Emphysema, a subset of COPD, occurs due to an abnormal inflammatory response to noxious gases or particles leading an influx of immunologic cells. Recent studies have demonstrated endothelial dysfunction in COPD subjects and are suggestive of a vascular phenotype present in COPD that is not fully characterized. We hypothesize that processes affecting the pulmonary vasculature lead to early changes important in the pathogenesis of COPD. This work focuses on the use of multidetector-row computed tomography (MDCT)-based measures of pulmonary blood flow (PBF), mean transit time (MTT) and pulmonary vascular volume (TPVV) to gain new insights into vasculature-related changes present in COPD. As a precursor to using perfusion MDCT imaging to phenotype lung disease, we demonstrated good regional correlation of PBF measurements obtained with MDCT imaging and fluorescent microspheres (FMS) at a FMS piece size resolution of 1.9 cm3 and regional volume level of 8-10 cm3. Additionally, we developed an ex vivo perfusion system, and applied quantitative image analysis techniques to study the lung preparation's stability over 120 minutes. We further validated CT-based PBF and MTT measurements by demonstrating physiologically appropriate responses to a range of flow rates with this new system. Finally, quantitative MDCT-based measurements were used to characterize a novel phenotype of emphysema and test hypotheses regarding vasculature-related changes in smokers and COPD subjects. We demonstrated increased heterogeneity in regional MTT and PBF measurements in smokers with preclinical emphysema compared with smokers with normal lung function and imaging studies and nonsmokers. This data is supportive of the notion that inflammatory-based vascular responses to hypoxia are occurring in smokers susceptible to COPD, but are successfully blocked in smokers without signs of emphysema. A new CT-based measure, TPVV, was studied and we demonstrate its association with total lung volume and body size metrics. TPVV measurements correlated with measures of COPD severity. A trend linking increased TPVV with increased endothelial dysfunction was observed, suggesting that pathological changes of COPD have an effect on the pulmonary vasculature. This work demonstrates the importance of functional information that can compliment structural, anatomical information to answer questions based on the lung physiology and pathological disease processes.

In the recent years, Dynamic Nuclear Polarization (DNP) has emerged as a very promising technique for enhancing the sensitivity of the magnetic resonance spectroscopy and imaging (MRSI). A number of nuclei, namely 13C, 15N, 29Si, 89Y, and 129Xe, have been successfully polarized and a few of them have been employed in the in-vivo studies for functional imaging and metabolism. Hyperpolarized 13C-labeled compounds have wide applications in the metabolic and perfusion studies and can be used for early stage disease diagnosis, response to treatment, prognosis etc. DNP has been demonstrated in the 31P nucleus in nucleotides triphosphates as an application for the structural analysis and identification techniques. In this work, 31P DNP has been successfully applied, optimized and demonstrated in Dimethyl Methyl Phosphonate (DMMP) for the first time. DMMP is a freely diffusible tracer and hyperpolarized DMMP can potentially be used in the perfusion studies using MR imaging and spectroscopic techniques. The polarization buildup and signal enhancements were optimized for two different radicals, a nitroxyl radical TEMPO and a trityl radical OX063. Microwave frequency sweeps were done for both the radicals to find out the optimum frequencies for maximum polarization, Maximum signal enhancement (¡Ö2300 folds) and maximum percent polarization buildup (2.15%) were achieved by polarizing DMMP with the radical OX063 at the microwave frequency of 94.080 GHz with a glassing matrix containing D2O and glycerol and by using D2O in the dissolution step. DMMP was hyperpolarized at the optimum conditions and injected in a mouse for in-vivo spectroscopy and imaging. The results show that hyperpolarized DMMP is a potential candidate for functional imaging and metabolism.

