Sistemas de tomografia por emissão de positrões para pequenos animais

The growing demand for PET scanners in preclinical studies combined with the high cost of those equipments increased the interest in the development of new high performance and low cost system, made possible due to the recent technological developments in the industry of radiation detection. Is this work, we present two low cost PET scanners. The first is the DRIM-PET, a PET scanner with improved spatial resolution through the determination of the depth-of-interaction of the photons in the detectors, correcting the parallax effect. The use of MPPCs and wavelength-shifting fibers for light detection allows to reduce the number of components, reducing the device cost. We present the performance characterization of an unitary cell of the DRIM-PET system, as a proof-of-concept, and we report a depth-of-interaction resolution of the order of 7mm. The other PET scanner presented is the EasyPET 3D, with capabilities of acquire volumetric images and execute spectroscopy. The use of a rotation system for the detecting cells allows to reduce the number of cells thus reducing the cost of the device, keeping high spatial resolution bellow 1.5mm, uniform along the FOV, which is variable up to 60mm. Image quality was evaluated using the NEMA NU-2008 standard, the commercial prototype for the first time shown and the first preclinical acquisitions are shown for 18F-FDG and 18F-NaF, for mouse brain and skeleton imaging, respectively. Finally, the development of a simulation toolkit written in GATE for the EasyPET prototype (2D), commercialized by the Italian company CAEN, SpA, allows students to perform simple tasks the simulate experimental procedures such as the evaluation of the effect of different coincidence time and energy windows for the reconstructed image, for radioactive sources at different locations within the FOV. The platform can be included in the official code EduGATE as a supplementary module.A crescente procura por tomógrafos PET para estudos pré-clínicos aliada ao elevado custo destes equipamentos, fez aumentar o interesse no desenvolvimento de novos sistemas de elevada performance a baixo custo, possibilitados pelos novos desenvolvimentos tecnológicos na industria de deteção de radiação. Dois sistemas de baixo custo são apresentados no âmbito deste trabalho. O primeiro é o DRIM-PET, um tomógrafo PET com melhorada resolução espacial através da determinação do ponto de interação da radiação nos detetores. A correção do efeito de paralaxe é feita usando MPPCs e fibras conversoras de luz para deteção da luz, mantendo um reduzido número de detetores. É apresentada a caracterização experimental de uma célula unitária do DRIM-PET como prova de conceito, onde a resolução espacial na determinação do ponto de interação obtida é da ordem de 7mm. O outro tomógrafo PET apresentado é o EasyPET 3D, com capacidade de aquisição de imagens em 3D e espectroscopia de raios. O uso de um sistema de rotação das células detectoras para aquisição de imagens permite reduzir o número de células, mantendo elevada resolução em posição, da ordem de 1.5mm, para um campo de visão variável até 60mm, reduzindo o custo do equipamento. A qualidade de imagem do dispositivo foi avaliada usando a norma NEMA NU-2008, o protótipo comercial apresentado e as primeiras aquisições pré-clínicas com 18F-FDG e 18F-NaF apresentadas, em imagens do cérebro e do esqueleto em ratos, respetivamente. Finalmente, o desenvolvimento de uma plataforma de simulação para o primeiro sistema EasyPET (2D), comercializado pela empresa CAEN, SpA, permite que estudantes executem tarefas simples que simulam as aquisições experimentais, como o efeito de diferentes janelas de tempo e energia para a imagem reconstruida, para fontes radioativas colocadas em diferentes localizações no FOV. A plataforma pode ser incluída no pacote EduGATE como um módulo suplementar.P. M. M. Correia is supported by the FCT (Lisbon) scholarship BD/52330/2013 under the PhD FCT program DAEPHYS, and is grateful to the I3N laboratory, funded by UID/CTM/50025/2013. This work was partially supported by project POCI-01-0145-FEDER-016855 and PTDC/BBB-IMG/4909/2014, and project easyPET nº 17823, through COMPETE, FEDER, POCI and FCT (Lisbon) programs.Programa Doutoral em Engenharia Civi

Confocal light sheet microscopy: micron-scale neuroanatomy of the entire mouse brain.

