Feature Tracking Technique Research Articles

Prognostic value of cardiac magnetic resonance global circumferential strain assessed by feature tracking techniques in asymptomatic patients with significant aortic regurgitation

Abstract Introduction Cardiac magnetic resonance feature tracking (CMR-FT) deformation techniques have gained significant interest in recent years. They provide a comprehensive evaluation of myocardial function and improve the reproducibility of echocardiography strain techniques. Purpose The aim of this study was to evaluate whether CMR-FT deformation parameters play a role predicting worse clinical evolution in patients with chronic significant aortic regurgitation (AR) not meeting guidelines intervention criteria. Methods We included 85 patients with significant AR (moderate, moderate/severe, and severe) referred for CMR. Only asymptomatic patients with preserved left ventricle ejection fraction (LVEF) were considered for inclusion. Other concomitant myocardiopathies were excluded. Conventional functional left chambers parameters as well as myocardial deformation were evaluated, including global longitudinal strain (GLS), global circumferential strain (GCS) and global radial strain (GRS). A composite clinical major outcome was assessed, including admission heart failure admission, need for aortic valvule replacement and all-cause mortality. Results The mean age of the sample was 62 years old. One third of the patients were females. Other clinical baseline characteristics were not significantly different between groups when compared with Chi-squared and T-test statistical analysis. Mean follow-up was 42 months (±31). 21 patients presented with the composited outcome previously described. End-diastolic and end-systolic volumes did not differ between groups. Mean end-diastolic volume (EDV) was 196 ± 6.1 mL and mean end-systolic volume (ESV) was 88 ± 3.4 mL. Mean values of CMR-FT GLS, GCS and GRS were -14.1%, 22.8% and -16.9% respectively. GCS was selected as the best predictor for the combined endpoint point, with and area under the ROC curve of 0.67. A GCS value <-17% was selected as the optimal cut-off point. This value predicted events as is shown in Kaplan-Meier curves (HR 3.6, CI 95% 1.42 - 9.02, p = 0.007). A multivariate analysis showed that this association was independent of left ventricle (LV) ejection fraction, LV volumes and left atrial (LA) volume. Conclusion CMR-FT deformation parameters are impaired in significant AR patients even if intervention criteria are not met. A value of GCS < -17% in this population could predict a worse clinical evolution and emerges as a promising new tool helping clinical decision making in this challenging population.Kaplan-Meier curve free-event survival

Implications of Myocardial Strain in Primary Mitral Regurgitation - A Cardiovascular Magnetic Resonance Study.

Chronic primary mitral regurgitation (MR) results in progressive left ventricular (LV) remodeling. Abnormal myocardial deformation (strain) can be present despite preserved ejection fraction. Cardiovascular magnetic resonance (CMR) feature-tracking techniques allow assessment of global longitudinal strain (GLS) from routine cine-images. The aim of this study was to evaluate the prognostic value of CMR feature-tracking derived GLS in patients with primary MR. Consecutive patients undergoing CMR for chronic MR from January 2012 to June 2018 were enrolled. Patient with LV ejection fraction <50% were excluded. The composite primary outcome aiming to detect decompensation related to MR comprised of 1) referral for mitral surgery due to symptoms or LV systolic dysfunction or 2) cardiovascular death. The secondary outcome was all-cause death. A total of 422 patients were followed for a median of 2.7 years, the primary endpoint was met in 93 patients (34 patients reported symptoms at baseline). On multivariable analysis, GLS≥ -16.6% was associated with primary outcome (hazard ratio 1.90,p=0.01). In moderate MR cohort, patient with GLS≥ -16.6% had worse event-free survival while no significant different in mild or severe MR groups. GLS≥ -16.0% remained associated with all-cause death after adjusting for other covariates including the MR severity (hazard ratio 2.24,p=0.02). In primary MR patients with preserved systolic function, GLS was associated with our composite outcomes and all-cause death. GLS may serve as a marker of cardiac dysfunction in primary MR patients with preserved systolic function allowing identification of patients likely to decompensate during observation.

Cardiac Magnetic Resonance Feature Tracking Analysis for Change in Right Ventricular Function After Cardioplegic Arrest

Using echocardiography to assess right ventricular (RV) function after cardioplegic arrest is challenging. Cardiac magnetic resonance (CMR) imaging is a superior alternative, with the feature tracking technique enabling quantitative assessment of myocardial deformation. This single-center, prospective study from 2020 to 2022 assessed RV function in 42 patients who underwent open heart surgery with cardioplegic arrest. CMR data were collected preoperatively, one week postoperatively, and at follow-up (6-12 months after surgery), and assessed using the CMR feature tracking technique. Postoperatively, there was no significant change in RV end-diastolic volume, but RV end-systolic volume significantly decreased, leading to a notable increase in RV ejection fraction. By follow-up, both RV end-diastolic and end-systolic volumes had significantly reduced compared with the preoperative values. Right ventricular longitudinal contractility decreased after surgery but recovered to the preoperative values by follow-up, while RV circumferential contractility improved postoperatively and remained superior to the preoperative levels at follow-up. On CMR imaging, significant changes in RV systolic motion were observed after cardioplegic arrest, with decreased longitudinal but increased circumferential contractility. At follow up, these changes had reverted to the preoperative patterns by the mid-term (6-12 months).

