| 1. |
- Kothapalli, Satya V.V.N. 1985-
(författare)
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Nano-Engineered Contrast Agents : Toward Multimodal Imaging and Acoustophoresis
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diagnostic ultrasound (US) is safer, quicker and cheaper than other diagnostic imaging modalities. Over the past two decades, the applications of US imaging has been widened due to the development of injectable, compressible and encapsulated microbubbles (MBs) that provide an opportunity to improve conventional echocardiographic imaging, blood flow assessment and molecular imaging. The encapsulating material is manufactured by different biocompatible materials such as proteins, lipids or polymers. In current research, researchers modify the encapsulated shell with the help of advanced molecular chemistry techniques to load them with dyes (for fluorescent imaging), nanoparticles and radioisotopes (for multimodal imaging) or functional ligands or therapeutic gases (for local drug delivery). The echogenicity and the radial oscillation of MBs is the result of their compressibility, which undoubtedly varies with the encapsulated shell characteristics such as rigidity or elasticity.In this thesis, we present acoustic properties of novel type of polyvinyl alcohol (PVA)-shelled microbubble (PVA-MB) that was further modified with superparamagnetic iron oxide nanoparticles (SPIONs) to work as a dual-modal contrast agent for magnetic resonance (MR) imaging along with US imaging. Apparently, the shell modification changes their mechanical characteristics, which affects their acoustic properties. The overall objective of the thesis is to investigate the acoustic properties of modified and unmodified PVA-MBs at different ultrasound parameters.The acoustic and mechanical characterization of SPIONs modified PVA-MBs revealed that the acoustical response depends on the SPION inclusion strategy. However they retain the same structural characteristics after the modification. The modified MBs with SPIONs included on the surface of the PVA shell exhibit a soft-shelled behavior and produce a higher echogenicity than the MBs with the SPIONs inside the PVA shell. The fracturing mechanism of the unmodified PVA-MBs was identified to be different from the other fracturing mechanisms of conventional MBs. With the interaction of high-pressure bursts, the air gas core is squeezed out through small punctures in the PVA shell. During the fracturing, the PVA-MBs exhibit asymmetric (other modes) oscillations, resulting in sub- and ultra-harmonic generation. Exploiting the US imaging at the other modes of the oscillation of the PVA-MBs would provide an opportunity to visualize very low concentrations of (down to single) PVA-MBs. We further introduced the PVA-MBs along with particles mimicking red blood cells in an acoustic standing-wave field to observe the acoustic radiation force effect. We observed that the compressible PVA-MBs drawn toward pressure antinode while the solid blood phantoms moved toward the pressure node. This acoustic separation method (acoustophoresis) could be an efficient tool for studying the bioclearance of the PVA-MBs in the body, either by collecting blood samples (in-vitro) or by using the extracorporeal medical procedure (ex-vivo) at different organs.Overall, this work contributes significant feedback for chemists (to optimize the nanoparticle inclusion) and imaging groups (to develop new imaging sequences), and the positive findings pave new paths and provide triggers to engage in further research.
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| 2. |
- Mårtensson, Mattias, et al.
(författare)
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Assessment of left ventricular volumes using simplified 3-D echocardiography and computed tomography - a phantom and clinical study
- 2008
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Ingår i: Cardiovascular Ultrasound. - : Springer Science and Business Media LLC. - 1476-7120. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To compare the accuracy of simplified 3-dimensional (3-D) echocardiography vs. multi-slice computed tomography (MSCT) software for the quantification of left ventricular (LV) volumes. Design: Three-D echocardiography (3-planes approach) and MSCT-CardIQ software were calibrated by measuring known volumes of 10 phantoms designed to closely mimic blood-endocardium interface. Subsequently, LV volumes were measured with both the methods in 9 patients referred routinely for coronary angiography and the agreement between the measurements was evaluated. Results: Simplified 3D-echocardiography provided higher degree of agreement between the measured and true phantom volumes (mean difference 0 +/- 1 ml, variation range + 4 to -4 ml) than MSCT software (mean difference 6 +/- 5 ml; variation range + 22 to -10 ml). The agreement between LV measurements in the patients was considerably poorer, with significantly larger volumes produced by MSCT (mean difference - 23 +/- 40 ml, variation between + 93 and -138 ml). Conclusion: Simplified 3-D echocardiography provides more accurate assessment of phantom volumes than MSCT-CardIQ software. The discrepancy between the results of LV measurements with the two methods is even greater and does not warrant their interchangeable diagnostic use.