Elucidating the neural pathways that underlie brain function is one of the greatest challenges in neuroscience. Light sheet based microscopy is a cutting edge method to map cerebral circuitry through optical sectioning of cleared mouse brains. However, the image contrast provided by this method is not sufficient to resolve and reconstruct the entire neuronal network. Here we combined the advantages of light sheet illumination and confocal slit detection to increase the image contrast in real time, with a frame rate of 10 Hz. In fact, in confocal light sheet microscopy (CLSM), the out-of-focus and scattered light is filtered out before detection, without multiple acquisitions or any post-processing of the acquired data. The background rejection capabilities of CLSM were validated in cleared mouse brains by comparison with a structured illumination approach. We show that CLSM allows reconstructing macroscopic brain volumes with sub-cellular resolution. We obtained a comprehensive map of Purkinje cells in the cerebellum of L7-GFP transgenic mice. Further, we were able to trace neuronal projections across brain of thy1-GFP-M transgenic mice. The whole-brain high-resolution fluorescence imaging assured by CLSM may represent a powerful tool to navigate the brain through neuronal pathways. Although this work is focused on brain imaging, the macro-scale high-resolution tomographies affordable with CLSM are ideally suited to explore, at micron-scale resolution, the anatomy of different specimens like murine organs, embryos or flies. (C) 2012 Optical Society of Americ

Single-shot ultrafast optical imaging

Single-shot ultrafast optical imaging can capture two-dimensional transient scenes in the optical spectral range at ≥100 million frames per second. This rapidly evolving field surpasses conventional pump-probe methods by possessing real-time imaging capability, which is indispensable for recording nonrepeatable and difficult-to-reproduce events and for understanding physical, chemical, and biological mechanisms. In this mini-review, we survey state-of-the-art single-shot ultrafast optical imaging comprehensively. Based on the illumination requirement, we categorized the field into active-detection and passive-detection domains. Depending on the specific image acquisition and reconstruction strategies, these two categories are further divided into a total of six subcategories. Under each subcategory, we describe operating principles, present representative cutting-edge techniques, with a particular emphasis on their methodology and applications, and discuss their advantages and challenges. Finally, we envision prospects for technical advancement in this field

A charge coupled device based optical tomographic instrumentation system for particle sizing.

This research investigates the use of charge coupled device (abbreviated as CCD) linear image sensors in an optical tomographic instrumentation system used for sizing particles. Four CCD linear image sensors are configured around an octagonal shaped flow pipe for a four projections system. The measurement system is explained and uses four CCD linear image sensors consisting of 2048 pixels with a pixel size of 14 micron by 14 micron. Hence, a high-resolution system is produced.Three main mathematical models based on the effects due to particles, light sources and diffraction are discussed. The models simulate the actual process in order to understand the limitations of the designed system.Detailed design of the optical tomography system is described, starting from the fabrication of the 'raybox 'of the lighting system, the design of the driving circuit in the detection system, the timing and synchronisation in the triggering system based on the PIC microcontroller and the data acquisition system.Image reconstruction for a four-projection optical tomography system is also discussed, where a simple optical model is used to relate attenuation due to variations in optical density, [R], within the measurement section. Expressed in matrix form this represents the forward problem in tomography [S][R]=[M] In practice, measurements [M] are used to estimate the optical density distribution by solving the inverse problem [R]=[S]-1[M]. Direct inversion of the sensitivity matrix, [S], is not possible and two approximations are considered and compared - the transpose and the pseudo inverse sensitivity matrices.The designed instrumentation system is calibrated using known test pieces and tested for accuracy, repeatability and consistency among measurements from different projections. The accuracy of the particle size measurement using the system is within 1 pixel i.e. + 14 micron (the maximum absolute error of 8.5 micron), with the maximum percentage error of 1.46%. Moreover, the system has a good repeatability and consistency - within 1.25 pixel. The range of particle size that has been tested using the system is between 0.18 mm up to 11 mm diameter. A spherical shaped and an irregular shaped particle are tested on the designed system to complete analysis of the overall performance of the system.This thesis is concluded with achievements of objectives of the research, followed with suggestions for future work

Characterization of multiphase flows integrating X-ray imaging and virtual reality

