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  • 1.
    Abtahi, Farhad
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems. Karolinska Institutet, Sweden.
    Hilderman, Marie
    Bruchfeld, Annette
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems. University of Borås, Sweden.
    Janerot-Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institutet, Sweden.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems. Karolinska Institutet, Sweden.
    Pro-inflammatory Blood Markers and Heart Rate Variability in Apnoea as a Reflection of Basal Vagal ToneManuscript (preprint) (Other academic)
    Abstract [en]

    Pro-inflammatory cytokines play a crucial role in inflammatory response, which istightly regulated by the nervous system to avoid the damage caused by inflammation. There isevidence for a cholinergic anti-inflammatory pathway that includes afferent and efferent vagalnerves that sense the inflammation and stimulate the anti-inflammatory response. Non-functionalanti-inflammatory response might lead to excessive and chronic inflammation e.g., rheumatoidarthritis (RA), inflammatory bowel disease (IBD), and poor outcome. Heart rate variability(HRV) has been proposed as a potential tool to monitor the level of anti-inflammatory activitythrough the monitoring of vagal activity. In this paper, the association of pro-inflammatorymarkers with HRV indices is evaluated. We used a database called “Heart Biomarker Evaluationin Apnea Treatment (HeartBEAT)” that consists of 6±2 hours of Electrocardiogram (ECG)recordings during nocturnal sleep from 318 patients at baseline and 301of them at 3 monthsfollow-up. HRV indices are calculated from ECG recordings of 5-360 minutes. The results showa statistically significant correlation between heart rate (HR) and pro-inflammatory cytokines,independent of duration of ECG analysis. HRV indices e.g., standard deviation of all RRintervals (SDNN) show an inverse relation to the pro-inflammatory cytokines. Longer ECGrecordings show a higher potential to reflect the level of anti-inflammatory response. In light oftheories for the cholinergic anti-inflammatory pathway, a combination of HR and HRV as areflection of basal vagal activity might be a potential prognostic tool for interventional guidance.

  • 2. Bak, Z
    et al.
    Sjöberg, F
    Eriksson, O
    Steinvall, I
    Janerot-Sjöberg, Birgitta
    Department of Clinical Physiology, Heart Centre, Linköping University Hospital, Sweden.
    Cardiac dysfunction after burns2008In: Burns, ISSN 0305-4179, E-ISSN 1879-1409, Vol. 34, no 5, p. 603-609Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: Using transoesophageal echocardiography (TEE) we investigated the occurrence, and the association of possible abnormalities of motion of the regional wall of the heart (WMA) or diastolic dysfunction with raised troponin concentrations, or both during fluid resuscitation in patients with severe burns.

    PATIENTS AND METHODS: Ten consecutive adults (aged 36-89 years, two women) with burns exceeding 20% total burned body surface area who needed mechanical ventilation were studied. Their mean Baux index was 92.7, and they were resuscitated according to the Parkland formula. Thirty series of TEE examinations and simultaneous laboratory tests for myocyte damage were done 12, 24, and 36h after the burn.

    RESULTS: Half (n=5) the patients had varying grades of leakage of the marker that correlated with changeable WMA at 12, 24 and 36h after the burn (p< or =0.001, 0.044 and 0.02, respectively). No patient had WMA and normal concentrations of biomarkers or vice versa. The mitral deceleration time was short, but left ventricular filling velocity increased together with stroke volume.

    CONCLUSION: Acute myocardial damage recorded by both echocardiography and leakage of troponin was common, and there was a close correlation between them. This is true also when global systolic function is not deteriorated. The mitral flow Doppler pattern suggested restrictive left ventricular diastolic function.

  • 3. Bak, Z
    et al.
    Sjöberg, F
    Rousseau, A
    Steinvall, I
    Janerot-Sjöberg, Birgitta
    Department of Clinical Physiology, Heart Center, Linköping University Hospital.
    Human cardiovascular dose-response to supplemental oxygen2007In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 191, no 1, p. 15-24Article in journal (Refereed)
    Abstract [en]

    AIM: The aim of the study was to examine the central and peripheral cardiovascular adaptation and its coupling during increasing levels of hyperoxaemia. We hypothesized a dose-related effect of hyperoxaemia on left ventricular performance and the vascular properties of the arterial tree.

    METHODS: Oscillometrically calibrated arterial subclavian pulse trace data were combined with echocardiographic recordings to obtain non-invasive estimates of left ventricular volumes, aortic root pressure and flow data. For complementary vascular parameters and control purposes whole-body impedance cardiography was applied. In nine (seven males) supine, resting healthy volunteers, aged 23-48 years, data was collected after 15 min of air breathing and at increasing transcutaneous oxygen tensions (20, 40 and 60 kPa), accomplished by a two group, random order and blinded hyperoxemic protocol.

    RESULTS: Left ventricular stroke volume [86 +/- 13 to 75 +/- 9 mL (mean +/- SD)] and end-diastolic area (19.3 +/- 4.4 to 16.8 +/- 4.3 cm(2)) declined (P < 0.05), and showed a linear, negative dose-response relationship to increasing arterial oxygen levels in a regression model. Peripheral resistance and characteristic impedance increased in a similar manner. Heart rate, left ventricular fractional area change, end-systolic area, mean arterial pressure, arterial compliance or carbon dioxide levels did not change.

    CONCLUSION: There is a linear dose-response relationship between arterial oxygen and cardiovascular parameters when the systemic oxygen tension increases above normal. A direct effect of supplemental oxygen on the vessels may therefore not be excluded. Proximal aortic and peripheral resistance increases from hyperoxaemia, but a decrease of venous return implies extra cardiac blood-pooling and compensatory relaxation of the capacitance vessels.

