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Multidimensional Magnetic Resonance Imaging (MRI) is a versatile tool for microstructure mapping. We use a diffusion weighted inversion recovery spin echo (DW-IR-SE) sequence with spiral readouts at ultra-strong gradients to acquire a rich diffusion-relaxation data set with sensitivity to myelin water. We reconstruct 1D and 2D spectra with a two-step convex optimization approach and investigate a variety of multidimensional MRI methods, including 1D multi-component relaxometry, 1D multi-component diffusometry, 2D relaxation correlation imaging, and 2D diffusion-relaxation correlation spectroscopic imaging (DR-CSI), in terms of their potential to quantify tissue microstructure, including the myelin water fraction (MWF). We observe a distinct spectral peak that we attribute to myelin water in multi-component T1 relaxometry, T1-T2 correlation, T1-D correlation, and T2-D correlation imaging. Due to lower achievable echo times compared to diffusometry, MWF maps from relaxometry have higher quality. Whilst 1D multi-component T1 data allows much faster myelin mapping, 2D approaches could offer unique insights into tissue microstructure and especially myelin diffusion.

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Disconnected branch pulmonary arteries are sparsely reported cases in prenatal diagnosis literature. We report a case of tetralogy of Fallot with disconnected branch pulmonary arteries, the left pulmonary artery (LPA) arising from an indirect ductus arteriosus (DA) from the base of the innominate artery in a right aortic arch, diagnosed by fetal echocardiography with 3D/4D spatiotemporal image correlation (STIC) imaging. Prenatal diagnosis led to early neonatal intervention to maintain blood flow to the LPA by stenting of the DA. Fetal echocardiographic evaluation (Voluson E10 systems, GE Healthcare, Zipf) with acquisition of images and volumes in the right ventricular outflow tract and three-vessel trachea view with rendering of 3D/4D STIC volume datasets to display images in high-definition color format. Prenatal evaluation was initially done at 17-week gestation in a 28-year-old pregnant female which showed tetralogy of Fallot (TOF). Subsequent evaluation at 34 weeks with 3D/4D STIC datasets showed a small main pulmonary artery (MPA) continuing into an adequately sized right pulmonary artery. The LPA was very small (Z-score -2.63), with no visible connection to MPA. Rendering of the 3D/4D STIC datasets revealed disconnected pulmonary arteries with the vertical DA from the base of the innominate artery in a right aortic arch, continuing as the LPA. Findings were confirmed on postnatal high-resolution CT pulmonary angiography and cardiac catheterization with subsequent stenting of the ductus. This report highlights the incremental benefit of advanced 3D/4D STIC rendering in accurate prenatal diagnosis of a rare anomaly of TOF with disconnected pulmonary arteries, leading to early neonatal intervention to preserve the blood supply to the left lung.

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Ghost imaging is a novel imaging technique that utilizes the intensity correlation property of an optical field to retrieve information of the scene being measured. Due to the advantages of simple structure, high detection efficiency, etc., ghost imaging exhibits broad application prospects in the fields of space remote sensing, optical encryption transmission, medical imaging, and so on. At present, ghost imaging is gradually developing toward practicality, in which ghost imaging of moving targets is becoming a much-needed breakthrough link. At this stage, we can improve the imaging speed and improve the imaging quality to seek a more optimized ghost imaging scheme for moving targets. Based on the principle of moving target ghost imaging, this review summarizes and compares the existing methods for ghost imaging of moving targets. It also discusses the research direction and the technical challenges at the current stage to provide references for further promotion of the instantiation of ghost imaging applications.

