published_or_final_version / Computer Science / Doctoral / Doctor of Philosophy

This dissertation presents the characterization and evaluation of a new radiological imaging modality, Toshiba Computed Radiography (TCR) 201. The characteristics of the TCR storage phosphor imaging plates such as energy-dependent x-ray quantum efficiency, stored signal decay, low exposure rate signal build-up, and spontaneous and stimulated gain measures are presented. The TCR 201 system is characterized by the signal transfer curve, the total root-mean-squared (rms) output noise, the signal-to-noise ratio, the modulation transfer function (MTF), its noise power spectrum (NPS), and the detective quantum efficiency (DQE). The system rms noise is photon-limited for exposures less than 1.0 mR, but has contributions from phosphor structure and quantization noise for exposures higher than 1.0 mR. The phosphor's information factor is shown to explain deviations from ideal photon-limited noise for exposures of less than 1.0 mR. The MTF of the system is measured for standard imaging plates, 10% at 2.8 lp/mm, and for high resolution imaging plates, 10% at 4.4 lp/mm. An expression for the NPS is statistically derived, and experimental measurements confirm the expression and show an increase in uncorrelated noise power above 1.0 mR which is consistent with rms measurements. Expressions for the DQE are presented. A psychophysical study is performed to directly compare the TCR to film/screen combinations in imaging low-contrast objects. The results of this study show the TCR provides better images for detectability as a function of exposure. Also, the use of the TCR 201 as a two dimensional dosimeter and in single-shot dual energy subtraction is presented.

University of Macau / Faculty of Health Sciences

Medical imaging informatics is one of the important research areas in radiology that studies how information available on medical images is retrieved, analyzed, and enhanced. Recent development in medical imaging informatics has resulted in improvement of diagnostic accuracy based on imaging examinations, as well as efficiency in clinical workflow. Computer aided diagnosis (CAD) and electronic patient record system (ePR) are both topics in medical imaging informatics that have matured from research concepts into commercially available computerized systems in clinical environment. The current challenges are to further broaden their scope of applications. In this thesis project, I developed a CAD system for interpreting PET/CT examinations and an ePR system for patient data integration in neurosurgery suites. Specifically, the CAD system in this project was designed to automatically diagnose nasopharyngeal carcinoma (NPC) on Positron emission tomography/computed tomography (PET/CT) examinations, which aimed to detect and classify both the primary NPC and its nodal metastasis. The regions of interests (ROIs) were segmented from the PET images and registered onto the CT in order to combine the imaging features from both modalities and the a priori anatomical knowledge of the suspicious lesion. These combined features were then classified by a support vector machine (SVM) to generate the final diagnosis result. The system was validated with 25 PET/CT examinations from 10 patients suffering from NPC, and the result produced by the system was compared to the gold standard of lesions manually contoured by experienced radiologists. The results confirmed that the system successfully distinguished all 53 genuine lesions from the mimickers due to normal physiological uptake and artifacts that also produced potentially confusing signals. The second part of the project involved development of an electronic patient record system (ePR) that integrated all the myriad of images and different types of clinical information before, during, and after neurosurgery operations, in order to enhance efficiency of work flow in this unique clinical environment. The system comprises of pre-, intra-, and post-operation modules which correspond to the different stages of the neurosurgery. The pre-op module was developed to store and categorize all images and data before the procedure to assist the surgeons in planning operation. The intra-op module integrates all the input signals, waveforms, images and videos that are produced by different imaging and physiological monitoring devices in the operation room during the surgery, and displays all the relevant information in a single large screen in real time to ease monitoring of the procedure. The post-op module helps surgeons to review all the data acquired from all the prior stages for follow-up of the treatment outcome. One-tumor case was utilized to test the pre-op module, and the signals and waveforms simulators were used to evaluate the performance of the intra-op module. In summary, two different medical informatics systems, a CAD and an ePR system were developed. Both showed promising results in laboratory tests. Future work would involve performance enhancement and feedback of the systems, and ultimately evaluation of these systems in the clinical environment. / published_or_final_version / Diagnostic Radiology / Master / Master of Philosophy