Enhancing robustness in asynchronous feature tracking for event cameras through fusing frame steams

Event cameras produce asynchronous discrete outputs due to the independent response of camera pixels to changes in brightness. The asynchronous and discrete nature of event data facilitate the tracking of prolonged feature trajectories. Nonetheless, this necessitates the adaptation of feature tracking techniques to efficiently process this type of data. In addressing this challenge, we proposed a hybrid data-driven feature tracking method that utilizes data from both event cameras and frame-based cameras to track features asynchronously. It mainly includes patch initialization, patch optimization, and patch association modules. In the patch initialization module, FAST corners are detected in frame images, providing points responsive to local brightness changes. The patch association module introduces a nearest-neighbor (NN) algorithm to filter new feature points effectively. The patch optimization module assesses optimization quality for tracking quality monitoring. We evaluate the tracking accuracy and robustness of our method using public and self-collected datasets, focusing on average tracking error and feature age. In contrast to the event-based Kanade–Lucas–Tomasi tracker method, our method decreases the average tracking error ranging from 1.3 to 29.2% and boosts the feature age ranging from 9.6 to 32.1%, while ensuring the computational efficiency improvement of 1.2–7.6%. Thus, our proposed feature tracking method utilizes the unique characteristics of event cameras and traditional cameras to deliver a robust and efficient tracking system.

Predictive value of global longitudinal strain measured by cardiac magnetic resonance imaging for left ventricular remodeling after acute ST-segment elevation myocardial infarction: a multi-centered prospective study

To evaluate the predictive value of global longitudinal strain (GLS) measured by cardiac magnetic resonance (CMR) feature-tracking technique for left ventricular remodeling (LVR) after percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI). A total of 403 patients undergoing PCI for acute STEMI were prospectively recruited from multiple centers in China.CMR examinations were performed one week (7±2 days) and 6 months after myocardial infarction to obtain GLS, global radial strain (GRS), global circumferential strain (GCS), ejection fraction (LVEF) and infarct size (IS).The primary endpoint was LVR, defined as an increase of left ventricle end-diastolic volume by ≥20% or an increase of left ventricle end-systolic volume by ≥15% from the baseline determined by CMR at 6 months.Logistic regression analysis was performed to evaluate the predictive value of CMR parameters for LVR. LVR occurred in 101 of the patients at 6 months after myocardial infarction.Compared with those without LVR (n=302), the patients in LVR group exhibited significantly higher GLS and GCS (P < 0.001) and lower GRS and LVEF (P < 0.001).Logistic regression analysis indicated that both GLS (OR=1.387, 95%CI: 1.223-1.573;P < 0.001) and LVEF (OR=0.951, 95%CI: 0.914-0.990;P=0.015) were independent predictors of LVR.ROC curve analysis showed that at the optimal cutoff value of-10.6%, GLS had a sensitivity of 74.3% and a specificity of 71.9% for predicting LVR.The AUC of GLS was similar to that of LVEF for predicting LVR (P=0.146), but was significantly greater than those of other parameters such as GCS, GRS and IS (P < 0.05);the AUC of LVEF did not differ significantly from those of the other parameters (P>0.05). In patients receiving PCI for STEMI, GLS measured by CMR is a significant predictor of LVR occurrence with better performance than GRS, GCS, IS and LVEF.

Divergence between left ventricular ejection fraction and global longitudinal strain by cardiac magnetic resonance as a new predictor of myocardial fibrosis burden in hypertrophic cardiomyopathy

