Feature Tracking Method Research Articles

Spatially varying WIndow based maximum likelihood Feature Tracking (SWIFT) Method for Glacier Surface Velocity Estimations

Glacier surface velocity is an important variable for glacier dynamics studies. Estimation of accurate surface velocity from remote sensing is a challenge, especially for glaciers with no in-situ observations. To overcome this challenge, a new method for glacier feature tracking named as SWIFT (Spatially varying WIndow based maximum likelihood Feature Tracking) has been proposed. This method utilises both optical data (to automatically determine the window size using the concept of Object Based Image Analysis) and Synthetic Aperture Radar (SAR) data (to perform feature tracking). The proposed method uses a spatially varying window size unlike other existing softwares that cannot provide the flexibility of a spatially varying window size. The proposed method has been tested and validated at three different glaciers (South Glacier, Canada; Chhota Shigri Glacier, India; and Tasman Glacier, New Zealand) for which field measured data were available. The obtained results for all three glaciers showed consistent improvement in estimated velocity by SWIFT when compared with spatially fixed window size-based estimates from normalized cross correlation-based Correlation Image Analysis Software (CIAS). Considering the data availability, the proposed SWIFT method has been implemented using a variety of SAR and optical satellite data to understand its performance/effectiveness for glacier surface velocity estimation. When validated against field measurements, the results from SWIFT gave an RMSE of 12.8 m/yr, 15.32 m/yr and 67.1 m/yr for South Glacier, Chhota Shigri Glacier and Tasman Glacier, respectively. Moreover, the RMSE of SWIFT estimates were observed to have an RMSE that was 19%-36% lower than the best performing spatially fixed window size.

Intensity/Inertial Integration-Aided Feature Tracking on Event Cameras

Achieving efficient and accurate feature tracking on event cameras is a fundamental step for practical high-level applications, such as simultaneous localization and mapping (SLAM) and structure from motion (SfM) and visual odometry (VO) in GNSS (Global Navigation Satellite System)-denied environments. Although many asynchronous tracking methods purely using event flow have been proposed, they suffer from high computation demand and drift problems. In this paper, event information is still processed in the form of synthetic event frames to better adapt to the practical demands. Weighted fusion of multiple hypothesis testing with batch processing (WF-MHT-BP) is proposed based on loose integration of event, intensity, and inertial information. More specifically, with inertial information acting as priors, multiple hypothesis testing with batch processing (MHT-BP) produces coarse feature-tracking solutions on event frames in a batch processing way. With a time-related stochastic model, a weighted fusion mechanism fuses feature-tracking solutions from event and intensity frames compared with other state-of-the-art feature-tracking methods on event cameras. Evaluation on public datasets shows significant improvements on accuracy and efficiency and comparable performances in terms of feature-tracking length.

A Rapid Dual Feature Tracking Method for Medical Equipments Assembly and Disassembly in Markerless Augmented Reality

Markerless Augmented Reality (MAR) is a superior technology that is currently used by the medical device assembler with aid in design, assembly, disassembly and maintenance operations. The medical assembler assembles the medical equipment based on the doctors requirement, they also maintains quality and sanitation of the equipment. The major research challenges in MAR are as follows: establish automatic registration parts, find and track the orientation of parts, and lack of depth and visual features. This work proposes a rapid dual feature tracking method i.e., combination of Visual Simultaneous Localization and Mapping (SLAM) and Matched Pairs Selection (MAPSEL). The main idea of this work is to attain high tracking accuracy using the combined method. To get a good depth image map, a Graph-Based Joint Bilateral with Sharpening Filter (GRB-JBF with SF) is proposed since depth images are noisy due to the dynamic change of environmental factors that affects tracking accuracy. Then, the best feature points are obtained for matching using Oriented Fast and Rotated Brief (ORB) as a feature detector, Fast Retina Key point with Histogram of Gradients (FREAK-HoG) as a feature descriptor, and Feature Matching using Rajsk’s distance. Finally, the virtual object is rendered based on 3D affine and projection transformation. This work computes the performance in terms of tracking accuracy, tracking time, and rotation error for different distances using MATLAB R2017b. From the observed results, it is perceived that the proposed method attained the least position error value about 0.1 cm to 0.3 cm. Also, rotation error is observed as minimal between 2.40 (Deg) to 3.10 and its average scale is observed as 2.7140. Further, the proposed combination consumes less time against frames compared with other combinations and obtained a higher tracking accuracy of about 95.14% for 180 tracked points. The witnessed outcomes from the proposed scheme display superior performance compared with existing methods.

