Abstract It is know that the crystal structure and the magnetic ordering in La1-xAxMnO3(A=Ca,Sr,Ba) may disrupted by introducing various defect. This disorder weakens the Hund coupling and, thus, the double-exchange interaction between Mn3+ and Mn4+. Combining with John-Teller distortion enhanced by the defects, the magnetoresistance (MR) effect is enhanced. Up to date, the generated defects were mostly columnar defects or chemical substitution defects. In this study we generated different type of defect, point defects, and inrestigate its effect on MR effect. La0.7Sr0.3MnO3 and La0.7A0.3MnO3 films were deposit on LaAiO3 (001) and SrTiO3 (001) substrates by pulse laser deposition technique. Films were patterned with a standard photolithography. Point defects were introduced by irradiated high (1.7 and 3MeV) and low (10KeV) energy protons. We found that, the low dose sample exhibits both conductivity and the low field MR enhancement. Which were believed due to introduce acceptor level and the magnetic structure defects. When the dose was high, the structure defects leaded strong scattering effect that lowed the conductivity. The MR in high dose sample was also enhanced near by transition temperature.

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine.

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / CT abdomen and pelvis is a widely-used imaging modality used in the evaluation of appendicitis but it carries risks of radiation. A recent retrospective review localizes all appendices (both normal and abnormal) below the level of the L1 vertebral body, obviating the need to scan superior to that level. This study is a retrospective review of prospectively-collected data from 171 consecutive pediatric patients presenting with clinical suspicion of acute appendicitis and undergoing “low FOV CT.” The low FOV CT uses the L1 vertebral body as the superior aspect of the exam instead of the of the dome of the diaphragm as in standard CT.

Numerous compact NMR spectrometers have been designed for an easy measurement of proton NMR spectra. High sensitivity and resolution can be reached even with low field spectrometers (LFNMR) (i.e. 60 MHz), thanks to great improvements in electronic hardware, which open up a wide field of analytical quantification and relaxation applications. A specificity of Low field NMR spectrometer is the use of a permanent and cryogen free magnet technology, avoiding the need for weekly and expensive cryogenic services. Here we present and describe a low field NMR spectrometer fabricated in our laboratory. This spectrometer (ECBLFNMR) operates at basic resonant frequencies ranging from 1 to 60 MHz, with standard sample diameter (5-10 mm). All the embedded hardware is very compact and requires only a 24 V DC power supply, so this spectrometer is portable, easy to install and has a small footprint. This ECBFLNMR is dedicated to education and quantification, and enables low-field NMR research. It may be coupled with scientific experiments not requiring high magnetic fields.

A retrospective study was performed to determine the prevalence of foot pathologies of horses subjected to magnetic resonance imaging for foot lameness and to determine the long-term outcome of horses after medical treatment. The MR studies of 95 horses were interpreted retrospectively by a boarded certified radiologist. Follow-up information was obtained from medical records, owners and referring veterinarians via telephone questionnaires. Long term response to treatment (minimum of 12 months) was recorded. Horses were divided in two different groups based on the diagnosis and on the treatment using intrasynovial antiinflammatory drugs or not. Logistic regression analysis was performed to compare the outcome between the two groups. The null hypothesis was that the proportion of horses treated successfully between treatment protocols was similar. A diagnosis based on magnetic resonance imaging was made in all horses. Approximately 30% of horses had ≥ 4 lesions, which were determined to be responsible for the lameness and 70% of horses had navicular bone abnormalities. Treatment was determined by individual clinician judgment. No significant difference was found in the long-term outcome between treatment groups. This result suggests that intrasynovial antiinflammatory drugs may not provide additional benefit over corrective shoeing, rest followed by controlled exercise in horses with lesions of structures associated with the navicular apparatus or the distal interphalangeal joint. / Master of Science

Magnetic resonance imaging is a non-invasive imaging modality that is used to produce detailed images of soft tissues within the human body. Typically, MRI scanners used in the clinical setting are high field systems because they have a magnetic field strength greater than 1.5 Tesla. The high magnetic field offers the benefit of high spatial resolution and high SNR. However, low filed systems can also produce high resolution MR images with the added benefit of imaging stiffer samples. In this study, a low field 0.5 T MR system was used to image various samples to demonstrate the capability of the low field system in acquiring MR images with resolution comparable to high field systems. Furthermore, the MR system was modified to one capable of performing low field MR Elastography (MRE), a technique that can non-destructively measure the mechanical properties of soft samples. Agarose gel phantom of 0.5% wt. and 1.0% wt. were used to validate the MRE system. Additionally, a rat brain was used to assess the sensitivity of the MRE system in measuring the mechanical properties of small tissues. The results illustrated that the low field MR system can acquire high resolution images and provide sufficient tissue contrast (e.g through long TE times (80 ms), which is not possible with high field systems). MRE results on gel phantoms illustrated the capability of the low field system to accurately measure the mechanical properties and the MRE testing of rat brain demonstrated the potential of the system to study biological tissues. Finally, the capability of low field MRI and MRE to assess the growth of tissue engineered bone has the potential to transform the field of tissue engineering.