  • 4. Bak, Zoltan
    et al.
    Sjöberg, Folke
    Hälsouniversitetet, Linköping University.
    Eriksson, Olle
    Steinvall, Ingrid
    Janerot-Sjoberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering.
    Hemodynamic changes during resuscitation after burns using the Parkland formula2009In: Journal of Trauma, ISSN 0022-5282, E-ISSN 1529-8809, Vol. 66, no 2, p. 329-336Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The Parkland formula (2-4 mL/kg/burned area of total body surface area %) with urine output and mean arterial pressure (MAP) as endpoints for the fluid resuscitation in burns is recommended all over the world. There has recently been a discussion on whether central circulatory endpoints should be used instead, and also whether volumes of fluid should be larger. Despite this, there are few central hemodynamic data available in the literature about the results when the formula is used correctly.

    METHODS: Ten burned patients, admitted to our unit early, and with a burned area of >20% of total body surface area were investigated at 12, 24, and 36 hours after injury. Using transesophageal echocardiography, pulmonary artery catheterization, and transpulmonary thermodilution to monitor them, we evaluated the cardiovascular coupling when urinary output and MAP were used as endpoints.

    RESULTS: Oxygen transport variables, heart rate, MAP, and left ventricular fractional area, did not change significantly during fluid resuscitation. Left ventricular end-systolic and end-diastolic area and global end-diastolic volume index increased from subnormal values at 12 hours to normal ranges at 24 hours after the burn. Extravascular lung water: intrathoracal blood volume ratio was increased 12 hours after the burn.

    CONCLUSIONS: Preload variables, global systolic function, and oxygen transport recorded simultaneously by three separate methods showed no need to increase the total fluid volume within 36 hours of a major burn. Early (12 hours) signs of central circulatory hypovolemia, however, support more rapid infusion of fluid at the beginning of treatment.

  • 5.
    Baranowski, Jacek
    et al.
    Linköping Heart Centre, University Hospital, Linköping University.
    Ahn, Henrik
    Linköping Heart Centre, University Hospital, Linköping University.
    Freter, Wolfgang
    Linköping Heart Centre, University Hospital, Linköping University.
    Nielsen, Niels-Erik
    Linköping Heart Centre, University Hospital, Linköping University.
    Nylander, Eva
    Linköping Heart Centre, University Hospital, Linköping University.
    Janerot-Sjöberg, Birgitta
    Linköping Heart Centre, University Hospital, Linköping University.
    Sandborg, Michael
    Linköping Heart Centre, University Hospital, Linköping University.
    Wallby, Lars
    Linköping Heart Centre, University Hospital, Linköping University.
    Echo-guided presentation of the aortic valve minimises contrast exposure in transcatheter valve recipients2011In: Catheterization and cardiovascular interventions, ISSN 1522-1946, E-ISSN 1522-726X, Vol. 77, no 2, p. 272-275Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: We have developed a method using transthoracic echocardiography in establishing optimal visualization of the aortic root, to reduce the amount of contrast medium used in each patient.

    BACKGROUND: During transcatheter aortic valve implantation, it is necessary to obtain an optimal fluoroscopic projection for deployment of the valve showing the aortic ostium with the three cusps aligned in the beam direction. This may require repeat aortic root angiograms at this stage of the procedure with a high amount of contrast medium with a risk of detrimental influence on renal function.

    METHODS: We studied the conventional way and an echo guided way to optimize visualisation of the aortic root. Echocardiography was used initially allowing easier alignment of the image intensifier with the transducer's direction.

    RESULTS: Contrast volumes, radiation/fluoroscopy exposure times, and postoperative creatinine levels were significantly less in patients having the echo-guided orientation of the optimal fluoroscopic angles compared with patients treated with the conventional approach.

    CONCLUSION: We present a user-friendly echo-guided method to facilitate fluoroscopy adjustment during transcatheter aortic valve implantation. In our series, the amounts of contrast medium and radiation have been significantly reduced, with a concomitant reduction in detrimental effects on renal function in the early postoperative phase.

  • 6.
    Broomé, Michael
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Maksuti, Elira
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Frenckner, Björn
    Janerot-Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Closed-loop real-time simulation model of hemodynamics and oxygen transport in the cardiovascular system2013In: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 12, no 1, p. 69-Article in journal (Refereed)
    Abstract [en]

    Background: Computer technology enables realistic simulation of cardiovascular physiology. The increasing number of clinical surgical and medical treatment options imposes a need for better understanding of patient-specific pathology and outcome prediction. Methods: A distributed lumped parameter real-time closed-loop model with 26 vascular segments, cardiac modelling with time-varying elastance functions and gradually opening and closing valves, the pericardium, intrathoracic pressure, the atrial and ventricular septum, various pathological states and including oxygen transport has been developed. Results: Model output is pressure, volume, flow and oxygen saturation from every cardiac and vascular compartment. The model produces relevant clinical output and validation of quantitative data in normal physiology and qualitative directions in simulation of pathological states show good agreement with published data. Conclusion: The results show that it is possible to build a clinically relevant real-time computer simulation model of the normal adult cardiovascular system. It is suggested that understanding qualitative interaction between physiological parameters in health and disease may be improved by using the model, although further model development and validation is needed for quantitative patient-specific outcome prediction.

  • 7. Chew, MS
    et al.
    Brandberg, J
    Janerot-Sjöberg, Birgitta
    Linköping University Hospital, Sweden.
    Sloth, E
    Hasenkam, JM
    Ask, P
    Color Doppler flow measurements using surface integration of velocity vectors (SIVV): Effect of colour flow gain, pulse repetition frequency and number of imaging planes2008In: Open Medical Imaging Journal, ISSN 1874-3471, Vol. 2, p. 56-61Article in journal (Refereed)
  • 8. Fröberg, Asa
    et al.
    Mårtensson, Mattias
    KTH, School of Technology and Health (STH), Medical Engineering.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering.
    Janerot-Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering.
    D'Hooge, Jan
    Arndt, Anton
    High variability in strain estimation errors when using a commercial ultrasound speckle tracking algorithm on tendon tissue2016In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 57, no 10, p. 1223-1229Article in journal (Refereed)
    Abstract [en]