Temporal Merge Tree Maps: A Topology-Based Static Visualization for Temporal Scalar Data.

Creating a static visualization for a time-dependent scalar field is a non-trivial task, yet very insightful as it shows the dynamics in one picture. Existing approaches are based on a linearization of the domain or on feature tracking. Domain linearizations use space-filling curves to place all sample points into a 1D domain, thereby breaking up individual features. Feature tracking methods explicitly respect feature continuity in space and time, but generally neglect the data context in which those features live. We present a feature-based linearization of the spatial domain that keeps features together and preserves their context by involving all data samples. We use augmented merge trees to linearize the domain and show that our linearized function has the same merge tree as the original data. A greedy optimization scheme aligns the trees over time providing temporal continuity. This leads to a static 2D visualization with one temporal dimension, and all spatial dimensions compressed into one. We compare our method against other domain linearizations as well as feature-tracking approaches, and apply it to several real-world data sets.

Myocardial Strain Derived from 13N-ammonia Positron Emission Tomography: Detection of Ischemia-Related Wall Motion Abnormality.

Background: Due to the limitation of spatial resolution, cardiac nuclear medicine images have not been applied to feature-tracking method to automatic extraction of myocardial contours. We have successfully applied the feature-tracking method to high-resolution cine 13N-ammonia positron emission tomography (PET) images to calculate the regional myocardial strains. Here, we investigate the potential of 13N-ammonia PET-derived strain to detect ischemia-related wall motion abnormality. Methods: Data of adenosine-stress/rest 13N-ammonia PET for 95 coronary artery disease patients was retrospectively analyzed. Using an original algorithm dedicated to 13N-ammonia PET, the longitudinal strain (LS) corresponding to the three main coronary artery territories [right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex coronary artery (LCX)] was calculated from semi-automatic endocardial contours extraction on cine 13N-ammonia PET images of the left ventricular long-axis. The presence of ischemia in three main territories was determined from rest and stress-perfusion images. Results: In all three coronary territories, LS at stress was significantly smaller at rest in the ischemic region RCA: -19.2±8.0% vs. -22.7±6.1%, LAD: -19.0±6.9% vs. -24.4±6.4%, LCX: -20.5%±7.6% vs. -22.6±6.9%). In contrast, in the non-ischemic region, there was no significant difference between the LS at stress and at rest. Receiver-operating-characteristic analysis revealed that using the optimal cutoff of the LS ratio of stress to rest, ischemia could be diagnosed with area under the curve of 0.82 in the RCA, 0.86 in the LAD, and 0.69 in the LCX. Conclusions: Myocardial strain derived from endocardial feature-tracking of 13N-ammonia PET cine imaging is reduced in the ischemia induced by adenosine-stress. The LS ratio of stress to rest may detect wall motion abnormality related to ischemia.

Relation of Left Atrial Flow, Volume, and Strain to Paroxysmal Atrial Fibrillation in Patients With Hypertrophic Cardiomyopathy

This study aims to characterize flow, volume, and strain of the left atrium in hypertrophic cardiomyopathy (HC) with atrial fibrillation (AF) using cine cardiovascular magnetic resonance (CMR) imaging. Cine CMR data for 144 patients with HC, including 29 patients with episodes of paroxysmal AF and 13 patients with persistent AF, were retrospectively analyzed. The vortex flow of the left atrial (LA, %) was measured using a vortex flow map and was used as an estimate of flow. The LA end-systolic volume index (ml/m2), LA ejection fraction (%) and global peak longitudinal LA strain (%) derived from a feature-tracking method were used as estimates of volume and strain. Vortex flow of the LA in patients with paroxysmal AF was significantly smaller than in patients without AF (vertical long-axis view; 26.7 ± 10.8% vs 33.2 ± 12.2%, p <0.005). The patients with paroxysmal AF had greater LA end-systolic volume index and global peak longitudinal LA strain and lower LA ejection fraction compared with those without AF. In conclusion, patients with HC with paroxysmal AF are characterized by small vortex flow, large volume, and decreased strain of LA on cine CMR.

