| 1. |
- Srikrishna, Meera, et al.
(författare)
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Comparison of Two-Dimensional- and Three-Dimensional-Based U-Net Architectures for Brain Tissue Classification in One-Dimensional Brain CT
- 2022
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Ingår i: Frontiers in Computational Neuroscience. - : Frontiers Media SA. - 1662-5188. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Brain tissue segmentation plays a crucial role in feature extraction, volumetric quantification, and morphometric analysis of brain scans. For the assessment of brain structure and integrity, CT is a non-invasive, cheaper, faster, and more widely available modality than MRI. However, the clinical application of CT is mostly limited to the visual assessment of brain integrity and exclusion of copathologies. We have previously developed two-dimensional (2D) deep learning-based segmentation networks that successfully classified brain tissue in head CT. Recently, deep learning-based MRI segmentation models successfully use patch-based three-dimensional (3D) segmentation networks. In this study, we aimed to develop patch-based 3D segmentation networks for CT brain tissue classification. Furthermore, we aimed to compare the performance of 2D- and 3D-based segmentation networks to perform brain tissue classification in anisotropic CT scans. For this purpose, we developed 2D and 3D U-Net-based deep learning models that were trained and validated on MR-derived segmentations from scans of 744 participants of the Gothenburg H70 Cohort with both CT and T1-weighted MRI scans acquired timely close to each other. Segmentation performance of both 2D and 3D models was evaluated on 234 unseen datasets using measures of distance, spatial similarity, and tissue volume. Single-task slice-wise processed 2D U-Nets performed better than multitask patch-based 3D U-Nets in CT brain tissue classification. These findings provide support to the use of 2D U-Nets to segment brain tissue in one-dimensional (1D) CT. This could increase the application of CT to detect brain abnormalities in clinical settings.
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| 2. |
- Srikrishna, Meera, et al.
(författare)
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CT-based volumetric measures obtained through deep learning: Association with biomarkers of neurodegeneration
- 2024
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Ingår i: Alzheimers & Dementia. - 1552-5260. ; 20:1, s. 629-640
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTIONCranial computed tomography (CT) is an affordable and widely available imaging modality that is used to assess structural abnormalities, but not to quantify neurodegeneration. Previously we developed a deep-learning-based model that produced accurate and robust cranial CT tissue classification.MATERIALS AND METHODSWe analyzed 917 CT and 744 magnetic resonance (MR) scans from the Gothenburg H70 Birth Cohort, and 204 CT and 241 MR scans from participants of the Memory Clinic Cohort, Singapore. We tested associations between six CT-based volumetric measures (CTVMs) and existing clinical diagnoses, fluid and imaging biomarkers, and measures of cognition.RESULTSCTVMs differentiated cognitively healthy individuals from dementia and prodromal dementia patients with high accuracy levels comparable to MR-based measures. CTVMs were significantly associated with measures of cognition and biochemical markers of neurodegeneration.DISCUSSIONThese findings suggest the potential future use of CT-based volumetric measures as an informative first-line examination tool for neurodegenerative disease diagnostics after further validation.HIGHLIGHTSComputed tomography (CT)-based volumetric measures can distinguish between patients with neurodegenerative disease and healthy controls, as well as between patients with prodromal dementia and controls.CT-based volumetric measures associate well with relevant cognitive, biochemical, and neuroimaging markers of neurodegenerative diseases.Model performance, in terms of brain tissue classification, was consistent across two cohorts of diverse nature.Intermodality agreement between our automated CT-based and established magnetic resonance (MR)-based image segmentations was stronger than the agreement between visual CT and MR imaging assessment.
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| 3. |
- Srikrishna, Meera, et al.
(författare)
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Deep learning from MRI-derived labels enables automatic brain tissue classification on human brain CT
- 2021
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Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 244
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Tidskriftsartikel (refereegranskat)abstract
- Automatic methods for feature extraction, volumetry, and morphometric analysis in clinical neuroscience typically operate on images obtained with magnetic resonance (MR) imaging equipment. Although CT scans are less expensive to acquire and more widely available than MR scans, their application is currently limited to the visual assessment of brain integrity and the exclusion of co-pathologies. CT has rarely been used for tissue classification because the contrast between grey matter and white matter was considered insufficient. In this study, we propose an automatic method for segmenting grey matter (GM), white matter (WM), cerebrospinal fluid (CSF), and intracranial volume (ICV) from head CT images. A U-Net deep learning model was trained and validated on CT images with MRI-derived segmentation labels. We used data from 744 participants of the Gothenburg H70 Birth Cohort Studies for whom CT and T1-weighted MR images had been acquired on the same day. Our proposed model predicted brain tissue classes accurately from unseen CT images (Dice coefficients of 0.79, 0.82, 0.75, 0.93 and 0.98 for GM, WM, CSF, brain volume and ICV, respectively). To contextualize these results, we generated benchmarks based on established MR-based methods and intentional image degradation. Our findings demonstrate that CT-derived segmentations can be used to delineate and quantify brain tissues, opening new possibilities for the use of CT in clinical practice and research.