Les maladies cardiovasculaires représentent la première cause de mortalité dans le monde, et un tiers de ces décès sont causés par la maladie coronaire et la rupture de plaques d'athérome vulnérables. L'altération hétérogène de la microcirculation coronaire est un phénomène précoce lié à de nombreux facteurs de risque cardiovasculaire qui peut fortement présager du développement ultérieur de la maladie coronaire, et conduire à l'apparition d'une hétérogénéité de la perfusion myocardique. La médecine nucléaire permet l'étude de la perfusion myocardique en routine clinique grâce à la réalisation de scintigraphies après injection d'un traceur radioactif du débit sanguin coronaire. L'analyse des images scintigraphiques de la perfusion permet actuellement le dépistage de l'ischémie myocardique, mais la capacité de la technique à mesurer l'hétérogénéité de la perfusion dans des zones apparemment normalement perfusées est inconnue. La première partie de cette thèse porte sur une étude clinique rétrospective visant à déterminer la faisabilité de la quantification de l'hétérogénéité de la perfusion du myocarde mesurée par tomographie d'émission monophotonique (TEMP) au Thallium-201 chez des patients diabétiques par rapport à des sujets sains. L'étude clinique a démontré la capacité du Thallium-201 en imagerie TEMP de routine à quantifier une hétérogénéité de la perfusion du myocarde plus importante chez des patients diabétiques par rapport à des individus normaux. La seconde partie de cette thèse teste l'hypothèse que l'hétérogénéité de la perfusion du myocarde pourrait être quantifiée en imagerie du petit animal TEMP au Thallium-201 et/ou au Technetium-99m-MIBI par une étude expérimentale chez deux modèles animaux de diabète, et serait en corrélation avec des altérations histologiques. L'absence de différence d'hétérogénéité de la perfusion myocardique entre les animaux diabétiques et contrôles suggère que les modèles animaux sont peu adaptés, ou que la technologie actuellement disponible ne semble pas satisfaisante pour obtenir des résultats similaires à l'étude clinique.

<p>Under 20 års tid har Perimed AB utvecklat och tillverkat LDPM- och LDPI-instrument som är baserade på en analog filterkonstruktion. De analoga komponenterna i konstruktionen är komplexa och icke-linjära med hänsyn till frekvens och de driver även med temperaturen. Funktionen hos konstruktionen beror också kraftigt av att de analoga komponenterna trimmas in under produktionen.</p><p>Det här examensarbetet syftar till att ta fram en alternativ design baserad kring en digital signal processor. Den digitala signalbehandlingsmetod som beskrivs baseras på väl förankrade laser-Doppler perfusionsteorier. Den implementerade signalbehandlingsalgoritmen beräknar perfusionen ur en samplad fotodetektorström, som har filtrerats till AC- och DC-komponenter med hjälp av ett analogt detektorkort. Algoritmen producerar en råperfusionssignal genom att beräkna en frekvensviktad summa av fotodetektorströmmens effektspektrum. Kompensation för detektorns brus och normalisering med ljusintensitet har också implementerats.</p><p>Den presenterade implementationen har verifierats mot ett exemplar av LDPM-enheten PF 5010 som har använts som referensinstrument vid alla mätningar. Mätningar in vitro har påvisat liknande mätresultat som referensinstrumentet för en referensvätska med hög perfusion och även för ett statiskt mätobjekt. Vidare har implementationen verifierats med mätningar in vivo på hud, vilket har påvisat nära nog identiska signalnivåer och gensvar på värmeprovokationer som referensinstrumentet.</p><p>Den demonstrerade uppfinningen förenklar tillverkningen av instrumenten eftersom antalet komponenter reduceras avsevärt och därmed antalet produktionstester. Användandet av en DSP reducerar dessutom instrumentets temperaturkänslighet eftersom den ersätter flera temperaturkänsliga komponenter.</p> / <p>For 20 years Perimed AB have been developing and manufacturing LDPM and LDPI instruments based on an analog filter construction. The analog components in the construction are complex and suffer from non-linear frequency dependency and temperature drifts. The functionality of the design is also heavily depending on analog components which need to be trimmed in the production.</p><p>In this thesis, an alternative design employing a digital signal processor is presented. The signal processing method used is based on well established laser Doppler perfusion theories. The implemented signal processing algorithm calculates the perfusion from a sampled photodetector current, pre-filtered into AC and DC components by an analog detector card. The algorithm produces a raw perfusion signal by calculating a frequency weighted sum of the power spectral density, PSD, of the photocurrent. Detector noise compensation and light intensity normalization of the signal has also been implemented.