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To mitigate the influence of satellite platform vibrations on space camera imaging quality, a novel approach is proposed to detect vibration parameters based on correlation imaging of rolling-shutter CMOS. In the meantime, a restoration method to address the image degradation of rolling-shutter CMOS caused by such vibrations is proposed. The vibration parameter detection method utilizes the time-sharing and row-by-row imaging principle of rolling-shutter CMOS to obtain relative offset by comparing two frames of correlation images from continuous imaging. Then, the space camera's vibration parameters are derived from the fitting curve parameters of the relative offset. According to the detected vibration parameters, the discrete point spread function is obtained, and the rolling-shutter CMOS image degradation caused by vibration is restored row by row. The verification experiments demonstrate that the proposed detection method for two-dimensional vibration achieves a relative accuracy of less than 1% in period detection and less than 2% in amplitude detection. Additionally, the proposed restoration method can enhance the MTF index by over 20%. The experimental results demonstrate that the detection method is capable of detecting high-frequency vibrations through low-frame-frequency image sequences, and it exhibits excellent applicability in both push-scan cameras and staring cameras. The restoration method effectively enhances the evaluation parameters of image quality and yields a remarkable restorative effect on degraded images.

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This study aims to investigate the depth distribution of Mohorovicic discontinuity (Moho) and its relationship with the tectonic pattern of the South China Sea and adjacent areas. To achieve this, the spatial characteristics of the full tensor gravity gradient data are analyzed to identify 17 large and deep faults and to divide the study area into 9 tectonic units with distinct geological structures. Using a three-dimensional (3D) interface inversion method, the Moho depth is determined, constrained by the Moho depth information obtained from sonar-buoy detection and submarine seismograph detection profiles. By analyzing the relationship between the distribution characteristics of Moho and tectonic units, the study summarizes the trend, relief, gradient of Moho, and crustal properties in the study area. Additionally, the seismically constrained Moho undulation combined with the gravity data, gravity gradient anomalies and unconstrained 3D correlation imaging are employed to study the crustal structure of the South China Sea, investigate the vertical and horizontal changes of the crustal structure, and reveal the large-scale crustal and regional structure of the South China Sea. Through the coupling analysis of shallow and deep structures, the study reveals that the gravity gradient anomalies and 3D correlation imaging are consistent with the variations of the Moho depth, indicating the presence of a trench-island arc-back arc basin system and the distribution of continental crust, oceanic crust, and transitional crust in the South China Sea.

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Self-assembling peptides (SAPs) have been increasingly studied as hydrogel-former gelators because they can create biocompatible environments. A common strategy to trigger gelation, is to use a pH variation, but most methods result in a change in pH that is too rapid, leading to gels with hardly reproducible properties. Here, we use the urea-urease reaction to tune gel properties, by a slow and uniform pH increase. We were able to produce very homogeneous and transparent gels at several SAP concentrations, ranging from c=1g/L to c=10g/L. In addition, by exploiting such a pH control strategy, and combining photon correlation imaging with dynamic light scattering measurements, we managed to unravel the mechanism by which gelation occurs in solutions of (LDLK)3-based SAPs. We found that, in diluted and concentrated solutions, gelation follows different pathways. This leads to gels with different microscopic dynamics and capability of trapping nanoparticles. At high concentrations, a strong gel is formed, made of relatively thick and rigid branches that firmly entrap nanoparticles. By contrast, the gel formed in dilute conditions is weaker, characterized by entanglements and crosslinks of very thin and flexible filaments. The gel is still able to entrap nanoparticles, but their motion is not completely arrested. These different gel morphologies can potentially be exploited for controlled multiple drug release.

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Room temperature phosphorescence (RTP) materials are characterized with emission after removing the excitation source. Such long-lived emission feature possesses great potential in biological fluorescence imaging because it enables a way regarding temporal dimension for separating the interference of autofluorescence and common noises typically encountered in conventional fluorescence imaging. Herein, we constructed a new type of mesoporous silica nanoparticles (MSNs)-based composite nanoparticles (NPs) with dual-color long-lived emission, namely millisecond-level green phosphorescence and sub-millisecond-level delayed red fluorescence by encapsulating a typical RTP dye and Rhodamine dye in the cavities of the MSNs with the former acting as energy donor (D) while the latter as acceptor (A). Benefiting from the close D-A proximity, energy match between the donor and the acceptor and the optimized D/A ratio in the composite NPs, efficient triplet-to-singlet Förster resonance energy transfer (TS-FRET) in the NPs occurred upon exciting the donor, which enabled dual-color long-lived emission. The preliminary results of dual-color correlation imaging of live cells based on such emission feature unequivocally verified the unique ability of such NPs for distinguishing the false positive generated by common emitters with single-color emission feature.

