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High Intensity Focused Ultrasound (HIFU) is a promising technique for the treatment of localized cancers. The ability to focus ultrasound precisely on a predetermined volume allows the possibility of selective tissue destruction at this position without damage to surrounding tissues. However, many difficulties remain in the treatment of deep-seated tumors. In this thesis, new therapeutic and monitoring techniques are proposed to address these problems, by using phased arrays of ultrasound transducers. Two monitoring techniques based on the detection of the displacements of the ultrasonic speckle are developed, and allowed us to image the changes in the temperature and the shear modulus during HIFU therapy. In-vitro ultrasound-guided experiments are performed. Secondly, the problem of organs motion during the treatment is addressed. A method for real-time tracking the 3D motion of tissues is combined with a 2D High Intensity Focused Ultrasound multi-channel system in order to correct the respiratory motion during HIFU therapies. In the last section of this thesis, a high power ultrasonic system is developed for transcranial HIFU brain therapy. The skulls aberrations are corrected using a time reversal mirror thanks to an implanted hydrophone. In-vivo experiments are conducted on 22 sheep with minimally invasive surgery. Finally, a non-invasive protocol based on CT scans of the entire skull is developed and allows the prediction of the skulls aberrations and the skull overheating.

A longitudinal pilot study to compare, in children with reduced overbite malocclusions associated with oral habits (finger-sucking and tongue-thrusting), the effects of the experimental Myofunctional Trainer (MFT; Myofunctional Research Co.) and the conventional Bluegrass appliance (BG) on dento-alveolar relations, tongue position, and on speech. Methods: The experimental group received the MFT appliance while the control group received the BG appliance. Dento-alveolar changes were assessed by cephalometry and study models. Longitudinal midsagittal 2-dimensional B-mode ultrasound scans of the tongue surface were performed to determine tongue position. Speech acceptability tests were also performed. Results & Conclusions: The BG appliance was successful in breaking the finger-sucking habit. The MFT appliance showed only partial success which could be attributed to lack of compliance. At the end of treatment, the open bite was reduced in both groups due to dento-alveolar changes. The BG appliance had a deleterious effect on speech acceptability while in place, while there was no such effect with the MFT appliance.

A longitudinal pilot study to compare, in children with reduced overbite malocclusions associated with oral habits (finger-sucking and tongue-thrusting), the effects of the experimental Myofunctional Trainer (MFT; Myofunctional Research Co.) and the conventional Bluegrass appliance (BG) on dento-alveolar relations, tongue position, and on speech. Methods: The experimental group received the MFT appliance while the control group received the BG appliance. Dento-alveolar changes were assessed by cephalometry and study models. Longitudinal midsagittal 2-dimensional B-mode ultrasound scans of the tongue surface were performed to determine tongue position. Speech acceptability tests were also performed. Results & Conclusions: The BG appliance was successful in breaking the finger-sucking habit. The MFT appliance showed only partial success which could be attributed to lack of compliance. At the end of treatment, the open bite was reduced in both groups due to dento-alveolar changes. The BG appliance had a deleterious effect on speech acceptability while in place, while there was no such effect with the MFT appliance.

Šio darbo tikslas – optimizuoti KTU Ultragarso Instituto sukurta ultragarsinės vizualizacijos sistemos modelį. Tam tikslui pasiekti, buvo išanalizuota ultragarsinių vizualizacijos sistemų bei ultragarsinių signalų sklidimo bendri principai bei buvo atlikta modelio naudojamų resursų analizė, kuri parodė, kad buvo neracionaliai išnaudojama operatyvioji atmintis, ko pasiekoje buvo naudojama virtualioji atmintis vietoje operatyviosios. Padarytos programos modelio modifikacijos ne tik pagreitino programos veikimo laiką, bet ir praplėtė skaičiavimo tikslumą iki teorinės begalybės. Skaidymo žingsnio ir modeliavimo tikslumo analizė parodė grafinę priklausomybę, kurios pagalba galima nesunkiai numatyti skaičiavimo laiką norimam tikslumui gauti. / The purpose of that work is to optimize KTU Ultrasonic Institute made supersonic visualization system. On that purpose the main principles of ultrasonic visualization systems and ultrasonic signals propagation were analyzed and the research of the used resources was made. This researched show that the program was using the memory irrationally, that caused usage of the virtual memory instead of Random Access Memory (RAM) which is much slower. Program modification caused increase of the program performance and extended the accuracy of the calculation to the theorycal infinity. The sampling point’s and modeling accuracy’s analysis showed graphical dependence how would it change with the bigger sampling point.

