The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
James G. Fujimoto - One of the best experts on this subject based on the ideXlab platform.
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correction of circumferential and Longitudinal Motion distortion in high speed catheter endoscope based optical coherence tomography
Biomedical Optics Express, 2021Co-Authors: Tan H. Nguyen, Osman O. Ahsen, Kaicheng Liang, Jason Zhang, Hiroshi Mashimo, James G. FujimotoAbstract:Catheter/endoscope-based optical coherence tomography (OCT) is a powerful modality that visualizes structural information in luminal organs. Increases in OCT speed have reduced Motion artifacts by enabling acquisition faster than or comparable to the time scales of physiological Motion. However Motion distortion remains a challenge because catheter/endoscope OCT imaging involves both circumferential and Longitudinal scanning of tissue. This paper presents a novel image processing method to estimate and correct Motion distortion in both the circumferential and Longitudinal directions using a single en face image from a volumetric data set. The circumferential Motion distortion is estimated and corrected using the en face image. Then Longitudinal Motion distortion is estimated and corrected using diversity of image features along the catheter pullback direction. Finally, the OCT volume is resampled and Motion corrected. Results are presented on synthetic images and clinical OCT images of the human esophagus.
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Correction of circumferential and Longitudinal Motion distortion in high-speed catheter/endoscope-based optical coherence tomography.
Biomedical optics express, 2020Co-Authors: Tan H. Nguyen, Osman O. Ahsen, Kaicheng Liang, Jason Zhang, Hiroshi Mashimo, James G. FujimotoAbstract:Catheter/endoscope-based optical coherence tomography (OCT) is a powerful modality that visualizes structural information in luminal organs. Increases in OCT speed have reduced Motion artifacts by enabling acquisition faster than or comparable to the time scales of physiological Motion. However Motion distortion remains a challenge because catheter/endoscope OCT imaging involves both circumferential and Longitudinal scanning of tissue. This paper presents a novel image processing method to estimate and correct Motion distortion in both the circumferential and Longitudinal directions using a single en face image from a volumetric data set. The circumferential Motion distortion is estimated and corrected using the en face image. Then Longitudinal Motion distortion is estimated and corrected using diversity of image features along the catheter pullback direction. Finally, the OCT volume is resampled and Motion corrected. Results are presented on synthetic images and clinical OCT images of the human esophagus.
Tiina M. Laitinen - One of the best experts on this subject based on the ideXlab platform.
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Carotid Wall Longitudinal Motion in Ultrasound Imaging: An Expert Consensus Review.
Ultrasound in medicine & biology, 2020Co-Authors: Fereshteh Yousefi Rizi, Heikki Yli-ollila, Spyretta Golemati, Monika Makūnaitė, Maciej Orkisz, Nassir Navab, Maureen J. Macdonald, Tiina M. Laitinen, Hamid BehnamAbstract:Motion extracted from the carotid artery wall provides unique information for vascular health evaluation. Carotid artery Longitudinal wall Motion corresponds to the multiphasic arterial wall excursion in the direction parallel to blood flow during the cardiac cycle. While this Motion phenomenon has been well characterized, there is a general lack of awareness regarding its implications for vascular health assessment or even basic vascular physiology. In the last decade, novel estimation strategies and clinical investigations have greatly advanced our understanding of the bi-axial behavior of the carotid artery, necessitating an up-to-date review to summarize and classify the published literature in collaboration with technical and clinical experts in the field. Within this review, the state-of-the-art methodologies for carotid wall Motion estimation are described, and the observed relationships between Longitudinal Motion-derived indices and vascular health are reported. The vast number of studies describing the Longitudinal Motion pattern in plaque-free arteries, with its putative application to cardiovascular disease prediction, point to the need for characterizing the added value and applicability of Longitudinal Motion beyond established biomarkers. To this aim, the main purpose of this review was to provide a strong base of theoretical knowledge, together with a curated set of practical guidelines and recommendations for Longitudinal Motion estimation in patients, to foster future discoveries in the field, toward the integration of Longitudinal Motion in basic science as well as clinical practice.
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Influence of cardiovascular risk factors on Longitudinal Motion of the common carotid artery wall.