Electrical parameter profiles of human breast images can be used to simulate and analyze the anticipated effects on tissue from its interaction with electromagnetic fields involved in the cancer treatment exposure. In part, the success of this approach depends on the accuracy and precision in identifying the different tissue types. In this work, we propose two methods of segmenting human breast images with malignant tumors. The first method of algorithmic partitioning of the image involves manual color-edge contouring of the tissues using a cursor and subsequent identification of the tissue types. For the second method, MRI T1 values and thresholds are used to perform segmentation and we investigate the potential of incorporating edge detection. The first method is effective, while the second lacks precision, but eliminates the need of manual contouring. The images are imported as BMP files into SEMCAD, an electromagnetic simulation tool based on finite-difference time-domain method, which recognizes the grouped tissues and creates a model of the image. The model allows the user to easily assign electrical parameter values to the grouped tissues, according to the measured values reported in the literature.

Orientador: José Ricardo de Arruda Miranda / Banca: José Roberto Saglieti / Banca: Eder Rezende Moraes / Resumo: A medicina nuclear é uma especialidade médica que se ocupa de técnicas de imagem para observar o estado fisiológico dos tecidos ou órgãos de forma não invasiva, através da marcação de moléculas participantes desses processos, com isótopos radioativos, originando assim os chamados radionuclídeos. O SPECT é um equipamento que se utiliza de imagens planares, obtidas de vários ângulos ao redor do objeto de interesse, e, através de algoritmos computacionais, obtêm uma imagem tomográfica dessas projeções. Sua origem remete há aproximadamente cinquenta anos atrás, com criação da Câmara Anger (Hall Anger, 1964). Durante todo esse tempo, embora tenha havido alguma evolução, a estrutura dessas gama câmaras praticamente ficou Inalterada. Os constantes avanços em pesquisas empregando cristais semicondutores nos exames cintilográficos, bem como a necessidade do surgimento de novos sistemas detectores, compactos, com maior poder de resolução e alta sensibilidade conjugados a crescente preocupação mundial com a minimização das doses de radiação ionizante utilizadas nos exames diagnósticos e terapias, impulsionou o desenvolvimento de novos sistemas detectores. Recentemente, duas Grandes Empresas lançaram comercialmente novos sistemas de detecção para aquisições tomográficas em medicina nuclear, utilizando detectores do estado sólido, mais especificamente cristais de telureto de cádmio e zinco (CZT). Algumas vantagens desse tipo de detector são a melhora sensível da relação sinal/ruído, o aumento da resolução espectral e espacial, o que em suma, resultam numa maior nitidez das imagens obtidas. O emprego desses detectores abre novas perspectivas para os protocolos de imagem. Entretanto, devido a inúmeros fatores, os equipamentos ditos CZT estão focados na área cardiológica, e devido a características próprias requerem a reformulação dos protocolos de aquisição de imagem além daqueles destinados ao ... / Abstract: Nuclear medicine is a medical specialty that deals with imaging techniques to observe the physiological status of the tissues or organs noninvasively, by dialing molecules participating in this process, with radioactive isotopes, thus giving the so-called radionuclides. The SPECT is a device that uses planar images, taken from different angles around the object of interest, and, through computer algorithms, obtains a tomographic image of those projections. Its origin refers for nearly fifty years ago, with the creation of the Chamber Anger (Anger Hall, 1964). Throughout this time, although there has been some evolution, the structure of these gamma cameras was virtually unchanged. The constant advances in research employing semiconductor crystals in scintigraphic examinations, as well as the need for the creation of new detectors systems, compacts, higher resolution and high sensitivity; combined with growing worldwide concern with minimization of doses of ionizing radiation used in diagnostic tests and therapies, spurred the development of new detector systems. Recently, two large companies launched commercially new detection systems for nuclear medicine tomographic acquisitions, using solid-state detectors, specifically crystals of zinc and cadmium telluride (CZT). Some advantages of this type of detector are sensitive improvement of signal / noise ratio, increased spectral and spatial resolution, which in short, resulting in greater clarity of the images obtained. The use of these detectors opens news perspectives for imaging protocols. However, due to numerous factors, equipment said CZT are focused on cardiology area, and due to the inherent characteristics, require reformulation of image acquisition protocols beyond those intended for Quality Control / Mestre

