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Marlevi, David, doktorandORCID iD iconorcid.org/0000-0003-1002-2070
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Publications (10 of 14) Show all publications
Marlevi, D., Kohr, H., Buurlage, J.-W., Gao, B., Batenburg, J. & Colarieti-Tosti, M. (2019). Multigrid reconstruction in tomographic imaging. IEEE Transactions on Radiation and Plasma Medical Sciences
Open this publication in new window or tab >>Multigrid reconstruction in tomographic imaging
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2019 (English)In: IEEE Transactions on Radiation and Plasma Medical Sciences, ISSN 2469-7311Article in journal (Refereed) Published
Abstract [en]

In this work, we present an efficient methodology for multigrid tomographic image reconstruction from non-truncated projection data. By partitioning the reconstruction domain and adapting the forward and backward operators, an image can be reconstructed accurately within multiple domains of varying discretisation or regularisation. We demonstrate the efficacy of the multigrid reconstruction principle using simulated data for quantitative assessment and experimental measurements from a μ-CT scanner for a clinically relevant use case scenario. A major advantage of using multiple reconstruction grids is the possibility to drastically reduce the number of unknowns in the inverse problem, and thereby the associated computational cost. This cost reduction helps to enlarge the class of available algorithms in applications with strict limitations on computation time or resources, and it enables full system resolution reconstruction of subregions that would otherwise be infeasible for the full field of view. The numerical experiments, along with a brief error analysis, show that the expected artefacts from coarse discretisation outside the region of interest become noticeable only for large differences in discretisation between subregions.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-264038 (URN)10.1109/TRPMS.2019.2942186 (DOI)
Note

QC 20191121

Available from: 2019-11-21 Created: 2019-11-21 Last updated: 2019-11-21Bibliographically approved
De Vecchi, A., Marlevi, D., Nordsletten, D. A., Ntalas, I., Leipsic, J., Bapat, V., . . . Niederer, S. A. (2018). Left ventricular outflow obstruction predicts increase in systolic pressure gradients and blood residence time after transcatheter mitral valve replacement. Scientific Reports, 8(1), Article ID 15540.
Open this publication in new window or tab >>Left ventricular outflow obstruction predicts increase in systolic pressure gradients and blood residence time after transcatheter mitral valve replacement
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 15540Article in journal (Refereed) Published
Abstract [en]

Left ventricular outflow tract (LVOT) obstruction is a relatively common consequence of transcatheter mitral valve replacement (TMVR). Although LVOT obstruction is associated with heart failure and adverse remodelling, its effects upon left ventricular hemodynamics remain poorly characterised. This study uses validated computational models to identify the LVOT obstruction degree that causes significant changes in ventricular hemodynamics after TMVR. Seven TMVR patients underwent personalised flow simulations based on pre-procedural imaging data. Different virtual valve configurations were simulated in each case, for a total of 32 simulations, and the resulting obstruction degree was correlated with pressure gradients and flow residence times. These simulations identified a threshold LVOT obstruction degree of 35%, beyond which significant deterioration of systolic function was observed. The mean increase from baseline (pre-TMVR) in the peak systolic pressure gradient rose from 5.7% to 30.1% above this threshold value. The average blood volume staying inside the ventricle for more than two cycles also increased from 4.4% to 57.5% for obstruction degrees above 35%, while the flow entering and leaving the ventricle within one cycle decreased by 13.9%. These results demonstrate the unique ability of modelling to predict the hemodynamic consequences of TMVR and to assist in the clinical decision-making process.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-247023 (URN)10.1038/s41598-018-33836-7 (DOI)000447707900055 ()2-s2.0-85055080797 (Scopus ID)
Note

QC 20190626

Available from: 2019-06-26 Created: 2019-06-26 Last updated: 2019-06-26Bibliographically approved
Maksuti, E., Larsson, D., Urban, M. W., Caidahl, K. & Larsson, M. (2017). Strain and strain rate generated by shear wave elastography in an ex vivo porcine aorta. In: 2017 IEEE International Ultrasonics Symposium (IUS): . Paper presented at 2017 IEEE International Ultrasonics Symposium, IUS 2017, Washington, United States, 6 September 2017 through 9 September 2017. IEEE Computer Society, Article ID 8091581.
Open this publication in new window or tab >>Strain and strain rate generated by shear wave elastography in an ex vivo porcine aorta
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2017 (English)In: 2017 IEEE International Ultrasonics Symposium (IUS), IEEE Computer Society, 2017, article id 8091581Conference paper (Refereed)
Abstract [en]