    Background: Ultrasound speckle tracking offers a non-invasive way of studying strain in the free Achilles tendon where no anatomical landmarks are available for tracking. This provides new possibilities for studying injury mechanisms during sport activity and the effects of shoes, orthotic devices, and rehabilitation protocols on tendon biomechanics. Purpose: To investigate the feasibility of using a commercial ultrasound speckle tracking algorithm for assessing strain in tendon tissue. Material and Methods: A polyvinyl alcohol (PVA) phantom, three porcine tendons, and a human Achilles tendon were mounted in a materials testing machine and loaded to 4% peak strain. Ultrasound long-axis cine-loops of the samples were recorded. Speckle tracking analysis of axial strain was performed using a commercial speckle tracking software. Estimated strain was then compared to reference strain known from the materials testing machine. Two frame rates and two region of interest (ROI) sizes were evaluated. Results: Best agreement between estimated strain and reference strain was found in the PVA phantom (absolute error in peak strain: 0.21 +/- 0.08%). The absolute error in peak strain varied between 0.72 +/- 0.65% and 10.64 +/- 3.40% in the different tendon samples. Strain determined with a frame rate of 39.4Hz had lower errors than 78.6Hz as was the case with a 22mm compared to an 11mm ROI. Conclusion: Errors in peak strain estimation showed high variability between tendon samples and were large in relation to strain levels previously described in the Achilles tendon.

  • 9. Gharehbaghi, A.
    et al.
    Ask, P.
    Nylander, E.
    Janerot-Sjoberg, Birgitta
    KTH, School of Technology and Health (STH). Karolinska Institutet.
    Ekman, I.
    Lindén, M.
    Babic, A.
    A hybrid model for diagnosing sever aortic stenosis in asymptomatic patients using phonocardiogram2015In: IFMBE Proceedings, Springer, 2015, p. 1006-1009Conference paper (Refereed)
    Abstract [en]

    This study presents a screening algorithm for severe aortic stenosis (AS), based on a processing method for phonocardiographic (PCG) signal. The processing method employs a hybrid model, constituted of a hidden Markov model and support vector machine. The method benefits from a preprocessing phase for an enhanced learning. The performance of the method is statistically evaluated using PCG signals recorded from 50 individuals who were referred to the echocardiography lab at Linköping University hospital. All the individuals were diagnosed as having a degree of AS, from mild to severe, according to the echocardiographic measurements. The patient group consists of 26 individuals with severe AS, and the rest of the 24 patients comprise the control group. Performance of the method is statistically evaluated using repeated random sub sampling. Results showed a 95% confidence interval of (80.5%-82.8%) /(77.8%- 80.8%) for the accuracy/sensitivity, exhibiting an acceptable performance to be used as decision support system in the primary healthcare center.

  • 10. Gharehbaghi, Arash
    et al.
    Borga, Magnus
    Janerot Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Ask, Per
    A novel method for discrimination between innocent and pathological heart murmurs2015In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 37, no 7, p. 674-682Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel method for discrimination between innocent and pathological murmurs using the growing time support vector machine (GTSVM). The proposed method is tailored for characterizing innocent murmurs (IM) by putting more emphasis on the early parts of the signal as IMs are often heard in early systolic phase. Individuals with mild to severe aortic stenosis (AS) and IM are the two groups subjected to analysis, taking the normal individuals with no murmur (NM) as the control group. The AS is selected due to the similarity of its murmur to IM, particularly in mild cases. To investigate the effect of the growing time windows, the performance of the GTSVM is compared to that of a conventional support vector machine (SVM), using repeated random sub-sampling method. The mean value of the classification rate/sensitivity is found to be 88%/86% for the GTSVM and 84%/83% for the SVM. The statistical evaluations show that the GTSVM significantly improves performance of the classification as compared to the SVM.

  • 11.
    Gharehbaghi, Arash
    et al.
    Linkoping Univ, Dept Biomed Engn, Physiol Measurements, Linkoping, Sweden..
    Ekman, Inger
    Linkoping Univ, Fac Hlth Sci, Dept Med & Hlth Sci, Dept Clin Physiol, Linkoping, Sweden..
    Ask, Per
    Linkoping Univ, Dept Biomed Engn, Physiol Measurements, Linkoping, Sweden..
    Nylander, Eva
    Linkoping Univ, Fac Hlth Sci, Dept Med & Hlth Sci, Dept Clin Physiol, Linkoping, Sweden.;Linkoping Univ, Ctr Med Image Sci & Visualizat, Linkoping, Sweden..
    Janerot Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Inst, Dept Clin Sci Intervent & Technol, Div Med Imaging & Technol, Stockholm, Sweden.;Karolinska Univ Hosp, Dept Clin Physiol, Stockholm, Sweden.;Karolinska Univ Hosp, Dept Med Technol, Stockholm, Sweden.;KTH Royal Inst Technol, Sch Technol & Hlth, Stockholm, Sweden..
    Assessment of aortic valve stenosis severity using intelligent phonocardiography2015In: International Journal of Cardiology, ISSN 0167-5273, E-ISSN 1874-1754, Vol. 198, p. 58-60Article in journal (Refereed)
  • 12.
    Grishenkov, Dmitry
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institute, Sweden.
    Adrian, Gonon
    Karolinska University Hospital, Sweden.
    Janerot Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institute, Sweden.
    In search of the optimal ultrasound heart perfusion imaging platform2015In: Journal of ultrasound in medicine, ISSN 0278-4297, E-ISSN 1550-9613, Vol. 34, no 9, p. 1599-1605Article in journal (Refereed)
    Abstract [en]

    Objective

    Quantification of the myocardial perfusion by contrast echocardiography (CEC) remains a challenge. Existing imaging phantoms used to evaluate the performance of ultrasound scanners do not comply with perfusion basics in the myocardium, where perfusion and motion are inherently coupled.

    Methods

    To contribute towards an improvement, we developed a CEC perfusion imaging platform based on isolated rat heart coupled to the ultrasound scanner. Perfusion was assessed using three different types of contrast agent: dextran-based Promiten®, phospholipid-shelled SonoVue®, and polymer-shelled MB-pH5-RT. The myocardial video-intensity was monitored over time from contrast administration to peak and two characteristic constants were calculated using exponential fit (A representing capillary volume and b representing inflow velocity).