Multiphase flows are used in a wide variety of industries, from energy production to pharmaceutical manufacturing. However, because of the complexity of the flows and difficulty measuring them, it is challenging to characterize the phenomena inside a multiphase flow. To help overcome this challenge, researchers have used numerous types of noninvasive measurement techniques to record the phenomena that occur inside the flow. One technique that has shown much success is X-ray imaging. While capable of high spatial resolutions, X-ray imaging generally has poor temporal resolution. This research improves the characterization of multiphase flows in three ways. First, an X-ray image intensifier is modified to use a high-speed camera to push the temporal limits of what is possible with current tube source X-ray imaging technology. Using this system, sample flows were imaged at 1000 frames per second without a reduction in spatial resolution. Next, the sensitivity of X-ray computed tomography (CT) measurements to changes in acquisition parameters is analyzed. While in theory CT measurements should be stable over a range of acquisition parameters, previous research has indicated otherwise. The analysis of this sensitivity shows that, while raw CT values are strongly affected by changes to acquisition parameters, if proper calibration techniques are used, acquisition parameters do not significantly influence the results for multiphase flow imaging. Finally, two algorithms are analyzed for their suitability to reconstruct an approximate tomographic slice from only two X-ray projections. These algorithms increase the spatial error in the measurement, as compared to traditional CT; however, they allow for very high temporal resolutions for 3D imaging. The only limit on the speed of this measurement technique is the image intensifier-camera setup, which was shown to be capable of imaging at a rate of at least 1000 FPS. While advances in measurement techniques for multiphase flows are one part of improving multiphase flow characterization, the challenge extends beyond measurement techniques. For improved measurement techniques to be useful, the data must be accessible to scientists in a way that maximizes the comprehension of the phenomena. To this end, this work also presents a system for using the Microsoft Kinect sensor to provide natural, non-contact interaction with multiphase flow data. Furthermore, this system is constructed so that it is trivial to add natural, non-contact interaction to immersive visualization applications. Therefore, multiple visualization applications can be built that are optimized to specific types of data, but all leverage the same natural interaction. Finally, the research is concluded by proposing a system that integrates the improved X-ray measurements, with the Kinect interaction system, and a CAVE automatic virtual environment (CAVE) to present scientists with the multiphase flow measurements in an intuitive and inherently three-dimensional manner

Development of a Single Sensor Approach for Capturing Three-Dimensional, Time Resolved Flame and Velocity Information

Performing non-intrusive measurements is the key to acquiring accurate information representative of what is being observed. The act of measuring often changes the environment being observed altering the information that is being obtained. Due to this, the community of fluid scientists have gravitated towards using laser-based measurements to observe the phenomena occurring in their experiments. The study of fluids has advanced since this point, utilizing techniques such as planar laser induced florescence (PLIF), particle image velocimetry (PIV), laser doppler velocimetry (LDV), particle doppler anemometry (PDA), etc. to acquire chemical species information and velocity information. These techniques, though, are inherently two-dimensional and cannot fully describe a flow field. In the area of reacting flow fields (combustion) acquiring the local fuel to air ratio information is increasingly important. Without it, scientist must rely on global one-dimensional metering techniques to correlate the fuel to air ratio of their flow field of interest. By knowing the fuel to air ratio locally and spatially across a flame, the location of products and reactants can be deduced, giving insight into any inefficiencies associated with a burner. Knowing the spatial fuel air field also gives insights into the density gradient associated with the flow field. Discussed in this work will be the development of a non-intrusive local fuel-air measurement technique and an expansion of the PIV technique into the third dimension, tomographic PIV, utilizing only one camera to do so for each measurement. The local fuel-air measurement is performed by recording two species (C2* and CH*) simultaneously and calibrating their ratio to the known fuel-air field. Tomographic PIV is performed by utilizing fiber coupling to acquire multiple viewpoints utilizing a single camera

3D Shape Reconstruction from Multiple Range Image Views

Shape reconstruction of different three dimensional objects using multiple range images has evolved recently within the recent past. In this research shape reconstruction of a three dimensional object using multiple range image views is investigated. Range images were captured using the Waikato Range Imager. This range images camera is novel in that it uses heterodyne imaging and is capable of acquiring range images with precision less than a millimeter simultaneously over a full field. Multiple views of small objects were taken and the FastRBF was explored as a mean of registration and surface rendering. For comparison to the real range data, simulated range data under noise free condition were also generated and reconstructed with the FastRBF tool box. The registration and reconstruction of simple object was performed using different views with the FastRBF toolbox. Analysis of the registration process showed that the translation error produced due to distortion during registration of different views hinders the process of reconstructing a complete surface. While analyzing the shape reconstruction using the FastRBF tool it is also determined that a small change in accuracy values can affect the interpolation drastically. Results of reconstruction of a real 3D object from multiple views are shown