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Background: The value of prenatal identification of morphology of ductus arteriosus in fetuses with congenital heart defects (CHD) with pulmonary atresia and duct-dependent pulmonary circulation (DDPC) in planning neonatal ductal stenting procedure is untested. The aim of the study is to analyze the utility of three-dimensional/four-dimensional (3D/4D) spatiotemporal image correlation (STIC) fetal echocardiography in delineating the morphology of ductus arteriosus in fetuses with DDPC undergoing neonatal ductal stenting. Methods: In this retrospective study (2017-22), prenatal imaging of pulmonary artery (PA) anatomy, aortic arch sidedness, and morphology of ductus arteriosus (ductal origin was classified as vertical/horizontal and ductal course as tortuous/straight) was done using 3D/4D STIC imaging and volume datasets. Prenatal findings were correlated with angiographic findings during stenting and the degree of agreement was calculated. Results: We included 27 fetuses with a prenatal diagnosis of CHD with DDPC who underwent neonatal ductal stenting. The accuracy of prenatal assessment of PA anatomy, branch PA stenosis, and arch sidedness was 100%, 92.6%, and 88.9%, respectively. The accuracy of prenatal assessment of ductal origin and course, compared with angiography, was 85.2% and 88.9%, respectively. Prenatal imaging had a diagnostic accuracy of 100% for vertical straight and horizontal tortuous ducts, 84.6% for vertical tortuous, and 67% for horizontal straight ducts. Duct stenting was successful in 25 (92.6%) babies; two died after the procedure from stent occlusion. Conclusion: Fetal echocardiography using 3D/4D STIC imaging enables accurate delineation of the morphology of ductus arteriosus in fetuses with DDPC, thereby aiding parental counseling and planning neonatal ductal stenting.

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Correlation plenoptic imaging (CPI) is a technique capable of acquiring the light field emerging from a scene of interest, namely, the combined information of intensity and propagation direction of light. This is achieved by evaluating correlations between the photon numbers measured by two high-resolution detectors. Volumetric information about the object of interest is decoded, through data analysis, from the measured four-dimensional correlation function. In this paper, we investigate the relevant aspects of the refocusing algorithm, a post-processing method that isolates the image of a selected transverse plane within the 3D scene, once applied to the correlation function. In particular, we aim at bridging the gap between existing literature, which only deals with refocusing algorithms in case of continuous coordinates, and the experimental reality, in which the correlation function is available as a discrete quantity defined on the sensors pixels.

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Diffraction-limited light-field imaging has been recently achieved by exploiting light spatial correlations measured on two high-resolution detectors. As in conventional light-field imaging, the typical operations of refocusing and 3D reconstruction are based on ray tracing in a geometrical optics context, and are thus well defined in the ideal case, both conceptually and theoretically. However, some properties of the measured correlation function are influenced by experimental features such as the finite size of apertures, detectors, and pixels. In this work, we take into account realistic experimental conditions and analyze the resulting correlation function through theory and simulation. We also provide an expression to evaluate the pixel-limited resolution of the refocused images, as well as a strategy for eliminating artifacts introduced by the finite size of the optical elements.

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BackgroundFetal echocardiography continues to be the first line investigation for detecting congenital heart diseases (CHD). As accurate and complete diagnosis of complex heart disease is often difficult in the first trimester due to small size of the fetal heart, confirmation/expanded description by fetopsy provides the best information for accurate counseling for future pregnancies. Although non invasive fetal autopsy alternatives have been investigated with favorable results, conventional autopsy remains the gold standard procedure used to confirm the fetal abnormalities. Case report: We describe a conotruncal anomaly diagnosed at 12 weeks gestation using spatiotemporal image. The fetopsy confirmed the diagnosis of Type I Truncus arteriosus. Conclusion: Four-dimensional STIC imaging provides incremental benefits in evaluation of fetal cardiac anomalies, and confirmation by autopsy findings allows further refinement of the diagnosis.