    Results

    Acquired experimental evidence demonstrates that the application of all three types of contrast agent allow ultrasonic estimation of myocardial perfusion in the isolated rat heart. Video-intensity maps show that an increase in contrast concentration increases the late plateau values, A, mimicking increased capillary volume. Estimated values of the flow, proportional to Axb, increase when the pressure of the perfusate column increases from 80 to 110 cm of water. This finding is in agreement with the true values of the coronary flow increase measured by the flowmeter attached to the aortic cannula.

    Conclusions

    The described CEC perfusion imaging platform holds promise for standardized evaluation and optimization of ultrasound contrast perfusion imaging where real time inflow curves at low acoustic power semi-quantitatively reflect coronary flow.

  • 13.
    Grishenkov, Dmitry
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institutet (KI), CLINTEC – Division of Medical Imaging and Technology.
    Adrian, Gonon
    Department of Clinical Physiology, Karolinska University Hospital.
    Weitzberg, Eddie
    Department of Physiology and Pharmacology, Karolinska Institutet.
    Lundberg, Jon
    Department of Physiology and Pharmacology, Karolinska Institutet, .
    Harmark, Johan
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Structural Biotechnology.
    Cerroni, Barbara
    Department of Chemical Sciences and Technologies, University of Rome Tor Vergata.
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    Janerot Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. CLINTEC, Department of Medical Imaging and Technology, Karolinska Institute.
    Ultrasound contrast agent loaded with nitric oxide as a theranostic microdevice: Theranostic contrast agent loaded with nitric oxide2015In: Drug Design, Development and Therapy, ISSN 1177-8881, E-ISSN 1177-8881, Vol. 9, p. 2409-2419Article in journal (Refereed)
    Abstract [en]

    The current study describes novel multifunctional polymer-shelled microbubbles (MBs) loaded with nitric oxide (NO) for integrated therapeutic and diagnostic applications, i.e. theranostics, of myocardial ischemia. We used gas filled MBs with an average diameter of 4 µm stabilized by a biocompatible shell of poly(vinyl)alcohol. In vitro acoustic tests showed a sufficient enhancement of the backscattered power (20 dB) acquired from the MBs suspension. The values of attenuation coefficient (0.8 dB/cm MHz) and phase velocities (1517 m/s) were comparable to those reported for the soft tissue. Moreover, polymer MBs demonstrate increased stability compared to clinically approved contrast agents with fracture threshold of about 900 kPa. In vitro chemiluminescence measurements demonstrated that dry powder of NO-loaded MBs releases its gas content in about 2 hours following an exponential decay profile with an exponential time constant equal 36 min. The application of high power ultrasound pulse (MI=1.2) on the MBs resuspended in saline decreases the exponential time constant from 55 to 4 min in air saturated solution and from 17 to 10 min in degased solution. Thus, ultrasound-triggered release of NO is achieved. Cytotoxicity tests indicate that phagocytosis of the MBs by macrophages starts within 6 to 8 hours. This is suitable time for initial diagnostics, treatment and monitoring of the therapeutic effect using single injection of the proposed multifunctional MBs.

  • 14.
    Grishenkov, Dmitry
    et al.
    Karolinska Institutet (KI), CLINTEC – Division of Medical Imaging and Technology.
    Gonon, Adrian
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    Janerot Sjöberg, Birgitta
    CLINTEC, Department of Medical Imaging and Technology, Karolinska Institute.
    Ultrasound contrast agent loaded with nitric oxide as a theranostic microdevise for myocardial ischemia2013Conference paper (Refereed)
    Abstract [en]

    Cardiovascular disease (CVD) accounts for 1/3 of total global deaths worldwide. The most widespread CVD is ischemic heart disease. It is the leading cause of death in both genders, equally diagnosed in developed and developing countries withmortality exponentially increasing with age. Efforts of healthcare system should be primary focused on prevention, timely detection, efficient differentiation and instant treatment of the disease.

  • 15.
    Grishenkov, Dmitry
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Kothapalli, Veeravenkata S.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Gonon, Adrian
    Karolinska University Hospital, Huddinge, Sweden .
    Janerot Sjöberg, Birgitta
    CLINTEC, Department of Medical Imaging and Technology, Karolinska Institute.
    Ultrasound contrast agent loaded with nitric oxide as a theranostic microdevise for myocardial ischemia2013In: European Heart Journal Cardiovascular Imaging: Abstracts of EUROECHO 2013 The Seventeenth Annual Meeting of the European Association of Echocardiography, 2013Conference paper (Refereed)
    Abstract [en]

    Cardiovascular disease (CVD) accounts for 1/3 of total global deaths worldwide. The most widespread CVD is ischemic heart disease. It is the leading cause of death in both genders, equally diagnosed in developed and developing countries with mortality exponentially increasing with age. Efforts of healthcare system should be primary focused on prevention, timely detection, efficient differentiation and instant treatment of the disease.

  • 16. Hubbert, Laila
    et al.
    Peterzén, Bengt
    Ahn, Henrik
    Janerot-Sjoberg, Birgitta
    Second harmonic echocardiography and spontaneous contrast during implantation of a left ventricular assist device2010In: ASAIO journal (1992), ISSN 1058-2916, E-ISSN 1538-943X, Vol. 56, no 5, p. 417-21Article in journal (Refereed)
    Abstract [en]

    Implantable mechanical left ventricular assist devices (LVADs) are used as a bridge or alternative to heart transplantation. Peroperative transesophageal echocardiography is commonly applied during implantation. Significant air embolism may occur as a result of air leakage at connections and anastomoses when LV filling becomes inadequate, and this must be prevented. Early suspicion and detection of air is mandatory to avoid negative circulatory effects. We hypothesized that monitoring of heart chamber size and occurrence of single air bubbles using second harmonic imaging (SHI) echocardiography may prevent risk for significant air embolism. After implantation of the LVAD in 10 calves, invasive hemodynamic monitoring and epicardial SHI were performed while increasing pump speed. Air bubbles in the ascending aorta were monitored and the left heart visualized for off-line dimensional analysis. Detection of air bubbles in the ascending aorta preceded their appearance in the left ventricle. They occurred exclusively but not always after a decrease in left atrial (LA) size. Decrease in LA pressure did not predict bubble detection or reduction in LA size. We conclude that SHI detects spontaneous ultrasound contrast during implantation of a LVAD and that a decrease in LA size is a warning that air embolism is imminent.

