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Browsing by Author "Casper, Andrew Jacob"

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    Design and implementation of a dual-mode ultrasound array driver.
    (2011-11) Casper, Andrew Jacob
    Ultrasound has a long history as an important medical diagnostic tool. Its non-ionizing nature and relative low cost has enabled this technology to gain widespread acceptance and use in hospitals worldwide. It's currently used to create images of many internal body structures allowing for rapid assessment by a physician. While it is in the diagnostic imaging context that ultrasound is most commonly used, it is however, not the only medical use of ultrasound. Ultrasound is also capable of non-invasively targeting organs and tissue for therapeutic benefits. These benefits can range from non-invasive drug delivery to tissue cauterization. Recent advances in piezocomposite transducer technology have allowed for a new generation of array transducers that are capable of both delivering ultrasound therapy, and imaging with the same device. These transducers, referred to as Dual-Mode Ultrasound Arrays (DMUAs), use the same elements for therapy and imaging, allowing for absolute registration between therapeutic and imaging coordinates. Therefore, realtime DMUA imaging provides unique form of feedback to the physician allowing her/him to identify and quantify the exposure to any obstacles in the path of the therapeutic beam. This feedback provides the basis for realtime resynthesis of the therapeutic beam to minimize the exposure to these obstacles while maximizing the exposure at the target. The advantages of the DMUA approach to image-guided surgery can be realized only with drivers that fully integrate the imaging and therapy functions in a seamless manner. This thesis describes the design and implementation of two real-time DMUA drivers. The first system was an enhancement of a previous design that allowed for the basic features of the DMUA system to be demonstrated. The second was a new design that allowed for a wider range of operation and the implementation of microsequencer to precisely control imaging and therapy sequences.
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    HIFU Monitoring and control With dual-mode ultrasound arrays
    (2013-11) Casper, Andrew Jacob
    The biological effects of high-intensity focused ultrasound (HIFU) have been known and studied for decades. HIFU has been shown capable of treating a wide variety of diseases and disorders. However, despite its demonstrated potential, HIFU has been slow to gain clinical acceptance. This is due, in part, to the difficulty associated with robustly monitoring and controlling the delivery of the HIFU energy. The non-invasive nature of the surgery makes the assessment of treatment progression difficult, leading to long treatment times and a significant risk of under treatment. This thesis research develops new techniques and systems for robustly monitoring HIFU therapies for the safe and efficacious delivery of the intended treatment. Systems and algorithms were developed for the two most common modes of HIFU delivery systems: single-element and phased array applicators. Delivering HIFU with a single element transducer is a widely used technique in HIFU therapies. The simplicity of a single element offers many benefits in terms of cost and overall system complexity. Typical monitoring schemes rely on an external device (e.g. diagnostic ultrasound or MRI) to assess the progression of therapy. The research presented in this thesis explores using the same element to both deliver and monitor the HIFU therapy. The use of a dual-mode ultrasound transducer (DMUT) required the development of an FPGA based single-channel arbitrary waveform generator and high-speed data acquisition unit. Data collected from initial uncontrolled ablations led to the development of monitoring and control algorithms which were implemented directly on the FPGA. Close integration between the data acquisition and arbitrary waveform units allowed for fast, low latency control over the ablation process. Results are presented that demonstrate control of HIFU therapies over a broad range of intensities and in multiple in vitro tissues. The second area of investigation expands the DMUT research to an ultrasound phased-array. The phased-array allows for electronic steering of the HIFU focus and imaging of the acoustic medium. Investigating the dual-mode ultrasound array (DMUA) required the design and construction of a novel ultrasound-guided focused ultrasound (USgFUS) platform. The platform consisted of custom hardware designed for the unique requirements of operating a phased-array in both therapeutic and imaging modes. The platform also required the development of FPGA based signal processing and GPU based beamforming algorithms for online monitoring of the therapy process. The results presented in this thesis represent the first demonstration of a real-time USgFUS platform based around a DMUA. Experimental imaging and therapy results from series of animal experiments, including a 12 animal GLP study, are presented. In addition, in vitro control results, which build upon the DMUT work, are presented.