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Piezoelectric transducers are convenient enablers for generating and receiving Lamb waves for damage detection. Fatigue cracks are one of the most common causes for the failure of metallic structures. Increasing emphasis on the integrity of critical structures creates an urgent need to monitor structures and to detect cracks at an early stage to prevent catastrophic failures. This paper presents a two-dimensional (2D) cross-correlation imaging technique that can not only detect a fatigue crack but can also precisely image the fatigue cracks in metallic structures. The imaging method was based on the cross-correlation algorithm that uses incident waves and the crack-scattered waves of all directions to generate the crack image. Fatigue testing for crack generation was then conducted in both an aluminum plate and a stainless-steel plate. Piezoelectric wafer transducer was used to actuate the interrogating Lamb wave. To obtain the scattered waves as well as the incident waves, a scanning laser Doppler vibrometer was adopted for acquiring time-space multidimensional wavefield, followed with frequency-wavenumber processing. The proof-of-concept study was conducted in an aluminum plate with a hairline fatigue crack. A frequency-wavenumber filtering method was used to obtain the incident wave and the scattered wave wavefields for the cross-correlation imaging. After this, the imaging method was applied to evaluate cracks on a stainless-steel plate generated during fatigue loading tests. The presented imaging method showed successful inspection and quantification results of the crack and its growth.

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BACKGROUND: Iron homeostasis is a critical biological process that may be disrupted in cocaine use disorder (CUD). In the brain, iron is required for neural processes involved in addiction and can be lethal to cells if unbound, especially in excess. Moreover, recent studies have implicated elevated brain iron in conditions of prolonged psychostimulant exposure. Thus, the purpose of this study was to examine iron in basal ganglia reward regions of individuals with CUD using an advanced imaging method called magnetic field correlation (MFC) imaging. METHODS: MFC imaging was acquired in 19 non-treatment-seeking individuals with CUD and 19 healthy control individuals (both male and female). Region-of-interest analyses for MFC group differences and within-group correlations with age and years of cocaine use were conducted in the globus pallidus internal segment (GPi), globus pallidus external segment, putamen, caudate nucleus, thalamus, and red nucleus. RESULTS: Individuals with CUD had significantly elevated MFC compared with control individuals within the GPi. In control individuals, MFC significantly increased with age in the GPi, globus pallidus external segment, putamen, and caudate nucleus. Conversely, there were no significant MFC within-group correlations in the CUD group. CONCLUSIONS: Individuals with CUD have excess iron in the GPi, as indexed by MFC, and lack the age-related gradual iron deposition seen in normal aging. Because the globus pallidus is critical for the transition of goal-directed behavior to compulsive behavior, significantly elevated iron in the GPi may contribute to the persistence of CUD. These findings implicate dysregulation of brain iron homeostasis in CUD and support pursuing this new line of research.

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This work aims to demonstrate that radial acquisition with k-space variant reduced-FOV reconstruction can enable real-time cardiac MRI with an affordable computation cost. Due to non-uniform sampling, radial imaging requires k-space variant reconstruction for optimal performance. By converting radial parallel imaging reconstruction into the estimation of correlation functions with a previously-developed correlation imaging framework, Cartesian k-space may be reconstructed point-wisely based on parallel imaging relationship between every Cartesian datum and its neighboring radial samples. Furthermore, reduced-FOV correlation functions may be used to calculate a subset of Cartesian k-space data for image reconstruction within a small region of interest, making it possible to run real-time cardiac MRI with an affordable computation cost. In a stress cardiac test where the subject is imaged during biking with a heart rate of >100 bpm, this k-space variant reduced-FOV reconstruction is demonstrated in reference to several radial imaging techniques including gridding, GROG and SPIRiT. It is found that the k-space variant reconstruction outperforms gridding, GROG and SPIRiT in real-time imaging. The computation cost of reduced-FOV reconstruction is ~2 times higher than that of GROG. The presented work provides a practical solution to real-time cardiac MRI with radial acquisition and k-space variant reduced-FOV reconstruction in clinical settings.

