| 1. |
- Kothapalli, Veera Venkata Satya Naray, 1985-, et al.
(författare)
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Unique pumping-out fracturing mechanism of a polymer-shelled contrast agent : An acoustic characterization and optical visualization
- 2014
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 62:3, s. 451-462
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Frånberg, Oskar, 1976-
(författare)
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Oxygen content in semi-closed rebreathing apparatuses for underwater use : Measurements and modeling
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present series of unmanned hyperbaric tests were conducted in order to investigate the oxygen fraction variability in semi-closed underwater rebreathing apparatuses. The tested rebreathers were RB80 (Halcyon dive systems, High springs, FL, USA), IS-Mix (Interspiro AB, Stockholm, Sweden), CRABE (Aqua Lung, Carros Cedex, France), and Viper+ (Cobham plc, Davenport, IA, USA). The tests were conducted using a catalytically based propene combusting metabolic simulator. The metabolic simulator connected to a breathing simulator, both placed inside a hyperbaric pressure chamber, was first tested to demonstrate its usefulness to simulate human respiration in a hyperbaric situation. Following this the metabolic simulator was shown to be a useful tool in accident investigations as well as to assess the impact of different engineering designs and physiological variables on the oxygen content in the gas delivered to the diver by the rebreathing apparatuses. A multi-compartment model of the oxygen fractions was developed and compared to the previously published single-compartment models. The root mean squared error (RMSE) of the multi-compartment model was smaller than the RMSE for the single-compartment model, showing its usefulness to estimate the impact of different designs and physiological variables on the inspired oxygen fraction.
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| 3. |
- Venkateshvaran, Ashwin, 1977-
(författare)
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Cardiac Performance, Ventricular-Vascular Interaction and Functional Alterations in Rheumatic Mitral Stenosis : A descriptive study employing novel hemodynamic and echocardiographic modalities
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The assessment of LV performance poses significant challenges in the setting of rheumatic mitral stenosis (MS) owing to an inherently load-altered state. A detailed characterization of arterial-ventricular coupling between subjects with isolated post-capillary pulmonary hypertension (Ipc-PH) and combined pre- and post-capillary pulmonary hypertension (Cpc-PH) has not been described. Diastolic pulmonary pressure gradient (DPG) has come under scrutiny owing to the occurrence of negative DPG values, and its prognostic implications are obscure. Mitral Annular (MA) geometry and alterations associated with successful percutaneous intervention remain unclear. The studies in this thesis aim to provide insights into these aspects of MS using novel hemodynamic and echocardiographic modalities.In Study I, load-independent indices of LV performance were analysed using the single-beat method in 106 MS subjects employing simultaneous bi-ventricular catheterization and echocardiography. MS subjects showcased significantly elevated arterial load, LV contractility and stiffness as compared with controls. Afterload was inversely associated with the severity of stenosis. Both LV elastance (Ees) and arterial elastance (Ea) returned to more normal levels immediately after PTMC, while LV stiffness demonstrated a further rise. In Study II, systemic arterial-ventricular (AV) coupling was analysed in PH subjects among 106 MS patients. Compared with Ipc-PH subjects, Cpc-PH group demonstrated elevated Ea and Ea/Ees ratio. Ea was associated with reduced LV deformation in both septal and lateral LV segments. Impact of the RV on the LV was limited to the septum. In Study III, 316 subjects with left heart disease (LHD) due to primary myocardial dysfunction or valvular disorders were studied to clarify the physiological and prognostic implications of DPGNEG. V-wave amplitude in the pulmonary artery wedge pressure (PAWP) curve was inversely associated with DPG at lower pulmonary vascular resistance (PVR), but not at higher levels. DPGNEG subjects showcased better prognosis as compared with positive, unelevated (< 7mmHg) DPG. In Study IV, mitral annular geometry was studied in 57 MS subjects undergoing PTMC employing 3D echocardiography. MS subjects demonstrated a more circular and flatter annulus, with significantly larger orthogonal diameters, annular circumference and area. Annular non-planarity and displacement demonstrated a tendency to normalize after PTMC. Baseline annular diameter demonstrated an association with post-procedural mitral regurgitation.In summary, AV coupling, DPGNEG and MA geometry assessment offers novel insights in MS.
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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- Bjällmark, Anna, et al.
(författare)
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A system to quantify and visualize ventricular rotation pattern of the heart
- 2009
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Patent (populärvet., debatt m.m.)abstract
- Different modalities have been used to describe the rotational motion of the ventricles of the heart and studies have indicated LV twist to be an additional integral component in LV function. So far, only amplitudes and timings of rotation have been reported, whereas no method is available to fully describe the rotation pattern of the ventricles. The object of the present application is to achieve a system that presents a novel way to quantify and visualize the ventricular rotation pattern of the heart. We present a novel method that assesses and describes the rotation pattern by calculating the rotation axis of the ventricle. Non- invasive image acquisition is required to collect rotation values from different positions of the myocardium. Thereafter, a kinematic model of a ventricle is constructed to determine the rotation planes at different levels of the heart. The motion of the rotation planes are visualized by plotting the normal vectors of the planes over time, i.e. the rotation axis of the planes. This new method is different to all other methods used today for assessing cardiac function, as it does not describe the amplitude of a motion but the relationship in motion between different parts within a ventricle. Preliminary results indicate that the rotation axis is more sensitive to changes in the rotation pattern than conventional measurements of ventricular rotation. This new method could be used for early detection of cardiac diseases and for selection of patients for and optimization of cardiac resynchronization therapy.
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