M. Weigel
University of BaselAuthor Of 2 Presentations
FC03.03 - Depicting multiple sclerosis pathology at 160μm isotropic resolution by human whole-brain postmortem 3T magnetic resonance imaging
Abstract
Background
Postmortem magnetic resonance imaging (MRI) of formalin-fixed healthy and diseased human brains with ultra-high spatial resolution has the great potential to depict tissue architecture in fine detail, allowing a deeper understanding of pathological processes. Whole-brain imaging is important since it provides neuroanatomic relationships, reference points across distant brain regions, and a comprehensive view of pathologies affecting the brain. However, ultra-high-resolution whole-brain postmortem MRI is challenging and has been so far almost exclusively performed at 7T with specialized hardware.
Objectives
To develop a 3D isotropic 160µm ultra-high-resolution imaging (URI) approach for human whole-brain ex vivo acquisitions on a standard clinical 3T MRI system. To explore the sensitivity and specificity of the approach to specific pathological features of multiple sclerosis (MS).
Methods
A fixed whole human brain from a patient with secondary progressive MS was investigated. Acquisitions were performed on a clinical 3T Siemens Prismafit MRI system with standard hardware components. URI is based on a gradient echo sequence similar to the 7T approach by Edlow et al. 2019. However, it allows to acquire an isotropic 160µm resolution with low hardware demands and to directly reconstruct the image data on the standard 3T MRI system. URI images display a strong, susceptibility-enhanced tissue contrast.
Results
The reconstructed URI images depicted with remarkable quality the diseased human MS brain at 3T field strength. URI allowed to distinguish fine anatomical details such as the subpial molecular layer, the stria of Gennari as well as some intrathalamic nuclei. Additionally, because of the unprecedented spatial resolution and contrast at 3T, URI permitted to easily identify the presence of subpial lesions, detailed features of intracortical lesions such the presence of incomplete/complete iron rims or patterns of iron accumulation in the entire lesion core in both cortical and white matter lesions (CLs/WMLs), lesions affecting the convoluted layers of the cerebellar cortex and nascent submillimetric CLs/WMLs.
Conclusions
URI provides a comprehensive microscopic insight into the whole-human brain at 3T through the micrometric resolution and a tissue-specific, susceptibility-enhanced contrast. We propose URI as an excellent approach to investigate microscopic brain changes of complex pathologies like MS.
PS16.04 - RimNet: A deep 3D multimodal MRI architecture for paramagnetic rim lesions assessment in multiple sclerosis
Abstract
Background
In multiple sclerosis (MS), perilesional chronic inflammation appears on in vivo 3T susceptibility-based magnetic resonance imaging (MRI) as non-gadolinium-enhancing paramagnetic rim lesions (PRL). A higher PRL burden has been recently associated with a more aggressive disease course. The visual detection of PRL by experts is time-consuming and can be subjective.
Objectives
To develop a multimodal convolutional neural network (CNN) capable of automatically detecting PRL on 3D-T2*w-EPI unwrapped phase and 3D-T2w-FLAIR images.
Methods
124 MS cases (87 relapsing remitting MS, 16 primary progressive MS and 21 secondary progressive MS) underwent 3T MRI (MAGNETOM Prisma and MAGNETOM Skyra, Siemens Healthcare, Erlangen, Germany). Two neurologists visually inspected FLAIR magnitude and EPI phase images and annotated 462 PRL. 4857 lesions detected by an automatic segmentation (La Rosa et al. 2019) without overlap with PRL were considered non-PRL. The prototype RimNet was built upon two single CNNs, each fed with 3D patches centered on candidate lesions in phase and FLAIR images, respectively. A two-step feature-map fusion, initially after the first convolutional block and then before the fully connected layers, enhances the extraction of low and high-level multimodal features. For comparison, two unimodal CNNs were trained with phase and FLAIR images. The areas under the ROC curve (AUC) were used for evaluation (DeLong et al. 1988). The operating point was set at a lesion-wise specificity of 0.95. The patient-wise assessment was conducted by using a clinically relevant threshold of four rim+ lesions per patient (Absinta et al. 2019).
Results
RimNet (AUC=0.943) outperformed the phase and FLAIR image unimodal networks (AUC=0.913 and 0.855, respectively, P’s <0.0001). At the operating point, RimNet showed higher lesion-wise sensitivity (70.6%) than the unimodal phase network (62.1%), but lower than the experts (77.7%). At the patient level, RimNet performed with sensitivity of 86.8% and specificity of 90.7%. Individual expert ratings yielded averaged sensitivity and specificity values of 76.3% and 99.4%, respectively.
Conclusions
The excellent performance of RimNet supports its further development as an assessment tool to automatically detect PRL in MS. Interestingly, the unimodal FLAIR network performed reasonably well despite the absence of a paramagnetic rim, suggesting that morphometric features such as volume or shape might be a distinguishable feature of PRL.
Presenter Of 1 Presentation
FC03.03 - Depicting multiple sclerosis pathology at 160μm isotropic resolution by human whole-brain postmortem 3T magnetic resonance imaging
Abstract
Background
Postmortem magnetic resonance imaging (MRI) of formalin-fixed healthy and diseased human brains with ultra-high spatial resolution has the great potential to depict tissue architecture in fine detail, allowing a deeper understanding of pathological processes. Whole-brain imaging is important since it provides neuroanatomic relationships, reference points across distant brain regions, and a comprehensive view of pathologies affecting the brain. However, ultra-high-resolution whole-brain postmortem MRI is challenging and has been so far almost exclusively performed at 7T with specialized hardware.
Objectives
To develop a 3D isotropic 160µm ultra-high-resolution imaging (URI) approach for human whole-brain ex vivo acquisitions on a standard clinical 3T MRI system. To explore the sensitivity and specificity of the approach to specific pathological features of multiple sclerosis (MS).
Methods
A fixed whole human brain from a patient with secondary progressive MS was investigated. Acquisitions were performed on a clinical 3T Siemens Prismafit MRI system with standard hardware components. URI is based on a gradient echo sequence similar to the 7T approach by Edlow et al. 2019. However, it allows to acquire an isotropic 160µm resolution with low hardware demands and to directly reconstruct the image data on the standard 3T MRI system. URI images display a strong, susceptibility-enhanced tissue contrast.
Results
The reconstructed URI images depicted with remarkable quality the diseased human MS brain at 3T field strength. URI allowed to distinguish fine anatomical details such as the subpial molecular layer, the stria of Gennari as well as some intrathalamic nuclei. Additionally, because of the unprecedented spatial resolution and contrast at 3T, URI permitted to easily identify the presence of subpial lesions, detailed features of intracortical lesions such the presence of incomplete/complete iron rims or patterns of iron accumulation in the entire lesion core in both cortical and white matter lesions (CLs/WMLs), lesions affecting the convoluted layers of the cerebellar cortex and nascent submillimetric CLs/WMLs.
Conclusions
URI provides a comprehensive microscopic insight into the whole-human brain at 3T through the micrometric resolution and a tissue-specific, susceptibility-enhanced contrast. We propose URI as an excellent approach to investigate microscopic brain changes of complex pathologies like MS.