Atherosclerosis, 2018Co-Authors: S. Helena Taivainen, Heikki Yli-ollila, Tiina M. Laitinen, Markus Juonala, Mika Kähönen, Olli T. Raitakari, Tomi LaitinenAbstract:Abstract Background and aims Carotid artery Longitudinal wall Motion (CALM) is a new biomarker, which can be measured together with carotid intima-media thickness and distensibility measurements in the same session. Our objective was to study the relationship between these indicators of vascular health and cardiovascular risk factors in a large and well-characterized study population. Methods The study population consisted of 465 subjects aged 30–45 years. Successful measurements were performed in 287 participants. Results The peak-to-peak and retrograde amplitudes of the Longitudinal Motion were inversely correlated with systolic blood pressure (SBP; r = −0.152, p Conclusions The magnitude of correlation coefficients between CALM parameters and risk factors was comparable with those for carotid intima-media thickness and distensibility. However, the correlation profile for various risk factors was different and CALM gives additional information regarding arteriosclerosis and risk factors.
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Transfer Function Analysis of the Longitudinal Motion of the Common Carotid Artery Wall.
Frontiers in physiology, 2016Co-Authors: Heikki Yli-ollila, Mika P. Tarvainen, Tomi Laitinen, Tiina M. LaitinenAbstract:The Longitudinal Motion of the carotid wall is a potential new measure of arterial stiffness. Despite the over decade long research on the subject, the driving force and the specific Longitudinal kinetics of the carotid wall has remained unclear. In this study, a transfer function analysis with 20 healthy subjects is presented to derive how the energy from the blood pressure moves the innermost arterial wall Longitudinally and how the kinetic energy is then transferred to the outermost arterial layer. The power spectrums display that the main kinetic energy of the Longitudinal Motion is on band 0-3 Hz with a peak on the 1.1 Hz frequency. There is a large variation among the individuals, how the energy from the blood pressure transfers into the Longitudinal Motion of the arterial wall since the main direction of the Longitudinal Motion varies individually and because early arterial stiffening potentially has an effect on the time characteristics of the energy transfer. The energy transfer from the innermost to the outermost wall layer is more straightforward: on average, a 17% of the Longitudinal amplitude is lost and an 18.9 ms delay is visible on the 1.0 Hz frequency.
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Principal Component Analysis of the Longitudinal Carotid Wall Motion in Association with Vascular Stiffness: A Pilot Study.
Ultrasound in medicine & biology, 2016Co-Authors: Heikki Yli-ollila, Mika P. Tarvainen, Tomi Laitinen, Tiina M. LaitinenAbstract:The Longitudinal Motion of the carotid wall during a heart cycle has a multiphasic waveform. Recent studies have examined the amplitude of this Motion. Instead of amplitude measurements, we focus on making a detailed characterization of the Motion waveform. Two-minute carotid ultrasound videos were obtained for 19 healthy volunteers, and a speckle tracking algorithm was used to measure the Motion of the carotid wall. Principal component analysis revealed the characteristic features of wall Motion and their relation to known arterial stiffness indices. By estimating two principal components, we could account for more than 92% of the variation in the Motion graphs. The first principal component derived from the Longitudinal Motion curves was significantly correlated to pulse pressure, indicating that the main dominant base waveform of the Longitudinal Motion was related to blood pressure. The second principal component derived from the Longitudinal Motion curves had multiple significant correlations to known stiffness indices, indicating that the stronger biphasic structure of the Motion curve, especially on the adventitia layer, was associated with higher distensibility and compliance, as well as reduced carotid artery stiffness. According to this study, the second principal component of the Longitudinal Motion may be a useful parameter reflecting vascular health.
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new indices of arterial stiffness measured from Longitudinal Motion of common carotid artery in relation to reference methods a pilot study
Clinical Physiology and Functional Imaging, 2016Co-Authors: Heikki Yliollila, Matti Weckström, Tomi Laitinen, Tiina M. LaitinenAbstract:Summary Background Longitudinal wall Motion of carotid artery is a useful but challenging parameter to measure. In this study, we tested our previously published Motion tracking algorithm and validated our method against applanation tonometry measurements. Methods and Results We measured the two-dimensional carotid artery wall Motion from 19 healthy subjects and, as a reference, performed applanation tonometry measurements in parallel with the ultrasound study. The results show that peak velocities (R = −0·484; P 0·05). The amplitudes of the Longitudinal Motion, between intima and adventitia, are related more to the physical size of the subject, as they correlated significantly with the height (R = 0·597; P<0·01) and weight (R = 0·562; P<0·05) of the subject as well as the cross-sectional dimension of the measured artery (R = 0·611; P<0·01). Furthermore, two new indices have been introduced, Polydeg and RAlength, with which to study the shape of the Longitudinal Motion curve; both parameters displayed significant correlation with arterial stiffness, for example augmentation index (R = 0·468; P<0·05 and R = 0·609; P<0·01, respectively). Conclusions The new Longitudinal Motion parameters presented here displayed clear potential to be used as novel stiffness indices.