Orientador: Maria Jaqueline Mamprim / Banca: Cláudia Valéria Suellner / Banca: Maria Lucia Gomes Lourenço / Banca: Ricardo Coelho Lehmkuhl / Banca: Ana Carolina Brandão de Campos Fonseca Pinto / Resumo: Colonoscopia virtual é uma nova modalidade de imagem que permite a reconstrução tridimensional (3D) da superfície endoluminal do cólon, com imagens semelhantes àquelas conseguidas na colonoscopia endoscópica. A técnica é utilizada na detecção de lesões tumorais colorretais de seres humanos. O objetivo do estudo foi de avaliar a viabilidade da colonoscopia virtual em cães e descrever as imagens obtidas. Foram utilizados 10 cães adultos, sem raça definida e que não possuíam sinais clínicos ou histórico de doenças gastrointestinais. Os arquivos DICOM (Comunicação de imagens digital em medicina) gerados pelo tomógrafo foram reconstruídos em imagens de colonoscopia virtual no software Voxar 3D. Nas imagens da colonoscopia virtual nos cães, visibilizou-se a estrutura tubular com vários anéis dispostos ao longo do campo de visão e a parede do cólon lisa e regular. Conclui-se que a colonoscopia virtual pode ser realizada em cães e mostrou-se uma alternativa viável para o diagnóstico das doenças colônicas decorrentes de deslocamentos / Abstract: Virtual colonoscopy is a new imaging modality that allows reconstruction of three-dimensional (3D) endoluminal surface of the colon, with images similar to those achieved in endoscopic colonoscopy. The technique is used in the detection of colorectal tumors in human beings. The aim of the study was to evaluate the feasibility of virtual colonoscopy in dogs and describe the obtained images. We used 10 adult mongrel dogs, which had no clinical signs or history of gastrointestinal diseases. The DICOM (Digital Imaging and Communications in Medicine) files generated by the CT images were reconstructed in virtual colonoscopy in Voxar 3D software. In the virtual colonoscopy images in dogs the tubular structure with several rings arranged along the field of view could be seen, and the colon wall smooth and regular. We concluded that virtual colonoscopy can be performed in dogs and proved to be a viable alternative for the diagnosis of colonic diseases caused by dislocations / Doutor

Made available in DSpace on 2014-08-13T14:50:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-07-01Bitstream added on 2014-08-13T18:01:36Z : No. of bitstreams: 1 000742391_20180701.pdf: 218298 bytes, checksum: c4913ebe2a6e42eeff7473eef5f9c436 (MD5) Bitstreams deleted on 2018-07-02T17:58:06Z: 000742391_20180701.pdf,. Added 1 bitstream(s) on 2018-07-02T17:58:58Z : No. of bitstreams: 1 000742391.pdf: 851690 bytes, checksum: e154e1e4762d25c0d409a7afaccd3e96 (MD5) Bitstreams deleted on 2018-07-02T19:54:16Z: 000742391.pdf,. Added 1 bitstream(s) on 2018-07-02T19:55:07Z : No. of bitstreams: 1 000742391.pdf: 851690 bytes, checksum: e154e1e4762d25c0d409a7afaccd3e96 (MD5) / Colonoscopia virtual é uma nova modalidade de imagem que permite a reconstrução tridimensional (3D) da superfície endoluminal do cólon, com imagens semelhantes àquelas conseguidas na colonoscopia endoscópica. A técnica é utilizada na detecção de lesões tumorais colorretais de seres humanos. O objetivo do estudo foi de avaliar a viabilidade da colonoscopia virtual em cães e descrever as imagens obtidas. Foram utilizados 10 cães adultos, sem raça definida e que não possuíam sinais clínicos ou histórico de doenças gastrointestinais. Os arquivos DICOM (Comunicação de imagens digital em medicina) gerados pelo tomógrafo foram reconstruídos em imagens de colonoscopia virtual no software Voxar 3D. Nas imagens da colonoscopia virtual nos cães, visibilizou-se a estrutura tubular com vários anéis dispostos ao longo do campo de visão e a parede do cólon lisa e regular. Conclui-se que a colonoscopia virtual pode ser realizada em cães e mostrou-se uma alternativa viável para o diagnóstico das doenças colônicas decorrentes de deslocamentos / Virtual colonoscopy is a new imaging modality that allows reconstruction of three-dimensional (3D) endoluminal surface of the colon, with images similar to those achieved in endoscopic colonoscopy. The technique is used in the detection of colorectal tumors in human beings. The aim of the study was to evaluate the feasibility of virtual colonoscopy in dogs and describe the obtained images. We used 10 adult mongrel dogs, which had no clinical signs or history of gastrointestinal diseases. The DICOM (Digital Imaging and Communications in Medicine) files generated by the CT images were reconstructed in virtual colonoscopy in Voxar 3D software. In the virtual colonoscopy images in dogs the tubular structure with several rings arranged along the field of view could be seen, and the colon wall smooth and regular. We concluded that virtual colonoscopy can be performed in dogs and proved to be a viable alternative for the diagnosis of colonic diseases caused by dislocations

