DataSheet1.docx

<p>Recent tract-based analyses provided evidence for the exploitability of 3D-SHORE microstructural descriptors derived from diffusion MRI (dMRI) in revealing white matter (WM) plasticity. In this work, we focused on the main open issues left: (1) the comparative analysis with respect to classical tensor-derived indices, i.e., Fractional Anisotropy (FA) and Mean Diffusivity (MD); and (2) the ability to detect plasticity processes in gray matter (GM). Although signal modeling in GM is still largely unexplored, we investigated their sensibility to stroke-induced microstructural modifications occurring in the contralateral hemisphere. A more complete picture could provide hints for investigating the interplay of GM and WM modulations. Ten stroke patients and ten age/gender-matched healthy controls were enrolled in the study and underwent diffusion spectrum imaging (DSI). Acquisitions at three and two time points (tp) were performed on patients and controls, respectively. For all subjects and acquisitions, FA and MD were computed along with 3D-SHORE-based indices [Generalized Fractional Anisotropy (GFA), Propagator Anisotropy (PA), Return To the Axis Probability (RTAP), Return To the Plane Probability (RTPP), and Mean Square Displacement (MSD)]. Tract-based analysis involving the cortical, subcortical and transcallosal motor networks and region-based analysis in GM were successively performed, focusing on the contralateral hemisphere to the stroke. Reproducibility of all the indices on both WM and GM was quantitatively proved on controls. For tract-based, longitudinal group analyses revealed the highest significant differences across the subcortical and transcallosal networks for all the indices. The optimal regression model for predicting the clinical motor outcome at tp3 included GFA, PA, RTPP, and MSD in the subcortical network in combination with the main clinical information at baseline. Region-based analysis in the contralateral GM highlighted the ability of anisotropy indices in discriminating between groups mainly at tp1, while diffusivity indices appeared to be altered at tp2. 3D-SHORE indices proved to be suitable in probing plasticity in both WM and GM, further confirming their viability as a novel family of biomarkers in ischemic stroke in WM and revealing their potential exploitability in GM. Their combination with tensor-derived indices can provide more detailed insights of the different tissue modulations related to stroke pathology.</p

A Perspective on Explainable Artificial Intelligence Methods: SHAP and LIME

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Postoperative imaging in two patients of the new group (patients. nos. 7 and 10).

<p>The presurgical ESI and ASL results are overlaid on the coregistered postoperative MRI scans for each patient. Two different sections are shown for each plane (sagittal, coronal and axial). The rising phase of activity and the statistical results from the one-versus-many analysis are presented for ESI and ASL, respectively.</p

ASL imaging results in the new group of six patients (patients nos. 7–12) with focal epilepsy.

<p>A) Regions of interest (ROIs) for the quantification of current density (CD) and cerebral blood flow (CBF) values at the same anatomical level in each subject. ROIs are superimposed over axial T1-weighted slices in MNI space. B) Statistical analysis results from the template-based comparison. CBF maps (normalized values) for the same axial slices reported in part A) are shown here for the control group (template) and patients, together with the statistical map. In all patients, only areas with a statistically significant decrease in perfusion as compared to the healthy subjects were detected (blue scale, FDR corrected, <i>q</i> < 0.05).</p

Quantification results from ESI and ASL in the six patients (patients nos. 7–12) with focal epilepsy.

<p>ESI indicates current density (CD) at 50% rising phase of the peak [μA/mm³], while ASL indicates cerebral blood flow (CBF) [ml/100g/min]. Only the values for the five most significant regions are reported. H = hippocampus; ITGa = inferior temporal gyrus, anterior division; TP = temporal pole; FOrC = frontal orbital cortex; TFCa = temporal fusiform cortex, anterior division; MTGa = middle temporal gyrus, anterior division; ITGp = inferior temporal gyrus, posterior part; FoC = frontal opercolum cortex; CoC = central opercolar cortex; PP = planum temporale; STGa = superior temporal gyrus, anterior division; FP = frontal pole; MTGp = middle temporal gyrus, posterior division.</p><p>Quantification results from ESI and ASL in the six patients (patients nos. 7–12) with focal epilepsy.</p

ASL imaging results in the six focal epilepsy patients described in the previous study (patients nos. 1–6).

<p>A) Regions of interest for quantification of current density (CD) and cerebral blood flow (CBF) values at the same anatomical level in each subject. ROIs are superimposed over axial T1-weighted slices in MNI space. B) Statistical analysis results from the template-based comparison. CBF maps (normalized values) for the same axial slices reported in part A) are shown here for the control group (template) and patients, together with the statistical map. Areas with a statistically significant decrease in perfusion (hypoperfusion), as compared to the healthy subjects, were detected in four patients (blue scale, FDR corrected, <i>q</i> < 0.05). Conversely, areas with a statistically significant increase in perfusion (hyperperfusion), as compared to the healthy subjects, were detected in two patients (yellow scale, FDR corrected, <i>q</i> < 0.05).</p

Imaging analysis results in the six patients (patients nos. 7–12) with focal epilepsy.

<p>ESI and ASL images of the same anatomical space were acquired for each patient and two axial sections are shown (z coordinates in native space). (A) Spike average: 256-channel EEG traces with a duration of 1 s (spike average). The global field power is used for the onset (red line). (B) ESI results: EEG source imaging at 50% rising phase of the peak (up) and at the peak (down). The scale indicates the current density (CD) [μA/mm³]. (C) ASL results. The scale indicates the cerebral blood flow (CBF) values [ml/100g/min].</p

Postoperative imaging in three patients from the previously described patient group (patients nos. 2, 4 and 6).

<p>The presurgical ESI and ASL results are overlaid on the coregistered postoperative MRI scans of each patient. Two different sections are shown for each plane (sagittal, coronal and axial). The rising phase of activity and the statistical results from the one-versus-many analysis are presented for ESI and ASL, respectively.</p

Parameter estimates for the normal perfusion template, computed from the control group.

<p>A) Mean CBF estimates expressed in normalized units. B) Within-subject variance, estimated from the temporal information given by the multiple repetitions, for a representative subject. C) Average within-subject variance in the control group. D) Between-subject variance estimated from the heteroscedastic model. Axial slices of interest are displayed in radiological convention.</p

Average spike voltage maps.

<p>Spike average (epochs of 1 s) of interictal activities visualized according to the projected location of the scalp electrodes in the six patients.</p