| 1. |
- Albinsson, John, et al.
(author)
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Iterative 2D tissue motion tracking in ultrafast ultrasound imaging
- 2018
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In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 8:5
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Journal article (peer-reviewed)abstract
- In order to study longitudinal movement and intramural shearing of the arterial wall with a Lagrangian viewpoint using ultrafast ultrasound imaging, a new tracking scheme is required. We propose the use of an iterative tracking scheme based on temporary down-sampling of the frame-rate, anteroposterior tracking, and unbiased block-matching using two kernels per position estimate. The tracking scheme was evaluated on phantom B-mode cine loops and considered both velocity and displacement for a range of down-sampling factors (k = 1-128) at the start of the iterations. The cine loops had a frame rate of 1300-1500 Hz and were beamformed using delay-and-sum. The evaluation on phantom showed that both the mean estimation errors and the standard deviations decreased with an increasing initial down-sampling factor, while they increased with an increased velocity or larger pitch. A limited in vivo study shows that the major pattern of movement corresponds well with state-of-the-art low frame rate motion estimates, indicating that the proposed tracking scheme could enable the study of longitudinal movement of the intima-media complex using ultrafast ultrasound imaging, and is one step towards estimating the propagation velocity of the longitudinal movement of the arterial wall.
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| 2. |
- Bohman, Elin, et al.
(author)
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Novel Evidence Concerning Lacrimal Sac Movement Using Ultra-High-Frequency Ultrasound Examinations of Lacrimal Drainage Systems
- 2021
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In: Ophthalmic Plastic and Reconstructive Surgery. - 1537-2677. ; 37:4, s. 334-340
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Journal article (peer-reviewed)abstract
- PURPOSE: Current hypothesis regarding the mechanism of active tear drainage is based on studies performed ex vivo or under nonphysiological conditions. Novel ultra-high-frequency ultrasound has the advantage of generating images with superior resolution, enabling measurements of low flow in small vessels, and the tracking of tissue motion in real time. The purpose of this study was to investigate the lacrimal drainage system and active drainage using this modality.METHODS: The upper lacrimal drainage system was investigated with 40-70 MHz ultrasound in 22 eyes in 13 patients. Irrigation confirmed a lacrimal obstruction in 10 eyes. Motion tracking was used to map movement of the lateral lacrimal sac wall and to measure flow when possible.RESULTS: The anatomy of the upper lacrimal drainage system was mapped in vivo, including the proximal canaliculi, which have not previously been imaged. The lacrimal sac lumen is slit shaped in its resting state but is distended when irrigated or if a nasolacrimal duct obstruction is present. Thus, the healthy lacrimal sac is not a cavity, and the medial retinaculum does not act against a stretched structure. Motion tracking visualized the "lacrimal pump," showing that the direction of motion of the lateral lacrimal sac wall is mainly in the sagittal plane during blinking.CONCLUSIONS: Ultra-high-frequency ultrasound allows detailed physiological monitoring of the upper lacrimal drainage system in vivo. Our findings suggest that current theories of active tear drainage need to be reappraised.
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| 5. |
- Cinthio, Magnus, et al.
(author)
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Minute roughness measurement using phase tracking for arterial wall diagnosis non-invasively in vivo
- 2007
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In: Ultrasonics Symposium, 2007. IEEE, vols 1-6. - 1051-0117. ; , s. 997-1000
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Conference paper (peer-reviewed)abstract
- Early diagnosis of atherosclerosis is essential as many of the risk factors are life-style dependent. We suggest a new method to measure minute roughness of the size of micrometers of the arterial wall. The method was evaluated using three silicone phantoms sized 13 fun, 23 itm and 33 pm, respectively. The mean of the measured heights of the phantoms were 8.1 mu m (SD 0.0), 23.3 mu m (SD 0.2) and 29.6 mu m (SD 0.1) in the forward direction, and 7.7 mu m (SI) 0.0), 21.9 mu m (SI) 0.2) and 27.3 mu m (SI) 3.6) In the backward direction, respectively. The phantom study shows very promising result and encourages to further evaluation and in vivo Investigations.
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| 6. |
- Cinthio, Magnus, et al.
(author)
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New Approaches in Arterial Characterisation
- 2008
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In: Proceedings of 11th International Symposium on Advanced Biomedical Ultrasound (Invited). ; , s. 3-8
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Conference paper (other academic/artistic)abstract
- —The aim of this paper is to briefly present the historyand the status of the arterial characterization of today as wellas summarize our work on two new approaches in arterialcharacterization – measurements of the longitudinal movementand the minute roughness of the arterial wall.
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| 7. |
- Meirza, Benjamin, et al.
