Sammanfattning I Sverige drabbas ca 10000 personer årligen av lungemboli (LE). En vanlig bakomliggande orsak till LE är djup ventrombos. Tromboserna brukar vanligen sitta i benets eller bäckenets djupa vener. För att påvisa LE krävs att patienten genomgår olika radiologiska metoder såsom t.ex. datortomografi (DT) eller lungscintigrafi. Syftet med denna studie är att beskriva radiologiska metodval vid utredning av LE, för- och nackdelar med de olika metoderna och i vilka fall respektive metod föredras.  I databasen Pubmed söktes vetenskapliga artiklar som analyserar vilken av de radiologiska metoderna som föredras vid LE. Åtta artiklar valdes ut. Båda metoderna, DT och lungscintigrafi, är viktiga för att ställa diagnos vid misstänkt LE.  DT är den metod som väljs som förstahandsmetod, detta på grund av stor tillgänglighet och snabbhet, vilket är en stor fördel. Lungscintigrafiteknik bör dock inte uteslutas eftersom de båda metoderna kan komplettera varandra.

<p>The behavior of light after interacting with a biological medium reveals a wealth of information that may be used to distinguish between normal and disease states. This may be achieved by simply imaging the morphology of tissues or individual cells, and/or by more sophisticated methods that quantify specific surrogate biomarkers of disease. To this end, the work presented in this dissertation demonstrates novel tools derived from low coherence interferometry (LCI) that quantitatively measure wavelength-dependent scattering and absorption properties of biological samples, with high spectral resolution and micrometer spatial resolution, to provide insight into disease states. </p><p>The presented work first describes a dual window (DW) method, which decomposes a signal sampled in a single domain (in this case the frequency domain) to a distribution that simultaneously contains information from both the original domain and the conjugate domain (here, the temporal or spatial domain). As the name suggests, the DW method utilizes two independently adjustable windows, each with different spatial and spectral properties to overcome limitations found in other processing methods that seek to obtain the same information. A theoretical treatment is provided, and the method is validated through simulations and experiments. With this tool, the spatially dependent spectral behavior of light after interacting with a biological medium may be analyzed to extract parameters of interest, such as the scattering and absorption properties. </p><p>The DW method is employed to investigate scattering properties of samples using Fourier domain LCI (fLCI). In this method, induced temporal coherence effects provide insight into structural changes in dominant scatterers, such as cell nuclei within tissue, which can reveal the early stages of cancerous development. fLCI is demonstrated in complex, three-dimensional samples using a scattering phantom and an ex-vivo animal model. The results from the latter study show that fLCI is able to detect changes in the morphology of tissues undergoing precancerous development. </p><p>The DW method is also employed to enable a novel form of optical coherence tomography (OCT), an imaging modality that uses coherence gating to obtain micrometer-scale, cross-sectional information of tissues. The novel method, named molecular imaging true color spectroscopic OCT (METRiCS OCT), analyses the depth dependent absorption of light to ascertain quantitative information of chromophore concentration, such as hemoglobin. The molecular information is also processed to yield a true color representation of the sample, a unique capability of this approach. A number of experiments, including hemoglobin absorbing phantoms and in-vivo imaging of a chick embryo model and dorsal skinfold window chamber model, demonstrate the power of the method. </p><p>The final method presented in this dissertation, consists of a spectroscopic approach that interrogates the dispersive biochemical properties of samples to independently probe the scattering and absorption coefficients. To demonstrate this method, named non-linear phase dispersion spectroscopy (NLDS), a careful analysis of LCI signals is presented. The method is verified using measurements from samples that scatter and absorb light. Lastly, NLDS is combined with phase microscopy to achieve molecular imaging with sub-micron spatial resolution. Imaging of red blood cells (RBCs) shows that the method enables highly sensitive measurements that can quantify hemoglobin content from single RBCs.</p> / Dissertation

Thesis (M.S.)--University of California, San Francisco, 2009. / Source: Masters Abstracts International, Volume: 47-06, page: 3491. Adviser: Earl Johnson.

Thesis (Ph. D.)--State University of New York at Buffalo, 1971. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 181-194).

