Background: The combination of positron emission tomography (PET) and magnetic resonance imaging (MRI) (PET-MRI) is a unique hybrid imaging modality mainly used in oncology and neurology. The MRI-based attenuation correction (MRAC) is crucial for correct quantification of PET data. A suitable phantom to validate quantitative results in PET-MRI is currently missing. In particular, the correction of attenuation due to bone is usually not verified by commonly available phantoms. The aim of this work was, thus, the development of such a phantom and to explore whether such a phantom might be used to validate MRACs. Method: Various materials were investigated for their attenuation and MR properties. For the substitution of bone, water-saturated gypsum plaster was used. The attenuation of 511 keV annihilation photons was regulated by addition of iodine. Adipose tissue was imitated by silicone and brain tissue by agarose gel, respectively. The practicability with respect to the comparison of MRACs was checked as follows: A small flask inserted into the phantom and a large spherical phantom (serving as a reference with negligible error in MRAC) were filled with the very same activity concentration. The activity concentration was measured and compared using clinical protocols on PET-MRI and different built-in and offline MRACs. The same measurements were carried out using PET-CT for comparison. Results: The phantom imitates the human head in sufficient detail. All tissue types including bone were detected as such so that the phantom-based comparison of the quantification accuracy of PET-MRI was possible. Quantitatively, the activity concentration in the brain, which was determined using different MRACs, showed a deviation of about 5% on average and a maximum deviation of 11% compared to the spherical phantom. For PET-CT, the deviation was 5%. Conclusions: The comparatively small error in quantification indicates that it is possible to construct a brain PET-MRI phantom that leads to MR-based attenuation-corrected images with reasonable accuracy.

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Optical spectroscopy is a real-time technique that holds promise as a potential surgical guidance tool. Fiber-optic diffuse reflectance spectroscopy (DRS) is a technique capable of intraoperative tissue differentiation. The common DRS focuses on estimating chromophore concentrations in the visible (VIS) wavelength range (400-1000 nm), where spectroscopic features of the blood, pigments, and tissue densities are present between 400 and 700 nm. Recently, extended-wavelength DRS (EWDRS), which extends the spectral window from the VIS through the short wave-infrared region (SWIR) up to 1800 nm, has emerged as a promising approach for identifying nerves and nerve bundles due to the SWIR including robust tissue absorption features associated with nerve-tissue related chromophores, including lipids, water and collagen proteins. One potential application of EWDRS is guiding minimally invasive surgical techniques, such as laparoscopy, where inadvertent injury to pelvic autonomic nerves (PANs) is a primary complication that can result in over 70% of patients suffering long-term side effects, including urinary incontinence and sexual dysfunction. There is a need for objective laparoscopic surgical guidance to precisely identify PANs from other tissues, and an improved basis for EWDRS development could assist clinical translation. Prior development of Fiber-optic DRS for tissue classification in the VIS greatly benefited from the application of modeling techniques for simulation of optical measurements, analysis, and fiber-probe design. Model-based analysis can inform fundamental understanding of measured signals in different measurement scenarios, such as the varying tissue morphologies possible in laparoscopic procedures, and guide application-specific fiber-probe design through comparison of unique illumination/collection geometries; however, the demonstration of these approaches in EWDRS is not widely reported. This dissertation focuses on the advancement of platforms for model-driven analysis of EWDRS for nerve identification. In order to advance the current state of EWDRS, a model-based characterization platform for analysis of a custom-developed fiber-optic EWDRS system was developed in Aim 1, which demonstrated agreement between data collected from optical phantoms, ex vivo microsurgical model, and Monte Carlo (MC) computational simulations of EWDRS measurements. In Aim 2, the model-based platform was used to perform a detailed analysis of two similar EWDRS fiber-optic probes, which indicated subtle differences in the depth-dependent measurement performance. Finally, in Aim 3, the custom EWDRS was prepared for adapting laparoscopic use to demonstrate laparoscopic measurement feasibility, including evaluation of placement variance and customized EWDRS package for short-distance transportation. The successful completion of this dissertation will enable improved analyses of EWDRS devices for a variety of future intraoperative applications. / Bioengineering

The increased probability that future battles will take place in cities can leave military organizations unprepared for future conflicts. Urban warfare requires a different tactical approach than battles in other terrain due to its unique complexity. Previous research on urban warfare tends to agree that combined arms contribute to urban tactical success but lacks on explanations for how it carries into effect inside cities.   This study will examine how combined arms can lead to tactical victory, in a theory-testing approach, by analyzing the U.S assaults on Aachen in 1944 and Fallujah in 2004 during Operation Phantom Fury. Since the Swedish Armed Forces can be considered tactically influenced by Robert Leonhards theory on combined arms, the purpose of this study is to examine the theory’s ability to explain tactical success in urban terrain. The results show that an attacking combined arms force with superior firepower can put the defending enemy in a dilemma. However, the dilemma creates unfavorable conditions for the Alcyoneus principle of the theory to explain why the attacking forces succeeded.

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Successful treatment alternatives for chronic pain conditions are limited. One type of chronic pain that can occur is the condition of phantom limb pain, which can occur after the loss of a limb. Many studies have researched the correlation between chronic pain, tactile acuity, and cortical reorganization. Sensory discrimination training has been shown to improve tactile acuity and be beneficial when trying to reduce the intensity and duration of the pain in chronic pain conditions. A device has been developed by the Center for Bionics and Pain Research, and it is intended to train sensory discrimination. How efficiently this device can train sensory discrimination and how much improvements in the tactile acuity in able-bodied participants can be achieved after using the device have been investigated in this study. 16 able-bodied subjects participated in the study. The subjects received five 40 minutes training sessions on five consecutive days. The assessment of the subjects’ tactile acuity was performed before the first training session and after the last training session. The tactile acuity was also assessed after one to two weeks to determine the long-term effect of the training. There were two psychophysical analyses to determine the participants’ tactile acuity, the two-point discrimination test and the monofilament test. The results showed a significant improvement in the two-point discrimination threshold after the five training sessions, thus showing evidence of the improvement in the tactile acuity after using the sensory discrimination training device. There was no significant improvement in the monofilament test.