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| 3. |
- Mårtensson, Mattias, et al.
(författare)
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Evaluation of tissue Doppler-based velocity and deformation imaging : a phantom study of ultrasound systems.
- 2011
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Ingår i: European Journal of Echocardiography. - : OXFORD UNIV PRESS. - 1525-2167 .- 1532-2114. ; 12:6, s. 467-476
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: The objective of this study was to test the accuracy and diagnostic interchangeability of tissue Doppler-based displacement, velocity, strain, and strain rate measurements in commercially used ultrasound (US) systems. METHODS AND RESULTS: Using an in-house made phantom, four different US scanner models were evaluated. Two different scanners of the same model were tested, and one scanner acquisition was tested twice with two generations of the same workstation giving six test results in total. The scanners were in active clinical use and are subject to regular maintenance checks. There were three displacement and four velocity results that stood out from the rest and could be regarded as accurate and interchangeable. Among the deformation measurements, three acceptable strain results were found while there were no acceptable strain rate results. Furthermore, the study showed that measurements from scanners of the same model, same acquisition post-processed on different workstations and repeated measurements from the same scanner, can yield disparate results. CONCLUSION: Measurements that are accurate and of interchangeable use can be found for displacement and velocity measurements, but are less likely to be found for strain and strain rate measurements. It is strongly recommended that the ability of each individual US scanner to measure displacement, velocity, strain, and strain rate is evaluated before it is introduced into clinical practice, and it must always be evaluated together with the workstation the scanner is intended to be used in conjunction with.
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| 4. |
- Sturm, Dennis
(författare)
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Wireless Multi-Sensor Feedback Systems for SportsPerformance Monitoring : Design and Development
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireless applications have become a common part of daily life. Whether it is mobile phones, the Wi-Fi router at home, the keycard which has replaced the car key, a radio frequency identification access system to a building or a Bluetooth headset for your computer or phone, the means of modern wireless data exchange is an omnipresent technology. In sports, the market is in its infancy for wireless, technical applications or gadgets. Only heart rate monitors and GPS watches are currently used by recreational athletes. Even though most of the larger sports equipment companies regularly launch new products related to sports performance monitoring and mobile phone technology, product innovation leaps are rare.In this work the design of a wireless sports performance measurement platform is presented. Using the example of kayaking, this platform is configured as a paddle performance measuring system, the Kayak XL System, which can monitor propulsive paddle force, paddle kinematics and boat velocity, interalia. A common mobile phone platform has been chosen as the user interface for this system. The design approach focussing on user requests, demands and expectations in combination with the process of iterative technical development are unveiled in this thesis. An evaluation of the system is presented and the work is finalised with an overview of further systems which have been designed based on the developed measurement platform. The Kayak XL System is a flexible system designed to be mounted onto any standard kayak paddle and installed in any competition kayak. Versatility, unobtrusiveness and usability were major design concerns. The developed system consists of four modules plus a software which has been designed for Android mobile phones. The phone communicates with each of the four modules trough Bluetooth radio. These four modules are also referred to as nodes and have specific measurement purposes. Two nodes have been designed to measure paddle force and kinematics, one node has the purpose to measure foot stretcher force and boat motion data, and the fourth node enables a more convenient method of calibrating paddle force measurement. The fourth node is therefore only needed prior to performance data acquisition. Results show that paddle and foot stretcher force can be measured with a resolution below 1N after calibration. Installing the paddle nodes on a previously configured paddle without repeated calibration is facilitated with the compromise of a doubled error margin. The default sampling frequency is set to 100 Hz and can, like all system parameters, be configured on the mobile phone. Real-time computation of complex performance parameters is only limited by the phone CPU. The system adds twice 109 g to the paddle and approximately 850 g to the kayak, excluding the mass of the mobile phone
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| 5. |
- Bjällmark, Anna, et al.