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Several new results are presented for applications involving the restoration of coherent signals and images from incomplete Fourier data. A closed form solution is derived for a class of iterative restoration algorithms. The closed form result may be used as a non-iterative implementation of the iterative algorithm. The closed form solution is also used to develop a simple, effective termination rule for the iterative algorithm. The utility of the new termination rule is demonstrated using simulated and experimental data. A solution technique is proposed for efficient restoration of bounded signals. The efficiency of the proposed technique is demonstrated via a one-dimensional slab dielectric profile inversion example. Finally, a difference image approach is proposed as a way to reduce the data requirements for 4-D magnetic resonance imaging of the cardiac cycle. The proposed technique is successfully applied to experimental MRI data, and future prospects for the approach are discussed.

A practical, field-capable, 3.0 to 5.0 μm mid-wave infrared Computed-Tomography Imaging Spectrometer (CTIS) has been demonstrated. The CTIS employs a simple optical system in order to measure the object cube without any scanning . The data is not measured directly, but in a manner which requires complicated post-processing to extract an estimate of the object's spectral radiance. The advantage of a snapshot imaging spectrometer is that it can collect information about a dynamic event which a standard scanning spectrometer could either miss or corrupt with temporal artifacts. Results were presented for reconstructions of laboratory targets with sampling up to 46 x 46 x 21 voxels over a variable field-of-view, or 0.1 μm spectral sampling. Demonstration of the snapshot capability has been performed on both static targets and targets with rapidly varying content. The contents of this dissertation are directed towards two ends. The primary undertaking is a realization of the theoretical model of the CTIS is a practical, field-capable MWIR instrument. The design, calibration, and operation of the MWIR CTIS are explained in detail in the text and appendices. Of additional interest is the advancement of the theory to improve the design and functionality of the spectrometer. A new algorithm for design of the holographic disperser component of the CTIS is introduced. The design process dramatically extends the set of possibilities for the disperser. In order to improve the reconstruction potential of the spectrometer, the analytic expressions which describe the CTIS have been expanded into a principal component basis set. The result is a technique for creating an initial estimate of the object and a technique for improving the reconstruction algorithm.

Current electron beam treatment planning algorithms are inadequate to calculate dose distributions in heterogeneous phantoms. Fast Monte Carlo algorithms are accurate in general but their clinical implementation needs validation. Calculations of electron beam dose distributions performed using the fast Monte Carlo system XVMC and the well-benchmarked general-purpose Monte Carlo code EGSnrc were compared with measurements. Irradiations were performed using the 9 MeV and 15 MeV beams from the Clinac 18 accelerator with standard conditions. Percent depth doses and lateral profiles were measured with thermoluminescent dosimeter and electron diode respectively. The accelerator was modelled using EGS4/BEAM, and using an experiment-based beam model. All measurements were corrected by EGSnrc calculated stopping power ratios. Overall, the agreement between measurement and calculation is excellent. Small remaining discrepancies can be attributed to the non-equivalence between physical and simulated lung material, precision in energy tuning, beam model parameters optimisation and detector fluence perturbation effects.

The technique of functional magnetic resonance imaging (fMRI) is rapidly developing from one of technical interest to wide clinical application. fMRI exploits the fact that brain neural activity produces a change in blood oxygenation level dependent (BOLD) response which is recorded at each point in the brain. In a typical experiment, a subject is given a stimulus or cognitive task, and the statistical question is to relate it to the BOLD response, usually via a linear model. The BOLD response is not instantaneous; it is delayed and smoothed by about 6 seconds. In this thesis we propose a rapid method of estimating and making inference about this delay. Our method is compared to other alternatives, and validated on an fMRI data set from an experiment in pain perception.

In positron emission mammography, the use of planar detector limits the angular coverage and introduces more noise than conventional positron emission tomography. / We first studied the sampling artifacts introduced from the use of discrete crystals. The images are reconstructed by back-projecting lines of response from and to the centroid of interaction within the crystal. We postulate that the sampling artifact should be reduced by allowing the lines of response to shift away from the centroid towards the next most probable crystal element. / We then studied noise in the peripheral region of the images. The solid angle function is an image uniformity correction function. The solid angle function is the last thing applied before the images are displayed. We postulate that image quality should improve by re-ordering the solid angle function and the smoothing algorithm. / These two techniques have shown an improvement in contrast, resolution, and noise. An ROC curve analysis showed an improvement of 9.5 % in accuracy.