Purpose: Ultrasound is prevalent in image-guided therapy as a safe, inexpensive, and widely available imaging modality. However, extensive training in interpreting ultrasound images is essential for successful procedures. An open-source ultrasound image simulator was developed to facilitate the training of ultrasound-guided spinal intervention procedures, thereby eliminating the need for an ultrasound machine from the phantom-based training environment. Methods: Anatomical structures and surgical tools are converted to surface meshes for data compression. Anatomical data is converted from segmented volumetric images, while the geometry of surgical tools is available as a surface mesh. The pose of the objects are either constants or live measurements from a pose tracking device. Intersection points between the surface models and the ultrasound scan lines are determined with a binary space partitioning tree. The scan lines are divided into segments and filled with grey values determined by an intensity calculation accounting for material properties, reflection, and attenuation parameters defined in a configuration file. The scan lines are then converted to a regular brightness-mode ultrasound image. Results: The simulator was tested in a tracked ultrasound imaging system, with a mock transducer tracked by an Ascension TrakStar electromagnetic tracker, on a spine phantom. A mesh model of the spine was created from CT. The simulated ultrasound images were generated at a speed of 50 frames per second, and a resolution of 820 x 616 pixels on a PC with a 3.4 GHz processor. A human subject trial was conducted to compare the learning performance of novice trainees with real and simulated ultrasound in the localization of the facet joints of a spine phantom. With 22 participants split into two equal groups and each participant localizing 6 facet joints, there was no statistical difference in the performance of the two groups, indicating that simulated ultrasound could indeed replace the real ultrasound in phantom-based ultrasonography training for spinal interventions. Conclusion: The ultrasound simulator was implemented and integrated into the open-source Public Library for Ultrasound (www.plustoolkit.org) and SlicerIGT (www.SlicerIGT.org) toolkits / Thesis (Master, Computing) -- Queen's University, 2013-07-24 12:28:57.201

Investigations into the safety of diagnostic ultrasound and mechanisms of therapeutic ultrasound have provided evidence of a number of cellular responses to ultrasound. These studies have mainly concentrated on cells in culture, while work on intact tissue employed mainly kHz ultrasound fields, although diagnostic and many therapeutic procedures are performed using MHz ultrasound. Vascular tissue is known to respond to a variety of physical and chemical signals, and so arteries were used as a model system in this thesis to study the effects of MHz ultrasound in vitro. Rings of equine carotid and lateral cecal mesenteric artery exhibited reversible, repeatable contraction on exposure to both pulsed and continuous wave 3.2 MHz ultrasound at acoustic powers up to 145 mW. Wall stress increased by up to 1.5% in carotid arteries and up to 2% in mesenteric arteries during exposure, and returned to basal levels after approximately 10 minutes. Contraction was endothelium independent, and was not affected by changes in the pulsing regime. The magnitude of contraction was dependent on the acoustic power, and the change in wall stress increased with increasing acoustic power in a linear fashion. The acoustic power dependence suggested the response was thermally mediated and this was confirmed by investigation of the response of arteries to non ultrasound generated heating, which also induced contraction. The effects of ultrasound and heating were also investigated in 1st order branches of the lateral cecal artery, as a model of a small artery. No response was observed in either case. In order to determine the cellular basis of the response of carotid and mesenteric arteries, the involvement of potassium ion channels in the response was investigated using a potassium channel blocker. The response of arteries to ultrasound was increased by inhibition of inward-rectifier potassium channels, which would otherwise help to return the cell membrane potential to the normal level. The change in wall stress was increased by 42% on average, confirming the involvement of these channels in the response. Contraction of arteries is mediated by an increase in intracellular calcium. The ion channel activity during non ultrasound generated heating was examined further by observation of intracellular calcium concentration using a fluorescent calcium sensitive dye. Increases in intracellular calcium were observed in carotid and large mesenteric arteries, which confirmed the thermal influence on ion channel function in these vessels. No such effect was observed in the smaller vessels.

No description available.