(author)
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Construction of an ultrasound phantom with micrometer-sized wall-less vessels
- 2019
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In: 2019 IEEE International Ultrasonics Symposium, IUS 2019. - 1948-5719 .- 1948-5727. - 9781728145976 - 9781728145969 ; 2019-October, s. 1209-1211
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Conference paper (peer-reviewed)abstract
- The development of new ultrasound imaging technologies that aim to resolve objects smaller than the conventional ultrasounds diffraction limit calls for new types of phantoms to evaluate these technologies. When it comes to vascular flow phantoms, this becomes challenging due to the difficulty of manufacturing phantoms with vessels smaller than 1 mm in diameter. Here we describe a novel manufacturing method to construct phantoms with micro-vessels with a size down to 88 μm using oil-based clear ballistic gel (Clear Ballistics, Greenville, SC, USA) as surrounding material. Clear ballistic gel is a long-term stable tissue-mimicking material with speed of sound around 1470 m/s.
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| 8. |
- Mozumi, Michiya, et al.
(author)
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Anti-Aliasing method for ultrasonic 2D phase-sensitive motion estimator
- 2020
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In: Japanese Journal of Applied Physics. - : IOP Publishing. - 0021-4922 .- 1347-4065. ; 59:SK
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Journal article (peer-reviewed)abstract
- A 2D motion estimator can estimate tissue motions and blood flow dynamics more accurately than a 1D motion estimator. In this study, we proposed a simple anti-Aliasing filter to unwrap the phase of the cross spectrum. The proposed method is evaluated by simulation mimicking steady flows, and the magnitude of the true velocity was changed from 200 to 2400 mm s-1. In the simulation, bias error was improved from 295.0% to 4.9% by the proposed method at a true velocity magnitude of 1600 mm s-1. Also, in the in vivo measurement of the left ventricle, the wrapping in the phase of the cross spectrum was corrected by the proposed method, and the directions of the blood velocity vectors were estimated more accurately.
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| 9. |
- Mozumi, Michiya, et al.
(author)
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Impact of spacing of ultrasound receiving beams on estimation of 2D motion velocity
- 2021
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In: Japanese Journal of Applied Physics. - : IOP Publishing. - 0021-4922 .- 1347-4065. ; 60:SD
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Journal article (peer-reviewed)abstract
- For more detailed measurement of cardiovascular motion and complex blood flow, a two-dimensional (2D) velocity estimation method is required in functional ultrasound imaging. The block matching method based on the correlation function is one of the standard 2D motion estimators. In this study, we investigated the effect of lateral sampling intervals of an ultrasonic B-mode image on the accuracy in velocity estimation. In simulation, bias error (BE) in estimated velocities became -13% with an ultrasonic center frequency of 7.5 MHz and spacings of receiving beams of 0.2 mm. Such a BE was improved from -13% to -1.4% by changing the spacings from 0.2 to 0.1 mm. In the in vivo experiment, the maximum velocity obtained with spacings of 0.2 mm was underestimated by -16% as compared to those obtained with 0.1 mm. Hence, the trend was similar to that in the simulation.
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| 10. |
- Nagai, Yoshifumi, et al.
(author)
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In vitro experiment using porcine artery for evaluation of ultrasonic measurement of arterial luminal surface profile
- 2014
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In: Journal of Medical Ultrasonics. - : Springer Science and Business Media LLC. - 1346-4523 .- 1613-2254. ; 41:4, s. 431-437
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Journal article (peer-reviewed)abstract
- Introduction In early-stage atherosclerosis, the luminal surface of the arterial wall becomes rough because of detachment of endothelial cells and degeneration of the internal elastic layer. Therefore, it would be useful if minute luminal surface roughness of the carotid arterial wall, which occurs in the early stage of atherosclerosis, could be measured noninvasively with ultrasound. The injured luminal surface is believed to have roughness of a few hundred micrometers. However, in conventional ultrasonography, the axial resolution of a B-mode image depends on the ultrasonic wavelength (150 mu m at ultrasonic center frequency of 10 MHz) because a B-mode image is constructed using the amplitude of the RF echo signal. Therefore, such surface roughness cannot be measured accurately from a conventional B-mode image. Recently, we successfully measured such minute surface profile transcutaneously using the phase shift of an ultrasonic echo from the carotid arterial wall. In our previous validation experiment, a silicone phantom with minute surface roughness of 10-20 mu m was measured. However, the feasibility of our proposed method has never been validated using biological tissues. Materials and methods In the present study, luminal surface roughness of a porcine artery was measured and the result was evaluated by comparing it with the result measured using a stylus profilometer. Results and conclusion The root mean squared difference between the surface roughness measured by ultrasound and the stylus profilometer was 10.5 mu m. This result proves that our proposed method can be used to measure minute surface roughness of biological tissue.
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