Abstract Funding Acknowledgements None. Background Hypertrophic cardiomyopathy (HCM) is the most frequently diagnosed inherited cardiomyopathy as well as the leading cause of sudden death in young people. Despite that, prompt diagnosis and prognosis of this condition are still challenging due to subtle progression and preserved left ventricular ejection fraction (LVEF) in most stages. Latest studies showed that myocardial strains could be the earliest indicator of function impairment and a good trait suggesting underlying fibrosis development. Purpose By applying the cardiac magnetic resonance (CMR) feature-tracking technique, our aim is to evaluate whether the divergence between the LVEF and global strains, apart from the strains themselves, could help predict the burden of myocardial fibrosis in HCM patients. Methods In this retrospective, cross-sectional study from June 2022 to June 2023, we included 35 HCM patients and 16 healthy controls with 3T-CMR. LVEF, left ventricular global longitudinal (LVGLS), circumferential (LVGCS), and radial (LVGRS) strains were derived from short-axis Cine images. To assess the divergence, ratios of LVEF to LVGLS, LVGCS, and LVGRS absolute values (namely EF-GLS, EF-GCS, and EF-GRS, respectively) were calculated. The ratios helped emphasise that a persisting high/normal LVEF and/or a lower strain magnitude would produce a larger discrepancy between these two variables. Fibrosis was assessed by LGE amount (%LGE to LV mass, threshold of +5 SD). Two-sample t-Test, linear and binary logistic regression were the main statistical tests used. Results The global strain measures all expressed notable impairment in HCM groups compared to healthy controls (LVGLS [-12.04±3.9 vs -19.42±2%, p&amp;lt;0.001]; LVGCS [-16.37±4.1 vs -19.3±2.1, p=0.002]; LVGRS [28.06±9.9 vs 33.8±6.5%, p=0.018] while sharing the same range of LVEF [59.09±9.9 vs 59.44±5.3, p=0.87). The ratios of EF-GLS, EF-GCS, and EF-GRS also showed statistically significant differences between the two groups. In the HCM group, LVGLS and EF-GLS ratio showed the strongest correlations with %LGE (r = 0.855 and r = 0.708, p&amp;lt;0.001). A regression equation can also be derived to estimate the amount of LGE from the EF-GLS ratio: %LGE = 3.967 EF-GLS - 0.22. To determine predictive power toward the severity of fibrosis, the EF-GLS ratio showed the best performance, in which a threshold of 4.96 had sensitivity and specificity of 73.7% and 93.8% to predict LGE ≥ 15% LV mass (Area Under the Curve [AUC]: 0.717; 95% CI: 0.521–0.913). Conclusion Our study demonstrated that the ratio of LVEF to LV global longitudinal strain exhibited a great capability to reflect LV dysfunction and predict myocardial fibrosis severity with good accuracy. Derived easily from the routine Cine-CMR image, this new deformation parameter has great potential to be used in clinical practice to better diagnose and manage hypertrophic cardiomyopathy.Clinical characteristics of groupsResults in graphs

Efficient Crowd Anomaly Detection Using Sparse Feature Tracking and Neural Network

Crowd anomaly detection is crucial in enhancing surveillance and crowd management. This paper proposes an efficient approach that combines spatial and temporal visual descriptors, sparse feature tracking, and neural networks for efficient crowd anomaly detection. The proposed approach utilises diverse local feature extraction methods, including SIFT, FAST, and AKAZE, with a sparse feature tracking technique to ensure accurate and consistent tracking. Delaunay triangulation is employed to represent the spatial distribution of features in an efficient way. Visual descriptors are categorised into individual behaviour descriptors and interactive descriptors to capture the temporal and spatial characteristics of crowd dynamics and behaviour, respectively. Neural networks are then utilised to classify these descriptors and pinpoint anomalies, making use of their strong learning capabilities. A significant component of our study is the assessment of how dimensionality reduction methods, particularly autoencoders and PCA, affect the feature set’s performance. This assessment aims to balance computational efficiency and detection accuracy. Tests conducted on benchmark crowd datasets highlight the effectiveness of our method in identifying anomalies. Our approach offers a nuanced understanding of crowd movement and patterns by emphasising both individual and collective characteristics. The visual and local descriptors facilitate high-level analysis by closely relating to semantic information and crowd behaviour. The analysis observed shows that this approach offers an efficient framework for crowd anomaly detection, contributing to improved crowd management and public safety. The proposed model achieves accuracy of 99.5 %, 96.1%, 99.0% and 88.5% in the UMN scenes 1, 2, and 3 and violence in crowds datasets, respectively.

Two-Decadal Glacier Changes in the Astak, a Tributary Catchment of the Upper Indus River in Northern Pakistan

Snow and ice melting in the Upper Indus Basin (UIB) is crucial for regional water availability for mountainous communities. We analyzed glacier changes in the Astak catchment, UIB, from 2000 to 2020 using remote sensing techniques based on optical satellite images from Landsat and ASTER digital elevation models. We used a surface feature-tracking technique to estimate glacier velocity. To assess the impact of climate variations, we examined temperature and precipitation anomalies using ERA5 Land climate data. Over the past two decades, the Astak catchment experienced a slight decrease in glacier area (−1.8 km2) and the overall specific mass balance was −0.02 ± 0.1 m w.e. a−1. The most negative mass balance of −0.09 ± 0.06 m w.e. a−1 occurred at elevations between 2810 to 3220 m a.s.l., with a lesser rate of −0.015 ± 0.12 m w.e. a−1 above 5500 m a.s.l. This variation in glacier mass balance can be attributed to temperature and precipitation gradients, as well as debris cover. Recent glacier mass loss can be linked to seasonal temperature anomalies at higher elevations during winter and autumn. Given the reliance of mountain populations on glacier melt, seasonal temperature trends can disturb water security and the well-being of dependent communities.

