abstract: The effect of earthquake-induced liquefaction on the local void ratio distribution of cohesionless soil is evaluated using x-ray computed tomography (CT) and an advanced image processing software package. Intact, relatively undisturbed specimens of cohesionless soil were recovered before and after liquefaction by freezing and coring soil deposits created by pluviation and by sedimentation through water. Pluviated soil deposits were liquefied in the small geotechnical centrifuge at the University of California at Davis shared-use National Science Foundation (NSF)-supported Network for Earthquake Engineering Simulation (NEES) facility. A soil deposit created by sedimentation through water was liquefied on a small shake table in the Arizona State University geotechnical laboratory. Initial centrifuge tests employed Ottawa 20-30 sand but this material proved to be too coarse to liquefy in the centrifuge. Therefore, subsequent centrifuge tests employed Ottawa F60 sand. The shake table test employed Ottawa 20-30 sand. Recovered cores were stabilized by impregnation with optical grade epoxy and sent to the University of Texas at Austin NSF-supported facility at the University of Texas at Austin for high-resolution CT scanning of geologic media. The local void ratio distribution of a CT-scanned core of Ottawa 20-30 sand evaluated using Avizo® Fire, a commercially available advanced program for image analysis, was compared to the local void ratio distribution established on the same core by analysis of optical images to demonstrate that analysis of the CT scans gave similar results to optical methods. CT scans were subsequently conducted on liquefied and not-liquefied specimens of Ottawa 20-30 sand and Ottawa F60 sand. The resolution of F60 specimens was inadequate to establish the local void ratio distribution. Results of the analysis of the Ottawa 20-30 specimens recovered from the model built for the shake table test showed that liquefaction can substantially influence the variability in local void ratio, increasing the degree of non-homogeneity in the specimen. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2013

Submitted by Fernanda Rodrigues de Lima (fernanda.rlima@ufpe.br) on 2018-07-20T22:10:35Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Marcos Antônio Dórea Machado.pdf: 2233914 bytes, checksum: b98eee9403ebcdd88d55481bc0692500 (MD5) / Approved for entry into archive by Alice Araujo (alice.caraujo@ufpe.br) on 2018-07-23T17:59:48Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Marcos Antônio Dórea Machado.pdf: 2233914 bytes, checksum: b98eee9403ebcdd88d55481bc0692500 (MD5) / Made available in DSpace on 2018-07-23T17:59:48Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Marcos Antônio Dórea Machado.pdf: 2233914 bytes, checksum: b98eee9403ebcdd88d55481bc0692500 (MD5) Previous issue date: 2017-02-10 / O equipamento PET, os parâmetros de aquisição e a reconstrução de imagens em exames oncológicos de PET têm impacto tanto na qualidade das imagens quanto na quantificação da atividade metabólica dos tumores. Neste trabalho é apresentado um método para otimizar os parâmetros de aquisição de imagens em exames FDG-F18 PET/CT de tumores sólidos, a partir do ruído no simulador IEC/NEMA e na região do fígado de 88 pacientes. O algoritmo de reconstrução Point Spread Function (PSF), harmonizado de acordo com os critérios da European Association of Nuclear Medicine (EANM), foi usado para gerar imagens superiores em termos de ruído. Assim, as medidas de ruído no simulador IEC/NEMA foram correlacionadas às quantificações dos coeficientes de recuperação de contraste máximos (CRCmax), em que os limites adotados pela EANM para CRCmax foram usados como critérios de qualidade que definem a relação ótima entre parâmetros de aquisição, ruído e quantificações. Adicionalmente, o ruído na região do fígado de 48 pacientes foi caracterizado para as reconstruções OSEM e PSF (CRCmáx harmonizados) com densidades de contagens tipicamente usadas em uma rotina clínica. Outro conjunto de 40 imagens em modo lista da região do fígado de pacientes foi usado para gerar 160 imagens com um amplo espectro de densidade de contagens, a fim de compreender o ruído em diferentes contextos de densidade de contagens. Aquisição de imagens com aproximadamente 350 MBq.s/kg no simulador IEC/NEMA apresentou variabilidade da quantificação em conformidade aos limites da EANM, que corresponde a um ruído no simulador de CV = 8,7%. Este mesmo parâmetro de aquisição quando aplicado a um paciente, resulta em um ruído de CV = 7,1% na região do fígado, que pode ser usado como uma medida de garantia da qualidade na rotina de exames. Entretanto, a região entre 200-320 MBq.s/kg sugere oferecer quantificações de SUVmáx reprodutíveis pois o ruído no fígado mostrou-se controlado nesta região de densidade de contagens. O uso do SUVpeak mostrou-se ainda mais reprodutível, incluindo a região entre 100-200 MBq.s/kg. Este método representa