(författare)
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Effects of hemodialysis on the cardiovascular system: Quantitative analysis using wave intensity wall analysis and tissue velocity imaging
- 2010
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Ingår i: Heart and Vessels. - : Springer Science and Business Media LLC. - 0910-8327 .- 1615-2573.
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Tidskriftsartikel (refereegranskat)abstract
- Cardiovascular disease is the leading cause of death in patients with end stage renal disease (ESRD). The aim of this study was to investigate the changes in cardiovascular function induced by a single session of hemodialysis (HD) by the analysis of cardiovascular dynamics using wave intensity wall analysis (WIWA) and of systolic and diastolic myocardial function using tissue velocity imaging (TVI). Grey-scale cine loops of the left common carotid artery, conventional echocardiography and TVI images of the left ventricle were acquired before and after HD in 45 patients (17 women, mean age 54) with ESRD. The WIWA indexes, W1 preload-adjusted W1, W2 and preload-adjusted W2, and the TVI variables, isovolumic contraction velocity (IVCV), isovolumic contraction time (IVCT), peak systolic velocity (PSV), displacement, isovolumic relaxation velocity (IVRV), isovolumic relaxation time (IVRT), peak early diastolic velocity (E’) and peak late diastolic velocity (A’), were compared before and after HD. The WIWA measurements showed significant increases in W1 (p < 0.05) and preload-adjusted W1 (p < 0.01) after HD. W2 was significantly decreased (p < 0.05) after HD, whereas the change in preload-adjusted W2 was not significant. Systolic velocities, IVCV (p < 0.001) and PSV (p < 0.01), were increased after HD, whereas the AV-plane displacement were decreased (p < 0.01). For the measured diastolic variables, E’ was significantly decreased (p < 0.01) and IVRT was significantly prolonged (p < 0.05), after HD. A few correlations were found between WIWA and TVI variables. The WIWA and TVI measurements indicate that a single session of HD improves systolic function. The load dependency of the diastolic variables seems to be more pronounced than for the systolic variables. Preload-adjusted wave intensity indexes may contribute in the assessment of true LV contractility and relaxation.
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| 6. |
- Bjällmark, Anna, et al.
(författare)
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Ultrasonographic strain imaging is superior to conventional non-invasive measures of vascular stiffness in the detection of age-dependent differences in the mechanical properties of the common carotid artery
- 2010
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Ingår i: European Journal of Echocardiography. - : Oxford University Press (OUP). - 1525-2167 .- 1532-2114. ; 11:7, s. 630-636
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Elastic properties of large arteries have been shown to deteriorate with age and in the presence of atherosclerotic vascular disease. In this study, the performance of ultrasonographic strain measurements was compared to conventional measures of vascular stiffness in the detection of age-dependent differences in the elastic properties of the common carotid artery.Methods and results: In 10 younger (25-28 years, 4 women) and 10 older (50-59 years, 4 women) healthy individuals, global and regional circumferential and radial strain variables were measured in the short-axis view of the right common carotid artery using ultrasonographic two-dimensional (2D) strain imaging with recently introduced speckle tracking technique. Conventional elasticity variables, elastic modulus (Ep) and β stiffness index, were calculated using M-mode sonography and non-invasive blood pressure measurements. Global and regional circumferential systolic strain and strain rate values were significantly higher (p < 0.001, p < 0.01 for regional late systolic strain rate) in the younger individuals, whereas the values of conventional elasticity variables in the same group were lower (p < 0.05). Among all strain and conventional elasticity variables, principal component analysis and its regression extension identified only circumferential systolic strain variables as contributing significantly to the observed discrimination between the younger and older age groups.Conclusion: Ultrasonographic 2D-strain imaging is a sensitive method for the assessment of elastic properties in the common carotid artery, being in this respect superior to conventional measures of vascular elasticity. The method has potential to become a valuable non-invasive tool in the detection of early atherosclerotic vascular changes.
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| 7. |
- Carlsson, Camilla, et al.