  • 17. Hubbert, Laila
    et al.
    Peterzén, Bengt
    Traff, Stefan
    Janerot-Sjoberg, Birgitta
    Universitetssjukhuset i Linköping.
    Ahn, Henrik
    Axial flow pump treatment during myocardial depression in calves: an invasive hemodynamic and echocardiographic tissue Doppler study.2008In: ASAIO journal (1992), ISSN 1058-2916, E-ISSN 1538-943X, Vol. 54, no 4, p. 367-71Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate flow characteristics and myocardial function after implantation of an axial pump left ventricular assist device while varying afterload and during progressive myocardial depression. Ten calves were included, seven of which fulfilled the protocol. Invasive hemodynamic monitoring and echocardiography with color-coded systolic tissue Doppler velocity (TD velocity) were used during prepump conditions, at three different pump speeds, during modification of the systemic vascular resistance (SVR), and during increasing degrees of beta-blockade. The TD velocity decreased with the myocardial function whereas left ventricular size, fractional shortening, and pump speed did not correlate significantly with the TD velocity. The TD velocity correlated significantly with native stroke volume, heart rate, SVR and cardiac output but none of these alone could explain more than 20% of the changes in TD velocity. The axial flow pump studied is effective in unloading the severely depressed heart and has a high capacity for maintaining an adequate cardiac output, regardless of differing hemodynamic conditions, pump speed or decreasing LV function. Echocardiography with volumetric rendering and TD velocity imaging are valuable tools for monitoring and quantifying residual myocardial function during pump treatment.

  • 18.
    Janerot-Sjöberg, Birgitta
    et al.
    Linköping University Hospital, Sweden.
    Winter, Reidar
    Karolinska University Hospital, Huddinge, Stockholm, Sweden.
    Engvall, Jan
    Brodin, Lars-Åke
    Mobile bedside diagnostic techniques2008In: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, Vol. 105, no 43, p. 3025-30Article in journal (Refereed)
  • 19. Karlsson, M G D
    et al.
    Hübbert, L
    Lönn, U
    Janerot-Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering.
    Casimir-Ahn, H
    Wårdell, K
    Myocardial tissue motion influence on laser Doppler perfusion monitoring using tissue Doppler imaging.2004In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 42, no 6, p. 770-6Article in journal (Refereed)
    Abstract [en]

    Tissue motion of the beating heart generates large movement artifacts in the laser Doppler perfusion monitoring (LDPM) signal. The aim of the study was to use tissue Doppler imaging (TDI) to localise intervals during the cardiac cycle where the influence of movement artifacts on the LDPM signal is minimum. TDI velocities and LDPM signals were investigated on three calves, for normal heartbeat and during occlusion of the left anterior descending coronary artery. Intervals of low tissue velocity (TDIint, < 1 cm s(-1)) during the cardiac cycle were identified. During occlusion, these intervals were compared with low LDPM signal intervals (LDPMint, <50% compared with baseline). Low-velocity intervals were found in late systole (normal and occlusion) and late diastole (normal). Systolic intervals were longer and less sensitive to heart rate variation compared with diastolic ones. The overlap between LDPMint and TDIint in relation to TDIint length was 84+/-27% (n = 14). The LDPM signal was significantly (p < 0.001, n = 14) lower during occlusion if calculated during minimum tissue motion (inside TDIint), compared with averaging over the entire cardiac cycle without taking tissue motion into consideration. In conclusion, movement artifacts are reduced if the LDPM signal is correlated to the ECG and investigated during minimum wall motion. The optimum interval depends on the application; late systole and late diastole can be used.

  • 20.
    Kothapalli, Satya V. V. N.
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Wiklund, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Janerot-Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering. Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Paradossi, Gaio
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering. Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Investigation of polymer-shelled microbubble motions in acoustophoresis2016In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 70, p. 275-283Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to explore the trajectory motion of microsize (typically smaller than a red blood cell) encapsulated polymer-shelled gas bubbles propelled by radiation force in an acoustic standing-wave field and to compare the corresponding movements of solid polymer microbeads. The experimental setup consists of a microfluidic chip coupled to a piezoelectric crystal (PZT) with a resonance frequency of about 2.8 MHz. The microfluidic channel consists of a rectangular chamber with a width, w, corresponding to one wavelength of the ultrasound standing wave. It creates one full wave ultrasound of a standing-wave pattern with two pressure nodes at w/4 and 3w/4 and three antinodes at 0, w/2, and w. The peak-to-peak amplitude of the electrical potential over the PZT was varied between 1 and 10 V. The study is limited to no-flow condition. From Gor'kov's potential equation, the acoustic contrast factor, Phi, for the polymer-shelled microbubbles was calculated to about -60.7. Experimental results demonstrate that the polymer-shelled microbubbles are translated and accumulated at the pressure antinode planes. This trajectory motion of polymer-shelled microbubbles toward the pressure antinode plane is similar to what has been described for other acoustic contrast particles with a negative Phi. First, primary radiation forces dragged the polymer-shelled microbubbles into proximity with each other at the pressure antinode planes. Then, primary and secondary radiation forces caused them to quickly aggregate at different spots along the channel. The relocation time for polymer-shelled microbubbles was 40 times shorter than that for polymer microbeads, and in contrast to polymer microbeads, the polymer-shelled microbubbles were actuated even at driving voltages (proportional to radiation forces) as low as 1 V. In short, the polymer-shelled microbubbles demonstrate the behavior attributed to the negative acoustic contrast factor particles and thus can be trapped at the antinode plane and thereby separated from particles having a positive acoustic contrast factor, such as for example solid particles and cells. This phenomenon could be utilized in exploring future applications, such as bioassay, bioaffinity, and cell interaction studies in vitro in a well-controlled environment.

