Permanent breast seed implant brachytherapy (PBSI) is a recently developed form of treatment for early-stage breast cancer which can be completed in a single day procedure. Due to the reduced treatment burden, PBSI has the potential to benefit many women. However the technique has not been widely implemented, potentially related to the lack of a standardized, reproducible procedure and a high level of operator dependence. Challenges relating to target visualization uncertainties and the reliance on free-hand 2D ultrasound (US) guidance potentially inhibit adoption of the technique. This work aims to evaluate the current PBSI procedure to identify uncertainties and potential sources of errors in the current technique and develop methods to ameliorate these issues to potentially increase treatment accuracy, standardize the procedure, and reduce user-dependence. A comprehensive assessment of the current PBSI procedure was performed to identify any trends or systematic errors in the placement of seeds and establish the effects of seed placement accuracy on the treatment. Baseline seed placement accuracy, assessed in a 20 patient cohort was observed to be 9(5) mm. Random displacements of seeds from their planned position contributed significantly to the overall accuracy. No trends or systematic errors were observed across the aggregate population, however intra-patient systematic offsets were observed. The potential effects of visualization of the post-lumpectomy cavity (seroma) on treatment delivery was investigated using spatially registered CT and 3DUS images. Planning the treatment on CT, as is standard practice, resulted in less than optimal coverage to target volumes defined on US in the majority of cases. The effects of intra-operative adjustments relating to the visualization differences on the two modalities was assessed by shifting the CT-based treatment plan to centre on the US-defined seroma. Such shifts were shown to potentially contribute to the systematic displacements observed in PBSI delivery, and also had significant dosimetric effects on the planned target volumes. The impact of seroma visualization on PBSI implant accuracy was further assessed through the evaluation of CT and 3DUS images acquired for PBSI patients. Correlations were observed between the seed placement accuracy and the inter-user variability of seroma definition on CT (r = 0.74, p = 0.01) and the volume difference of the seroma on the two modalities (r = 0.65, p = 0.04), indicating that discrepancies in target delineation can impact treatment accuracy. The systematic displacements of the implants were observed to be correlated with the visualization metrics, however random displacements were independent of seroma delineation. Deviations in needle positioning during insertion may not be realized until the implant is complete, thus contributing to the random inaccuracies in seed placement. A purpose built 3DUS scanning system was investigated for its use in guiding needle insertion. Registration of the treatment template with the imaging system was validated to provide accurate target localization for needle insertion. Adjustments and re-insertion of needles under 3DUS guidance provided significant improvements to the needle positioning accuracy. A simulated implant with the guidance system indicated that overall treatment accuracy may be improved through the clinical implementation of such a system. Efforts to improve seroma definition during treatment planning and image guidance during the delivery can significantly increase seed placement accuracy and reduce the need for subjective intra-operative adjustments to the setup and needle positioning. Standardization of such advanced imaging techniques can greatly benefit the PBSI procedure by reducing user dependence and help to promote implementation. / Graduate / 2018-09-22

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The objective of this research is to develop large signal modeling and optimization methods for Capacitive Micromachined Ultrasonic Transducers (CMUTs), especially when they are used in an array configuration. General modeling and optimization methods that cover a large domain of CMUT designs are crucial, as many membrane and array geometry combinations are possible using existing microfabrication technologies. Currently, large signal modeling methods for CMUTs are not well established and nonlinear imaging techniques utilizing linear piezoelectric transducers are not applicable to CMUTs because of their strong nonlinearity. In this work, the nonlinear CMUT behavior is studied, and a feedback linearization method is proposed to reduce the CMUT nonlinearity. This method is shown to improve the CMUT performance for continuous wave applications, such as high-intensity focused ultrasound or harmonic imaging, where transducer linearity is crucial. In the second part of this dissertation, a large signal model is developed that is capable of transient modeling of CMUT arrays with arbitrary electrical terminations. The developed model is suitable for iterative design optimization of CMUTs and CMUT based imaging systems with arbitrary membrane and array geometries for a variety of applications. Finally, a novel multi-pulse method for nonlinear tissue and contrast agent imaging with CMUTs is presented. It is shown that the nonlinear content can be successfully extracted from echo signals in a CMUT based imaging system using a multiple pulse scheme. The proposed method is independent of the CMUT geometry and valid for large signal operation. Experimental results verifying the developed large signal CMUT array model, proposed gap feedback and multi-pulse techniques are also presented.

There is increasing interest in right ventricular function as an important determinant of cardiac output. However, the chamber is difficult to study, because of its shape and relationship to the left ventricle. Invasive studies, radionuclide studies and two-dimensional echocardiography are all useful approaches, but all have serious limitations. Systolic time intervals, best measured by pulsed Doppler ultrasound in the proximal pulmonary artery, offer one method of assessing right ventricular systolic function. Previous "normal" ranges, however, could be criticised on many counts. I present data from carefully checked normal controls and compare to previous publications, and explore variability and relationships between the various systolic time intervals. Most variables have skewed frequency distributions; the ranges are somewhat wider than previously described; most heart rate corrections are found to have serious limitations; and the effect of age is explored. Complete heart block offers a model to study the the effects of varying atrioventricular intervals whilst the ventricular rate is held unphysiologically steady by an artificial pacemaker. Given the current controversy about the merits of single- versus dual-chamber pacing, the issue is of topical interest also. The effect of varying the "P-R" interval within the physiological range is explored, and "optimal" ranges identified. A curious "nadir" effect, previously unknown, was discovered. When P waves followed paced QRS complexes at about 50-100ms, forward flow into the pulmonary artery (as judged from systolic time intervals) fell in most patients, and in some subjects virtually ceased. As a small included invasive part of the study showed, this was accompanied by falls in RV systolic pressure and rises in right atrial pressure. This study demonstrates that right ventricular systolic time intervals can be used to study right ventricular function in pacing situations, and is further evidence of the unsatisfactory nature of single-chamber ventricular pacing.