(författare)
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Initial experience with a thin single segment pressure and conductance catheter for measurement of left ventricular volume
- 2001
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Ingår i: Annual Reports of the Research Reactor Institute, Kyoto University. ; , s. 103-106
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Konferensbidrag (refereegranskat)abstract
- Aims: To evaluate a thin and soft multifunctionalcatheter for the simultaneous real time monitoring of leftventricular volume and pressure with special consideration toside elTects such as interference with normal cardiacelectrophysiology.Methods and results: In four pigs, pressure and volumewere simultaneously recorded by using the thin single segmentpressure and conductance catheter. Measurements were doneunder varied cardiac conditions: at baseline, during preloadreduction and afterload Increase. Volumes were calibrated withintracardiac ultrasound measurements. During preloadreduction the pressure and volume decreased as expected. Acautious afterload increase resulted in a corresponding pressureand volume increase, the maximum of the pressure curvechanged from early to late. Both SV and EDV increased. Thevery few arrhythmias were mainly caused by surgicalinterference.Conclusion: The present study demonstrates that our thinsingle segment conductance catheter for the simultaneousmeasurement of LV volume and pressure has a performancethat warrants further development with the goal to make themethod available for human use. In particular, the catheter didnot cause any arrhythmias.
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| 8. |
- Govind, Satish C., et al.
(författare)
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Differing myocardial response to a single session of hemodialysis in end-stage renal disease with and without type 2 diabetes mellitus and coronary artery disease
- 2006
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Ingår i: Cardiovascular Ultrasound. - : Springer Science and Business Media LLC. - 1476-7120. ; 4:9
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Tidskriftsartikel (refereegranskat)abstract
- Background: Though hemodialysis (HD) acutely improves cardiac function, the impact of background diseases like coronary artery disease (CAD) and Type 2 diabetes (DM) in the setting of end-stage renal disease (ESRD) is not known. Tissue velocity echocardiography (TVE) offers a fast choice to follow changes in myocardial function after HD in ESRD with concomitant DM and/or CAD. Methods: 46 subjects (17 with ESRD, Group 1; 15 with DM, Group 2; 14 with DM+CAD, Group 3) underwent standard and TVE prior to and shortly after HD. Besides standard Doppler variables, regional myocardial systolic and diastolic velocities, as well as systolic strain rate were post processed. Results: Compared with pre-HD, post-HD body weight (kg) significantly decreased in all the three groups (51 ± 9 vs. 48 ± 8, 62 ± 10 vs.59 ± 10, and 61 ± 9 vs. 58 ± 9 respectively; all p < 0.01). Left ventricular end diastolic dimensions (mm) also decreased post- HD (46 ± 5 vs. 42 ± 7, 53 ± 7 vs. 50 ± 7, 51 ± 7 vs. 47 ± 8 respectively; all p < 0.01). Regional longitudinal peak systolic velocity in septum (cm/s) significantly increased post-HD in Group 1(5.7 ± 1.6 vs. 7.2 ± 2.3; p < 0.001) while remained unchanged in the other two groups. Similar trends were noted in other left ventricular walls. When the myocardial velocities (cm/s) were computed globally, the improvement was seen only in Group 1 (6.3 ± 1.5 vs. 7.9 ± 2.0; p < 0.001). Global early regional diastolic velocity (cm/s) improved in Group 1, remained unchanged in Group 2, while significantly decreased in Group 3(-5.9 ± 1.3 vs. -4.1 ± 1.8; p < 0.01). Global systolic strain rate (1/sec) increased in the first 2 Groups but remained unchanged (-0.87 ± 0.4 vs. -0.94 ± 0.3; p = ns) in Group 3. Conclusion: A single HD session improves LV function only in ESRD without coexistent DM and/or CAD. The present data suggest that not only dialysis-dependent changes in loading conditions but also co-existent background diseases determine the myocardial response to HD.
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| 9. |
- Govind, Satish C., et al.