  • 21.
    Kothapalli, Satya V.V.N.
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Wiklund, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Janerot Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institutet, Sweden; Karolinska University Hospital, Sweden .
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institutet, Sweden; Karolinska University Hospital, Sweden .
    Investigation of Polymer-Shelled Microbubble Motions in AcoustophoresisManuscript (preprint) (Other academic)
    Abstract [en]

    The objective of this paper is to explore the trajectory motion of microsize (typically smaller than a redblood cell) encapsulated polymer-shelled gas bubbles propelled by radiation force in an acousticstanding-wave field and to compare the corresponding movements of solid polymer microbeads. Theexperimental setup consists of a microfluidic chip coupled to a piezoelectric crystal (PZT) with aresonance frequency of about 2.8 MHz. The microfluidic channel consists of a rectangular chamberwith a width, w, corresponding to one wavelength of the ultrasound standing wave. It creates one fullwave ultrasound of a standing-wave pattern with two pressure nodes at4w and43w and threeantinodes at 0,2w , and w. The peak-to-peak amplitude of the electrical potential over the PZT wasvaried between 1 and 10 volts. From Gor’kov’s potential equation, the acoustic contrast factor, Φ, forthe polymer-shelled microbubbles was calculated to about -60.7. Experimental results demonstratethat the polymer-shelled microbubbles are translated and accumulated at the pressure antinode planes.This trajectory motion of polymer-shelled microbubbles toward the pressure antinode plane is similarto what has been described for other acoustic contrast particles with a negative Φ. First, primaryradiation forces dragged the polymer-shelled microbubbles into proximity with each other at thepressure antinode planes. Then, secondary radiation forces caused them to aggregate at different spotsalong the channel. The relocation time for polymer-shelled microbubbles was 40 times shorter thanthat for polymer microbeads, and in contrast to polymer microbeads, the polymer-shelledmicrobubbles were actuated even at driving voltages (proportional to radiation forces) as low as 1 volt.In short, the polymer-shelled microbubbles demonstrate the behavior attributed to the negativeacoustic contrast factor particles and thus can be trapped at the antinode plane and thereby seperatedfrom solid particles, such as cells. This phenomenon could be utilized in exploring future applications,such as bioassay, bioaffinity, and cell interaction studies in vitro in a well-controlled environment.

  • 22.
    Kothapalli, Veera Venkata Satya Naray
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Daeichin, Verya
    Department of Biomedical Engineering, Thoraxcenter, Erasmus MC,.
    Mastik, Frits
    Department of Biomedical Engineering, Thoraxcenter, Erasmus MC.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Janerot Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering. Karolinska Institutet, Sweden; Karolinska University Hospital, Sweden .
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    de Jong, N.
    Department of Biomedical Engineering, Thoraxcenter, Erasmus MC.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institutet, Sweden; Karolinska University Hospital, Sweden .
    Unique pumping-out fracturing mechanism of a polymer-shelled contrast agent: An acoustic characterization and optical visualization2014In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 62, no 3, p. 451-462, article id 7055440Article in journal (Refereed)
    Abstract [en]

    This work describes the fracturing mechanism of air-filled microbubbles (MBs) encapsulated by a cross-linked poly(vinyl alcohol) (PVA) shell. The radial oscillation and fracturing events following the ultrasound exposure were visualized with an ultrahigh-speed camera, and backscattered timedomain signals were acquired with the acoustic setup specific for harmonic detection. No evidence of gas emerging from defects in the shell with the arrival of the first insonation burst was found. In optical recordings, more than one shell defect was noted, and the gas core was drained without any sign of air extrusion when several consecutive bursts of 1 MPa amplitude were applied. In acoustic tests, the backscattered peak-to-peak voltage gradually reached its maximum and exponentially decreased when the PVA-based MB suspension was exposed to approximately 20 consecutive bursts arriving at pulse repetition frequencies of 100 and 500 Hz. Taking into account that the PVA shell is porous and possibly contains large air pockets between the cross-linked PVA chains, the aforementioned acoustic behavior might be attributed to pumping gas from these pockets in combination with gas release from the core through shell defects. We refer to this fracturing mechanism as pumping-out behavior, and this behavior could have potential use for the local delivery of therapeutic gases, such as nitric oxide.

  • 23. Kvikliene, Adriana
    et al.
    Jurkonis, Rytis
    Ressner, Marcus
    Hoff, Lars
    Jansson, Tomas
    Janerot-Sjöberg, Birgitta
    Linkoping Univ Hosp, Ctr Heart, Dept Clin Physiol.
    Lukosevicius, Arūnas
    Ask, Per
    Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles: simulation and experiment.2004In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 42, no 1-9, p. 301-7Article in journal (Refereed)
    Abstract [en]

    The propagation of diagnostic ultrasonic imaging pulses in tissue and their interaction with contrast micro bubbles is a very complex physical process, which we assumed to be separable into three stages: pulse propagation in tissue, the interaction of the pulse with the contrast bubble, and the propagation of the scattered echo. The model driven approach is used to gain better knowledge of the complex processes involved. A simplified way of field simulation is chosen due to the complexity of the task and the necessity to estimate comparative contributions of each component of the process. Simulations are targeted at myocardial perfusion estimation. A modified method for spatial superposition of attenuated waves enables simulations of low intensity pulse pressure fields from weakly focused transducers in a nonlinear, attenuating, and liquid-like biological medium. These assumptions enable the use of quasi-linear calculations of the acoustic field. The simulations of acoustic bubble response are carried out with the Rayleigh-Plesset equation with the addition of radiation damping. Theoretical simulations with synthesised and experimentally sampled pulses show that the interaction of the excitation pulses with the contrast bubbles is the main cause of nonlinear scattering, and a 2-3 dB increase of second harmonic amplitude depends on nonlinear distortions of the incident pulse.