a base para um estudo que possa identificar o protocolo de aquisição otimizado, para vários equipamentos e tipos de reconstrução, a fim de executar exames de PET/CT com baixa posologia atendendo aos critérios de harmonização da EANM. / The PET/CT scanner, the image acquisition and the reconstruction parameters in oncological PET affect the image quality and the quantification of tumor activity. In this work, we presented a method for image acquisition optimization of FDG-F18 PET/CT examinations in solid tumors by using noise metrics in the IEC/NEMA phantom and in the liver of 88 subjects. The Point Spread Function (PSF) reconstruction algorithm, harmonized according to he European Association of Nuclear Medicine (EANM), was used to generate superior images in terms of noise. Then, we used the IEC/NEMA phantom to correlate noise and maximum contrast recovery coefficient (CRCmáx) quantitation measurements which the EANM CRCmáx limits were adopted as criteria to define the optimal relations among acquisition parameters, noise and quantification. Additionally, the noise in the liver of 48 subjects was characterized for OSEM and PSF reconstructions (CRCmáx harmonized) by using clinical count densities typically used in clinical routine. Another set of 40 list mode images from the liver was used to generate 160 images with a wide range count density spectrum in order to understand the noise characteristics in different count density context. Image acquisitions of about 350 MBq.s/kg in the IEC/NEMA phantom presented CRCmáx variability within EANM limits, which corresponds to 8.7% noise in phantom. Such image acquisition parameter provides 7.1% noise in the liver, which might be used as a quality assurance measurement in clinical routine. However, the 200-320 MBq.s/kg range may pose reproducible SUVmáx quantitation since noise in liver was satisfactorily controlled for such count density spectrum. When SUVpeak was used, it presented even better reproducibility, including the 100-200 MBq.s/kg spectrum. The presented method provides the basis to more robust studies to identify the optimal acquisition parameter for different scanners and reconstructions in order to perform low-dose FDF-F18 PET/CT according to EANM harmonization criteria.

Abstract Imaging of the head and spine with CT and/or MRI was performed on 125 Northern Finnish NF1 patients to evaluate the CNS lesions in patients of different ages and their role in diagnosis and follow-up. Manifestations of NF1 in the head were more common in children than in adults. 77% of the children and 33% of the adults had T2 hyperintense brain lesions. Optic gliomas were present in 29% of the patients, in 44% of the children and 10 % of the adults. 8% of the patients had other intracranial tumours . Spinal lesions were seen in 75% of the patients. Hyperintense T2 lesions were most common in the age group of 5 to 9 years. During follow-up of the children, the lesions diminished in 25%, remained unchanged in 36%, showed mixed behaviour in 20% and disappeared in 10%. In 15% they increased in size and number. In one patient a malignant tumour developed at the site of a T2 lesion. Optic gliomas were located intraorbitally and/or prechiasmally in 94%, chiasmally and/or at the hypothalamus in 58% and in other optic areas in 14% of the patients. 52 % of the intraorbital gliomas were bilateral. The gliomas remained unchanged in 68% of the children and 50% of the adults. Other lesions included plexiform neurofibromas, sphenoid bone dysplasias and hydrops of the optic sheath. Optic glioma was more common in children with T 2 hyperintense brain lesions than without them. The other brain tumours included six astrocytomas, including an affected mother and her son. In one patient the astrocytoma regressed spontaneously. Hydrocephalus was seen in 5% of the patients. T2 hyperintense brain lesions were more common and numerous in macrocephaly; all macrocephalic children, but only 59% of the normocephalic children were affected. All children without T2 lesions were normocephalic. The brain measurements did not reveal any specific area to be responsible for macrocephaly. Spinal postural changes and dural ectasias were more common in adults. The spinal cord was affected in two patients. Spinal neurofibromas were seen in 19% of the children and 55% of the adults. Even young children may have severe manifestations. In one family a rare familial type of spinal neurofibromatosis (FSNF) was observed in four adults with bilateral spinal neurofibromas at all levels of the spine. Although both CT and MRI were valuable in CNS imaging, MRI proved to be the method of choice in detecting T2 hyperintense brain lesions, in evaluating the intracranial extent of optic gliomas and hydrops of the optic sheath and lesions of the spinal cord and nerves. MR imaging proved necessary for evaluating the extent of NF1 manifestations and helpful in the diagnosis, screening and follow-up of NF1 patients.