The predictive role of cardiac magnetic resonance imaging in determining thalassemia patients with intermediately to highly probable pulmonary hypertension.

We sought to determine the cardiac magnetic resonance (CMR) indicators of intermediately to highly probable pulmonary hypertension (IHpPH) in patients with thalassemia referred for myocardial iron overload assessments to prevent further cardiac complications. The study population consisted of 152 patients with thalassemia (major or intermedia) (49.3% women, mean age=33±10.1years) who underwent non-contrast CMR and echocardiographic examinations on the same day. Functional, T2*, and global strain parameters via a feature-tracking method were extracted from CMR. The probability of PH was defined based on the tricuspid regurgitation velocity and echocardiographic parameters. The catheterization-derived hemodynamic data of patients with moderate to high probable PH was registered. Twenty-two (14.5%) patients suffered from IHpPH. The multivariate logistic regression analysis revealed that the right ventricular end-systolic volume index (RVESVI) was the strongest of all the CMR parameters for the prediction of IHpPH (OR: 1.044, 95% CI: 1.021-1.067). The other powerful IHpPH predictor was age (OR: 1.066, 95% CI: 1.009-1.126). A cutoff point of greater than 47ml for RVESVI (AUC: .801, 95% CI: .728-.861) was found to predict IHpPH with 73.91% sensitivity and 70.31% specificity. The single most robust CMR-derived strain parameter for IHpPH prediction was the right ventricular global longitudinal strain (OR: .887, 95% CI: .818-.961). A p value of less than 0.05 was considered significant. Both CMR functional and global strain parameters were strong predictors of IHpPH in our patients with thalassemia.

Metode Natural Feature Tracking dan Fast Corner Detection dengan Teknik Virtual Button Pada Aplikasi Sistem Pernafasan Manusia

At this time the development of information and communication technology has developed very rapidly. As in smartphones, the technology contained in smartphones today has an important role for human activities. The technology that is currently being implemented on smartphones is Augmented Reality. Augmented reality can be used in all fields of human activity, one of which is in the field of education. The purpose of this research is to develop an educational media about the organs of the human respiratory system that is interactive and can be understood by users such as students. In this study, 2 methods were used, namely Fast Corner Detection and Natural Feature Tracking Methods to read a marker which would later bring up information and also use the virtual button technique in the application. In testing using 5 smartphones. The results of testing at an angle of 60o and 90o the five smartphones can detect markers. The distance test has different results from the smallest having a minimum distance of ±70 cm to a maximum distance of ±150 cm. In tests based on light intensity, the five smartphones can detect markers at light intensities above 5 lux

Asynchronous event feature generation and tracking based on gradient descriptor for event cameras

Recently, the event camera has become a popular and promising vision sensor in the research of simultaneous localization and mapping and computer vision owing to its advantages: low latency, high dynamic range, and high temporal resolution. As a basic part of the feature-based SLAM system, the feature tracking method using event cameras is still an open question. In this article, we present a novel asynchronous event feature generation and tracking algorithm operating directly on event-streams to fully utilize the natural asynchronism of event cameras. The proposed algorithm consists of an event-corner detection unit, a descriptor construction unit, and an event feature tracking unit. The event-corner detection unit addresses a fast and asynchronous corner detector to extract event-corners from event-streams. For the descriptor construction unit, we propose a novel asynchronous gradient descriptor inspired by the scale-invariant feature transform descriptor, which helps to achieve quantitative measurement of similarity between event feature pairs. The construction of the gradient descriptor can be decomposed into three stages: speed-invariant time surface maintenance and extraction, principal orientation calculation, and descriptor generation. The event feature tracking unit combines the constructed gradient descriptor and an event feature matching method to achieve asynchronous feature tracking. We implement the proposed algorithm in C++ and evaluate it on a public event dataset. The experimental results show that our proposed method achieves improvement in terms of tracking accuracy and real-time performance when compared with the state-of-the-art asynchronous event-corner tracker and with no compromise on the feature tracking lifetime.

