Spatio-Temporal Analysis of Abrasion Susceptibility Effect on Land Cover in the Coastal Area of Bantul Regency, Yogyakarta, Indonesia

Shoreline dynamics naturally occur in coastal areas, and over time, are also influenced by anthropogenic processes taking place both on-site and upstream. Bordering the Indian Ocean, the coastal area of Bantul Regency in the Special Region of Yogyakarta is faced with typical strong and high waves that induce changes in its shoreline dynamics and activities. Consequently, tourism, a leading economic sector in the area, often needs to adjust to such changes. Here, shorelines were extracted from the spatial data of time-series Sentinel 2A imagery (2015, 2016, 2017, 2018, 2019, and 2020) using water index transformation, MNDWI, while the land cover changes were analyzed using the Decision Tree classification. Based on the results, accretion appeared most significant from 2016 to 2017, creating an additional 22.32 ha. In contrast, shoreline change from 2019 until 2020 indicated the most severe abrasion that led to a loss of 34.89 ha. The highest rate of landward shoreline change was 41.58 m/year.

The potential role of T2*-weighted multi-echo data image combination as an imaging marker for intraplaque hemorrhage in carotid plaque imaging

Background Carotid atherosclerotic plaques with intraplaque hemorrhage (IPH) are associated with elevated stroke risk. IPH is predominantly imaged based on paramagnetic properties of the upstream hemoglobin degradation product methemoglobin. This is an explorative observational study to test the feasibility of a spoiled gradient echo based T2* weighted MRI sequence (3D MEDIC) for carotid plaque imaging, and to compare signs suggestive of the downstream degradation product hemosiderin on 3D MEDIC with signs of methemoglobin on a T1wBB sequence. Methods Patients with recent TIA or stroke were selected based on the presence on non-calcified plaque components on CTA to promote an enriched prevalence of IPH in the material. Patients (n = 42) underwent 3T MRI with 3D MEDIC and 2D turbo spin echo T1w black blood (T1wBB). Images were independently evaluated by two neuroradiologists and Cohens Kappa was used for inter-reader agreement for each sequence. Results The technical feasibility for 3D MEDIC, was 34/42 patients (81%). Non-calcified plaque components with susceptibility effect without simultaneous T1-shortening—a combination suggestive of hemosiderin, was seen in 13/34 of the plaques. An equally large group display elevated T1w signal in combination with signal loss on 3D MEDIC, a combination suggestive of both hemosiderin and methemoglobin. Cohen’s kappa for inter-reader agreement was 0.64 (CI 0.345–0.925) for 3D MEDIC and 0.94 (CI 0.81–1.00) for T1wBB. Conclusions 3D MEDIC shows signal loss, without elevated T1w signal on T1wBB, in non-calcified tissue in many plaques in this group of patients. If further studies, including histological verification, confirm that the 3D MEDIC susceptibility effect is indeed caused by hemosiderin, 3D MEDIC could aid in the detection of IPH, beyond elevation of T1w signal.

Immunogenetic Epidemiology of Multiple Sclerosis in 14 Continental Western European Countries

Human leukocyte antigen (HLA), a system involved in immune response to foreign antigens and in autoimmunity, has been strongly implicated in multiple sclerosis (MS). Prior research has shown that HLA DRB1*15:01 exerts the strongest susceptibility effect, although other HLA alleles have been implicated in both susceptibility to, and protection against, MS. Here we utilized an immunogenetic epidemiological approach to evaluate correlations between the population frequencies of 127 HLA Class I and II alleles and the population prevalence of MS in 14 Continental Western European countries to identify an HLA profile for MS. The results of these analyses, which largely corroborated prior findings and revealed several novel and highly robust HLA associations with MS, revealed a larger number of protective HLA alleles than susceptibility alleles, particularly for HLA Class I. Given the role of HLA in pathogen elimination and autoimmunity, these findings point to a contributory role of exposure to pathogens in the absence of protective HLA in underlying the inflammation and autoimmunity associated with MS.