Diante das vantagens do uso do ultra-som na confecção de cavidades retrógradas, o presente estudo avaliou pontas lisas, diamantadas e despolidas quanto ao tempo usado para confecção das cavidades, presença de sujidade e infiltração do corante rodamina a 0,2%. Após os tratamentos endodônticos e apicectomias dos trinta e quatro dentes uniradiculares estudados, estes foram divididos em três grupos de 10; de acordo com a ponta usada para o retropreparo. A confecção das cavidades retrógradas consistiu de duas fases: fase 1 (a ponta de ultra-som deveria atingir 3mm de profundidade, não visualização de sujidade a “olho nu", preparo com características de classe I), e fase 2 (uso da ponta de ultra -som correspondente a cada grupo por mais 40 segundos). Ao final de cada fase, os espécimes foram avaliados sob microscópio óptico com aumento de 20X e fotografados. Quatro examinadores analisaram a presença de sujidade nas superfícies retropreparadas. O tempo gasto para a confecção da fase 1 foi anotado. Em seguida, todos os espécimes submeteram-se a retrobturação com MTA. Passado período de 72 horas, foram imersos em solução de rodamina a 0,2% e clivados após 24 horas. A hemi-parte que continha maior infiltração de cada espécime, foi a considerada. Os resultados mostraram que as pontas despolidas necessitam de menos tempo para confecção de cavidades retrógradas. Após mais 40 segundos de preparo (fase 2), houve diminuição na quantidade de sujidade, em todos os grupos, não havendo diferença estatística significante entre os grupos. Em relação a infiltração do corante rodamina a 0,2%, os resultados mostraram não haver diferença estatística significante, quando da comparação entre os preparos confeccionados por pontas lisas, diamantadas e despolidas e retrobturados pelo MTA. Concluímos, portanto, que o tipo de ponta de ultra-som influencia no tempo de preparo, apesar de não exercer influência na infiltração do MTA. Vale ressaltar que a presença de sujidade é intensamente minimizada quando da complementação dos preparos por mais 40 segundos. / Given the advantages of the use of ultrasound in the preparation of retrograde cavities, the present study evaluated the smooth, diamond -coated and use of no polished tips regarding the time required for the preparation of cavities, the presence of dirt and the penetration of the 0,2% rhodamine dye solution. After the apicectomy and endodontic treatment of the thirty-four single -rooted teeth studied, we divided them into 3 groups of 10 according to the tip used in the rootend preparation. Four roots were used as positive and negative controls. The preparation of the retrograde cavities consisted of two phases: phase 1 (the ultrasound tip should reach 3mm of depth; dirt should not be spotted by the naked eye; preparation with class I characteristics), and phase 2 (use of the ultrasound tip corresponding to each group for more than 40 seconds). At the end of each phase, the specimens were evaluated under an optical microscope that enhanced them 20X, and were then photographed. Four examiners analyzed the presence of dirt in the root-end preparation surfaces. The time spent in phase 1 was recorded. All the specimens were then root-end filling with MTA. After 72 hours, they were submerged in a 0,2% rhodamine solution and cleaved after 24 hours. We then analyzed the hemi-part that contained the highest penetration. The results showed that the no polished tips require shorter time in the preparation of retrograde cavities. After over 40 seconds of preparation (phase 2), there was a reduction in the amount of dirt in all the groups studied, with no signify cant differences between the groups. As regards the penetration of the rhodamine dye at 0,2%, the results did not show statistically significant differences as regards preparations with smooth, diamondcoated and no polished tips, and root-end filling with MTA. Therefore , we concluded that the type of ultrasound tip influences the preparation time, even though it has no influence on the penetration of MTA. It is important to stress that the presence of dirt is highly minimized when the preparation is complemented by 40 more seconds.

Drinking water sources are vulnerable to a broad range of contaminant threats. Recent U.S. legislation has focused on protecting public health from pathogens while also managing disinfection byproducts (DBPs) and organic contaminants. Chlorine is known to react with organic matter to form DBPs, thus alternative disinfection schemes are desirable. The goal of our research was to evaluate synergistic inactivation of E. coli with chlorine and sonication in a flow through system. Laboratory experiments were conducted to determine the impact of chlorine dose (0 to 1 mg/L), cavitation intensity (90 to 150 watts) and contact time (0 to 16 minutes) on inactivation. Tests were conducted with a probe system and a flow through cavitation device. Results showed that sonication alone was ineffective for the conditions tested. Sonication applied simultaneously with chlorine did not improve inactivation compared to each disinfectant alone.

This thesis presents an experimental study of a bovine vertebra using transmission and pulse-echo methods and a preliminary investigation to guide a screw insertion into a pedicle using TomoScan phased array unit. The results show the cancellous bone has higher attenuation than the cortical bone for 1.0-5.0 MHz. The optimal frequencies for imaging are found to be 3.5 and 5.0 MHz. When the sample is filled with water with the cancellous core removed, all reflections from the layers and screw are visible; however when the core is present, only reflections from the top cortex are identifiable. For the preliminary study, size and placement of the transducer array are important. When the ultrasound beam is normal to the pedicle surface, echoes from the pedicle layers and the steel bit are strong; otherwise, signals are weak and not even identifiable. Larger aperture size will enhance the signal-to-noise ratio but deteriorate lateral resolution.

