Digital tomosynthesis is a novel three-dimensional imaging technology that utilizes limited number of X-ray projection images to improve the diagnosis and detection of lesions. In recent years, tomosynthesis has been used in a variety of clinical applications such as dental imaging, angiography, chest imaging, bone imaging, and breast imaging. The goal of our research is to develop a framework to enable flexible optimization and comparison of image reconstruction and imaging configurations.

Bladder artifacts during bone single photon emission computed tomography (SPECT) is a common source of errors. The extent and severity of bladder artifacts have been described for filtered back projection (FBP) reconstruction. OSEM may help to address this poor record of bladder artifacts, which render up to 20% of the images unreadable. Aims and objectives To evaluate the relationship of the bladder to acetabulum ratio in guiding the choice of the number of iterations and subsets used for OSEM reconstruction, for reducing bladder artifacts found on FBP reconstruction. Materials and Methods 105 patients with various indications for bone scans were selected and planar and SPECT images were acquired. The SPECT images were reconstructed with both filtered back projection and OSEM using four different combinations of iterations and subsets. The images were given to three well experienced Nuclear Physicians who were blinded to the diagnosis and type of reconstruction used. They then labelled images from the best to the worst after which the data was analysed. The bladder to acetabulum ratio for each image was determined which was then correlated with the different iterations and subsets used. Results The study demonstrated that reconstruction using OSEM led to better lesion detectability compared to filtered back projection in 87.62% of cases. It further demonstrated that the iterations and subsets used for reconstruction of an image correlates to the bladder to acetabulum ratio. Four iterations and 8 subsets yielded the best results in 48.5% of the images whilst two iterations and 8 subsets yielded the best results in 33.8%. The number of reconstructed images which yielded the best results with 2 iterations and 8 subsets were the same as or more than those with 4 iterations and 8 subsets when the bladder/acetabulum ratio was between 0.2-0.39. A ratio below 0.2 or above 0.39 supports the usage of 4 iterations and 8 subsets over 2 iterations and 8 subsets. Conclusion Bladder to acetabulum ratio can be used to select the optimum number of iterations and subsets for reconstruction of bone SPECT for accurate characterization of lesions. This study also confirms that reconstruction with OSEM (vs FBP) leads to better lesion detectability and characterisation. / Dissertation (MSc)--University of Pretoria, 2011. / Nuclear Medicine / unrestricted

In this thesis, coda waves recorded by local seismographic networks will be analyzed to estimate the three-dimensional spatial distribution of scatterers (SDS). This will be done by using the single scattering approximation. This approach leads to a huge system of equations that can not be solved by traditional methods. For the first time, we will use the Simultaneous Iterative Reconstructive Technique (SIRT) to solve this kind of system in seismological applications. SIRT is slow but provides a means to carry out the inversion with greater accuracy. There is also a very fast non-iterative method that allows to carry out the inversion 102 times faster, with a higher resolution and reasonable accuracy: the Filtered Back-Projection (FBP). If one wishes to use this technique it is necessary to adapt it to the geometry of our problem. This will be done for the first time in this thesis. The theory necessary to carry out the adaptation will be developed and a simple expression will be derived to carry out the inversion.FBP and SIRT are then used to determine the SDS in southern India. Results are almost independent of the inversion method used and they are frequency dependent. They show a remarkably uniform distribution of the scattering strength in the crust around GBA. However, a shallow (0-24 km) strong scattering structure, which is only visible at low frequencies, seems to coincide with de Closepet granitic batholith which is the boundary between the eastern and western parts of the Dharwar craton.Also, the SDS is estimated for the Galeras volcano, Colombia. Results reveal a highly non-uniform SDS. Strong scatterers show frequency dependence, which is interpreted in terms if the scale of the heterogeneities producing scattering. Two zones of strong scattering are detected: the shallower one is located at a depth from 4 km to 8 km under the summit whereas the deeper one is imaged at a depth of ~37 km from the Earth's surface. Both zones may be correlated with the magmatic plumbing system beneath Galeras volcano. The second strong scattering zone may be probably related to the deeper magma reservoir that feeds the system.

No description available.

X-Ray Computed Tomography is irreplaceable medical imaging system. Quantitative evaluation is day to day routine used for clean run of this imaging system. The master’s thesis is focused on quantitative evaluation of first and third generation X-Ray CT. First of all is about subjective and objective evaluation of space and energetic resolution. Space resolution is evaluated in space and frequency domain. Energetic resolution is represent by low contrast resolution method. Application “Kvantitativní hodnocení kvality CT RTG zobrazení” created for this thesis is used for creation of reconstruction image and quantitative evaluation. This application was created with consideration of its usage in subjects about image processing. The master’s thesis contains results of quantitative evaluation X-Ray CT created with this application and proposal of lab work.

