40 research outputs found

    Design of a programmable micro-ultrasound research platform

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    To foster innovative uses of micro-ultrasound in biomedicine, it is beneficial to develop flexible research-purpose systems that allow researchers to easily reconfigure its system-level operations such as transmit firing sequence and receive processing. In this paper, we present the development of a programmable micro-ultrasound research platform that is capable of realizing various micro-imaging algorithms. The research platform comprises a linear-array-based scanning front-end and a PC-based data processing back-end, which employs a graphical processing unit (GPU) as the processor core. The front-end operations can be configured from the PC via the parallel port and the two blocks are synchronized by an external clock. Acquired data from the front-end is first digitized and relayed to the PC through an data acquisition card (200 MHz, 14-bit). They are then transferred to the GPU (GTX 275) in which the image formation is carried out via multi-thread processing. Results are displayed on-screen in real-time and can be saved to the PC's hard disk for offline analysis. Through a module-based programming approach, this platform can facilitate realization of custom-designed imaging algorithms developed by researchers. In this work, B-mode imaging and adaptive color flow imaging have been implemented as demonstrations of the research platform's programmability. The performance results show that real-time processing frame rates can be achieved for both imaging modes. © 2010 IEEE.published_or_final_versionThe 2010 IEEE International Ultrasonics Symposium, San Diego, CA., 11-14 October 2010. In Proceedings of IEEE IUS, 2010, p. 1980-198

    A programmable, cost-effective, real-time high frequency ultrasound imaging board based on high-speed FPGA

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    2010-2011 > Academic research: refereed > Refereed conference paperAccepted ManuscriptPublishe

    A programmable, cost-effective, real-time high frequency ultrasound imaging board based on high-speed FPGA

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    High frequency (>20MHz) ultrasound imaging has made it possible to delineate small structures with fine spatial resolution. Previously, a high frequency high frame rate imaging system had been developed for small animal cardiac imaging. This paper presents further development of a programmable, low-cost, real-time high frequency ultrasound imaging board based on high-speed FPGA. Utilization of FPGA facilitates programmable applications with high flexibility. The printed circuit board (PCB) design achieves cost-effectiveness and compactness. The PCI bus interface allows high speed data transfer and real-time imaging. The dedicated front-end electronics showed a minimum detectable signal of 18μV, allowing a 50dB dynamic range at a total gain of 50dB. The high-speed analog to digital converter (ADC) with a typical 10.8 bit ENOB was employed to accomplish high speed data acquisition. Algorithms such as band-pass filter, envelope detection and digital scan converter were implemented in the FPGA with high speed and high flexibility. Finally, wire phantom experiment showed good performance of such a programmable and compact design.Department of Health Technology and Informatic

    Ex-vivo and In-vivo Characterization of Human Accommodation

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    A completely satisfying approach to restoring accommodation still needs to be developed. Besides, there are considerable discrepancies between objective and subjective trials to evaluate the therapeutic success. A substantial biomechanical understanding of all structures and processes involved in accommodation as well as presbyopia are needed to develop promising new strategies. This contribution focuses on developing advanced imaging techniques to create a basic understanding of accommodation and presbyopia and to evaluate existing concepts for restoring accommodation. Besides, the emphasis is also on replacing stiff presbyopic lenses by a material that imitates the young crystalline lens

    Novel Techniques for Tissue Imaging and Characterization Using Biomedical Ultrasound

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    The use of ultrasound technology in the biomedical field has been widely increased in recent decades. Ultrasound modalities are considered more safe and cost effective than others that use ionizing radiation. Moreover, the use of high-frequency ultrasound provides means of high-resolution and precise tissue assessment. Consequently, ultrasound elastic waves have been widely used to develop non-invasive techniques for tissue assessment. In this work, ultrasound waves have been used to develop non-invasive techniques for tissue imaging and characterization in three different applications.;Currently, there is a lack of imaging modalities to accurately predict minute structures and defects in the jawbone. In particular, the inability of 2D radiographic images to detect bony periodontal defects resulted from infection of the periodontium. They also may carry known risks of cancer generation or may be limited in accurate diagnosis scope. Ultrasonic guided waves are sensitive to changes in microstructural properties, while high-frequency ultrasound has been used to reconstruct high-resolution images for tissue. The use of these ultrasound techniques may provide means for early diagnosis of marrow ischemic disorders via detecting focal osteoporotic marrow defect, chronic nonsuppurative osteomyelitis, and cavitations in the mandible (jawbone). The first part of this work investigates the feasibility of using guided waves and high frequency ultrasound for non-invasive human jawbone assessment. The experimental design and the signal/image processing procedures for each technique are developed, and multiple in vitro studies are carried out using dentate and non-dentate mandibles. Results from both the ultrasonic guided waves analysis and the high frequency 3D echodentographic imaging suggest that these techniques show great potential in providing non-invasive methods to characterize the jawbone and detect periodontal diseases at earlier stages.;The second part of this work describes indirect technique for characterization via reconstructing high-resolution microscopic images. The availability of well-defined genetic strains and the ability to create transgenic and knockout mice makes mouse models extremely significant tools in different kinds of research. For example, noninvasive measurement of cardiovascular function in mouse hearts has become a valuable need when studying the development or treatment of various diseases. This work describes the development and testing of a single-element ultrasound imaging system that can reconstruct high-resolution brightness mode (B-mode) images for mouse hearts and blood vessels that can be used for quantitative measurements in vitro. Signal processing algorithms are applied on the received ultrasound signals including filtering, focusing, and envelope detection prior to image reconstruction. Additionally, image enhancement techniques and speckle reduction are adopted to improve the image resolution and quality. The system performance is evaluated using both phantom and in vitro studies using isolated mouse hearts and blood vessels from APOE-KO and its wild type control. This imaging system shall provide a basis for early and accurate detection of different kinds of diseases such as atherosclerosis in mouse model.;The last part of this work is initialized by the increasing need for a non-invasive method to assess vascular wall mechanics. Endothelial dysfunction is considered a key factor in the development of atherosclerosis. Flow-mediated vasodilatation (FMD) measurement in brachial and other conduit arteries has become a common method to assess the endothelial function in vivo. In spite of the direct relationship that could be between the arterial wall multi-component strains and the FMD response, direct measurement of wall strain tensor due to FMD has not yet been reported in the literature. In this work, a noninvasive direct ultrasound-based strain tensor measuring (STM) technique is presented to assess changes in the mechanical parameters of the vascular wall during post-occlusion reactive hyperemia and/or FMD, including local velocities and displacements, diameter change, local strain tensor and strain rates. The STM technique utilizes sequences of B-mode ultrasound images as its input with no extra hardware requirement. The accuracy of the STM algorithm is assessed using phantom, and in vivo studies using human subjects during pre- and post-occlusion. Good correlations are found between the post-occlusion responses of diameter change and local wall strains. Results indicate the validity and versatility of the STM algorithm, and describe how parameters other than the diameter change are sensitive to reactive hyperemia following occlusion. This work suggests that parameters such as local strains and strain rates within the arterial wall are promising metrics for the assessment of endothelial function, which can then be used for accurate assessment of atherosclerosis