Die therapeutischen Möglichkeiten des metastasierten Prostatakarzinoms (Pca) haben sich durch die neuen Substanzen Docetaxel und Abirateron deutlich verbessert. Das prostataspezifische Membranantigen (PSMA) stellt für die Diagnose und Therapie des Pca´s einen vielversprechenden Angriffspunkt dar. PSMA wird in Prostatakarzinomzellen überexprimiert und dient als Zielstruktur für nicht-invasives bildgebendes Verfahren und Lutetium-177-PSMA-Radioligandentherapie als Therapieoption. Der CXCR4-Rezeptor wird an unterschiedlichen Zelltypen und Organen exprimiert. Seine Überexpression wird mit einer Metastasierung und schlechter Prognose assoziiert. Gallium-68-PSMA PET/CT liefert genaue Kenntnisse bezüglich Ausbreitung und Fortschreiten des Tumorgeschehens. Die vorliegende Arbeit untersucht die Zusammenhänge zwischen Expression von PSMA und CXCR4 in Verbindung mit etablierten Therapeutika und versucht Wege aufzuzeichnen, welche durch Erhöhung der PSMA-Expression zur verbesserten Sensitivität des PSMA PET/CT führen könnten, wodurch der personalisierte Therapieansatz weiter optimiert werden kann. / Novel therapeutic agents such as docetaxel and abiraterone have significantly improved treatment strategies for metastatic prostate cancer in recent years. Prostate-specific membrane antigen (PSMA) represents a promising target for diagnosis and therapy of prostate cancer. PSMA is over expressed in prostate cancer cells providing a target structure for non-invasive imaging and Lutetium-177-PSMA radioligand therapy. The CXCR4-receptor is expressed on different cell types and organs. Its over expression is associated with metastasis and poor prognosis. PET/CT imaging with Gallium-68-labelled PSMA ligands provide relevant information regarding tumor staging and progression. The present study investigates the interaction between expression of PSMA and CXCR4 considering established therapeutic agents to improve sensitivity of PSMA PET/CT imaging and optimize personalized cancer medicine.

Die Kombination von Positronen-Emissions-Tomographie (PET) und Röntgen-Computertomographie (CT) in Form moderner PET/CT-Geräte ermöglicht die Nutzung der CT-Information zur Korrektur der Photonenschwächung in der PET. Allerdings können Bewegungen, die zum Beispiel durch die Atmung hervorgerufen werden können, zu einer fehlerhaften Schwächungskorrektur führen. Die Einführung von zeitlich aufgelöster Bildgebung für beide Modalitäten (4D-PET/4D-CT) ermöglicht nicht nur die Auflösung von periodischen Bewegungen, sondern auch die Reduktion dieser Fehler in der Schwächungskorrektur. Dazu werden die einzelnen Datensätze des 4D-PET, die jeweils einer bestimmten Bewegungsphase entsprechen, mit dem entsprechenden CT-Datensatz dieser Atemphase schwächungskorrigiert. In der vorliegenden Arbeit wurde diese phasenkorrelierte Schwächungskorrektur des 4D-PET mit dem 4D-CT am Universitästsklinikum Dresden installierten PET/CT ermöglicht und anhand von Phantomexperimenten mit anderen Schwächungskorrekturmethoden für 4D-PET verglichen. Dazu musste zunächst die Aufnahme von 4D-CT an dem verwendeten PET/CT ermöglicht und dessen Synchronität mit dem 4D-PET hergestellt werden. Außerdem wurde ein vorhandenes Atemphantom so modifiziert, dass es typische Bewegungen von Bronchialkarzinomen in zwei Dimensionen und mit zwei möglichen Atemmustern simuliert. Die phasenkorrelierte Schwächungskorrektur führte zu einer quantitativ korrekten Wiederherstellung des Aktivitätsvolumens, der darin enthaltenen Aktivität sowie der Bewegungsamplitude und stellt somit die beste der hier verglichenen 4D-PET-Schwächungskorrekturmethoden dar. Diese Ergebnisse lassen vermuten, dass die phasenkorrelierte Schwächungskorrektur auch bei klinischer Anwendung eine signifikante Verbesserung in oben genannten Punkten darstellt. Dies sollte in Zukunft an Patientendaten überprüft werden. / The combination of Positron Emission Tomography (PET) and Computed Tomography (CT) in one device allows the use of CT-information for attenuation correction in PET. Though motion, for example induced by respiration, can cause inaccurate attenuation correction. The implementation of time-resolved imaging methods for both modalities (4D-PET/4D-CT) enables not only the resolution of motion but also the reduction of artifacts caused by attenuation correction. Therefore, the single datasets of the 4D-PET that are related to a individual respiratory phase, are attenuation corrected with the corresponding dataset of the 4D-CT. This phase correlated attenuation correction of the 4D-PET with the 4D-CT was implemented at