UA Open Access Publishing Fund / Background: Emergency medicine milestones released by the Accreditation Council for Graduate Medical Education require residents to demonstrate competency in bedside ultrasound (US). The acquisition of these skills necessitates a combination of exposure to clinical pathology, hands-on US training, and feedback. Objectives: We describe a novel simulation-based educational and assessment tool designed to evaluate emergency medicine residents’ competency in point-of-care echocardiography for evaluation of a hypotensive patient with chest pain using bedside US. Methods: This was a cross-sectional study conducted at an academic medical center. A simulation-based module was developed to teach and assess the use of point-of-care echocardiography in the evaluation of the hypotensive patient. The focus of this module was sonographic imaging of cardiac pathology, and this focus was incorporated in all components of the session: asynchronous learning, didactic lecture, case-based learning, and hands-on stations. Results: A total of 52 residents with varying US experience participated in this study. Questions focused on knowledge assessment demonstrated improvement across the postgraduate year (PGY) of training. Objective standardized clinical examination evaluation demonstrated improvement between PGY I and PGY III; however, it was noted that there was a small dip in hands-on scanning skills during the PGY II. Clinical diagnosis and management skills also demonstrated incremental improvement across the PGY of training. Conclusion: The 1-day, simulation-based US workshop was an effective educational and assessment tool at our institution.

A commonly used process for the formation of ceramic wall tile bodies is powder compaction. Variations in density in wall tile bodies introduced by the compaction process can cause rejection at later stages of production. Quality control equipment currently employed does not identify reject bodies in the unfired state. Scope exists to reduce production costs by the timely removal of reject bodies in the unfired state. In this thesis an ultrasonic non-destructive technique is presented which allows the mapping of the density variations found in wall tile bodies in the unfired and fired states to an accuracy of ± 0.5%. An effective medium theory for the propagation of ultrasound in porous media is developed. The significance of the dependence of Young's modulus on density in determining the relationship between compression wave propagation velocity and density is explored. Using a vibrational resonance technique, it is shown that the evolution of Young's modulus and Poisson's ratio in the wall tile body material are very sensitive to the conditions used for the firing operation. The Biot two-phase theory of acoustic propagation in fluid saturated porous media which considers dissipation due to friction between the fluid and porous frame is reviewed, and the applicability to the wall tile body material assessed. It is shown that this dissipation mechanism is insignificant for this particular material. A modification is made to the model in an attempt to include dissipation due to the inelasticity and scattering of the porous frame. The results show that the two-phase theory reduces to an effective medium theory in the limit of the saturating fluid being air. The thesis concludes that density variations in wall tile bodies can be measured using and ultrasonic technique and that an effective medium theory can be used to describe the propagation of ultrasound in porous media.

Background: Ultrasound is safe and painless, produces pictures of the inside of the body using sound waves (not use ionizing radiation), thus there is no radiation exposure to the patient. The thyroid gland is among the most commonly imaged glands using ultrasound due to the limitation of clinical examination. The Radiographers' skills in ultrasound differ according to the country and the basic formations. And throught this study we want to emphasize about the role of radiographer. Aim: The porpuse of this study is determine the volume and morphological characteristics of normal thyroid order to get reference values for young adults. Material and Method: We selected 204 students consist of male and female from Danang University of Medical Technology And Pharmacy were studied. Mean age of our subjects was 22 (range 18-25) all of them were healthy and with normal thyroid gland status. Descriptive statistics and analytic statistic was used. Results: In our study, the thyroid volume between female and male is different. The total thyroid volume significantly correlated with individual’s height, weight, body surface area and body mass index. The mean of total thyroid volume was 7.44 ± 2.09ml (range 3.51-14.57). The thyroid volume was best correlated with height (r = 0.44; p = 0.0001). Conclusion: Knowledge about the size of the thyroid gland is important in following the thyroid diseases and the examination of the gland. The radiographer's role is very important in determining the volume of thyroid.Radiographer is an important member of the diagnostic health care team.

Background: Emergency medicine milestones released by the Accreditation Council for Graduate Medical Education require residents to demonstrate competency in bedside ultrasound (US). The acquisition of these skills necessitates a combination of exposure to clinical pathology, hands-on US training, and feedback. Objectives: We describe a novel simulation-based educational and assessment tool designed to evaluate emergency medicine residents' competency in point-of-care echocardiography for evaluation of a hypotensive patient with chest pain using bedside US. Methods: This was a cross-sectional study conducted at an academic medical center. A simulation-based module was developed to teach and assess the use of point-of-care echocardiography in the evaluation of the hypotensive patient. The focus of this module was sonographic imaging of cardiac pathology, and this focus was incorporated in all components of the session: asynchronous learning, didactic lecture, case-based learning, and hands-on stations. Results: A total of 52 residents with varying US experience participated in this study. Questions focused on knowledge assessment demonstrated improvement across the postgraduate year (PGY) of training. Objective standardized clinical examination evaluation demonstrated improvement between PGY I and PGY III; however, it was noted that there was a small dip in hands-on scanning skills during the PGY II. Clinical diagnosis and management skills also demonstrated incremental improvement across the PGY of training. Conclusion: The 1-day, simulation-based US workshop was an effective educational and assessment tool at our institution.

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