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A fully non-contact laser-based nondestructive inspection (NDI) system is developed to detect and visualize damage in structures. The study focuses on the size quantification and characterization of a barely visible impact damage (BVID) in a honeycomb composite panel. The hardware consists of a Q-switched Nd:YAG pulse laser that probes the panel by generating broadband guided waves via thermo-elastic expansion. The laser, in combination with a set of galvano-mirrors is used to raster scan over a two-dimensional surface covering the damaged region of an impacted quasi-isotropic [60/0/-60]s honeycomb composite panel. The out-of-plane velocities are measured at a fixed location normal to the surface by a laser Doppler vibrometer (LDV). An ultrasonic full wavefield assembled from the three-dimensional space-time data matrix in the interrogated area is first acquired and then processed for imaging the impacted damage area. A wavenumber filtering technique in terms of wave vectors is applied to distinguish the forward and backward wavefields in the wavenumber-frequency domain. A zero-lag cross correlation (ZLCC) imaging condition is then employed in the space-frequency domain for damage imaging. The ZLCC imaging condition consists of cross correlating the incident and reflected wavefields in the entire scanned region. The condition not only images the damage boundary between incident and reflected waves outside the damage region but also, for longer time windows, enables to capture the momentary standing waves formed within the damaged region. The ZLCC imaging condition imaged two delaminated region: a main delamination, which was a skewed elliptic with major and minor axis lengths roughly 17 mm and 10 mm respectively, and a secondary delamination region approximately 6 mm by 4 mm, however, which can only be shown at higher frequency range around 80-95 kHz. To conclude, the ZLCC results were in very good agreement with ultrasonic C-scan and X-ray computed tomographic (X-ray CT) scan results. Since the imaging condition is performed in the space-frequency domain, the imaging from ZLCC can also reveal resonance modes which are shown in the main delaminated area by windowing a narrow frequency band sequentially.

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PURPOSE: Correlation imaging is a previously developed high-speed MRI framework that converts parallel imaging reconstruction into the estimate of correlation functions. The presented work aims to demonstrate this framework can provide a speed gain over parallel imaging by estimating k-space variant correlation functions. METHODS: Because of Fourier encoding with gradients, outer k-space data contain higher spatial-frequency image components arising primarily from tissue boundaries. As a result of tissue-boundary sparsity in the human anatomy, neighboring k-space data correlation varies from the central to the outer k-space. By estimating k-space variant correlation functions with an iterative self-calibration method, correlation imaging can benefit from neighboring k-space data correlation associated with both coil sensitivity encoding and tissue-boundary sparsity, thereby providing a speed gain over parallel imaging that relies only on coil sensitivity encoding. This new approach is investigated in brain imaging and free-breathing neonatal cardiac imaging. RESULTS: Correlation imaging performs better than existing parallel imaging techniques in simulated brain imaging acceleration experiments. The higher speed enables real-time data acquisition for neonatal cardiac imaging in which physiological motion is fast and non-periodic. CONCLUSION: With k-space variant correlation functions, correlation imaging gives a higher speed than parallel imaging and offers the potential to image physiological motion in real-time. Magn Reson Med 79:1483-1494, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