Este projeto teve como objetivo a construção e automatização de um espectrômetro de baixo custo que tem como principal aplicação a caracterização de meios porosos. Para realizar a caracterização de um meio poroso é necessário que o campo magnético externo aplicado não seja intenso para diminuir os problemas relacionados com a diferença de susceptibilidade magnética na interface fluido-solido. Por este motivo, foi construído um magneto resistivo de baixo campo, operando na frequência de próton de 2MHz (0.047 Tesla) e de simples design. Para manter o equipamento com custo mais baixo possível foram construídos em laboratório a fonte de alimentação do magneto, um amplificador ajustado para 2MHz e os componentes λ/4 e os softwares necessários. O software desenvolvido tem a finalidade de controlar a placa de geração e aquisição de radiofrequência que foi adquirida pela empresa Spincore, denominada RadioProcessor. Para esta finalidade optou-se pela construção de uma nova API na linguagem C++, utilizando a API original do RadioProcessor como base, de forma a montar um conjunto de funções simples e intuitivas para a utilização do espectrômetro. Além disso, foi realizada a integração de uma linguagem script à biblioteca, que dá acesso ao usuário a todas as funções básicas de programação, permitindo que um usuário com pouca habilidade de programação possa criar um programa para o controle total do equipamento de forma simples e também tornando o software maleável, sendo possível que novas funções sejam integradas. Isso abre espaço para que o equipamento possa ser utilizado para outras aplicações além das citadas anteriormente. Somada à nova biblioteca, uma interface gráfica foi desenvolvida, a qual compreende o programa de controle do equipamento e também funções para tratamento e visualização de dados, como a transformada inversa de Laplace e transformada de Fourier. / The objective of this project was the assembling and automatization of a low cost NMR spectrometer for the characterization of porous media. The study of porous media through NMR spectroscopy requires a low intensity magnetic field in order to avoid the problems related to the difference of magnetic susceptibility on the fluid-solid interface. For that reason, a low field electromagnet, operating on the proton frequency of 2MHz (0.047 Tesla) and of simple design was built. As to keep all the equipment as low cost as possible, the following components were also assembled in laboratory: the magnets power supply, a 2MHz amplifier, the quarter-wave components and the necessary softwares. The goal of the software developed was to control the RF generation and acquisition board, which was acquired from the enterprise Spincore, further named RadioProcessor. To achieve this goal, it was decided the development of a new API, in the C++ language, which uses the original boards API as a base in order to assemble a group of functions that are simpler and more intuitive to the end user. In addition, a script language was integrated to the APIs library, allowing users with little programming knowledge to write a program which controls the whole equipment in an easy way and also adding flexibility to the software, as it becomes easy to add new functions. This permits that the equipment be easily changed to include other applications in the future. Finally, a graphical interface was developed, which comprehends the equipment control software and the visualization of the data.

Nuclear magnetic resonance (NMR) is a common tool utilized in core analysis. NMR can reveal important information about pore structure, fluid configuration and wettability. However, standard NMR core analysis techniques look at the sample as a whole or only at thin slices. Two NMR pulse sequences are introduced that allow for the determination of relaxation time or diffusion-relaxation time distributions as a function of sample height. One-dimensional T 2 and D-T 2 profiles can be determined with a low-field Maran Ultra spectrometer by implementing nuclear magnetic resonance imaging techniques. Frequency encoding gradients impart spatial resolution to the measurements and allow for the creation of T, and D-T 2 profiles without having to perform multiple slice selective measurements. The first technique, denoted as RARE, relies solely on resolving transverse relaxation, T 2 , as a function of height. The second method, D-T 2 profiling, allows for the determination of both the diffusion coefficient, D, and T 2 as a function of height. The ability to resolve D in addition to T 2 allows fluids with overlapping relaxation times to be distinguished, and therefore it is not necessary to use D 2 O in order to differentiate the water signal from the oil signal. Implementation of these two methods allows for the determination of porosity and saturation profiles. Experiments were performed with a sandpack in order to demonstrate the applicability of these two techniques, and saturation profiles of a sandpack were determined at various stages of the flooding process.