Tan H. Nguyen - One of the best experts on this subject based on the ideXlab platform.
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correction of circumferential and Longitudinal Motion distortion in high speed catheter endoscope based optical coherence tomography
Biomedical Optics Express, 2021Co-Authors: Tan H. Nguyen, Osman O. Ahsen, Kaicheng Liang, Jason Zhang, Hiroshi Mashimo, James G. FujimotoAbstract:Catheter/endoscope-based optical coherence tomography (OCT) is a powerful modality that visualizes structural information in luminal organs. Increases in OCT speed have reduced Motion artifacts by enabling acquisition faster than or comparable to the time scales of physiological Motion. However Motion distortion remains a challenge because catheter/endoscope OCT imaging involves both circumferential and Longitudinal scanning of tissue. This paper presents a novel image processing method to estimate and correct Motion distortion in both the circumferential and Longitudinal directions using a single en face image from a volumetric data set. The circumferential Motion distortion is estimated and corrected using the en face image. Then Longitudinal Motion distortion is estimated and corrected using diversity of image features along the catheter pullback direction. Finally, the OCT volume is resampled and Motion corrected. Results are presented on synthetic images and clinical OCT images of the human esophagus.
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Correction of circumferential and Longitudinal Motion distortion in high-speed catheter/endoscope-based optical coherence tomography.
Biomedical optics express, 2020Co-Authors: Tan H. Nguyen, Osman O. Ahsen, Kaicheng Liang, Jason Zhang, Hiroshi Mashimo, James G. FujimotoAbstract:Catheter/endoscope-based optical coherence tomography (OCT) is a powerful modality that visualizes structural information in luminal organs. Increases in OCT speed have reduced Motion artifacts by enabling acquisition faster than or comparable to the time scales of physiological Motion. However Motion distortion remains a challenge because catheter/endoscope OCT imaging involves both circumferential and Longitudinal scanning of tissue. This paper presents a novel image processing method to estimate and correct Motion distortion in both the circumferential and Longitudinal directions using a single en face image from a volumetric data set. The circumferential Motion distortion is estimated and corrected using the en face image. Then Longitudinal Motion distortion is estimated and corrected using diversity of image features along the catheter pullback direction. Finally, the OCT volume is resampled and Motion corrected. Results are presented on synthetic images and clinical OCT images of the human esophagus.
Junmin Wang - One of the best experts on this subject based on the ideXlab platform.
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Longitudinal Motion Based Lightweight Vehicle Payload Parameter Real-Time Estimations
Journal of Dynamic Systems Measurement and Control, 2012Co-Authors: Xiaoyu Huang, Junmin WangAbstract:This paper proposes a Longitudinal Motion based payload parameter estimator (PPE) design for four-wheel-independently driven lightweight vehicles (LWVs), whose dynamics and control are substantially affected by their payload variations due to the LWVs' significantly reduced sizes and weights. Accurate and real-time estimation of payload parameters, including payload mass and its onboard planar location, will be helpful for LWV control (particularly under challenging driving conditions) and load monitoring. The proposed estimation method consists of three steps in sequential: tire effective radius identification for undriven wheels at constant speed driving; payload mass estimation during acceleration–deceleration period; and payload planar location estimation (PPLE). The PPLE is divided into two parts: a tire nominal normal force estimator (NNFE) based on a recursive least squares algorithm using signals generated by the redundant inputs, and a parameter calculator combining these estimated nominal normal forces. The prototype LWV is a lightweight electric ground vehicle (EGV) with separable torque control of the four wheels enabled by four in-wheel motors, which allow redundant input injections in the designed maneuvers. Experimental results obtained on an EGV road test show that the proposed PPE is capable of accurately estimating payload parameters, and it is independent of other unknown parameters such as tire-road friction coefficient.
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adaptive vehicle speed control with input injections for Longitudinal Motion independent road frictional condition estimation
IEEE Transactions on Vehicular Technology, 2011Co-Authors: Yan Chen, Junmin WangAbstract:This paper presents a novel real-time tire-road friction coefficient estimation method that is independent of vehicle Longitudinal Motion for ground vehicles with separable control of the front and rear wheels. The tire-road friction coefficient information is of critical importance for vehicle dynamic control systems and intelligent autonomous vehicle applications. In this paper, the vehicle Longitudinal-Motion-independent tire-road friction coefficient estimation method consists of three main components: 1) an observer to estimate the internal state of a dynamic LuGre tire model; 2) an adaptive control law with a parameter projection mechanism to track the desired vehicle Longitudinal Motion in the presence of tire-road friction coefficient uncertainties and actively injected braking excitation signals; and 3) a recursive least square estimator that is independent of the control law, to estimate the tire-road friction coefficient in real time. Simulation results based on a high-fidelity CarSim full-vehicle model show that the system can reliably estimate the tire-road friction coefficient independent of vehicle Longitudinal Motion.