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Temperature perception has long been classified as a somesthetic function solely. However, in recent years several studies brought evidence that temperature perception also takes place in the olfactory system of rodents. Temperature has been described as an effective stimulus for sensory neurons of the Grueneberg ganglion located at the entrance of the nose. Here, we investigate whether a neuronal trace of temperature stimulation can be observed in the glomeruli and mitral cells of the olfactory bulb, using calcium imaging and fast line-scanning microscopy. We show in the Xenopus tadpole system that the γ-glomerulus, which receives input from olfactory neurons, is highly sensitive to temperature drops at the olfactory epithelium. We observed that thermo-induced activity in the γ-glomerulus is conveyed to the mitral cells innervating this specific neuropil. Surprisingly, a substantial number of thermosensitive mitral cells were also chemosensitive. Moreover, we report another unique feature of the γ-glomerulus: it receives ipsilateral and contralateral afferents. The latter fibers pass through the contralateral bulb, cross the anterior commissure, and then run to the ipsilateral olfactory bulb, where they target the γ-glomerulus. Temperature drops at the contralateral olfactory epithelium also induced responses in the γ-glomerulus and in mitral cells. Temperature thus appears to be a relevant physiological input to the Xenopus olfactory system. Each olfactory bulb integrates and codes temperature signals originating from receptor neurons of the ipsilateral and contralateral nasal cavities. Finally, temperature and chemical information is processed in shared cellular networks.

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PURPOSE: This study aims to (i) develop a new high-speed MRI approach by implementing correlation imaging in wavelet-space, and (ii) demonstrate the ability of wavelet-space correlation imaging to image human anatomy with involuntary or physiological motion. METHODS: Correlation imaging is a high-speed MRI framework in which image reconstruction relies on quantification of data correlation. The presented work integrates correlation imaging with a wavelet transform technique developed originally in the field of signal and image processing. This provides a new high-speed MRI approach to motion-free data collection without motion monitoring or data segmentation. The new approach, called "wavelet-space correlation imaging", is investigated in brain imaging with involuntary motion and chest imaging with free-breathing. RESULTS: Wavelet-space correlation imaging can exceed the speed limit of conventional parallel imaging methods. Using this approach with high acceleration factors (6 for brain MRI, 16 for cardiac MRI, and 8 for lung MRI), motion-free images can be generated in static brain MRI with involuntary motion and nonsegmented dynamic cardiac/lung MRI with free-breathing. CONCLUSION: Wavelet-space correlation imaging enables high-speed MRI in the presence of involuntary motion or physiological dynamics without motion monitoring or data segmentation.

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The presented work aims to develop a generalized linear approach to image reconstruction with arbitrary sampling trajectories for high-speed MRI. This approach is based on a previously developed image reconstruction framework, "correlation imaging". In the presented work, correlation imaging with arbitrary sampling trajectories is implemented in a multi-dimensional hybrid space that is formed from the physical sampling space and a virtually defined space. By introducing an undersampling trajectory with both uniformity and randomness in the hybrid space, correlation imaging may take advantage of multiple image reconstruction mechanisms including coil sensitivity encoding, data sparsity and information sharing. This hybrid-space implementation is demonstrated in multi-slice 2D imaging, multi-scan imaging, and radial dynamic imaging. Since more information is used in image reconstruction, it is found that hybrid-space correlation imaging outperforms several conventional techniques. The presented approach will benefit clinical MRI by enabling correlation imaging to be used to accelerate multi-scan clinical protocols that need different sampling trajectories in different scans.

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The aim of our study was to determine the agreement between two different methods for calculating the mean vascularization index (VI) of ovarian stroma using spatio-temporal image correlation-high definition flow (STIC-HDF) technology. Stored 4-D STIC-HDF volume data for ovaries of 34 premenopausal women were assessed retrospectively. We calculated the mean VI from the VI values derived for each 3-D volume within the STIC sequence. Then, the examiner subjectively selected the two volumes with the highest and lowest color signals, respectively. We averaged these two values. Agreement between VI measurements was estimated by calculating intra-class correlation coefficients. The intra-class correlation coefficient for the VI was 0.999 (95% confidence interval: 0.999-1.000). The mean time needed to calculate the mean VI using the entire 4-D STIC sequence was significantly longer than the mean time needed to calculate the average value from the volumes with the highest and lowest color signals determined by the operator (p < 0001). We conclude that there is significant agreement between the two methods. Calculating the average VI from the highest and lowest values is less time consuming than calculating the mean VI from the complete STIC sequence.

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