In order to generate trackable shear waves in soft tissues, transmitted pulses in shear wave elastography (SWE) are longer than conventional clinical ultrasound pulses. Nevertheless, they typically obey mechanical and thermal regulatory limits. In arterial applications, specific safety concerns may arise, as acoustic radiation (ARF)-induced stresses and strain rates could potentially affect the arterial wall. The aim of this study was to assess ARF-induced strain and strain rates in ex vivo arteries. A porcine aorta (diameters 8.5 mm, wall thickness 1.2 mm) was pressurized by a saline-filled water column at 60 and 120 mmHg. A Verasonics V1 system and a L7-4 transducer were used to generate the ARF in the middle of the anterior wall (F-number = 1, push length = [100, 200, 300] μs) and to perform plane-wave imaging (10 kHz). Cumulative axial displacement was estimated using 2D auto-correlation. The axial strain rate was calculated as the time-derivative of the axial strain, obtained by spatial linear regression of the displacement inside the anterior wall. The ex vivo peak strain and strain rate were compared with peak strain and strain rate values induced by the blood pressure changes in two healthy individuals and two patients with coronary artery disease at rest and measured by a dedicated in house speckle tracking algorithm. ARF-induced ex vivo peak strains were in the range 0.3-1% and strain rates in the range 6-23 s-1. Peak values were more affected by longer push duration than pressurization level. In vivo physiological peak strain was 33% and strain rate was 2 s-1. ARF-induced strain rates in vivo are likely to be lower than those assessed in this ex vivo setup due to ultrasound attenuation and the effect of surrounding tissue. Therefore, the results of the performed study suggest that SWE could be used in a safe manner for arterial applications even though specific effects of high strain rates are to be explored.

Place, publisher, year, edition, pages
IEEE Computer Society, 2017
Series
IEEE International Ultrasonics Symposium, IUS, ISSN 1948-5719
Keywords
Acoustic radiation force, Artery, Safety, Shear wave elastography, Strain, Strain rate
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:kth:diva-220744 (URN)10.1109/ULTSYM.2017.8091581 (DOI)000416948400025 ()2-s2.0-85039434244 (Scopus ID)9781538633830 (ISBN)
Conference
2017 IEEE International Ultrasonics Symposium, IUS 2017, Washington, United States, 6 September 2017 through 9 September 2017
Funder
Swedish Research Council, 2015-04237
Note

QC 20180105

Available from: 2018-01-05 Created: 2018-01-05 Last updated: 2018-01-12Bibliographically approved
Maksuti, E., Larsson, D., Urban, M. W., Caidahl, K. & Larsson, M. (2017). Strain and strain rate generated by shear wave elastography in ex vivo porcine aortas. In: IEEE International Ultrasonics Symposium, IUS: . Paper presented at 2017 IEEE International Ultrasonics Symposium, IUS 2017, 6 September 2017 through 9 September 2017. IEEE Computer Society
Open this publication in new window or tab >>Strain and strain rate generated by shear wave elastography in ex vivo porcine aortas
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2017 (English)In: IEEE International Ultrasonics Symposium, IUS, IEEE Computer Society , 2017Conference paper, Published paper (Refereed)
Abstract [en]

In shear wave elastography (SWE), acoustic radiation forces (ARF) are employed to generate shear waves within the tissue. Although the transmitted pulses are longer than those in conventional clinical ultrasound, they typically obey the mechanical and thermal regulatory limits. In arterial applications, specific safety concerns may arise, as ARF-induced stresses and strain rates could potentially affect the arterial wall. A previous simulation study (Doherty et al., J Biomech, 2013 Jan; 46(1):83-90) showed that stresses imposed by the ARF used in SWE are orders of magnitude lower than those caused by blood pressure. ARF-induced strain rates have not been investigated yet, therefore the aim of this study was to assess such strain rates in an ex vivo setup.