Takotsubo syndrome: left atrial and ventricular myocardial strain impairment in the subacute and convalescent phases assessed by CMR.

We investigated the differences in impairment of left ventricle (LV) and left atrium (LA) contractile dysfunction between subacute and convalescent takotsubo syndrome (TTS), using myocardial strain analysis by cardiac magnetic resonance (CMR) feature-tracking technique. We retrospectively selected 50 patients with TTS clinical-radiological diagnosis who underwent CMR within 30days since symptoms onset: 19 studied during the early subacute phase (sTTS, ≤ 7days) and 31 during the convalescence (cTTS, 8-30days). We measured the following: LV global longitudinal, circumferential, and radial strain (lvGLS, lvGCS, lvGRS) and strain rate (SR) and LA reservoir (laS_r), conduit (laS_cd), and booster pump strain (laS_bp) and strain rate (laSR_r, laSR_cd, laSR_bp). Patients were compared with 30 age- and sex-matched controls. All patients were women (mean age 63years). TTS patients showed altered LV- and LA-strain features, compared to controls. sTTS was associated with increased laS_bp (12.7% versus 9.8%) and reduced lvEF (47.4% versus 54.8%), lvGLS (-12.2% versus 14.6%), and laS_cd (7.0% versus 9.5%) compared to cTTS (p ≤ 0.029). The interval between symptoms onset and CMR was correlated with laS_bp (r = -0.49) and lvGLS (r = 0.47) (p = 0.001 for both). At receiver operating characteristics analysis, laS_bp was the best discriminator between sTTS and cTTS (area under the curve [AUC] 0.815), followed by lvGLS (AUC 0.670). LA dysfunction persists during the subacute and convalescence of TTS. laS_bp increases in subacute phase with progressive decrease during convalescence, representing a compensatory mechanism of LV dysfunction and thus a useful index of functional recovery. Atrial strain has the potential to enhance the delineation of cardiac injury and functional impairment in TTS patients, assisting in the identification of individuals at higher risk and facilitating the implementation of more targeted and personalized medical therapies. • In TTS, after ventricular recovery, atrial dysfunction persists assessable with CMR feature tracking. • Quantitative assessment of atrial strain discriminates atrial functions: reservoir, conduit, and booster pump. • Atrial booster pump changes after acute TTS, regardless of ventricular function. • Atrial strain may serve as a temporal marker in TTS.

Role of feature tracking cardiac magnetic resonance imaging in early detection of cardiac dysfunction in β-thalassemia patients recovered from COVID-19: A cross-sectional study.

β-Thalassemia patients may have cardiac complications due to iron overload, which puts them at higher risk of cardiac complications induced by coronavirus disease 2019 (COVID-19) compared with the normal population. The present study aims to evaluate early cardiovascular complications following iron overload in β-thalassemia patients who had early recovery from COVID-19 by cardiac magnetic resonance imaging (MRI) and feature-tracking technique. Thirty-two confirmed COVID-19-recovered β-thalassemia cases were evaluated within 3 weeks to 3 months after a positive reverse-transcriptase polymerase chain reactionCOVID-19 test. Both the heart and liver of all patients were examined using cardiac MRI. We analyzed 32 patients with mean age of 32.84 ± 6.45 years at baseline. Left ventricular global strain values were significantly associated with myocardial T2*. A cut-off value of -15.08% for global longitudinal strain (GLS) with sensitivity and specificity of 90% and 61.1% (p = 0.017), 32.33% for global radial strain (GRS) with sensitivity and specificity of 80% and 94.4% (p = 0.001) and -16.21 for global circumferential strain(GCS), with sensitivity and specificity of 80% and 89.9% (p = 0.013) may indicate cardiac iron overload. GLS, GRS, and GCS were significantly decreased in patients with myocardial T2* <20 ms (iron overload), while no significant change was observed in the right and left ventricular ejection fraction (RV- and LVEF). Cardiac MRI feature-tracking may be helpful in the early detection of cardiac complications resulting from iron overload in β-thalassemia patients who had early recovery from COVID-19.

Healthy Adult Left and Right Ventricular Torsion and Torsion Rates With MR-Feature Tracking.