the PET/CT installed at the Universitätsklinikum Dresden. For that purpose the acquisition of 4D-CT was implemented at the PET/CT and its synchronisation with the 4D-PET was verified. Furthermore the new attenuation correction method was compared with other attenuation correction methods by performing phantom experiments. Therefore an exisisting respiratory phantom had to be modified to perform typical lung tumor motion in two dimensions with two possible patterns of respiration. The phase correlated attenuation correction leads to a quantitatively correct restauration of the activity volume, its total activity and its motion amplitude. Compared with other correction methods, the phase correlated attenuation correction shows the best results in all examined criteria. This findings suggest that the clinical application of the phase correlated attenuation correction will also lead to a significant improvement in all mentioned points. This has to be verified by analyzing patient data.

Thesis advisor: Sarah McMenamin / Thyroid hormone (TH) facilitates developmental transitions, particularly by modulating cell proliferation and differentiation. Its role in regulating skeletal growth is well documented. Previous work from our lab and others have demonstrated that hypo- and hyperthyroid fish display changes in bone shape, ossification and the timing of ossification5. Zebrafish (Danio rerio) develop bone quickly, grow indefinitely throughout their lives, are highly amenable for imaging, and are a valuable model for skeletal biology research. Using Danio rerio, we sought to study the long-term effects of TH on bone density by rearing and comparing normal euthyroid (Eu) with a transgenically thyroid-ablated hypothyroid (TH-) and mutant hyperthyroid (TH+) fish. We found that TH strongly affects bone density and volume. We further hypothesize that TH is critical for the timing and fidelity of skeletogenesis. In hormone-dysregulated fish, we found that massive bone and cartilage exostoses grow on the dentary. Thyroid hormone’s effects are highly bone-specific: in TH- fish, we see reduced density in many craniofacial bones, but also increased volume and mineralization in other regions of the dentary. These data suggest that TH plays a critical role in coordinating bone mineralization with growth. / Thesis (MS) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

Computed tomography (CT) is an imaging technique that uses x-ray and computers to create cross-sectional images of structures. Stereotactic CT-guided biopsy is defined as the use of a stable apparatus to direct and perform tissue biopsies under CT guidance. For the brain, the principal advantage of stereotactic CT guidance over other biopsy techniques is its high accuracy in getting a sample from deep-seated lesions. The objectives of this study were to create an inexpensive CT-guided stereotactic device adaptable to different canine head sizes and to test the accuracy of the device for needle placement in deep-seated brain targets. A biopsy device was created that consists of four main components: a CT table fixation device, a head fixture, a needle fixture , and motion control system. Accuracy was tested using 16 head and neck specimens obtained from dogs euthanitized for reasons unrelated to the brain. Deep-seated (caudate nucleus and pituitary gland) targets were identified on CT. After a 5 mm craniotomy, the biopsy needle, with CT monitoring, was progressively introduced into the target. The final needle track distance was measured on CT. The brain was removed and sliced to verify placement of the needle tip within the target and to measure the actual needle track distance. The total cost of materials and construction for the stereotactic CT-guided biopsy device was $785.00. No difference in needle placement accuracy was identified for caudate and pituitary targets. Based on assessments by 2 independent observers, the caudate target was successfully hit 75% of the time. Pituitary targets were successfully hit 96.8 % of the time. Actual needle track lengths were an average of 3.2 mm less that the track length measured on CT. This difference was most likely due to incomplete staining of the bevel part of the needle track on gross specimens. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / The advances in health care technology help physicians make more accurate diagnoses about the health conditions of their patients. Positron Emission Tomography/Computed Tomography (PET/CT) is one of the many tools currently used to diagnose health and disease in patients. PET/CT explorations are typically used to detect: cancer, heart diseases, disorders in the central nervous system. Since PET/CT studies can take up to 60 minutes or more, it is impossible for patients to remain motionless throughout the scanning process. This movements create motion-related artifacts which alter the quantitative and qualitative results produced by the scanning process. The patient's motion results in image blurring, reduction in the image signal to noise ratio, and reduced image contrast, which could lead to misdiagnoses. In the literature, software and hardware-based techniques have been studied to implement motion correction over medical files. Techniques based on the use of an external motion tracking system are preferred by researchers because they present a better accuracy. This thesis proposes a motion correction system that uses 3D affine registrations using particle swarm optimization and an off-the-shelf Microsoft Kinect camera to eliminate or reduce errors caused by the patient's motion during a medical imaging study.

http://pubs.rsna.org/doi/full/10.1148/radiol.2015150416 / 京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19575号 / 医博第4082号 / 新制||医||1013(附属図書館) / 32611 / 京都大学大学院医学研究科医学専攻 / (主査)教授 平岡 眞寛, 教授 YOUSSEFIAN Shohab, 教授 増永 慎一郎 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Concerns arise in radiation therapy for head and neck cancers when dental prostheses are involved. These prostheses are high-density materials that induce image artifacts in computed tomography (CT) scans used for dose calculation. Two approaches are utilized in mitigating the impact of these artifacts on the accuracy of dose calculation. First, metal artifact reduction (MAR) algorithms or dual-energy CT scans are used to recover image quality. Second, a planning protocol is adopted whereby residual artifacts are manually contoured and assigned appropriate densities. This study evaluated the current planning process using a holistic approach. In this work, an axial section of a head phantom containing dental implants at the level of the oral cavity was constructed and scanned using various protocols on two different commercial scanners; Philips and Siemens, to assess the appearance of artifacts. An MVCT image set was merged with the corresponding kVCT image to improve visualization of the dental implants for use in density overrides. Three ion chamber measurement points in the simulated mouth facilitated the determination of measured dose which was compared to calculated dose at various single beam irradiation geometries. The influence of density override values on agreement between calculation and measurement was investigated for each geometry and imaging modality. Percent error was computed, and initial results compared to results manipulated by use of; a CT density table (Head); density overrides of walls and wax; and density overrides of walls, wax, and effective density of saturation regions. The study established that normal tissue doses are not significantly affected by metal artifact reduction (MAR) algorithms, and improvements in dose calculation compared to uncorrected CT images are small. Furthermore, the inclusion of a MVCT image set improved implant visualization reducing the treatment planning time while providing more information. Evidence led to the deduction that manual overrides of effective density for clipped OMAR CT pixels reduce dose calculation errors. When the phantom was configured with amalgam and Co-Cr-Mo alloy dental implants the effective density of these implants was found to be 4.5 g/cm3. When the phantom was configured with implants containing amalgam and gold, the effective density of amalgam in the presence of gold was 5.5 g/cm3 while gold had an effective density of 6.5 g/cm3. The median and maximum range of errors for the uncorrected images were ± 0.6 % and 7.4% respectively for the phantom configured with amalgam and Co-Cr-Mo (tray one) and ± 0.5 % and 18.1 % respectively for the phantom containing amalgam and gold (tray two). The median and maximum range of errors for the corrected images after applying overrides of effective densities were ± 0.5 % and 4.7% respectively for tray one and ± 0.3 % and 7.7 % respectively for tray two. In conclusion, introduction of density overrides of walls, wax and effective density of high-density materials can reduce the errors induced by metal artifacts and improve the accuracy of dose calculations in treatment planning systems to deliver the relevant dose to a target organ. / Thesis / Master of Science (MSc)