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  • 1.
    Ahlström, Christer
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Rask, Peter
    Örebro university.
    Karlsson, Jan-Erik
    Nylander, Eva
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Dahlström, Ulf
    Linköpings universitet, Institutionen för medicin och hälsa, Kardiologi. Linköpings universitet, Hälsouniversitetet.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Feature Extraction for Systolic Heart Murmur Classification2006Ingår i: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 34, nr 11, s. 1666-1677Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heart murmurs are often the first signs of pathological changes of the heart valves, and they are usually found during auscultation in the primary health care. Distinguishing a pathological murmur from a physiological murmur is however difficult, why an “intelligent stethoscope” with decision support abilities would be of great value. Phonocardiographic signals were acquired from 36 patients with aortic valve stenosis, mitral insufficiency or physiological murmurs, and the data were analyzed with the aim to find a suitable feature subset for automatic classification of heart murmurs. Techniques such as Shannon energy, wavelets, fractal dimensions and recurrence quantification analysis were used to extract 207 features. 157 of these features have not previously been used in heart murmur classification. A multi-domain subset consisting of 14, both old and new, features was derived using Pudil’s sequential floating forward selection (SFFS) method. This subset was compared with several single domain feature sets. Using neural network classification, the selected multi-domain subset gave the best results; 86% correct classifications compared to 68% for the first runner-up. In conclusion, the derived feature set was superior to the comparative sets, and seems rather robust to noisy data.

  • 2.
    Arzani, Amirhossein
    et al.
    IIT.
    Dyverfeldt, Petter
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Ebbers, Tino
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Shadden, Shawn C
    IIT.
    In Vivo Validation of Numerical Prediction for Turbulence Intensity in an Aortic Coarctation2012Ingår i: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 40, nr 4, s. 860-870Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper compares numerical predictions of turbulence intensity with in vivo measurement. Magnetic resonance imaging (MRI) was carried out on a 60-year-old female with a restenosed aortic coarctation. Time-resolved three-directional phase-contrast (PC) MRI data was acquired to enable turbulence intensity estimation. A contrast-enhanced MR angiography (MRA) and a time-resolved 2D PCMRI measurement were also performed to acquire data needed to perform subsequent image-based computational fluid dynamics (CFD) modeling. A 3D model of the aortic coarctation and surrounding vasculature was constructed from the MRA data, and physiologic boundary conditions were modeled to match 2D PCMRI and pressure pulse measurements. Blood flow velocity data was subsequently obtained by numerical simulation. Turbulent kinetic energy (TKE) was computed from the resulting CFD data. Results indicate relative agreement (error a parts per thousand 10%) between the in vivo measurements and the CFD predictions of TKE. The discrepancies in modeled vs. measured TKE values were within expectations due to modeling and measurement errors.

  • 3.
    Jönsson, Björn
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Kärlkirurgi. Linköpings universitet, Hälsouniversitetet.
    Laurent, Claes
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Skau, Tommy
    Linköpings universitet, Institutionen för medicin och vård, Kärlkirurgi. Linköpings universitet, Hälsouniversitetet.
    Lindberg, Lars-Göran
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    A new probe for ankle systolic pressure measurement using Photoplethysmography (PPG)2005Ingår i: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 33, nr 2, s. 232-239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An automated method for ankle systolic pressure measurement, less operator dependent than the standard continuous wave (CW) Doppler technique, would imply an advantage both in patient measurements and in epidemiological studies. We present a new photoplethysmographic (PPG) probe that uses near-infrared light (880 nm) to detect pulsatory blood flow underneath the distal end of a standard pneumatic cuff. The probe is adapted to the anatomical conditions at the ankle, permitting recording of pressures in both ankle arteries separately. The validity of the equipment was tested with CW Doppler-derived systolic pressures and invasive blood pressure measurements for reference. In 20 healthy subjects, visual analysis of the PPG curves revealed a mean difference between CW Doppler and PPG measurements of –0.5 mmHg (SD 6.9). Corresponding results for the anterior and posterior tibial arteries separately were –1.8 mmHg (SD 6.2) and 0.9 mmHg (SD 7.3), respectively. A correct probe position was essential for the results. In direct recordings from the dorsalis pedis artery in 10 intensive care patients, PPG underestimated systolic pressure in the anterior tibial artery by 4.5 mmHg (SD 12.1). With further development, the PPG probe, integrated in the pneumatic cuff, may simplify measurements of ankle systolic pressures.

  • 4.
    Lantz, Jonas
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Gupta, Vikas
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Medicinska fakulteten.
    Henriksson, Lilian
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Karlsson, Matts
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Persson, Anders
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Diagnostikcentrum, Röntgenkliniken i Linköping. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Carlhäll, Carl-Johan
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Region Östergötland, Hjärt- och Medicincentrum, Fysiologiska kliniken US. Linköpings universitet, Medicinska fakulteten.
    Ebbers, Tino
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Hjärt- och Medicincentrum, Fysiologiska kliniken US. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Impact of Pulmonary Venous Inflow on Cardiac Flow Simulations: Comparison with In Vivo 4D Flow MRI2019Ingår i: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 47, nr 2, s. 413-424Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Blood flow simulations are making their way into the clinic, and much attention is given to estimation of fractional flow reserve in coronary arteries. Intracardiac blood flow simulations also show promising results, and here the flow field is expected to depend on the pulmonary venous (PV) flow rates. In the absence of in vivo measurements, the distribution of the flow from the individual PVs is often unknown and typically assumed. Here, we performed intracardiac blood flow simulations based on time-resolved computed tomography on three patients, and investigated the effect of the distribution of PV flow rate on the flow field in the left atrium and ventricle. A design-of-experiment approach was used, where PV flow rates were varied in a systematic manner. In total 20 different simulations were performed per patient, and compared to in vivo 4D flow MRI measurements. Results were quantified by kinetic energy, mitral valve velocity profiles and root-mean-square errors of velocity. While large differences in atrial flow were found for varying PV inflow distributions, the effect on ventricular flow was negligible, due to a regularizing effect by mitral valve. Equal flow rate through all PVs most closely resembled in vivo measurements and is recommended in the absence of a priori knowledge.