Efficacy of Novel Noncontrast Cardiac Magnetic Resonance Methods in Indicating Fibrosis in Hypertrophic Cardiomyopathy.

Objective In hypertrophic cardiomyopathy (HCM), myocardial fibrosis is routinely shown by late gadolinium enhancement (LGE) in cardiac magnetic resonance (CMR) imaging. We evaluated the efficacy of 2 novel contrast-free CMR methods, namely, diffusion-weighted imaging (DWI) and feature-tracking (FT) method, in detecting myocardial fibrosis. Methods This cross-sectional study was conducted on 26 patients with HCM. Visual and quantitative comparisons were made between DWI and LGE images. Regional longitudinal, circumferential, and radial strains were compared between LGE-positive and LGE-negative segments. Moreover, global strains were compared between LGE-positive and LGE-negative patients as well as between patients with mild and marked LGE. Results All 3 strains showed significant differences between LGE-positive and LGE-negative segments (P < 0.001). The regional longitudinal and circumferential strain parameters showed significant associations with LGE (P < 0.001), while regional circumferential strain was the only independent predictor of LGE in logistic regression models (OR: 1.140, 95% CI: 1.073 to 1.207, P < 0.001). A comparison of global strains between patients with LGE percentages of below 15% and above 15% demonstrated that global circumferential strain was the only parameter to show impairment in the group with marked myocardial fibrosis, with borderline significance (P=0.09). A review of 212 segments demonstrated a qualitative visual agreement between DWI and LGE in 193 segments (91%). The mean apparent diffusion coefficient was comparable between LGE-positive and LGE-negative segments (P=0.51). Conclusions FT-CMR, especially regional circumferential strain, can reliably show fibrosis-containing segments in HCM. Further, DWI can function as an efficient qualitative method for the estimation of the fibrosis extent in HCM.

Visual analysis of density and velocity profiles in dense 3D granular gases

Granular multiparticle ensembles are of interest from fundamental statistical viewpoints as well as for the understanding of collective processes in industry and in nature. Extraction of physical data from optical observations of three-dimensional (3D) granular ensembles poses considerable problems. Particle-based tracking is possible only at low volume fractions, not in clusters. We apply shadow-based and feature-tracking methods to analyze the dynamics of granular gases in a container with vibrating side walls under microgravity. In order to validate the reliability of these optical analysis methods, we perform numerical simulations of ensembles similar to the experiment. The simulation output is graphically rendered to mimic the experimentally obtained images. We validate the output of the optical analysis methods on the basis of this ground truth information. This approach provides insight in two interconnected problems: the confirmation of the accuracy of the simulations and the test of the applicability of the visual analysis. The proposed approach can be used for further investigations of dynamical properties of such media, including the granular Leidenfrost effect, granular cooling, and gas-clustering transitions.

Establishing Robust Feature Point Detection and Tracking Methods for Face Orientation

Establishing Robust Feature Point Detection and Tracking Methods for Face Orientation

Left ventricular myocardial strain assessed by cardiac magnetic resonance feature tracking in patients with rheumatoid arthritis