  • 24.
    Larsson, Malin K.
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Larsson, Matilda
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Nowak, Greg
    Paradossi, Gaio
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Janerot Sjöberg, Birgitta
    KTH, School of Technology and Health (STH), Medical Engineering.
    Caidahl, Kenneth
    Bjällmark, Anna
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Endocardial border delineation capability of a novel multimodal polymer-shelled contrast agent2014In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 12, p. 24-Article in journal (Refereed)
    Abstract [en]

    Background: A novel polymer-shelled contrast agent (CA) with multimodal and target-specific potential was developed recently. To determine its ultrasonic diagnostic features, we evaluated the endocardial border delineation as visualized in a porcine model and the concomitant effect on physiological variables. Methods: Three doses of the novel polymer-shelled CA (1.5 ml, 3 ml, and 5 ml [5 x 10(8) microbubbles (MBs)/ml]) and the commercially available CA SonoVue (1.5 ml [2-5 x 10(8) MBs/ml]) were used. Visual evaluations of ultrasound images of the left ventricle were independently performed by three observers who graded each segment in a 6-segment model as either 0 = not visible, 1 = weakly visible, or 2 = visible. Moreover, the duration of clinically useful contrast enhancement and the left ventricular opacification were determined. During anesthesia, oxygen saturation, heart rate, and arterial pressure were sampled every minute and the effect of injection of CA on these physiological variables was evaluated. Results: The highest dose of the polymer-shelled CA gave results comparable to SonoVue. Thus, no significant difference in the overall segment score distribution (2-47-95 vs. 1-39-104), time for clinically sufficient contrast enhancement (20-40 s for both) and left ventricular overall opacification was found. In contrast, when comparing the endocardial border delineation capacity for different regions SonoVue showed significantly higher segment scores for base and mid, except for the mid region when injecting 1.5 ml of the polymer-shelled CA. Neither high nor low doses of the polymer-shelled CA significantly affected the investigated physiological variables. Conclusions: This study demonstrated that the novel polymer-shelled CA can be used in contrast-enhanced diagnostic imaging without influence on major physiological variables.

  • 25. Li, Y.
    et al.
    Tesselaar, E.
    Borges, J. B.
    Böhm, S. H.
    Sjöberg, F.
    Janerot-Sjöberg, Birgitta
    KTH, School of Technology and Health (STH).
    Hyperoxia affects the regional pulmonary ventilation/perfusion ratio: an electrical impedance tomography study2014In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 58, no 6, p. 716-725Article in journal (Refereed)
    Abstract [en]

    Background The way in which hyperoxia affects pulmonary ventilation and perfusion is not fully understood. We investigated how an increase in oxygen partial pressure in healthy young volunteers affects pulmonary ventilation and perfusion measured by thoracic electrical impedance tomography (EIT). Methods Twelve semi-supine healthy male volunteers aged 21-36 years were studied while breathing room air and air-oxygen mixtures (FiO2) that resulted in predetermined transcutaneous oxygen partial pressures (tcPO2) of 20, 40 and 60kPa. The magnitude of ventilation (Zv) and perfusion (ZQ)-related changes in cyclic impedance variations, were determined using an EIT prototype equipped with 32 electrodes around the thorax. Regional changes in ventral and dorsal right lung ventilation (V) and perfusion (Q) were estimated, and V/Q ratios calculated. Results There were no significant changes in Zv with increasing tcPO2 levels. ZQ in the dorsal lung increased with increasing tcPO2 (P=0.01), whereas no such change was seen in the ventral lung. There was a simultaneous decrease in V/Q ratio in the dorsal region during hyperoxia (P=0.04). Two subjects did not reach a tcPO2 of 60kPa despite breathing 100% oxygen. Conclusion These results indicate that breathing increased concentrations of oxygen induces pulmonary vasodilatation in the dorsal lung even at small increases in FiO2. Ventilation remains unchanged. Local mismatch of ventilation and perfusion occurs in young healthy men, and the change in ventilation/perfusion ratio can be determined non-invasively by EIT.

  • 26. Löf, M.
    et al.
    Olausson, H.
    Boström, K.
    Janerot-Sjöberg, Birgitta
    Karolinska Institutet, CLINTEC.
    Sohlström, A.
    Forsum, E.
    Changes in basal metabolic rate during pregnancy in relation to changes in body weight and composition, cardiac output, insulin-like growth factor I, and thyroid hormones and in relation to fetal growth2005In: American Journal of Clinical Nutrition, ISSN 0002-9165, E-ISSN 1938-3207, Vol. 81, no 3, p. 678-685Article in journal (Refereed)
    Abstract [en]

    Background: The total energy cost of pregnancy is largely due to an elevated basal metabolic rate (BMR). Large variations in the BMR response to pregnancy have been reported, but the factors associated with this variability are incompletely known. Objective: The objective was to identify factors associated with variability in the BMR response to pregnancy. Design: In 22 healthy women, BMR, body weight (BW), total body fat (TBF), fat-free mass (FFM), circulatory variables, serum concentrations of insulin-like growth factor I (IGF-I), and thyroid hormones were measured before pregnancy and in gestational weeks 14 and 32. BMR and BW were also measured in gestational weeks 8,20, and 35. Fetal weight was estimated in gestational week 31. Results: In gestational week 14, the increase in BMR correlated significantly with the corresponding increase in BW and with the prepregnancy percentage of TBF. Together these variables explained approximate to 40% of the variability in the BMR response. In gestational week 32, the increase in BMR correlated significantly with the corresponding changes in BW, TBF, FFM, IGF-I, cardiac output, and free triiodothyronine. The increase in BW in combination with fetal weight or with the elevated concentration of IGF-I in serum explained approximate to 60% of the variability in the increase in BMR. Conclusions: Weight gain and the prepregnancy percentage of TBF-ie, factors related to the maternal nutritional situation-are important factors with regard to the variability in the BMR response to pregnancy. Thus, it is important to consider the nutritional situation before and during gestation when assessing pregnancy energy requirements.