Este projeto teve como objetivo a construção e automatização de um espectrômetro de baixo custo que tem como principal aplicação a caracterização de meios porosos. Para realizar a caracterização de um meio poroso é necessário que o campo magnético externo aplicado não seja intenso para diminuir os problemas relacionados com a diferença de susceptibilidade magnética na interface fluido-solido. Por este motivo, foi construído um magneto resistivo de baixo campo, operando na frequência de próton de 2MHz (0.047 Tesla) e de simples design. Para manter o equipamento com custo mais baixo possível foram construídos em laboratório a fonte de alimentação do magneto, um amplificador ajustado para 2MHz e os componentes λ/4 e os softwares necessários. O software desenvolvido tem a finalidade de controlar a placa de geração e aquisição de radiofrequência que foi adquirida pela empresa Spincore, denominada RadioProcessor. Para esta finalidade optou-se pela construção de uma nova API na linguagem C++, utilizando a API original do RadioProcessor como base, de forma a montar um conjunto de funções simples e intuitivas para a utilização do espectrômetro. Além disso, foi realizada a integração de uma linguagem script à biblioteca, que dá acesso ao usuário a todas as funções básicas de programação, permitindo que um usuário com pouca habilidade de programação possa criar um programa para o controle total do equipamento de forma simples e também tornando o software maleável, sendo possível que novas funções sejam integradas. Isso abre espaço para que o equipamento possa ser utilizado para outras aplicações além das citadas anteriormente. Somada à nova biblioteca, uma interface gráfica foi desenvolvida, a qual compreende o programa de controle do equipamento e também funções para tratamento e visualização de dados, como a transformada inversa de Laplace e transformada de Fourier. / The objective of this project was the assembling and automatization of a low cost NMR spectrometer for the characterization of porous media. The study of porous media through NMR spectroscopy requires a low intensity magnetic field in order to avoid the problems related to the difference of magnetic susceptibility on the fluid-solid interface. For that reason, a low field electromagnet, operating on the proton frequency of 2MHz (0.047 Tesla) and of simple design was built. As to keep all the equipment as low cost as possible, the following components were also assembled in laboratory: the magnets power supply, a 2MHz amplifier, the quarter-wave components and the necessary softwares. The goal of the software developed was to control the RF generation and acquisition board, which was acquired from the enterprise Spincore, further named RadioProcessor. To achieve this goal, it was decided the development of a new API, in the C++ language, which uses the original boards API as a base in order to assemble a group of functions that are simpler and more intuitive to the end user. In addition, a script language was integrated to the APIs library, allowing users with little programming knowledge to write a program which controls the whole equipment in an easy way and also adding flexibility to the software, as it becomes easy to add new functions. This permits that the equipment be easily changed to include other applications in the future. Finally, a graphical interface was developed, which comprehends the equipment control software and the visualization of the data.

Abstract This study aimed to assess the value of B-mode, nonenhanced and enhanced power Doppler ultrasonography (US), fine-needle aspiration biopsy (FNAB) and magnetic resonance (MR) imaging as adjunctive tools in breast diagnostics. The findings were compared to histology. The mammograms and US images of 84 palpable breast lesions were retrospectively reviewed, 63 of them also blindly. The cytologic reports of 57 lesions were reviewed. Eighty-one (96%) of all the 84 lesions, and 52 of the 53 cancers were visible as a local abnormality at US. The sensitivity, specificity, and overall accuracy of FNAB cytology was 92%, 83%, and 88%, respectively. There were no false negative malignancies in the three modalities combined. Sixty-five lesions not unequivocally benign at mammography were examined with B-mode, unenhanced and enhanced power Doppler US. Vascularity was also analyzed quantitatively. The sensitivity, specificity, and overall accuracy of the morphologic evaluation was 100%, 10%, and 57%, respectively. Rounded lesions were more vascular than spiculated lesions, but vascular assessment was only helpful when supporting a benign morphology. Forty breast lesions were examined with dynamic MR imaging and power Doppler US by obtaining time-signal intensity curves, which were analyzed morphologically and quantitatively. The shape of the MR curve acchieved 90% accuracy in differentiating between benign and malignant lesions. It enabled also differentiation between fibroadenomas and malignancies. The accuracy of the US curve was 38%. Quantitatively, statistically significant differences were found using all the MR variables, except between fibroadenomas and malignancies. Using the US variables, no significant difference was found. Twenty-eight patients (34 breasts) were examined by dynamic low-field and high-field MR imaging. The images were analyzed separately by two radiologists paying attention to lesion morphology and enhancement kinetics. In 27 breasts, results were compared to biopsy. Kappa statistics was used to compare the performance between the MR-scanners and readers. The sensitivity was 100% and 100%, the specificity 82% and 73%, and the accuracy 93% and 89% at low and high field, respectively. The inter-MR-scanner kappa value was 0.77 (substantial agreement), while the inter-observer kappa value was 0.86 and 0.81 at low and high field, respectively (almost perfect agreement).