Place, publisher, year, edition, pages
IEEE Computer Society, 2017
National Category
Medical Equipment Engineering
Identifiers
urn:nbn:se:kth:diva-227077 (URN)10.1109/ULTSYM.2017.8092757 (DOI)2-s2.0-85039461127 (Scopus ID)9781538633830 (ISBN)
Conference
2017 IEEE International Ultrasonics Symposium, IUS 2017, 6 September 2017 through 9 September 2017
Note

QC 20180518

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-05-18Bibliographically approved
Maksuti, E., Widman, E., Larsson, D., Urban, M. W., Larsson, M. & Bjällmark, A. (2016). ARTERIAL STIFFNESS ESTIMATION BY SHEAR WAVE ELASTOGRAPHY: VALIDATION IN PHANTOMS WITH MECHANICAL TESTING. Ultrasound in Medicine and Biology, 42(1), 308-321
Open this publication in new window or tab >>ARTERIAL STIFFNESS ESTIMATION BY SHEAR WAVE ELASTOGRAPHY: VALIDATION IN PHANTOMS WITH MECHANICAL TESTING
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2016 (English)In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 42, no 1, p. 308-321Article in journal (Refereed) Published
Abstract [en]

Arterial stiffness is an independent risk factor found to correlate with a wide range of cardiovascular diseases. It has been suggested that shear wave elastography (SWE) can be used to quantitatively measure local arterial shear modulus, but an accuracy assessment of the technique for arterial applications has not yet been performed. In this study, the influence of confined geometry on shear modulus estimation, by both group and phase velocity analysis, was assessed, and the accuracy of SWE in comparison with mechanical testing was measured in nine pressurized arterial phantoms. The results indicated that group velocity with an infinite medium assumption estimated shear modulus values incorrectly in comparison with mechanical testing in arterial phantoms (6.7 +/- 0.0 kPa from group velocity and 30.5 +/- 0.4 kPa from mechanical testing). To the contrary, SWE measurements based on phase velocity analysis (30.6 +/- 3.2 kPa) were in good agreement with mechanical testing, with a relative error between the two techniques of 8.8 +/- 6.0% in the shear modulus range evaluated (40-100 kPa). SWE by phase velocity analysis was validated to accurately measure stiffness in arterial phantoms.

Keywords
Accuracy, Arterial phantom, Arterial stiffness, Group velocity, Lamb waves, Mechanical testing, Phase velocity, Poly(vinyl alcohol), Shear modulus, Shear wave elastography
National Category
Medical Image Processing
Identifiers
urn:nbn:se:kth:diva-181377 (URN)10.1016/j.ultrasmedbio.2015.08.012 (DOI)000367733800032 ()26454623 (PubMedID)2-s2.0-84957007046 (Scopus ID)
Funder
VINNOVA, 2011-01365Swedish Research Council, 2012-2795
Note

QC 20160203

Available from: 2016-02-03 Created: 2016-02-01 Last updated: 2019-08-21Bibliographically approved
Bassan, G., Larsson, D., Nordenfur, T., Bjällmark, A. & Larsson, M. (2015). Acquisition of multiple mode shear wave propagation in transversely isotropic medium using dualprobe setup. In: : . Paper presented at Medicinteknikdagarna,13-14 oktober 2015.
Open this publication in new window or tab >>Acquisition of multiple mode shear wave propagation in transversely isotropic medium using dualprobe setup
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2015 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Medical Image Processing
Identifiers
urn:nbn:se:kth:diva-179082 (URN)
Conference
Medicinteknikdagarna,13-14 oktober 2015
Note

QC 20160318

Available from: 2015-12-10 Created: 2015-12-10 Last updated: 2016-03-18Bibliographically approved
Larsson, D., Spuhler, J. H., Nordenfur, T., Hoffman, J., Colarieti-Tosti, M., Gao, H. & Larsson, M. (2015). Patient-specific flow simulation of the left ventricle from 4D echocardiography - feasibility and robustness evaluation. In: 2015 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS): . Paper presented at IEEE International Ultrasonics Symposium (IUS), OCT 21-24, 2015, Taipei, TAIWAN. IEEE
Open this publication in new window or tab >>Patient-specific flow simulation of the left ventricle from 4D echocardiography - feasibility and robustness evaluation
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2015 (English)In: 2015 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS), IEEE , 2015Conference paper, Published paper (Refereed)
Abstract [en]