  • 5.
    Rausch, Manuel K.
    et al.
    Stanford University School of Engineering, USA.
    Bothe, Wolfgang
    Stanford University School of Engineering, USA.
    Kvitting, John-Peder Escobar
    Stanford University School of Engineering, USA.
    Swanson, Julia C.
    Stanford University School of Engineering, USA.
    Ingels, Neil B.
    Stanford University School of Engineering, USA.
    Miller, D. Craig
    Stanford University School of Engineering, USA.
    Kuhl, Ellen
    Stanford University School of Engineering, USA.
    Characterization of mitral valve annular dynamics in the beating heart2011Ingår i: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 39, nr 6, s. 1690-1702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this study is to establish a mathematical characterization of the mitral valve annulus that allows a precise qualitative and quantitative assessment of annular dynamics in the beating heart. We define annular geometry through 16 miniature markers sewn onto the annuli of 55 sheep. Using biplane videofluoroscopy, we record marker coordinates in vivo. By approximating these 16 marker coordinates through piecewise cubic splines, we generate a smooth mathematical representation of the 55 mitral annuli. We time-align these 55 annulus representations with respect to characteristic hemodynamic time points to generate an averaged baseline annulus representation. To characterize annular physiology, we extract classical clinical metrics of annular form and function throughout the cardiac cycle. To characterize annular dynamics, we calculate displacements, strains, and curvature from the discrete mathematical representations. To illustrate potential future applications of this approach, we create rapid prototypes of the averaged mitral annulus at characteristic hemodynamic time points. In summary, this study introduces a novel mathematical model that allows us to identify temporal, regional, and inter-subject variations of clinical and mechanical metrics that characterize mitral annular form and function. Ultimately, this model can serve as a valuable tool to optimize both surgical and interventional approaches that aim at restoring mitral valve competence.

  • 6.
    Smedby, Örjan
    Department of Diagnostic Radiology, Uppsala University.
    Geometric risk factors for atherosclerosis in the aortic bifurcation: a digitized angiography study.1996Ingår i: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 24, nr 4, s. 481-488Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To clarify the relationship between arterial geometry and atherosclerosis at the aortic bifurcation, angiograms of 84 patients with slight or moderate atherosclerosis were studied by computerized image analysis. The degree of atherosclerosis involvement was assessed as angiographic edge roughness. The branching angles were found to be related to edge roughness of the left outer wall and the right side of the aorta. The position of the flow divider was related to edge roughness of the medial wall of the right common iliac and the right side of the aorta. For these two locations, there were also significant relationships to the area ratio, i.e., the ratio between cross-sectional areas distal and proximal to the bifurcations. On the basis of these findings, the concept of "geometric risk factors" for atherosclerosis and the potential influence of blood flow on atherogenesis are discussed.

  • 7.
    Smedby, Örjan
    Department of Diagnostic Radiology, Uppsala University.
    Geometrical risk factors for atherosclerosis in the femoral artery: a longitudinal angiographic study.1998Ingår i: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 26, nr 3, s. 391-397Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to study the evolution of atherosclerosis in the superficial femoral artery in relation to local factors of vascular geometry, image processing of digitized angiograms was carried out in 237 hyperlipidemic patients before and after a three-year period of lipid-lowering treatment. The degree of atherosclerosis was measured as edge roughness, which was calculated separately for inner curves, outer curves, and straight segments and, in a subgroup of 110 patients, for segments with and without branches on either side of the artery. Initially, inner curves had significantly higher roughness values than outer curves, and outer curves higher than straight segments. After three years, there was an increase of borderline significance in the outer curves, and the difference between inner and outer curves was no longer significant. In several subpopulations, the increase in outer curve roughness was clearly significant. When branched and nonbranched segments were compared, the only significant difference was at the second examination where segments with a lateral branch had higher roughness of the medial edge than those without such a branch. It is concluded that curves are more likely than bifurcations to constitute a geometric risk factor for atherosclerosis, but it remains to explain the causal mechanism for this factor.

  • 8.
    Smedby, Örjan
    et al.
    Department of Diagnostic Radiology, Uppsala University.
    Bergstrand, L
    Tortuosity and atherosclerosis in the femoral artery: what is cause and what is effect?1996Ingår i: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 24, nr 4, s. 474-480Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Earlier studies have demonstrated a correlation between tortuosity and atherosclerosis in the femoral artery. One conceivable explanation is that atherosclerosis causes an elongation of the artery, resulting in vessel tortuosity, another is that blood flow phenomena (such as flow separation) due to the vessel geometry may affect the progression of atherosclerosis. To determine which of these hypotheses is most likely, a group of 232 hyperlipidemic patients was followed with angiography for 3 years during lipid-lowering treatment. After digitization of the films, a tortuosity value and an atherosclerosis measure (edge roughness) were computed. In the group with lower tortuosity values, there was a significant (p < 0.0001) decrease in edge roughness, but not in the group with a higher tortuosity values. On the other hand, neither the group with higher edge roughness values nor that with lower edge roughness values displayed a significant change in tortuosity. When tortuosity, roughness, and treatment were studied simultaneously, only the effect of tortuosity on roughness change was significant. These findings are more consistent with tortuosity influencing the development of atherosclerosis than with its being a consequence of atherosclerosis.

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