    Development of a real-time high-resolution 3D ultrasound imaging system

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    In this work a real-time high-resolution 3D ultrasound imaging system is developed, allowing the 3D acquisition and imaging of high-resolution ultrasound data for biomedical applications. The system uses ultrasound transducers in the ranges of 30 to 100 MHz, and allows full access of the radiofrequency (RF) ultrasound data for the 3D image reconstruction. This work includes the development of two graphical user interfaces in C++ to interact with a high-resolution ultrasound system and to image the high-resolution ultrasound data. In addition, a methodology is described and implemented in the system for 3D ultrasound reconstruction and visualization. The development of these GUIs allows easy 3D high-resolution ultrasound acquisition and imaging to any user with basic knowledge in ultrasound and with only minimal and faster training in the system and the GUIs. This capability opens the system to any researcher or person interested in performing experimentations with high-resolution ultrasound.;The high-resolution 3D ultrasound imaging system is tested to assess atherosclerosis using different mouse models. To assess atherosclerosis, a series of in vitro studies are performed to 3D scan vessels of mouse aortas and carotids vessels with atherosclerosis, as well as mouse hearts with atherosclerosis. The apolipoprotein E-knockout (APOE) and the apolipoprotein E-A1 adenosine receptor double knockout (DKO) mice model with their wild type control (C57) are used. Three-dimensional reconstructions were rendered showing good matches with the samples morphology. In addition, 3D sections of the data are reconstructed showing atherosclerotic plaque in the samples. The 3D ultrasound reconstruction allows for us to analyze a sample from outside and inside by rotating around any angle and cropping non-relevant data, allowing us to observe shape and appearance of the 3D structures. Finally, after reconstructing and analyzing the 3D ultrasound images, a 3D quantitative assessment of atherosclerotic plaque is performed. After analyzing the samples, the plaque lesions of DKO mouse model exhibits smaller areas than those of the APOE mouse model. Additionally, the C57 mouse model is clean of any atherosclerosis. These findings are in agreement with a previous study of our group for these mouse models

    Calibration of ultrasound scanners for surface impedance measurement

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    The primary objective of this research was to investigate the feasibility of calibrating ultrasound scanners to measure surface impedance from reflection data. The method proposed uses calibration curves from known impedance interfaces. This plot, or calibration curve, may then be used, with interpolation, to relate measured grey level to impedance for the characterization of tissue specimens with unknown properties. This approach can be used independent of different medical ultrasound scanner systems to solve for reproducible tissue impedance values without offline data processing and complicated custom electronics. Two medical ultrasound machines from different manufacturers were used in the experiment; a 30 MHz and a 7.5 MHz machine. The calibration curves for each machine were produced by imaging the interfaces of a vegetable oil floating over varying salt solutions. To test the method, porcine liver, kidney, and spleen acoustical impedances were determined by relating measured grey levels to reflection coefficients using calibration curves and then inverting the reflection coefficients to obtain impedance values. The 30 MHz ultrasound machine’s calculated tissue impedances for liver, kidney, and spleen were 1.476 ± 0.020, 1.486 ± 0.020, 1.471 ± 0.020 MRayles respectively. The 7.5 MHz machine’s tissue impedances were 1.467 ± 0.088, 1.507 ± 0.088, and 1.457 ± 0.088 MRayles respectively for liver, kidney and spleen. The differences between the two machines are 0.61%, 1.41%, and 0.95% for the impedance of liver, kidney, and spleen tissue, respectively. If the grey level is solely used to characterize the tissue, then the differences are 45.9%, 40.3%, and 39.1% for liver, kidney, and spleen between the two machines. The results support the hypothesis that tissue impedance can be determined using calibration curves and be consistent between multiple machines

    An open system for intravascular ultrasound imaging

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    Author name used in this publication: Cheng, Wang FaiInvited conference paper2011-2012 > Academic research: refereed > Invited conference paperVersion of RecordPublishe
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