Contrast enhanced ultrasound offers a unique method to measure the blood flow, perfusion, vascular volume and morphology of microvascular networks. This is achieved by exploiting the ability of microbubble contrast agents to be disrupted and preferentially detected with contrast specific imaging techniques – using a method known as disruption-replenishment. In its current form, disruption-replenishment suffers from poor reproducibility and accuracy, largely due to the inappropriate application of a mono-exponential model of microbubble replenishment, and an incomplete understanding of the dependencies of the measurement. In this thesis, we hypothesize that disruption-replenishment measurements can be improved by applying a perfusion model that considers the physical elements of the measurement, including the haemodynamics and morphology of the vascular system, the ultrasound field distribution and microbubble properties. We present a flexible, theoretical framework to model microbubble replenishment within the microvasculature. The replenishment model is further developed by in vitro and in vivo validation, and clinical translation in a trial of anti-angiogenic therapy in patients, resulting in a proposed clinical protocol. The presented formalism was shown to be more robust and demonstrated better agreement of both fitting quality and estimates of flow velocity when compared to the established model (accuracy to within 3-9%). The reproducibility of repeated in vivo disruption-replenishment flow measurements was 11.9% using the proposed perfusion model compared to 24% using the established model. Variability of clinical perfusion measurements was also reduced with a method that discards the contribution of flow from larger arteries. Excluding the large vessel component in clinical measurements of tumour blood volume decreased the inter-plane variability by up to 20%. The proposed perfusion model can be used to generate parametric maps of vascularity through which additional quantitative parameters become available. These improvements will help translate the method of disruption-replenishment into routine clinical practice and clinical trials.

Contrast enhanced ultrasound offers a unique method to measure the blood flow, perfusion, vascular volume and morphology of microvascular networks. This is achieved by exploiting the ability of microbubble contrast agents to be disrupted and preferentially detected with contrast specific imaging techniques – using a method known as disruption-replenishment. In its current form, disruption-replenishment suffers from poor reproducibility and accuracy, largely due to the inappropriate application of a mono-exponential model of microbubble replenishment, and an incomplete understanding of the dependencies of the measurement. In this thesis, we hypothesize that disruption-replenishment measurements can be improved by applying a perfusion model that considers the physical elements of the measurement, including the haemodynamics and morphology of the vascular system, the ultrasound field distribution and microbubble properties. We present a flexible, theoretical framework to model microbubble replenishment within the microvasculature. The replenishment model is further developed by in vitro and in vivo validation, and clinical translation in a trial of anti-angiogenic therapy in patients, resulting in a proposed clinical protocol. The presented formalism was shown to be more robust and demonstrated better agreement of both fitting quality and estimates of flow velocity when compared to the established model (accuracy to within 3-9%). The reproducibility of repeated in vivo disruption-replenishment flow measurements was 11.9% using the proposed perfusion model compared to 24% using the established model. Variability of clinical perfusion measurements was also reduced with a method that discards the contribution of flow from larger arteries. Excluding the large vessel component in clinical measurements of tumour blood volume decreased the inter-plane variability by up to 20%. The proposed perfusion model can be used to generate parametric maps of vascularity through which additional quantitative parameters become available. These improvements will help translate the method of disruption-replenishment into routine clinical practice and clinical trials.

Thesis (Ph.D.)--Drexel University, 2007. / Includes abstract and vita. Includes bibliographical references (leaves 70-74).