  • 27. Ressner, M.
    et al.
    Kvikliene, A.
    Hoff, L.
    Jurkonis, R.
    Jansson, T.
    Janerot Sjöberg, Birgitta
    Department of Clinical Physiology, Heart Centre, University Hospital.
    Lukosevicius, A.
    Ask, P.
    Backscattered ultrasound from contrast microbubbles: effects of tissue and bubble interaction2004In: PROCEEDINGS OF THE 26TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-7, 2004, Vol. 2, p. 849-852Conference paper (Refereed)
    Abstract [en]

    The propagation of diagnostic ultrasonic imaging pulses in tissue and their interaction with contrast microbubbles is a complex physical process. Our model driven approach is used to gain better knowledge of the different processes involved in the generation of the backscattered contrast echo. It can be divided into three separable stages: linear and non-linear wave propagation in tissue, the resulting echo from the pulse interaction with the contrast microbubble, and the propagation of the scattered echo. A simplified approach of field simulation is chosen due to the complexity of the task and necessity to estimate comparative contributions of each component of the process. A modified method for spatial superposition of attenuated waves was further developed to enable simulations of low intensity pulse fields in nonlinear attenuating and liquid-like biological medium using weakly focused transducers. Simulations of the acoustic bubble response are carried out with Rayleigh-Plesset equation with the addition of the radiation damping. Theoretical simulations show that contrast bubbles interaction with excitation pulses is the main cause of nonlinear distortions, and a 2-3 dB increase of second harmonic amplitude depends on nonlinear distortions of incident pulse.

  • 28. Ressner, M.
    et al.
    Kvikliene, A.
    Hoff, L.
    Jurkonis, R.
    Jansson, T.
    Janerot Sjöberg, Birgitta
    Department of Clinical Physiology, Heart Centre, University Hospital.
    Lukosevicius, A.
    Ask, P.
    Ultrasound Contrast Microbubbles: Simulations and in vitro experiments2005In: European Medical and Biological Engineering Conference Proceedings, 2005, Vol. 11, no 1, p. 3-4Conference paper (Refereed)
  • 29. Ressner, Marcus
    et al.
    Jansson, Tomas
    Cedefamn, Jonny
    Ask, Per
    Janerot-Sjöberg, Birgitta
    Department of Medicine and Health, Linköping University, Linköping, Sweden.
    Contrast biases the autocorrelation phase shift estimation in Doppler tissue imaging2009In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 35, no 3, p. 447-457Article in journal (Refereed)
    Abstract [en]

    Quantitative assessment of regional myocardial function at rest and during stress with Doppler tissue imaging (DTI) plays an important role in daily routine echocardiography. However, reliable visual analysis is largely dependent on image quality and adequate border delineation, which still remains a challenge in a significant number of patients. In this respect, an ultrasound contrast agent (UCA) is often used to improve visualization in patients with suboptimal image quality. The knowledge of how DTI measurements will be affected by UCA present in the tissue is therefore of significant importance for an accurate interpretation of local myocardial motion. The aim of this paper was to investigate how signal contribution from UCA and nonlinear wave propagation influence the performance of the autocorrelation phase shift estimator used for DTI applications. Our results are based on model experiments with a clinical 2-D grayscale scanner and computational simulations of the DTI velocity estimator for synthetically-derived pulses, simulated bubble echoes and experimentally-sampled RF data of transmitted pulses and backscattered contrast echoes. The results show that destruction of UCA present in the tissue will give rise to an apparent bidirectional velocity bias of individual velocity estimates, but that spatial averaging of individual velocity measurements within a region-of-interest will result in a negative bias (away from the transducer) of the estimated mean or mean peak velocity. The UCA destruction will also have a significant impact on the measured integrated mean velocity over time, i.e., displacement. To achieve improved visualization with UCA during DTI-examinations, we either recommend that it is performed at low acoustic powers, mechanical index <or=0.3, thereby minimizing the effects from bubble rupture, or that each Doppler pulse package is preceded by a destruction burst similar to "Flash imaging" to clear the target area of contrast microbubbles.

  • 30. Rousseau, A.
    et al.
    Bak, Z.
    Janerot Sjöberg, Birgitta
    Department of Clinical Physiology, Heart Centre, University Hospital, Linköping, Sweden.
    Sjöberg, F.
    Acute hyperoxaemia-induced effects on regional blood flow, oxygen consumption and central circulation in man2005In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 183, no 3, p. 231-240Article in journal (Refereed)
    Abstract [en]

    AIM: Despite numerous in vitro and animal studies, circulatory effects and mechanisms responsible for the vasoconstriction seen during hyperoxaemia are yet to be ascertained. The present study set out to: (i) set up a non-invasive human model for the study of hyperoxia-induced cardiovascular effects, (ii) describe the dynamics of this effect and (iii) determine whether hyperoxaemia also, by vasoconstriction alters oxygen consumption (O(2)). METHODS: The study comprised four experiments (A, B, C and D) on healthy volunteers examined before, during and after 100% oxygen breathing. A: Blood flow (mL min(-1).100 mL(-1) tissue), venous occlusion plethysmography was assessed (n = 12). B: Blood flow was recorded with increasing transcutaneous oxygen tension (P(tc)O(2)) levels (dose-response) (n = 8). C: Heart rate (HR), stroke volume, cardiac output (CO) and systemic vascular resistance (SVR) was assessed using echocardiography (n = 8). D: O(2) was measured using an open circuit technique when breathing an air-O(2) mix (fraction of inhaled oxygen: F(i)O(2) = 0.58) (n = 8). RESULTS: Calf blood flow decreased 30% during O(2) breathing. The decrease in calf blood flow was found to be oxygen dose dependent. A similar magnitude, as for the peripheral circulation, of the effect on central parameters (HR/CO and SVR) and in the time relationship was noted. Hyperoxia did not change O(2). An average of 207 (93) mL O(2) per subject was washed in during the experiments. CONCLUSION: This model appears suitable for the investigation of O(2)-related effects on the central and peripheral circulation in man. Our findings, based on a more comprehensive (central/peripheral circulation examination) evaluation than earlier made, suggest significant circulatory effects of hyperoxia. Further studies are warranted to elucidate the underlying mechanisms.

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