PurposeThe aim of the study was to assess a relationship between the occurrence of rheumatoid arthritis (RA) and its selected clinical parameters, and left ventricular myocardial strain.Material and methodsFifty-six subjects were qualified for the study: 30 RA patients and 26 subjects without rheumatoid diseases. The study design included taking medical history, assessment of the disease activity using selected scales of activity, collecting samples of venous blood to assess selected laboratory parameters and the assessment of cardiac magnetic resonance (CMR). Using the feature tracking method, the following parameters of the left ventricular myocardial strain were assessed: longitudinal strain (LS), radial strain (RS) and circumferential strain (CS).ResultsRegarding global values, peak LS and peak CS were statistically significantly lower in RA patients than in the control group. In the whole study group, the factors independently related to low global LS peaks were as follows: occurrence of RA, occurrence of arterial hypertension, increased activity of antibodies against cyclic citrullinated peptide and increased concentration of neutrophil gelatinase-associated lipocalin. The occurrence of RA, occurrence of diabetes, tobacco smoking, higher activity of antibodies against cyclic citrullinated peptide and current use of methotrexate are the risk factors for low peak of global CS. The current use of steroids constitutes a protecting factor against low global CS peaks.ConclusionIn subjects with no clinically manifested cardiac damage, RA is associated with a deteriorated left ventricular systolic function assessed by left ventricular myocardial strain measured by CMR feature tracking.

Quantification of myocardial strain in patients with isolated left ventricular non-compaction and healthy subjects using deformable registration algorithm: comparison with feature tracking

BackgroundSystolic dysfunction of the left ventricle is frequently associated with isolated left ventricular non-compaction (iLVNC). Clinically, the ejection fraction (EF) is the primary index of cardiac function. However, changes of EF usually occur later in the disease course. Feature tracking (FT) and deformable registration algorithm (DRA) have become appealing techniques for myocardial strain assessment.MethodsThirty patients with iLVNC (36.7 ± 13.3 years old) and fifty healthy volunteers (42.3 ± 13.6 years old) underwent cardiovascular magnetic resonance (CMR) examination on a 1.5 T MR scanner. Strain values in the radial, circumferential, longitudinal directions were analyzed based on the short-axis and long-axis cine images using FT and DRA methods. The iLVNC patients were further divided based on the ejection fraction, into EF ≥ 50% group (n = 11) and EF < 50% group (n = 19). Receiver-operating-characteristic (ROC) analysis was performed to assess the diagnostic performance of the global strain values. Intraclass correlation coefficient (ICC) analysis was used to evaluate the intra- and inter-observer agreement.ResultsGlobal radial strain (GRS) was statistically lower in EF ≥ 50% group compared with control group [GRS (DRA)/% vs. controls: 34.6 ± 7.0 vs. 37.6 ± 7.2, P < 0.001; GRS (FT)/% vs. controls: 37.4 ± 13.2 vs. 56.9 ± 16.4, P < 0.01]. ROC analysis of global strain values derived from DRA and FT demonstrated high area under curve (range, 0.743–0.854). DRA showed excellent intra- and inter-observer agreement of global strain in both iLVNC patients (ICC: 0.995–0.999) and normal controls (ICC: 0.934–0.996). While for FT analysis, global radial strain of normal controls showed moderate intra-observer (ICC: 0.509) and poor inter-observer agreement (ICC: 0.394).ConclusionsIn patients with iLVNC, DRA can be used to quantitatively analyze the strain of left ventricle, with global radial strain being an earlier marker of LV systolic dysfunction. DRA has better reproducibility in evaluating both the global and segmental strain.

ROLE OF EARTH OBSERVATION DATA AND HYDROLOGICAL MODELING IN SUPPORTING UN SDGs IN NORTH WEST HIMALAYA

Abstract. The sustainable usage and accurate assessment of water resources in North West Himalaya (NWH) is very important for respective policy makers. NWH receives precipitation from both southwest and northeast monsoon system. The detailed assessment of current and future water resources and hydrological cycle component for NWH river basins using earth observation (EO) satellites and hydrological models is very critical for attaining United Nations sustainable development goals (SDGs) namely, climate action, affordable and clean energy, clean water and sanitation and building resilient infrastructure. Present work highlights the role of various EO sensors and hydrological models and ground based instruments for improved assessment of water resources of NWH river basins. The complete inventory of NWH surface water (including glacier lakes of UK, HP), snow cover, delta SWE and glaciers database was accomplished with Remote Sensing (RS) datasets. Similarly, glacier velocity was estimated for all major glaciers of NWH using feature tracking and differential interferometry (DInSAR) methods. Fully distributed grid based hydrological model was setup for entire NWH and model calibration/validation was done for Beas, Satluj, Upper Ganga and Jhelum river basins. Quantification of relative contribution of snowmelt, glacier melt and rainfall-runoff was estimated for Bhagirathi basin upto Uttarkashi. An extensive network of automatic weather stations (AWS), 27 nos, 10 snow depth sensors, 04 digital water level recorders, two snow pack analysers and 06 long wave solar radiation sensors were installed in various sites of HP and UK for hydro-meteorological data collection, model simulation and validation. A future climate change simulations were done for Beas and Jhelum basins using CORDEX 4.5 and 8.5 scenarios from 2006–2100. Number of flood peaks were found to be increasing in number as well as decrease in total snow fall.