In recent years, computational fluid dynamics (CFD) simulations on in-silico models of the heart have provided a valuable insight into cardiac hemodynamic behaviour. However, so far most models have been either based on simplified geometries or on imaging acquisitions with relatively low temporal resolution. It has been suggested that models based entirely on subject-specific ultrasonic images should be used to capture transient flow changes. Therefore, the aim of this study is to present a pathway from routine 4D echocardiography to a patient-specific flow simulation of the left ventricle (LV), evaluating the model robustness and clinical feasibility. The created pathway consisted of initial LV segmentation and mitral/aortic valve positioning, being subsequently used as input for the CFD simulations (based on solving the Navier-Stokes equation using an Arbitrary Lagrangian-Eulerian approach). The output consisted of 4D blood flow velocities and relative pressures in the entire LV. On five subjects, the model robustness was evaluated with regards to variations in singular boundary conditions. The clinical feasibility of the output was compared to clinical PW Doppler measurements and, as a proof-of-concept, synthetic contrast enhanced ultrasound images were simulated on the flow field using the COLE-method. Results indicated a relatively robust model, with variations in regional flow of approximately 5.1/6.2% and 9.7/7.0% for healthy and pathological subject respectively (end diastole/end systole). Furthermore, showing similar behaviour to clinical Doppler measurements the technique serves as a promising tool for future clinical investigations. Additionally, the ability of simulating synthetic ultrasound images further underlines the applicability of the pathway, being potentially useful in studies on improved echocardiographic image analysis.

Place, publisher, year, edition, pages
IEEE, 2015
Series
IEEE International Ultrasonics Symposium, ISSN 1948-5719
Keywords
Patient-specific, Flow simulation, Ultrasound simulation, 4D Echocardiography, Computational Fluid Dynamics
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-180168 (URN)10.1109/ULTSYM.2015.0233 (DOI)000366045700279 ()2-s2.0-84961989695 (Scopus ID)978-1-4799-8182-3 (ISBN)
Conference
IEEE International Ultrasonics Symposium (IUS), OCT 21-24, 2015, Taipei, TAIWAN
Note

QC 20160112

Available from: 2016-01-12 Created: 2016-01-07 Last updated: 2016-01-14Bibliographically approved
Widman, E., Maksuti, E., Larsson, D., Urban, M. W., Bjallmark, A. & Larsson, M. (2015). Shear wave elastography plaque characterization with mechanical testing validation: a phantom study.. Physics in Medicine and Biology, 60(8), 3151-3174
Open this publication in new window or tab >>Shear wave elastography plaque characterization with mechanical testing validation: a phantom study.
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2015 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 60, no 8, p. 3151-3174Article in journal (Refereed) Published
Abstract [en]

Determining plaque vulnerability is critical when selecting the most suitable treatment for patients with atherosclerotic plaque. Currently, clinical non-invasive ultrasound-based methods for plaque characterization are limited to visual assessment of plaque morphology and new quantitative methods are needed. In this study, shear wave elastography (SWE) was used to characterize hard and soft plaque mimicking inclusions in six common carotid artery phantoms by using phase velocity analysis in static and dynamic environments. The results were validated with mechanical tensile testing. In the static environment, SWE measured a mean shear modulus of 5.8±0.3kPa and 106.2±17.2kPa versus 3.3±0.5kPa and 98.3±3.4kPa measured by mechanical testing in the soft and hard plaques respectively. Furthermore, it was possible to measure the plaques' shear moduli throughout a simulated cardiac cycle. The results show good agreement between SWE and mechanical testing and indicate the possibility for in vivo arterial plaque characterization using SWE.