This dissertation thesis deals with the methods for processing image data in X-ray microtomography and digital holographic microscopy. The work aims to achieve significant acceleration of algorithms for tomographic reconstruction and image reconstruction in holographic microscopy by means of optimization and the use of massively parallel GPU. In the field of microtomography, the new GPU (graphic processing unit) accelerated implementations of filtered back projection and back projection filtration of derived data are presented. Another presented algorithm is the orientation normalization technique and evaluation of 3D tomographic data. In the part related to holographic microscopy, the individual steps of the complete image processing procedure are described. This part introduces the new orignal technique of phase unwrapping and correction of image phase damaged by the occurrence of optical vortices in the wrapped image phase. The implementation of the methods for the compensation of the phase deformation and for tracking of cells is then described. In conclusion, there is briefly introduced the Q-PHASE software, which is the complete bundle of all the algorithms necessary for the holographic microscope control, and holographic image processing.

[ES] La tomografía por emisión de positrones (PET, del inglés Positron Emission Tomography) es una técnica de medicina nuclear en la que se genera una imagen a partir de la detección de rayos gamma en coincidencia. Estos rayos son producidos dentro de un paciente al que se le inyecta una radiotrazador emisor de positrones, los cuales se aniquilan con electrones del medio circundante. El proceso de adquisición de eventos de interacción, tiene como unidad central el detector del escáner PET, el cual se compone a su vez de un cristal de centelleo, encargado de transformar los rayos gamma incidentes en fotones ópticos dentro del cristal. La finalidad es entonces, determinar las coordenadas de impacto dentro del cristal de centelleo con la mayor precisión posible, para que, a partir de dichos puntos, se pueda reconstruir una imagen. A lo largo de la historia, los detectores basados en cristales pixelados han representado la elección por excelencia para la la fabricación de escáneres PET. En está tesis se evalúa el impacto en la resolución espacial del escáner PET MINDView, desarrollado dentro del séptimo programa Marco de la Unión Europea No 603002, el cual se basa en el uso de cristales monolíticos. El uso de cristales monolíticos, facilita la determinación de la profundidad de interacción (DOI - del inglés Depth Of Interaction) de los rayos gamma incidentes, aumenta la precisión en las coordenadas de impacto determinadas, y disminuye el error de paralaje que se induce en cristales pixelados, debido a la dificultad para determinar la DOI. En esta tesis, hemos logrado dos objetivos principales relacionados con la medición de la resolución espacial del escáner MINDView: la adaptación del un algoritmo de STIR de Retroproyección Filtrada en 3D (FBP3DRP - del inglés Filtered BackProjection 3D Reproyected) a un escáner basado en cristales monolíticos y la implementación de un algoritmo de Retroproyección y filtrado a posteriori (BPF - BackProjection then Filtered). Respecto a la adaptación del algoritmo FBP, las resoluciones espaciales obtenidas varían en los intervalos [2 mm, 3,4 mm], [2,3 mm, 3,3 mm] y [2,2 mm, 2,3 mm] para las direcciones radial, tangencial y axial, respectivamente, en el primer prototipo del escáner MINDView dedicado a cerebro. Por otra parte, en la implementación del algoritmo de tipo BPF, se realizó una adquisición de un maniquí de derenzo y se comparó la resolución obtenida con el algoritmo de FBP y una implementación del algoritmo de subconjuntos ordenados en modo lista (LMOS - del inglés List Mode Ordered Subset). Mediante el algoritmo de tipo BPF se obtuvieron valores pico-valle de 2.4 a lo largo de los cilindros del maniquí de 1.6 mm de diámetro, en contraste con las medidas obtenidas de 1.34 y 1.44 para los algoritmos de FBP3DRP y LMOS, respectivamente. Lo anterior se traduce en que, mediante el algoritmo de tipo BPF, se logra mejorar la resolución para obtenerse un valor promedio 1.6 mm. / [CAT] La tomografia per emissió de positrons és una tècnica de medicina nuclear en la qual es genera una imatge a partir de la detecció de raigs gamma en coincidència. Aquests raigs són produïts dins d'un pacient a què se li injecta una radiotraçador emissor de positrons, els quals s'aniquilen amb electrons de l'medi circumdant. El procés de adquición d'esdeveniments d'interacció, té com a unitat central el detector de l'escàner PET, el qual es compon al seu torn d'un vidre de centelleig, encarregat de transformar els raigs gamma incidents en fotons òptics dins el vidre. La finalitat és