Evaluation and Optimization of Motion Correction in Spinal Cord fMRI Preprocessing

Motion correction is an essential step in the preprocessing of functional magnetic resonance imaging (fMRI) data, improving the temporal signal to noise ratio (tSNR) and removing unwanted variance. Because of the characteristics of the spinal cord (non-rigidity, surrounded by moving organs), motion correction becomes especially challenging. We compared the efficiency of different motion correction protocols and suggest a preferred method for spinal cord fMRI data. Here we acquired gradient-echo echo-planar-imaging axial lumbar spinal cord fMRI data during painful mechanical stimulation of the left lower extremity of 15 healthy volunteers on a 3T scanner. We compared multiple motion correction techniques: 2D and 3D FLIRT realignment with and without slice-wise regulation, SliceCorr (implemented in the Spinal Cord Toolbox) and proposed a method 3D FLIRT in addition to Slice Regulation (SLiceReg) along the spinal cord. TSNR, image entropy, DVARS, image Sum of Absolute Differences and number of activated voxels in the spinal cord from GLM analysis to evaluate the performance of multiple motion correction procedures. The tSNR and DVARS 3D FLIRT + SLiceReg were significantly improved over other realignment methods (p<0.001). In comparison, tSNR=14.20±0.02 and DVARS=165.77±1.54 were higher than other methods. Additionally, the number of activated voxels of the statistical map in our suggested method was higher than the other realignment methods (p<0.05). Our results illustrated the proposed motion correction algorithm that integrated 3D motion correction and 2D slicewise regularization along spinal cord curvature could improve subject-level processing outputs by reducing the effects of motions. Our proposed protocols can improve subject-level analysis, especially in lumbar region that suffers from involuntary motions and signal loss due to susceptibility effect more than other spinal cord regions.

Abstract TMP45: Usefulness of Susceptibility Vessel Sign With Bright Vessel Appearance in Acute Ischemic Stroke

Background: Red thrombi, composed of fibrin and trapped erythrocytes, have magnetic susceptibility effect. Susceptibility vessel sign (SVS) is visualized more sensitively using susceptibility weighted imaging (SWI) than T2*-weighted imaging. Bright vessel appearance (BVA) on arterial spin labeling (ASL) imaging can visualize occluded arterial segment by arterial transit artifact, more sensitively in small and peripheral branches. We investigated the usefulness of SWI-SVS with BVA to visualize different thrombus and predict stroke mechanisms. Methods: From a total of 564 stroke cases who admitted to Seoul National University Hospital in 2014, the authors collected eligible cases with the following inclusion criteria; (1) Lesion-documented ischemic stroke (N=425); (2) SWI and ASL MRI performed (N=407); (3) Symptomatic arterial occlusion with BVA (N=141). All images were analyzed for the presence and location of SWI-SVS and BVA. The location of SWI-SVS and BVA were classified into (1) proximal, large arteries; distal ICA, M1/2, A1, P1, basilar artery, V4 and (2) peripheral, small arteries; M3/4, P2/3, A2/3, lenticulostriate arteries, three cerebellar arteries. The relationships between SWI-SVS in the presence of BVA and stroke etiologies are explored. Results: Male was 58.2% (n=82) and mean age was 65.7±14.3. Thirty-four percent (n=48/141) of BVA and 30.3% (n=30/99) of SVS was located within small, peripheral arteries. SWI-SVS was more commonly associated with other determined etiology (20.2% vs. 4.8%) and cardioembolism (39.4% vs. 14.3%), but less with large artery atherosclerosis (26.3% vs. 69.0%, P <0.01) compared to the patients without SWI-SVS. Cancer-related hypercoagulability (60%, n=12/20) was most common in other determined cases with SWI-SVS. Multivariate analysis showed that SWI-SVS was an independent predictor of other determined etiology (adjusted OR, 7.20; 95% CI, 1.48-34.99) and cardioembolism (adjusted OR, 5.76; 95% CI, 1.27-26.02) Conclusions: SWI-SVS with BVA may predict ischemic stroke of cardioembolism and other determined etiology. Occlusions of small, peripheral arteries are well visualized with BVA and composition of thrombus can be identified by SWI-SVS.

Relative Hypodense Vertebral Artery Sign on Computerized Tomography in Atherosclerotic Near Occlusion

A 52-year-old white male presented with an acute onset of slurred speech along with hypoesthesia in the entire left arm. The acute computed tomography (CT) showed relative hypodensity in the intracranial segment of left vertebral artery (VA) that was not present in historical images, pointing to the possible lack of flow. The site of occlusion was confirmed by magnetic resonance imaging (MRI) that showed susceptibility effect in the affected artery. By means of historical native CT comparison the site of VA thrombosis was correctly predicted. Local atherosclerotic thrombosis of the VA could be relatively hypodense on native CT and still have positive susceptibility weighted imaging (SWI) sign.