Made available in DSpace on 2014-08-13T14:50:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-28Bitstream added on 2014-08-13T17:59:54Z : No. of bitstreams: 1 000769600.pdf: 1575517 bytes, checksum: 984a7c3b764225da6366789021db60c8 (MD5) / A Radiologia Computadorizada (CR – do inglês Computed Radiology) tem sido amplamente utilizada para auxiliar o diagnóstico médico em hospitais e clínicas em todo o mundo. Entretanto a rotina clínica comumente utiliza cartas de técnicas empregadas em sistemas tela-filme na aquisição de imagens em sistemas de detecção CR. As normativas internacionais já estabeleceram parâmetros de testes de controle de qualidade em CR. Entretanto as normativas nacionais trabalham para essa construção. Estudos recentes apontam métodos de otimização de imagens em sistema de detecção CR para exames de crânio, pelve e tórax para pacientes adulto e padrão sem se reportarem a exames de mão. Muitas doenças que acometem as mãos hoje em dia utilizam o exame de raios X como exame auxiliar para diagnóstico. Vale salientar que a técnica utilizada deve fornecer imagens com o máximo de informações possíveis para um diagnóstico seguro, com a menor dose ao paciente, e com redução de custos para a instituição onde os exames são realizados. Neste estudo um fantoma homogêneo de mão foi desenvolvido para ser utilizado no processo de otimização de imagens de mão utilizando sistema CR. Nesse procedimento foram quantificadas as espessuras de distintos tecidos que constituem um fantoma antropomórfico de mão a partir de exames de tomografia computadorizada. O mesmo procedimento foi adotado para 30 exames retrospectivos de pacientes do Hospital das Clínicas da Faculdade de Medicina de Botucatu- UNESP (HCFMB-UNESP). Os resultados obtidos apresentaram concordância entre as espessuras de tecidos que constituem o fantoma antropomórfico e a amostragem de pacientes avaliados, apresentando variações entre 12,63% e 6,48% para tecidos moles e ósseos, respectivamente. O fantoma homogêneo foi utilizado no processo de calibração do feixe de raios X, produzindo técnicas testes. Essas técnicas foram aplicadas em um fantoma antropomórfico de ... / Computed Radiology (CR) has been widely used to assist medical diagnosis in hospitals and clinics worldwide. However clinical routine commonly use charts of techniques used in screen-film systems to obtain images in the detection CR systems. The international standards already established parameters of quality control tests in CR. However the national normative work for this construction. Recent studies suggest methods for optimizing images on CR systems for skull, pelvis and thorax exams for adult standard patients without reporting the exams of hand. Many diseases affecting hands today use the X-ray examination as an aid to diagnosis. It is noteworthy that the technique should provide images with maximum possible information for a safety diagnosis, with the lowest dose to the patient, and cost savings to the institution where the exams are performed. In this study a homogeneous phantom hand was developed to be used in the optimization of hand images using CR system. In this procedure were quantified thicknesses of different tissues that constitute an anthropomorphic phantom hand from CT scans. The same procedure was adopted for retrospective examinations of 30 patients of the Hospital das Clinicas, of School Medicine of Botucatu, UNESP (HCFMB-UNESP). The results showed agreement between the thicknesses of tissues that constitute the anthropomorphic phantom and sampling of patients, presenting variations between 12.63% and 6.48% for soft tissue and bone, respectively. The homogeneous phantom was used in the calibration of the X-ray beam process, producing tests technical. These techniques were applied in an anthropomorphic phantom hand from CT scans. The same procedure was adoped for retrospective examinations of 30 patients of the Hospital das Clinicas, of School Medicine of Botucatu, UNESP (HCFMB-UNESP). The results showed agreement between the thicknesses of tissues that constitute the anthropomorphic phantom and sampling of ...