(författare)
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Impaired Myocardial Functional Reserve in Hypertension and Diabetes Mellitus Without Coronary Artery Disease: Searching for the Possible Link With Congestive Heart Failure in the Myocardial Doppler in Diabetes (MYDID) Study II
- 2006
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Ingår i: American Journal of Hypertension. - : Oxford University Press (OUP). - 0895-7061 .- 1941-7225. ; 19:8, s. 851-857
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Tidskriftsartikel (refereegranskat)abstract
- Background: Although the impact of type 2 diabetes mellitus (DM) and hypertension (HTN) on myocardial function has recently been studied using tissue Doppler echocardiography (TDE), the independent role of both conditions, and the influence of other risk factors on myocardial function has not been completely defined, particularly in absence of coronary artery disease (CAD). The aim of this study was to assess the myocardial functional reserve in patients with DM or HTN with apparently normal left ventricular (LV) systolic function. Methods: Standard and dobutamine stress echocardiography using TDE was performed in 128 subjects: 59 had DM, 20 had HTN, 27 had both DM and HTN (HTN + DM), and 22 subjects were controls (C). Subjects with known CAD and depressed LV function were excluded. In addition, standard two-dimensional and Doppler measurements, LV regional peak systolic (PSV), early (E') and late (A') diastolic velocities, strain (S%) and strain rate (SR), were assessed at rest and peak stress. Results: The LV mass did not differ, although relative wall thickness was significantly higher in subjects with HTN + DM and HTN. The PSV did not differ at rest but was lowest in subjects with HTN + DM at peak stress. The E' wave velocity was significantly lower in subjects with HTN + DM both at rest and during peak stress, as were S% and SR. Conclusions: The addition of DM to HTN has a negative effect on LV systolic and diastolic functions. A depressed myocardial functional reserve might be postulated as one of the pathophysiologic mechanisms for the excessive occurrence of congestive heart failure in patients with DM or HTN.
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| 10. |
- Govind, Satish C., et al.
(författare)
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Isolated Type 2 Diabetes mellitus Causes Myocardial Dysfunction That Becomes Worse in the Presence of Cardiovascular Diseases : Results of the Myocardial Doppler in Diabetes (MYDID): Study 1
- 2005
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Ingår i: Cardiology. - : S. Karger AG. - 0008-6312 .- 1421-9751. ; 103:4, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Patients with type 2 diabetes mellitus (DM) often suffer disproportionately and have a worse outcome when burdened with cardiovascular complications compared with those without DM. A specific heart muscle disease reportedly caused by DM per se may explain this. We sought to investigate whether an echo Doppler diagnosis of such a myocardial disease is clinically relevant in DM with or without coexistent coronary artery disease (CAD) and/or hypertension ( HTN). Subjects and Methods: Two hundred subjects (127 males, 73 females, 56 +/- 10 years) including controls (n=23), patients with HTN (n=20), CAD (n=35), uncomplicated DM (n=59), DM+HTN (n=27), DM+ CAD (n=16) and DM+CAD+HTN (n=20) underwent tissue Doppler-enhanced dobutamine stress echocardiography. Myocardial function was assessed by measuring left ventricular myocardial peak systolic velocity (PSV) and early diastolic velocity at rest and during peak stress, besides measurements of standard Doppler variables. Results: Average left ventricular PSV at rest was significantly lower in CAD (4.7 +/- 1.5) compared with controls (5.7 center dot +/- 1.2) and in DM+CAD+HTN (4.6 +/- 1.4) compared with DM (5.6 +/- 1.3; all p < 0.05). During peak stress, lower PSV persisted in CAD (9.5 +/- 3.1) and DM+CAD+HTN (8.1 +/- 2.7), while appearing de novo in DM (11.3 +/- 2.6) and HTN (11.0 +/- 2.3) unlike in the controls (12.5 +/- 2.5; all p < 0.001). When pooled together, DM subjects with CAD and/or HTN or both had significantly lower PSV (9.1 +/- 2.7) than those without (10.0 +/- 2.8; p < 0.001). Early diastolic velocity response was equally lower in both groups compared with the controls. Conclusion: The results suggest that dobutamine stress unmasks myocardial functional disturbances caused by uncomplicated DM. The discrete disturbances become quantitatively more pronounced in the presence of coexistent cardiovascular diseases.
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