG, PET and MRI. Multimodal studies that combine measures of physiological activity with knowledge of neuroanatomical and connectivity damage have also illuminated the multifactorial function-structure relationships that underlie impairment and recovery following TBI. SUMMARY The combined use of multiple neuroimaging modalities, with focus on individual longitudinal studies, has the potential to accurately classify impairments, enhance sensitivity of prognoses, inform targets for interventions and precisely track spontaneous and intervention-driven recovery.
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Reduced Cortical Complexity in Cirrhotic Patients with Minimal Hepatic Encephalopathy. Neural Plast 2020; 2020:7364649. [PMID: 32256557 PMCID: PMC7104259 DOI: 10.1155/2020/7364649] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 01/28/2020] [Accepted: 02/12/2020] [Indexed: 01/09/2023] Open
Abstract
Purpose Gray matter volume loss, regional cortical thinning, and local gyrification index alteration have been documented in minimal hepatic encephalopathy (MHE). Fractal dimension (FD), another morphological parameter, has been widely used to describe structural complexity alterations in neurological or psychiatric disease. Here, we conducted the first study to investigate FD alterations in MHE. Methods and Materials We performed high-resolution structural magnetic resonance imaging on cirrhotic patients with MHE (n = 20) and healthy controls (n = 21). We evaluated their cognitive performance using the psychometric hepatic encephalopathy score (PHES). The regional FD value was calculated by Computational Anatomy Toolbox (CAT12) and compared between groups. We further estimated the association between patients' cognitive performance and FD values. Results MHE patients presented significantly decreased FD values in the left precuneus, left supramarginal gyrus, right caudal anterior cingulate cortex, right isthmus cingulate cortex, right insula, bilateral pericalcarine cortex, and bilateral paracentral cortex compared to normal controls. In addition, the FD values in the right isthmus cingulate cortex and right insula were shown to be positively correlated with patients' cognitive performance. Conclusion Aberrant cortical complexity is an additional characteristic of MHE, and FD analysis may provide novel insight into the neurobiological basis of cognitive dysfunction in MHE.
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Krohn S, Froeling M, Leemans A, Ostwald D, Villoslada P, Finke C, Esteban FJ. Evaluation of the 3D fractal dimension as a marker of structural brain complexity in multiple-acquisition MRI. Hum Brain Mapp 2019; 40:3299-3320. [PMID: 31090254 DOI: 10.1002/hbm.24599] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 01/26/2019] [Accepted: 04/04/2019] [Indexed: 12/24/2022] Open
Abstract
Fractal analysis represents a promising new approach to structural neuroimaging data, yet systematic evaluation of the fractal dimension (FD) as a marker of structural brain complexity is scarce. Here we present in-depth methodological assessment of FD estimation in structural brain MRI. On the computational side, we show that spatial scale optimization can significantly improve FD estimation accuracy, as suggested by simulation studies with known FD values. For empirical evaluation, we analyzed two recent open-access neuroimaging data sets (MASSIVE and Midnight Scan Club), stratified by fundamental image characteristics including registration, sequence weighting, spatial resolution, segmentation procedures, tissue type, and image complexity. Deviation analyses showed high repeated-acquisition stability of the FD estimates across both data sets, with differential deviation susceptibility according to image characteristics. While less frequently studied in the literature, FD estimation in T2-weighted images yielded robust outcomes. Importantly, we observed a significant impact of image registration on absolute FD estimates. Applying different registration schemes, we found that unbalanced registration induced (a) repeated-measurement deviation clusters around the registration target, (b) strong bidirectional correlations among image analysis groups, and (c) spurious associations between the FD and an index of structural similarity, and these effects were strongly attenuated by reregistration in both data sets. Indeed, differences in FD between scans did not simply track differences in structure per se, suggesting that structural complexity and structural similarity represent distinct aspects of structural brain MRI. In conclusion, scale optimization can improve FD estimation accuracy, and empirical FD estimates are reliable yet sensitive to image characteristics.
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Affiliation(s)
- Stephan Krohn
- Department of Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany.,Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Berlin, Germany.,Computational Cognitive Neuroscience Laboratory, Freie Universität Berlin, Berlin, Germany
| | - Martijn Froeling
- Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Alexander Leemans
- Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Dirk Ostwald
- Computational Cognitive Neuroscience Laboratory, Freie Universität Berlin, Berlin, Germany.,Center for Adaptive Rationality, Max-Planck Institute for Human Development, Berlin, Germany
| | - Pablo Villoslada
- Center of Neuroimmunology, Institut d'Investigacions Biomediques August Pi Sunyer (IDIBAPS), Barcelona, Spain
| | - Carsten Finke
- Department of Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany.,Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Francisco J Esteban
- Systems Biology Unit, Department of Experimental Biology, Universidad de Jaén, Jaén, Spain
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