The clinical value of myocardial torsion quantification in prognostic assessment and risk stratification of various cardiovascular diseases is gradually being recognized. However, normal values of left and right ventricular (LV and RV) torsion and torsion rates (TRs) have not been fully determined, and their correlation with age and gender has not been well studied. To establish normal ranges of biventricular torsion, peak systolic and diastolic TRs using magnetic resonance feature tracking (MR-FT) technique based on a large sample of healthy adults, and further investigate their relationship with age and gender. Retrospective. 566 Healthy adults (312 males, aged 43 ± 10 years; 254 females, aged 43 ± 11 years). 1.5T/gradient echo. Biventricular torsion, peak systolic, and diastolic TRs. Shapiro-Wilk test, Student's t-test, Mann-Whitney-U test, linear regression, intraclass correlation coefficient, Bland-Altman analysis. Differences were regarded as statistically significant at P < 0.05. Women demonstrated greater magnitudes of left ventricle (LV) torsion (1.23 ± 0.44 vs. 1.00 ± 0.42°/cm), peak systolic TR (9.69 ± 3.70 vs. 8.27 ± 3.73°/cm*sec), peak diastolic TR (-7.78 ± 2.82 vs. -6.06 ± 2.44°/cm*sec), and RV torsion (2.20 ± 1.23 vs. 1.65 ± 1.11°/cm*sec), peak systolic TR (16.07 ± 8.18 vs. 12.62 ± 7.08°/cm*sec), peak diastolic TR (-15.39 ± 6.53 vs. -11.70 ± 6.03°/cm*sec). For both genders, the magnitudes of LV and RV torsion, peak systolic, and diastolic TRs increased linearly with age. All the measurements of biventricular torsion, peak systolic and diastolic TRs achieved good to excellent intraobserver and interobserver reproducibility, with all intraclass correlation coefficients >0.70. The present study systematically provided age- and sex-stratified reference values for LV and RV torsion and TRs using MR-FT technique. Women and aging are associated with greater magnitudes of biventricular torsion, peak systolic, and diastolic TRs. 3 TECHNICAL EFFICACY: Stage 2.

Right ventricular global strain in patients with hypertrophic cardiomyopathy with and without right ventricular hypertrophy

PurposeRegardless of whether there are morphological abnormalities of right ventricle in hypertrophic cardiomyopathy (HCM) patients, the exact contribution of right ventricular (RV) global strains remains unresolved. We aimed to study the prognostic value of RV global strains in HCM patients with and without RV hypertrophy (RVH). MethodA total of 358 HCM patients who underwent the CMR examination and carried out the follow-up were finally included in this retrospective study. The endpoint was a composite of all-cause mortality, aborted SCD, and heart failure readmission. RV hypertrophy (RVH) was defined as maximal RVWT ≥ 5 mm at end-diastole. RV global strains (RV global longitudinal strain (GLS) and RV global circumferential strain (GCS) were measured in HCM patients by cardiac MRI feature tracking technique. The intraobserver and interobserver reproducibility were evaluated. Receiver-operating characteristic curves and Kaplan–Meier curves, cox proportional hazards regression, Likelihood ratio test and Integrated Discrimination Improvement (IDI) analysis were performed. P-value were corrected for multiple testing when using many covariables by a false discovery rate adjustment. ResultsOver a median follow-up of 25 (range 3–54) months, 49 patients reached the composite endpoints. HCM patients were divided into the RVH group and non-RVH groups. In the multivariate cox proportional hazards regression, after adjusting multiple clinical and imaging variables, RV GLS and RV GCS were independently associated with the composite endpoints in the RVH group (HR: 1.123; 95 % CI: 1.048–1.205; P = 0.002) and non-RVH group (HR: 1.174; 95 % CI: 1.031–1.337; P = 0.015), respectively. And The IDI index of models improved when adding RV GLS (IDI = 0.030, p < 0.001) and RV GLS (IDI = 0.056, p = 0.020), respectively. ConclusionsRV GLS and RV GCS are independent predictors of HCM with RVH and without RVH, respectively. RV GLS in the RVH group and RV GCS in the non-RVH group provide additional values for predicting the risk of adverse events.

Augmented Reality-Assisted Deep Reinforcement Learning-Based Model towards Industrial Training and Maintenance for NanoDrop Spectrophotometer.

The use of augmented reality (AR) technology is growing in the maintenance industry because it can improve efficiency and reduce costs by providing real-time guidance and instruction to workers during repairs and maintenance tasks. AR can also assist with equipment training and visualization, allowing users to explore the equipment's internal structure and size. The adoption of AR in maintenance is expected to increase as hardware options expand and development costs decrease. To implement AR for job aids in mobile applications, 3D spatial information and equipment details must be addressed, and calibrated using image-based or object-based tracking, which is essential for integrating 3D models with physical components. The present paper suggests a system using AR-assisted deep reinforcement learning (RL)-based model for NanoDrop Spectrophotometer training and maintenance purposes that can be used for rapid repair procedures in the Industry 4.0 (I4.0) setting. The system uses a camera to detect the target asset via feature matching, tracking techniques, and 3D modeling. Once the detection is completed, AR technologies generate clear and easily understandable instructions for the maintenance operator's device. According to the research findings, the model's target technique resulted in a mean reward of 1.000 and a standard deviation of 0.000. This means that all the rewards that were obtained in the given task or environment were exactly the same. The fact that the reward standard deviation is 0.000 shows that there is no variability in the outcomes.