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CDC - Vehicle-Longitudinal-Motion-independent real-time tire-road friction coefficient estimation
49th IEEE Conference on Decision and Control (CDC), 2010Co-Authors: Yan Chen, Junmin WangAbstract:Tire-road friction coefficient information is of critical importance for vehicle dynamic control such as yaw stability control, trajectory tracking control, and rollover prevention for both manned and unmanned applications. Existing tire-road friction coefficient estimation approaches often require certain levels of vehicle Longitudinal and/or lateral Motion excitations (e.g. accelerating, decelerating, and steering) to satisfy the persistence of excitation condition for reliable estimations. Such excitations may undesirably interfere with vehicle Motion controls. By utilizing the actuation redundancy, this paper presents a novel, real-time, tire-road friction coefficient estimation method that is independent of vehicle Longitudinal Motion for ground vehicles with separable control of front and rear wheels. A dynamic LuGre tire model is utilized in this study. An observer is proposed to estimate the internal state in a LuGre tire model. An adaptive control law with a parameter projection mechanism is designed to track the desired vehicle Longitudinal Motion in the presence of tire-road friction coefficient uncertainties and an actively-injected persistently exciting input signal. An RLS estimator was employed to estimate the tire-road friction coefficient in real-time. Simulation results based on a full-vehicle CarSim® model show that the system can reliably estimate the tire-road friction coefficient independent of vehicle Longitudinal Motion.
Heikki Yli-ollila - One of the best experts on this subject based on the ideXlab platform.
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Carotid Wall Longitudinal Motion in Ultrasound Imaging: An Expert Consensus Review.
Ultrasound in medicine & biology, 2020Co-Authors: Fereshteh Yousefi Rizi, Heikki Yli-ollila, Spyretta Golemati, Monika Makūnaitė, Maciej Orkisz, Nassir Navab, Maureen J. Macdonald, Tiina M. Laitinen, Hamid BehnamAbstract:Motion extracted from the carotid artery wall provides unique information for vascular health evaluation. Carotid artery Longitudinal wall Motion corresponds to the multiphasic arterial wall excursion in the direction parallel to blood flow during the cardiac cycle. While this Motion phenomenon has been well characterized, there is a general lack of awareness regarding its implications for vascular health assessment or even basic vascular physiology. In the last decade, novel estimation strategies and clinical investigations have greatly advanced our understanding of the bi-axial behavior of the carotid artery, necessitating an up-to-date review to summarize and classify the published literature in collaboration with technical and clinical experts in the field. Within this review, the state-of-the-art methodologies for carotid wall Motion estimation are described, and the observed relationships between Longitudinal Motion-derived indices and vascular health are reported. The vast number of studies describing the Longitudinal Motion pattern in plaque-free arteries, with its putative application to cardiovascular disease prediction, point to the need for characterizing the added value and applicability of Longitudinal Motion beyond established biomarkers. To this aim, the main purpose of this review was to provide a strong base of theoretical knowledge, together with a curated set of practical guidelines and recommendations for Longitudinal Motion estimation in patients, to foster future discoveries in the field, toward the integration of Longitudinal Motion in basic science as well as clinical practice.
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Influence of cardiovascular risk factors on Longitudinal Motion of the common carotid artery wall.
Atherosclerosis, 2018Co-Authors: S. Helena Taivainen, Heikki Yli-ollila, Tiina M. Laitinen, Markus Juonala, Mika Kähönen, Olli T. Raitakari, Tomi LaitinenAbstract:Abstract Background and aims Carotid artery Longitudinal wall Motion (CALM) is a new biomarker, which can be measured together with carotid intima-media thickness and distensibility measurements in the same session. Our objective was to study the relationship between these indicators of vascular health and cardiovascular risk factors in a large and well-characterized study population. Methods The study population consisted of 465 subjects aged 30–45 years. Successful measurements were performed in 287 participants. Results The peak-to-peak and retrograde amplitudes of the Longitudinal Motion were inversely correlated with systolic blood pressure (SBP; r = −0.152, p Conclusions The magnitude of correlation coefficients between CALM parameters and risk factors was comparable with those for carotid intima-media thickness and distensibility. However, the correlation profile for various risk factors was different and CALM gives additional information regarding arteriosclerosis and risk factors.