llavors, determinar les coordenades d'impacte dins el vidre de centelleig amb la major precisió possible, perquè, a partir d'aquests punts, es pugui reconstruir una imatge. Al llarg de la història, els detectors basats en cristalls pixelats han representat l'elecció per excellència per a la la fabricació d'escàners PET. En aquesta tesi s'avalua l'impacte en la resolució espacial de l'escàner PET MINDView, desenvolupat dins el setè programa Marc de la Unió Europea No 603.002, el qual es basa en l'ús de vidres monolítics. L'ús de vidres monolítics, facilita la determinació de la profunditat d'interacció dels raigs gamma incidents, augmenta la precisió en les coordenades d'impacte determinades, i disminueix l'error de parallaxi que s'indueix en cristalls pixelats, a causa de la dificultat per determinar la DOI. En aquesta tesi, hem aconseguit dos objectius principals relacionats amb el mesurament de la resolució espacial de l'escàner MINDView: l'adaptació de l'un algoritme de STIR de Retroprojecció Filtrada en 3D a un escàner basat en cristalls monolítics i la implementació d'un algoritme de Retroprojecció i filtrat a posteriori. Pel que fa a l'adaptació de l'algoritme FBP3DRP, les resolucions espacials obtingudes varien en els intervals [2 mm, 3,4 mm], [2,3 mm, 3,3 mm] i [2,2 mm, 2,3 mm] per les direccions radial, tangencial i axial, respectivament, en el primer prototip de l'escàner MINDView dedicat a cervell. D'altra banda, en la implementació de l'algoritme de tipus BPF, es va realitzar una adquisició d'un maniquí de derenzo i es va comparar la resolució obtinguda amb l'algorisme de FBP3DRP i una implementació de l'algoritme de subconjunts ordenats en mode llista (LMOS - de l'anglès List Mode Ordered Subset). Mitjançant l'algoritme de tipus BPF es van obtenir valors pic-vall de 2.4 al llarg dels cilindres de l'maniquí de 1.6 mm de diàmetre, en contrast amb les mesures obtingudes de 1.34 i 1.44 per als algoritmes de FBP3DRP i LMOS, respectivament. L'anterior es tradueix en que, mitjançant l'algoritme de tipus BPF, s'aconsegueix millorar la resolució per obtenir-se un valor mitjà 1.6 mm. / [EN] Positron Emission Tomography (PET) is a medical imaging technique, in which an image is generated from the detection of gamma rays in coincidence. These rays are produced within a patient, who is injected with a positron emmiter radiotracer, from which positrons are annihilated with electrons in the media. The event acquisition process is focused on the scanner detector. The detector is in turn composed of a scintillation crystal, which transform the incident ray gamma into optical photons within the crystal. The purpose is then to determine the impact coordinates within the scintillation crystal with the greatest possible precision, so that, from these points, an image can be reconstructed. Throughout history, detectors based on pixelated crystals have represented the quintessential choice for PET scanners manufacture. This thesis evaluates the impact on the spatial resolution of the MINDView PET scanner, developed in the seventh Framework program of the European Union No. 603002, which detectors are based on monolithic crystals. The use of monolithic crystals facilitates the determination of the depth of interaction (DOI - Depth Of Interaction) of the incident gamma rays, increases the precision in the determined impact coordinates, and reduces the parallax error induces in pixelated crystals, due to the difficulties in determining DOI. In this thesis, we have achieved two main goals related to the measurement of the spatial resolution of the MINDView PET scanner: the adaptation of an STIR algorithm for Filtered BackProjection 3D Reproyected (FBP3DRP) to a scanner based on monolithic crystals, and the implementation of a BackProjection then Filtered algorithm (BPF). Regarding the FBP algorithm adaptation, we achieved resolutions ranging in the intervals [2 mm, 3.4 mm], [2.3 mm, 3.3 mm] and [2.2 mm, 2.3 mm] for the radial, tangential and axial directions, respectively. On the an acquisition of a derenzo phantom was performed to measure the spacial resolution, which was obtained using three reconstruction algorithms: the BPF-type algorithm, the FBP3DRP algorithm and an implementation of the list-mode ordered subsets algorithm (LMOS). Regarding the BPF-type algorithm, a peak-to-valley value of 2.4 were obtain along rod of 1.6 mm, in contrast to the measurements of 1.34 and 1.44 obtained for the FBP3DRP and LMOS algorithms, respectively. This means that, by means of the BPF-type algorithm, it is possible to improve the resolution to obtain an average value of 1.6 mm. / Sánchez Góez, S. (2020). Algoritmo de reconstrucción analítico para el escáner basado en cristales monolíticos MINDView [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/159259