Association between left ventricular strain and fibrosis in severe aortic regurgitation with preserved ejection fraction: a magnetic resonance and histology study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Institutional Grant Na Homolce Hospital Background The presence and extent of myocardial fibrosis are associated with poor outcomes in patients with severe aortic regurgitation. In the present study, we tested a correlation between left ventricular (LV) strain derived by using feature-tracking cardiac magnetic resonance (MRI) and diffuse myocardial fibrosis percentage (DMF%) at quantitative histology. Methods A study population included 23 patients (age 51 ± 12 years, 78% males) who underwent perioperative myocardial biopsy during aortic valve surgery for severe aortic regurgitation and who had a satisfactory pre-surgery MRI. Myocardial specimens obtained with a deep needle technique from the basal interventricular septum were stained with picrosirius red, digitalized, and analyzed using Image J software by a pathologist blinded to imaging findings. The DMF% was calculated as a ratio of the total collagen content to the total area. MRI-derived global longitudinal-(GLS), circumferential- (GCS), and radial (GRS) strain, as well as their ratio to heart rate and systolic blood pressure, were assessed using a feature-tracking technique by a certified imager blinded to histological analysis. Results Compared to normal values, all patients showed increased DMF% (19 ± 9%) and decreased GLS (15 ± 2%) despite preserved LV ejection fraction (64 ± 7%). Out of all the imaging parameters, only GLS/heart rate ratio, GCS/heart rate ratio and extracellular volume fraction showed a significant correlation with DMF% (Table 1, Figure 1). In contrast, GLS and GCS only tended to correlate with DMF%. The remaining parameters including GRS did not show a significant association. Patients with focal midwall scar in late gadolinium enhancement imaging (n=8, 35%), which was mainly localized in the basal septum, had similar GLS as than patients without focal scar (14.5±2.3 vs 15.3±2.3, p = 0.768). Conclusions Feature-tracking-derived ratios of LV GLS and GCS over heart rate are the most promising indices for non-invasive assessment of diffuse myocardial fibrosis in severe aortic regurgitation with preserved ejection fraction. Figure 1 Legend Correlation of a GLS/HR ratio 1A) and GLS 1B) with diffuse myocardial fibrosis %. Myocardial histology stained with Picrosirius red (collagen fibers are in red).

Feature-Based Scanning LiDAR-Inertial Odometry Using Factor Graph Optimization

Localization of a mobile robot in the absence of an absolute position sensor often relies on techniques such as visual or lidar-inertial odometry. While lidar has many advantages, the most capable sensors use scanning mechanisms, leading to motion-distorted scans. Previous strategies used to account for robot motion when performing state estimation and outlier rejection have drawbacks for use on highly dynamic, resource-constrained robots such as spacecraft during descent and landing. In this paper we develop a novel probabilistic factor for the inclusion of scanning lidar features, and an accompanying outlier rejection methodology. By using well-established, efficient feature tracking techniques, our image processing front end is both reliable and amenable to FPGA implementation, both of which are critical for operation on a spacecraft. We demonstrate our technique on a dataset from simulated planetary descent and landing. The results show that our system can be used to perform accurate lidar-inertial odometry, even in highly dynamic scenarios.

Analysis of bi-atrial function using CMR feature tracking and long-axis shortening approaches in patients with diastolic dysfunction and atrial fibrillation.