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| 4. |
- Srikrishna, Meera
(författare)
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Deriving biomarkers from computed tomography using deep learning
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- X-ray computed tomography (CT) and magnetic resonance imaging (MRI) are widely used structural neuroimaging modalities. For brain atrophy assessment and volumetric quantification using automated methods, MRI is the preferred modality due to its superior soft tissue contrast. In neurodegenerative disease diagnostics, CT scanning is generally used in primary care centres to visually assess brain integrity and to potentially exclude causes of cognitive impairment in the general assessment of neurodegeneration. In comparison to MRI, CT is a fast, affordable, and widely available neuroimaging modality. Currently, only semi-quantitative visual rating methods are established for atrophy assessment on CT, and these are subjective, time-consuming, and dependent on a trained expert. Automated methods to quantify brain volumes in CT are, however, underexplored. The purpose of this thesis was thus to develop automated methods to identify CT-based imaging markers and to assess their potential as a diagnostic aid for neurodegenerative diseases. Studies I and II evaluated the use of deep learning models trained on MR-derived labels to segment brain tissue classes from head CT images. In Study III and IV, the clinical applications of the deep-learning-derived CT-based measures were explored. In Study I, two-dimensional (2D) U-Net-based deep learning models were successfully trained on CT images with labels generated by segmenting paired MR images in order to automatically segment grey matter, white matter, cerebrospinal fluid, brain volume, and intracranial volume. High spatial overlap scores and high volumetric correlations were observed between deep-learning-derived CT-based segmentations and MR-derived maps for all tissue classes indicating that model-derived tissue volumes were highly comparable to MR-derived volumes. In Study II, patch-based 3D segmentation networks for CT brain tissue classification were developed and the segmentation performance of 2D- and 3D-based segmentation networks were compared to evaluate which model is more suitable for anisotropic CT brain tissue classification. Our study demonstrated that slice-wise-processed 2D U-Nets perform better than patch-based 3D U-Nets in anisotropic CT brain tissue classification. In Study III, we showed that CT-based atrophy measures can be employed to differentiate between patients with Alzheimer’s disease, prodromal Alzheimer’s disease, vascular dementia, prodromal vascular dementia and healthy controls with accuracy levels comparable to MR-derived atrophy measures. CT-based atrophy measures strongly correlated with relevant MR-based and biochemical markers of neurodegeneration as well as with cognitive impairment. This study indicated that CT-based atrophy measures have great potential to offer diagnostic support in the first-line assessment of neurodegenerative diseases. In Study IV, ventricular cerebrospinal fluid (VCSF) volumes were derived from CT images using U-Net models trained on both MR-derived labels and labels manually derived from CT scans using a transfer-learning approach. Further, CT-based volumetry was evaluated for assessing ventricle volume change post-shunt surgery in idiopathic normal pressure hydrocephalus (iNPH). We demonstrated that CT-based volumetric measures could distinguish iNPH patients from cognitively normal individuals with high accuracy and the presence of a shunt had little to no effect on the model performance. Strong volumetric correlations were observed between automatically and manually derived CT-VCSF maps, indicating a strong potential for automated CT-derived VCSF volumetry in the clinical assessment of iNPH with comparable performance to visual assessments. Together, our findings describe novel automated methods for CT brain image segmentation that make a quantitative assessment of neurodegenerative change accessible to many more patients, as CT is far more accessible, cheaper, and faster than MRI.
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| 5. |
- Young, Peter N.E., et al.
(författare)
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Imaging biomarkers in neurodegeneration : Current and future practices
- 2020
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Ingår i: Alzheimer's Research and Therapy. - : Springer Science and Business Media LLC. - 1758-9193. ; 12:1
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Forskningsöversikt (refereegranskat)abstract
- There is an increasing role for biological markers (biomarkers) in the understanding and diagnosis of neurodegenerative disorders. The application of imaging biomarkers specifically for the in vivo investigation of neurodegenerative disorders has increased substantially over the past decades and continues to provide further benefits both to the diagnosis and understanding of these diseases. This review forms part of a series of articles which stem from the University College London/University of Gothenburg course "Biomarkers in neurodegenerative diseases". In this review, we focus on neuroimaging, specifically positron emission tomography (PET) and magnetic resonance imaging (MRI), giving an overview of the current established practices clinically and in research as well as new techniques being developed. We will also discuss the use of machine learning (ML) techniques within these fields to provide additional insights to early diagnosis and multimodal analysis.
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