Evaluation and Comparison of Quantitative Right Ventricular Strain Assessment by Cardiac Magnetic Resonance in Pulmonary Hypertension Using Feature Tracking and Deformable Registration Algorithms

Deformable registration algorithms (DRA) has been used to detect left ventricular myocardial changes, however, its clinical utility in right ventricular (RV) function has not been evaluated. In this study, we aim to evaluate and compare quantitative RV strain assessment by cardiac magnetic resonance in pulmonary hypertension (PH) using feature tracking (FT) and DRA. Thirty patients were confirmed to have PH using right heart catheterization, and 16 healthy controls were evaluated with cardiac magnetic resonance. Global and segmental RV strain was measured by DRA and FT methods. Intraclass correlation coefficients (ICCs), coefficient of variation, and Bland-Altman analysis were used to assess and compare the interobserver and intraobserver variability of the DRA and FT methods. DRA was more sensitive than FT in the detection of RV circumferential and septal dysfunction. The global longitudinal strain (GLS) obtained by the two methods was reduced in mild-moderate PH patients (mean pulmonary artery pressure≤45 mm Hg), and the GLS and global circumferential strain (GCS) were reduced in severe PH patients (mean pulmonary artery pressure >45 mm Hg). DRA and FT methods demonstrate similar observer agreement in global strain using ICC (ICC greater than 0.90), but RV strain derived from DRA had lower variability using COV ([8%-14%] for DRA versus [11%-39%] for FT).For segmental longitudinal strain, DRA showed higher ICC and lower COV compared with that of the FT method. Correlations between RVEF and RV global strain parameters were strong (p < 0.01):GLS-DRA, r = -0.696; GLS-FT, r = -0.832; GCS-DRA, r = -0.745; and GCS-FT, r = -0.817. GLS-DRA was weakly correlated with mPAP (r = 0.385, p < 0.05).In multiple linear regression analysis, RVEF and mPAP were independent predictors of GLS-DRA (R2 = 0.57, p < 0.01). The DRA method is more sensitive and robust for RV myocardial strain measurements than FT method.

Augmented reality using Natural Feature Tracking (NFT) method for learning media of makharijul huruf

Makharijul huruf is the place of the letter hijaiyah (Arabic letters) from alif to ya. If someone mistakes in reciting a letter on al-Qur’an then the meaning of the word or sentence may be different from the meaning of the original word. Few learning media that provides information about makharijul huruf such as school academic books, books of tajwid al-Qur’an, etc. However, to make terms of visual and audio clearer we can use augmented reality technology as a learning media. Augmented reality for makharijul huruf requires a marker of hijaiyah in printing form. Tracking marker in this research using Natural Feature Tracking (NFT) method. In the application of learning this makharijul huruf will produce a 3D object visualization of the oral organs and audio sounds hijaiyah letters and explanations about makharijul huruf. The results of black box testing and beta testing states that this application can be accepted by users by obtaining a percentage of 91%. It can be concluded that applications built functionally have produced results as expected.