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Transfer Function Analysis of the Longitudinal Motion of the Common Carotid Artery Wall.
Frontiers in physiology, 2016Co-Authors: Heikki Yli-ollila, Mika P. Tarvainen, Tomi Laitinen, Tiina M. LaitinenAbstract:The Longitudinal Motion of the carotid wall is a potential new measure of arterial stiffness. Despite the over decade long research on the subject, the driving force and the specific Longitudinal kinetics of the carotid wall has remained unclear. In this study, a transfer function analysis with 20 healthy subjects is presented to derive how the energy from the blood pressure moves the innermost arterial wall Longitudinally and how the kinetic energy is then transferred to the outermost arterial layer. The power spectrums display that the main kinetic energy of the Longitudinal Motion is on band 0-3 Hz with a peak on the 1.1 Hz frequency. There is a large variation among the individuals, how the energy from the blood pressure transfers into the Longitudinal Motion of the arterial wall since the main direction of the Longitudinal Motion varies individually and because early arterial stiffening potentially has an effect on the time characteristics of the energy transfer. The energy transfer from the innermost to the outermost wall layer is more straightforward: on average, a 17% of the Longitudinal amplitude is lost and an 18.9 ms delay is visible on the 1.0 Hz frequency.
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Principal Component Analysis of the Longitudinal Carotid Wall Motion in Association with Vascular Stiffness: A Pilot Study.
Ultrasound in medicine & biology, 2016Co-Authors: Heikki Yli-ollila, Mika P. Tarvainen, Tomi Laitinen, Tiina M. LaitinenAbstract:The Longitudinal Motion of the carotid wall during a heart cycle has a multiphasic waveform. Recent studies have examined the amplitude of this Motion. Instead of amplitude measurements, we focus on making a detailed characterization of the Motion waveform. Two-minute carotid ultrasound videos were obtained for 19 healthy volunteers, and a speckle tracking algorithm was used to measure the Motion of the carotid wall. Principal component analysis revealed the characteristic features of wall Motion and their relation to known arterial stiffness indices. By estimating two principal components, we could account for more than 92% of the variation in the Motion graphs. The first principal component derived from the Longitudinal Motion curves was significantly correlated to pulse pressure, indicating that the main dominant base waveform of the Longitudinal Motion was related to blood pressure. The second principal component derived from the Longitudinal Motion curves had multiple significant correlations to known stiffness indices, indicating that the stronger biphasic structure of the Motion curve, especially on the adventitia layer, was associated with higher distensibility and compliance, as well as reduced carotid artery stiffness. According to this study, the second principal component of the Longitudinal Motion may be a useful parameter reflecting vascular health.
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New indices of arterial stiffness measured from Longitudinal Motion of common carotid artery in relation to reference methods, a pilot study.
Clinical physiology and functional imaging, 2015Co-Authors: Heikki Yli-ollila, Tomi Laitinen, Matti Weckström, Tiina M. LaitinenAbstract:Longitudinal wall Motion of carotid artery is a useful but challenging parameter to measure. In this study, we tested our previously published Motion tracking algorithm and validated our method against applanation tonometry measurements. We measured the two-dimensional carotid artery wall Motion from 19 healthy subjects and, as a reference, performed applanation tonometry measurements in parallel with the ultrasound study. The results show that peak velocities (R = -0·484; P<0·05) and accelerations (R = -0·524; P<0·05) of the Longitudinal Motion between intima and adventitia layers exhibit a greater correlation with the arterial stiffness parameters, for example the augmentation index than the corresponding amplitude of the Longitudinal Motion (R = -0·132; P>0·05). The amplitudes of the Longitudinal Motion, between intima and adventitia, are related more to the physical size of the subject, as they correlated significantly with the height (R = 0·597; P<0·01) and weight (R = 0·562; P<0·05) of the subject as well as the cross-sectional dimension of the measured artery (R = 0·611; P<0·01). Furthermore, two new indices have been introduced, Polydeg and RAlength, with which to study the shape of the Longitudinal Motion curve; both parameters displayed significant correlation with arterial stiffness, for example augmentation index (R = 0·468; P<0·05 and R = 0·609; P<0·01, respectively). The new Longitudinal Motion parameters presented here displayed clear potential to be used as novel stiffness indices. © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.
