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<p>Ultrasound can be used for a variety of therapeutic purposes. High-intensity focused ultrasound (HIFU) has progressed over the past decade to become a viable therapeutic method and is valuable as a non-invasive alternative to many surgical procedures. Ultrasonic thermal therapies can also be used to release thermally sensitive liposomes encapsulating chemotherapeutic drugs. In the brain, the permeability of the blood-brain barrier to drugs, antibodies, and gene transfer can be increased with a mechanical mechanism using ultrasound and contrast agent.</p><p>The work presented in this dissertation tests the hypothesis that a diagnostic system can be used for combined imaging and therapeutic applications. In order to evaluate the effectiveness of a diagnostic system for use in therapeutic applications, a set of non-destructive tests is developed that can predict the potential for high acoustic output. A rigorous, nondestructive testing regimen for standard, diagnostic transducers to evaluate their potential for therapeutic use is formulated. Based on this work, transducer heating is identified as the largest challenge. The design and evaluation of several custom diagnostic transducers with various modifications to reduce internal heating are described. These transducers are compared with diagnostic controls using image contrast, face heating, hydrophone, and ARFI displacement measurements. From these results, we conclude that the most promising design is a passively and actively cooled, PZT-4 multilayer composite transducer, while the acoustically lossless lens and capactive micro-machined transducers evaluated herein are determined to be ineffective.</p><p>Three therapeutic applications are evaluated for the combined system. Image-guided spot ablations, such as in the treatment of early stage liver cancers, could not be successfully performed; however, the additional acoustic output requirements are determined to be on the order of 2.4 times those that can be currently produced without transducer damage in a clinically relevant amount of time (10-20 seconds per spot). The potential of a diagnostic system for a hyperthermia application is shown by producing temperatures for the duration necessary to release chemotherapeutic agents from thermally-activated liposomes without damage to the transducer. Finally, a mechanically-based therapeutic method for opening the BBB with ultrasonic contrast agent and specialized sonication regimes under ultrasonic B-mode guidance is demonstrated.</p><p>These studies indicate that a diagnostic system is capable of both moderate thermal and mechanical therapeutic applications under co-registered image-guidance.</p> / Dissertation

Thesis submitted in fulfilment of the requirements for the degree of Doctor of Technology: Radiography in the Faculty of Health and Wellness Sciences at the Cape Peninsula University of Technology 2013 / Background. Ultrasound has until recently been regarded as a sophisticated examination reserved for tertiary health care. In reality it is well suited to the district or primary health-care situation. A DVT (deep vein thrombosis) is an important complication of the treatment of TB and this can lead to more devastating sequelae such as a pulmonary embolus. Many DVTs are clinically silent, making the diagnosis difficult. Method. This study was a prospective, longitudinal observational study. The study documented the incidence of DVTs and their onset, assessed certain aspects in an attempt to identify some risk factors, and noted the most common position of the DVT in a TB population. The feasibility of a sonographer-led ultrasound clinic for the diagnosis of DVTs was also assessed. This was achieved by screening the in-patient population at a district TB hospital. The participants received up to four routine duplex Doppler compression ultrasound examinations of the venous system of the lower extremities on week 0, week 4, week 8 and week 14. In addition a single abdominal ultrasound was performed at week 0. Results The incidence of DVTs in this TB population was 15.3%. A median of day 10 from commencing TB treatment was identified as the most common day to develop a DVT. The popliteal vein was the most frequent position for a DVT. Several statistically significant factors were identified, including a decreased ambulatory status, TB regimen and the use of anticoagulants. Only 52% of the DVTs were clinically symptomatic. The clinical evaluation for a DVT diagnosis in this study population had a sensitivity of 52.4% and a specificity of 65.3%. The positive predictive value (PPV) was 21.7%. Of the abdominal ultrasound reports there were 75.5% (281) abnormal reports, 22.5% (n = 90) normal reports and 4.5% (n = 18) with no report. Conclusion This body of work has shown how an effective ultrasound service can be provided at a district level TB hospital successfully administered by a trained ultrasonographer. This also facilitated a screening service to diagnose both symptomatic and asymptomatic deep vein thromboses in newly diagnosed tuberculosis patients. This study confirmed a higher rate of DVT in newly diagnosed TB patients than has been previously seen. It also provided detail on additional risk factors. The study illustrates the poor performance of clinical signs and symptoms as a trigger for further investigation for the confirmation of a DVT. Given the frequency and impact of the embolic complications of DVT, this study provides a strong justification for further research into routine serial ultrasonic screening and/or prophylactic antithrombolytics in newly diagnosed TB patients. As well as the DVT ultrasound scans there was the ancillary service offered by the research sonographers. This included an abdominal scan that detected abdominal pathology in 75% of the scans performed. An ultrasound scan is not pathognomonic but it does provide significant insight into the extent of some of the abdominal pathologies seen in TB patients. The information provided from this study gives a good indication of the problem that DVTs present in this population and the complexities of the disease TB. It is hoped that the results from this study will better equip the medical team in the non-tertiary situation to be vigilant for the presence of a DVT and educate them on the usefulness of the ultrasound scan.

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This thesis deals with ultrasound blood flow meter design with emphasis on practical implementation of such device. This medical device is used in ultrasound diagnostic, especially for measuring direction and velocity of blood flow in superficial vessels. This thesis contains consecutive design including description of individual function blocks. Documents for making double-sided printed circuit are included as well.

The progress in ultrasound techniques goes hand in hand with increasing of diagnostic machine acoustic outputs. Ultrasound biological effects can adversely influence the development of human fetus. Recent studies of thermal effect on biological tissues are usually based on simulation of simple ultrasound transducers. The aim of this work is to build a flexible model of diagnostic system to simulate temperature increase during fetal development. Different types of ultrasound probes were used for generation of acoustic field with simulated piezoelectric element properties. Optimized linear and phased arrays were modeled with dynamic beam steering and focus. Computer simulations were concentrated on extreme conditions in obstetric ultrasonography and 3D tissue model was compared with real ultrasound probes measurements. To detect temperature increase, the bone tissue phantom was used. Results point out potential risks for fetus with diagnostic ultrasound probes. Based on the results of this work, practical recommendations increasing safety of obstetric examinations were drawn.

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