The goal of this research is to improve an extractive metallurgy process based on solvent extraction. This process should fit the exploitation of small local copper-rich deposits. In these conditions, the plant has to be as compact as possible in order to be easily transported from one location to a subsequent one. Improved extraction kinetics could ensure a high throughput of the plant despite its compactness. In addition, the extraction reagent should not be damaging for the environnement. On this basis, we propose to use ultrasound-assisted solvent extraction. The main idea is to increase the extraction kinetics by forming an emulsion in place of a dispersion thanks to the intense cavitation produced by ultrasound. The benefit of this method is to improve the copper extraction kinetics by increasing the interfacial surface area and decreasing the width of the diffusion layer. We studied the implementation of an highly branched decanoic acid (known as Versatic- 10®acid) as a copper extraction reagent dispersed in kerosene. Emulsification is monitored through the Sauter diameter of the organic phase droplets in aqueous phase. This diameter is measured during pulsed and continuous ultrasound irradiation via a static light scattering technique. The phenomenon of emulsification of our system by ultrasound is effective, and the emulsification process carried out in the pulsed ultrasound mode is at least as efficient as the emulsification obtained under continuous mode. No improvement of emulsification is observed beyond a threshold time of the ultrasound impulse. This may be attributed to a competition between disruption and coalescence. The use of mechanical stirring combined with pulsed ultrasound allows to control the droplet size distribution. In presence of ultrasound, the extraction kinetics of Versatic-10 acid is multiplied by a factor ten, and therefore reached a value similar to the kinetics observed without ultrasound with an industrial extractant such as LIX-860I®(Cognis). Extraction kinetics measurements are carried out by monitoring the copper ion concentration in the aqueous phase with an electrochemical cell. We conclude that ultrasound-assisted emulsification can be implemented under certain conditions. Emulsification is a first step, and the following destabilization step has to be studied. The device using ultrasound-assisted emulsification should be followed by an efficient settling-coalescing device. A possible solution would be to promote emulsion destabilization by increasing the ionic strength with an addition of MgSO4, a salt that is not extracted by the extraction reagent in the considered range of pH.

Diagnostic ultrasound is a non-invasive image modality commonly used to diagnose multiple diseases. Sonographers and physicians have to devote a substantial amount of time learning how the combination of the various parameters of the ultrasound system affects the resulting ultrasound information among its different modalities. The primary objective of this thesis is to create a mechanistic ultrasound simulation method that could achieve near real-time performance to teach and train sonographers and physicians. A major bottleneck for achieving real-time performance with available tools was the transducer field simulation method that uses the impulse response technique. To address this problem a new simulation approach was developed. This project was realized in a three-phase approach, specifically to simulate spectral Doppler. In first place, it was shown that is possible to mechanistically simulate the sample volume power distribution using a novel method based on an array of point sources to represent the transducer geometry. Secondly, by comparison with the Field II results, it was demonstrated that the time-domain signal could be closely reproduced using point sources. Finally, by treating the array of point sources as point receivers, the received signal was compared with the results from Field II, and again, good agreement was achieved. Simulation results were compared against the standard simulation method for a number of examples involving steady and pulsatile flow, for which the spectrograms were compared against Field II. Also presented are preliminary results obtained using the point source approach to simulate B-mode images. As well, methods are described for generating Doppler spectrograms from the results of computation fluid dynamics velocity fields obtained in realistic arterial geometrical models. It is pointed out that the successful simulation of the time domain signal opens the possibility for real-time simulation of other ultrasound modes.

A prototype acoustic streaming pump for microfluidic applications was developed. A novel integration scheme was devised based on the acoustic reflector concept. Numerical simulations were conducted to predict the flow patterns around the transducer. Ultrasound transducers using P(VDF-TrFE) as the piezoelectric element were fabricated using lithography-based microfabrication technology. Silicon channels were fabricated using anisotropic etching. A heat-press bonding technique was adopted to bond the transducers with the silicon chips using CYTOP fluoropolymer as the adhesive. The piezoelectric transducers were characterized to have a resonance frequency of 82 MHz. Micro-PIV experiments were performed in the near and far-fields of the ultrasonic transducer/pump. The near field experiments showed complex flow patterns that could enhance mixing. Estimates of the pumping pressure were obtained using transient flow velocities in the far-field. Conservative estimates indicate the total back pressure the micropump can pump against is 39 Pa. Future research directions were suggested.

Cleft lip and/or palate is a craniofacial condition that can lead to complex speech disorders. In particular, the auditory-perceptual speech assessments of individuals with cleft palate can be difficult because cleft-type compensatory articulations may be outside of English phonology. Therefore, it is desirable to supplement auditory-perceptual assessments with instrumental measurements. In the first study, thirteen participants with cleft-type compensatory articulations completed ultrasound speech exams. The stimuli were repeated VCV combinations (target consonants: [t], [k], [s], [sh], [n], [ng]; vowel contexts: [a], [i], [u]). Ultrasound imaging confirmed auditory-perceptual impressions and revealed covert articulatory movements. In the second study, six participants were assessed after a course of speech therapy. Outcomes were recorded on a severity metric with categories describing auditory-perceptual and motor aspects of speech errors. The severity metric quantified the incremental changes in both dimensions. Based on the research presented, further investigations of cleft palate speech using ultrasound are warranted.