Made available in DSpace on 2014-06-11T19:23:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-22Bitstream added on 2014-06-13T20:10:26Z : No. of bitstreams: 1 000749206.pdf: 2362410 bytes, checksum: f4f84a869a32983e7c75a2cda7ba0e17 (MD5) / A medicina nuclear é uma especialidade médica que se ocupa de técnicas de imagem para observar o estado fisiológico dos tecidos ou órgãos de forma não invasiva, através da marcação de moléculas participantes desses processos, com isótopos radioativos, originando assim os chamados radionuclídeos. O SPECT é um equipamento que se utiliza de imagens planares, obtidas de vários ângulos ao redor do objeto de interesse, e, através de algoritmos computacionais, obtêm uma imagem tomográfica dessas projeções. Sua origem remete há aproximadamente cinquenta anos atrás, com criação da Câmara Anger (Hall Anger, 1964). Durante todo esse tempo, embora tenha havido alguma evolução, a estrutura dessas gama câmaras praticamente ficou Inalterada. Os constantes avanços em pesquisas empregando cristais semicondutores nos exames cintilográficos, bem como a necessidade do surgimento de novos sistemas detectores, compactos, com maior poder de resolução e alta sensibilidade conjugados a crescente preocupação mundial com a minimização das doses de radiação ionizante utilizadas nos exames diagnósticos e terapias, impulsionou o desenvolvimento de novos sistemas detectores. Recentemente, duas Grandes Empresas lançaram comercialmente novos sistemas de detecção para aquisições tomográficas em medicina nuclear, utilizando detectores do estado sólido, mais especificamente cristais de telureto de cádmio e zinco (CZT). Algumas vantagens desse tipo de detector são a melhora sensível da relação sinal/ruído, o aumento da resolução espectral e espacial, o que em suma, resultam numa maior nitidez das imagens obtidas. O emprego desses detectores abre novas perspectivas para os protocolos de imagem. Entretanto, devido a inúmeros fatores, os equipamentos ditos CZT estão focados na área cardiológica, e devido a características próprias requerem a reformulação dos protocolos de aquisição de imagem além daqueles destinados ao... / Nuclear medicine is a medical specialty that deals with imaging techniques to observe the physiological status of the tissues or organs noninvasively, by dialing molecules participating in this process, with radioactive isotopes, thus giving the so-called radionuclides. The SPECT is a device that uses planar images, taken from different angles around the object of interest, and, through computer algorithms, obtains a tomographic image of those projections. Its origin refers for nearly fifty years ago, with the creation of the Chamber Anger (Anger Hall, 1964). Throughout this time, although there has been some evolution, the structure of these gamma cameras was virtually unchanged. The constant advances in research employing semiconductor crystals in scintigraphic examinations, as well as the need for the creation of new detectors systems, compacts, higher resolution and high sensitivity; combined with growing worldwide concern with minimization of doses of ionizing radiation used in diagnostic tests and therapies, spurred the development of new detector systems. Recently, two large companies launched commercially new detection systems for nuclear medicine tomographic acquisitions, using solid-state detectors, specifically crystals of zinc and cadmium telluride (CZT). Some advantages of this type of detector are sensitive improvement of signal / noise ratio, increased spectral and spatial resolution, which in short, resulting in greater clarity of the images obtained. The use of these detectors opens news perspectives for imaging protocols. However, due to numerous factors, equipment said CZT are focused on cardiology area, and due to the inherent characteristics, require reformulation of image acquisition protocols beyond those intended for Quality Control