National Category
Medical Image Processing
Identifiers
urn:nbn:se:kth:diva-164418 (URN)10.1088/0031-9155/60/8/3151 (DOI)000352525200013 ()25803520 (PubMedID)2-s2.0-84927602186 (Scopus ID)
Funder
Swedish Research CouncilVINNOVA, 2011-01365
Note

QC 20150518

Available from: 2015-04-27 Created: 2015-04-17 Last updated: 2017-08-15Bibliographically approved
Widman, E., Maksuti, E., Larsson, D., Urban, M., Caidahl, K., Bjällmark, A. & Larsson, M. (2014). Feasibility of shear wave elastography for plaque characterization. In: IEEE International Ultrasonics Symposium, IUS: . Paper presented at 2014 IEEE International Ultrasonics Symposium, IUS 2014, 3 September 2014 through 6 September 2014 (pp. 1818-1821).
Open this publication in new window or tab >>Feasibility of shear wave elastography for plaque characterization
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2014 (English)In: IEEE International Ultrasonics Symposium, IUS, 2014, p. 1818-1821Conference paper, Published paper (Refereed)
Abstract [en]

Determining plaque vulnerability is critical when selecting the most suitable treatment for patients with atherosclerotic plaque in the common carotid artery and quantitative characterization methods are needed. In this study, shear wave elastography (SWE) was used to characterize soft plaque mimicking inclusions in three atherosclerotic arterial phantoms by using phase velocity analysis in a static environment. The results were validated with axial tensile mechanical testing (MT). SWE measured a mean shear modulus of 5.8 ± 0.3 kPa and 25.0 ± 1.2 kPa versus 3.0 kPa and 30.0 kPa measured by mechanical testing in the soft plaques and phantom walls respectively. The results show good agreement between MT and SWE for both the plaque and phantom wall.

Series
IEEE International Ultrasonics Symposium, IUS, ISSN 1948-5719 ; 6932274
Keywords
Carotid Artery, Mechanical Testing, Phase Velocity, Plaque Characterization, Shear Wave Elastography
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-167518 (URN)10.1109/ULTSYM.2014.0451 (DOI)000352792500449 ()2-s2.0-84910072590 (Scopus ID)9781479970490 (ISBN)
Conference
2014 IEEE International Ultrasonics Symposium, IUS 2014, 3 September 2014 through 6 September 2014
Note

QC 20150611

Available from: 2015-06-11 Created: 2015-05-22 Last updated: 2016-12-05Bibliographically approved
Nachtrab, F., Firsching, M., Speier, C., Uhlmann, N., Takman, P., Tuohimaa, T., . . . Sauerwein, C. (2014). NanoXCT: Development of a laboratory nano-CT system. In: Proceedings of SPIE - The International Society for Optical Engineering: . Paper presented at Developments in X-Ray Tomography IX, 18 August 2014 through 20 August 2014.
Open this publication in new window or tab >>NanoXCT: Development of a laboratory nano-CT system
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2014 (English)In: Proceedings of SPIE - The International Society for Optical Engineering, 2014Conference paper, Published paper (Refereed)
Abstract [en]

The NanoXCT project aims at developing a laboratory nano-CT system for non-destructive testing applications in the micro- and nano-technology sector. The system concept omits the use of X-ray optics, to be able to provide up to 1 mm FOV (at 285 nm voxel size) and down to 50 nm voxel size (at 0.175 mm FOV) while preserving the flexibility of state-of-the-art micro-CT systems. Within the project a suitable X-ray source, detector and manipulation system are being developed. To cover the demand for elemental analysis, the project will additionally include X-ray spectroscopic techniques. These will be reported elsewhere while this paper is focused on the imaging part of the project. We introduce the system concept including design goals and constraints, and the individual components. We present the current state of the prototype development including first results.

Keywords
Computed tomography, Nano-CT, Nano-focus, NanoXCT, Photon-counting X-ray detector, Timepix detector, Transmission tube, Imaging systems, Nondestructive examination, Spectroscopic analysis, Tomography, X ray apparatus, X ray spectroscopy, Timepix detectors, X-ray detector, Computerized tomography
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-167861 (URN)10.1117/12.2061752 (DOI)000344554400017 ()2-s2.0-84923031242 (Scopus ID)9781628412390 (ISBN)
Conference
Developments in X-Ray Tomography IX, 18 August 2014 through 20 August 2014
Note

QC 20150612

Available from: 2015-06-12 Created: 2015-05-22 Last updated: 2016-11-28Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1002-2070

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