Atrial function can be assessed using advancing cardiovascular magnetic resonance (CMR) post-processing methods: atrial feature tracking (FT) strain analysis or a long-axis shortening (LAS) technique. This study aimed to first compare the two FT and LAS techniques in healthy individuals and cardiovascular patients and then investigated how left (LA) and right atrial (RA) measurements are related to the severity of diastolic dysfunction or atrial fibrillation. Sixty healthy controls and 90 cardiovascular disease patients with coronary artery disease, heart failure, or atrial fibrillation, underwent CMR. LA and RA were analyzed for standard volumetry as well as for myocardial deformation using FT and LAS for the different functional phases (reservoir, conduit, booster). Additionally, ventricular shortening and valve excursion measurements were assessed with the LAS module. The measurements for each of the LA and RA phases were correlated (p < 0.05) between the two approaches, with the highest correlation coefficients occurring in the reservoir phase (LA: r = 0.83, p < 0.01, RA: r = 0.66, p < 0.01). Both methods demonstrated reduced LA (FT: 26 ± 13% vs 48 ± 12%, LAS: 25 ± 11% vs 42 ± 8%, p < 0.01) and RA reservoir function (FT: 28 ± 15% vs 42 ± 15%, LAS: 27 ± 12% vs 42 ± 10%, p < 0.01) in patients compared to controls. Atrial LAS and FT decreased with diastolic dysfunction and atrial fibrillation. This mirrored ventricular dysfunction measurements. Similar results were generated for bi-atrial function measurements between two CMR post-processing approaches of FT and LAS. Moreover, these methods allowed for the assessment of incremental deterioration of LA and RA function with increasing left ventricular diastolic dysfunction and atrial fibrillation. A CMR-based analysis of bi-atrial strain or shortening discriminates patients with early-stage diastolic dysfunction prior to the presence of compromised atrial and ventricular ejection fractions that occur with late-stage diastolic dysfunction and atrial fibrillation. • Assessing right and left atrial function with CMR feature tracking or long-axis shortening techniques yields similar measurements and could potentially be used interchangeably based on the software capabilities of individual sites. • Atrial deformation and/or long-axis shortening allow for early detection of subtle atrial myopathy in diastolic dysfunction, even when atrial enlargement is not yet apparent. • Using a CMR-based analysis to understand the individual atrial-ventricular interaction in addition to tissue characteristics allows for a comprehensive interrogation of all four heart chambers. In patients, this could add clinically meaningful information and potentially allow for optimal therapies to be chosen to better target the dysfunction.

Cine MR feature tracking analysis for diagnosing thymic epithelial tumors: a feasibility study

BackgroundTo assess the feasibility of the cine MR feature tracking technique for the evaluation of cardiovascular-induced morphological deformation in the diagnosis of thymic epithelial tumors (TETs).MethodsOur study population consisted of 43 patients with pathologically proven TETs including 10 low-grade thymomas, 23 high-grade thymomas, and 10 thymic carcinomas. Cine MR images were acquired using a balanced steady-state free precession sequence with short periods of breath-hold in the axial and oblique planes in the slice with the largest lesion cross-sectional area. The tumor margin was manually delineated in the diastolic phase and was automatically tracked for all other cardiac phases. The change rates of the long-to-short diameter ratio (∆LSR) and tumor area (∆area) associated with pulsation were compared between the three pathological groups using the Kruskal–Wallis H test and the Mann–Whitney U test. A receiver-operating characteristic (ROC) curve analysis was performed to assess the ability of each parameter to differentiate thymic carcinomas from thymomas.Results∆LSR and ∆area were significantly different among the three groups in the axial plane (p = 0.028 and 0.006, respectively) and in the oblique plane (p = 0.034 and 0.043, respectively). ∆LSR and ∆area values were significantly lower in thymic carcinomas than in thymomas in the axial plane (for both, p = 0.012) and in the oblique plane (p = 0.015 and 0.011, respectively). The area under the ROC curves for ∆LSR and ∆area for the diagnosis of thymic carcinoma ranged from 0.755 to 0.764.ConclusionsEvaluation of morphological deformation using cine-MR feature tracking analysis can help diagnose histopathological subtypes of TETs and identify thymic carcinomas preoperatively.

Left Atrial and Ventricular Strain Differentiates Cardiac Amyloidosis and Hypertensive Heart Disease: A Cardiac MR Feature Tracking Study

Strain measured by feature tracking technique represents the degree of deformation and reflects the systolic and diastolic function of the heart. Our purpose was to evaluate the differential diagnostic value and correlations of left atrial (LA) strain (LAS) and left ventricular (LV) strain (LVS) in cardiac amyloidosis (CA) and hypertensive heart disease (HHD) patients. We recruited 25 CA patients, 30 sex- and age-matched HHD patients and 20 healthy subjects totally. LAS and LVS were analyzed by CVI42 post-processing software. The efficiency of LAS and LVS in differentiating CA from HHD was compared by receiver operating characteristic curves analysis. Pearson or Spearman's analysis were used to assess the correlation between LAS and LV parameters. Both HHD and CA patients had impaired LVS, the gradient of increasing absolute values of longitudinal strain (LS) and radial strain (RS) from the basal to the apical myocardium was most pronounced in the CA group, its relative apical sparing of LS (RASLS) ratio reached 0.91 ± 0.02, significantly higher than other two groups (HHD: 0.72 ± 0.02; controls: 0.56 ± 0.01, all p <0.001). Additionally, except for the booster strain in the HHD group was preserved, all other LAS were reduced in patients' groups. The RASLS had the best differential diagnostic efficacy with an area under the curve (AUC) of 0.930 (p <0.001); The AUCs of LAS all greater than 0.850, above global LS (GLS) (AUC=0.770, p=0.001). LAS was notably correlated with LV ejection fraction (LVEF) and GLS, with reservoir strain having the greatest correlation with GLS (r=-0.828, p <0.001). The RASLS has high efficiency in guiding the differential diagnosis of CA and HHD with similar degree and presentation of LVH. Moreover, LAS values can also provide some useful information and they are closely linked with LV function, CMR feature tracking may provide assistance in the evaluation of LA-LV coupling.