Target detection and tracking based on improved HOG-color feature fusion

In the process of constructing the target appearance model, the traditional HOG feature does not take into account the relationship between adjacent regions when the image is segmented in the feature extraction process, resulting in the regional aliasing effect, and the single feature is inefficient in target detection and tracking. An improved HOG-color feature fusion method for target detection and tracking is proposed. Firstly, HOG feature and color feature were extracted from the target samples respectively. During the HOG feature extraction process, trilinear interpolation was used to eliminate regional aliasing effect. Secondly, Bhattacharyya distance is used to select the HOG feature after interpolation, and the appropriate feature is selected as the HOG feature. Then combine the HOG feature after selection with the color feature; Finally, the filter is obtained by learning the kernel correlation filter, and the image is correlated detected with the filter, and the response output is obtained. The experimental results show that this method is superior to the traditional HOG-color feature fusion target detection and tracking method in both tracking speed and tracking efficiency.

Retrievals of Sea Surface Current Vectors from Geostationary Satellite Data (Himawari-8/AHI)

An operational sea surface current (SSC) retrieval algorithm was developed using consecutive Himawari-8/AHI data based on a feature tracking method. Comparative analyses were conducted to determine the appropriate input data for the SSC retrieval algorithm. Investigation of the input data revealed some limitations in the use of single-band brightness temperatures caused by atmospheric features under moist conditions, especially in the mid- and low-latitude regions. Because of the motion of atmospheric features, cloud and cloud-contaminated pixels tended to contribute to the overestimation of SSC. To reduce overestimation, sea surface temperature images were used as input data and the feature tracking method was applied to calculate the displacement of the surface current vectors. The estimated currents were subjected to a quality control process to remove erroneous vectors. The accuracy of the retrieved surface currents was assessed by comparing the results with the quality-controlled currents obtained from surface drifters in the full-disk region of Himawari-8/AHI. The results revealed that the estimated current speeds and directions agreed with the drifter-based calculated values—the root-mean-square (bias) errors were 0.35 ms−1 (0.11 ms−1) and 33.28° (5.47°), respectively. The estimated current field showed diverse dynamic ocean features, such as a rotating feature around a mesoscale eddy and the characteristic meandering pattern of the Kuroshio Current. Hourly varying surface current fields from geostationary satellite data with high spatio-temporal resolution are expected to augment oceanic and atmospheric applications in real time.

P177 Left atrial strain in patients with cardiac amyloidosis. Relationship to left atrial amyloid deposition focusing on prognosis

Abstract Background In cardiac amyloidosis (CA), the left atrium (LA) is frequently infiltrated by the amyloid fibrils. It is currently known that LA strain is a marker of LA function and prognosis in many cardiac diseases, however its significance in CA remains unknown. Purpose Our aim was to investigate correlation between LA strain measured by Cardiovascular Magnetic Resonance (CMR) and amyloid deposit in LA, and also evaluate the LA strain on the prognostic significance. Methods and results Of 74 consecutive patients with biopsy-proven CA, we analyzed 42 patients (age 72 ± 10 years; 76 % males) with contrast-enhanced CMR, and examined LA late gadolinium enhancement (LGE) and CMR derived LA strain using feature tracking method. Of the 42 patients, 29 patients (69 %) was transthyretin cardiac amyloidosis (ATTR-CA) in the majority. We divided these 42 patients into two groups according to the CMR measured peak atrial longitudinal strain (PALS) (&amp;gt; = or &amp;lt; median); high-strain (&amp;gt; = 6.67 %, n = 21) and low-strain (＜ 6.67 %, n = 21) and compared the patient’s characteristics, blood test data, echocardiography and CMR parameters. There were no significant differences between two groups in these parameters but in the extent of LA-LGE (54 % vs 80 %, p = 0.008). The PALS correlated with the extent of LA-LGE (ρ= 0.50, p = 0.001). In multivariate analysis including LVEF, E/e’ and BNP, LA-LGE was an independent determinant of PALS. During three-year follow up, the LA strain significantly related to heart failure hospitalization in the ATTR-CA patients (p = 0.036)(Figure). Conclusions In CA patients, CMR measured LA longitudinal strain correlates with the LA-LGE. It also provides useful information for poor prognosis of patients with ATTR-CA. Abstract P177 Figure. Heart failure hospitalization in ATTR-CA