Prediction of cardiovascular events using myocardial strain ratio derived from 13N-ammonia positron emission tomography.

Myocardial flow reserve (MFR), derived from ammonia N-13 positron emission tomography (NH3-PET), can predict the prognosis of patients with various heart diseases. We aimed to investigate whether myocardial strain ratio (MSR) was useful in predicting MACE and allowed for further risk stratification of cardiovascular events in patients with ischemic heart disease (IHD) in addition to MFR. Ninety-five patients underwent NH3-PET because of IHD. MFR was determined as the ratio of hyperemic to resting myocardial blood flow (MBF). MSR was defined as the ratio of strains at stress and rest. The endpoint was major adverse cardiac events (MACE), including all-cause death, acute coronary syndrome, heart failure hospitalization, and revascularization. The ability to predict MACE was assessed using receiver operating characteristic (ROC) analysis, and the predictability of ME was analyzed using Kaplan-Meier analysis. The Cox proportional hazards regression model was used to calculate the hazard ratio (HR) with 95% confidence interval (CI). The ROC curve analysis demonstrated a cutoff of 0.93 for MACE with MSR (sensitivity and specificity of 77% and 71%, respectively). Patients with MSR < 0.93 displayed a significantly higher MACE rate than those with MSR ≥ 0.93 (p = 0.0036). The Cox proportional hazards regression analysis indicated that MSR was an independent marker that could predict MACE in imaging and clinical parameters (HR, 7.32; 95% CI: 1.59-33.7, p = 0.011). MSR was an independent predictor of MACE and was useful for further risk stratification in IHD. MSR has the potential for a new indicator of revascularization in patients with IHD. • We hypothesized that combining myocardial flow reserve (MFR) with the myocardial strain ratio (MSR) obtained by applying the feature-tracking technique to ammonia N-13 PET would make it predictive of major adverse cardiac events (MACE) compared to MFR alone. • MSR was an independent predictor of MACE, allowing for further risk stratification in addition to MFR in patients with ischemic heart disease. • MSR is a potential new indicator of revascularization.

Inter-field strength agreement of cardiovascular magnetic resonance cine-derived strain and strain rate measures: a randomised study

Abstract Background Left ventricular (LV) strain and strain rate measurements can be derived from routinely acquired cardiovascular magnetic resonance (CMR) cine images by feature tracking techniques. However, the inter-field strength agreement of strain measurements derived from these techniques is not known. We hypothesised that there would be excellent inter-field strength agreement (between 1.5 and 3 Tesla [T]) for the measurement of global strain and strain rate derived from cine imaging. Methods Prospective, randomised cross-over observational study. Healthy volunteers each underwent CMR scans at 1.5T and 3T within 30 minutes on the same day in a randomised order. Retrospectively ECG gated, short and long-axis balanced steady state free precession cine images were obtained using standardised acquisition parameters at both field strengths. Two software packages were used to derive LV global longitudinal, circumferential and long and short axis radial systolic strain, peak systolic, early diastolic and late diastolic strain rates. All strain values are expressed as positive numbers. Results Twenty-two subjects (mean age 36±12 years; 45% male) were studied. No differences in heart rate and blood pressure measurements during scanning were observed between field strengths. The abstract figure shows an example of strain analysis and Bland-Altman plots for global longitudinal and circumferential strain. Minimal bias was seen in all strain and strain rate measurements between field strengths using the first software package. Strain and strain rate values derived from long axis images (longitudinal and long axis radial) showed poor to fair agreement (intraclass correlation co-efficient (ICC) range 0.39–0.71), whereas measures derived from short axis images (circumferential and short axis radial) showed good to excellent agreement between field strengths (ICC range 0.78–0.91). Similar results were observed with the second software package, though the differences in agreement between long and short axis derived measures were less pronounced. Conclusion Longitudinal strain and strain rate measures derived from CMR feature tracking have poor inter-field strength agreement between 1.5T and 3T. By contrast, agreement of circumferential and short axis radial strain and strain rate measurements at 1.5T and 3T is good. These results need to be considered when assessing strain at different field strengths. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): United Kingdom National Institute for Health Research