</p><p>The presented digital implementation has been verified using the PF 5010 LDPM unit as a reference. In vitro measurements have shown similar behaviour as the reference in a highly perfused reference fluid as well as for a static scatterer. Furthermore, the DSP implementation has been verified on in vivo measurements of skin, showing nearly identical signal levels and response to heat provocation as the reference.</p><p>The demonstrated invention improves the manufacturability of the instruments since it reduces the number of electronic components significantly and thus, the amount of manufacturing tests. The DSP also reduces the temperature sensitivity of the instrument since it replaces several analog components sensitive to temperature changes.</p>

Grandes defectos óseos constituyen un reto para el campo clínico, ya que no puede ser reparado por el propio organismo, sino que requieren la implantación de injertos de hueso adecuado. Para superar los inconvenientes de los injertos procedentes de fuentes autólogas o allogeneicas, la ingeniería de tejidos óseos pretende sustituir el tejido perdido utilizando el cultivo de células in vitro sobre biomateriales porosos. El cultivo de células en grandes andamios porosos ha demostrado ser difícil, que requiere bioreactores, que se utilizan para el cultivo de tejidos y el estudio del comportamiento de células en 3D de los andamios. De interés especial es el condicionamiento mecánico de los tejidos cultivados por bioreactor de la ingeniería del tejido óseo, que es capaz de aumentar el potencial osteogénico de los injertos sintéticos.En este trabajo, dos sistemas de bioreactores fueron desarrollados para permitir comprender las propiedades bioactivas de andamios de diferentes materiales y la mecanoregulación del comportamiento de células o tejidos. Un sistema de bioreactor de perfusión in vitro fue desarrollado para el sembrado y cultivo de células incorporadas en cilindros de un biomaterial poroso. Varios estudios para la determinación de los parámetros del sembrado de células aplicable se llevaron a cabo, así como experimentos de cultivo de células bajo flujo de fluido constante con una estimulación mecánica adicional por alternancia del flujo.Un sistema de cámara ósea fue desarrollado como un bioreactor in vivo. El sistema produjo un defecto óseo grande en tibias de perros y permitió la implantación repetida de grandes andamios porosos de materiales diferentes. El tejido creciendo en los andamios permite extraer conclusiones sobre las propiedades de osteoconductividad u osteinductividad de los andamios. Además, un dispositivo de compresión se ha desarrollado para aplicar cargas cíclicas en los andamios en vivo para estudiar el efecto de la estimulación mecánica en el desarrollo de los tejidos.Los estudios con el sistema de perfusión desarrollado han demostrado que el sembrado de células en grandes andamios porosos es posible, lo que se considera crucial para el cultivo celular. El largo tiempo de cultivo de células mostró la proliferación de las células madre mesenquimales hasta dos semanas. El patrón de estimulación utilizado en el estudio aumentó la expresión de la osteocalcina, lo que indica una mayor actividad de las células, pero la ausencia de expresión de RunX2 y colágeno I impidió la determinación concluyente de la diferenciación.El sistema desarrollado de la cámara ósea demostró su funcionalidad en el entorno quirúrgico durante los experimentos in vivo. Complicaciones durante los experimentos no permitieron la aplicación de las cargas cíclicas de los andamios implantados. La formación de hueso retrasada debido al defecto óseo creado y material de andamios restantes no permitieron conclusiones definitivas acerca de las propiedades del material del andamio. Sin embargo, el estudio proporciona datos para el desarrollo futuro del dispositivo y protocolo clínico.Los estudios realizados constituyen una novedad en respecto a la creación de bioreactores para el estudio de la andamios porosos sintéticos de grandes dimensiones in vitro e in vivo. Los sistemas desarrollados constituyen la base para otros estudios en mecanobiología de las células óseas y los tejidos. / Large bone defects constitute a challenge for the clinical field, because they cannot be repaired by the body itself, but require the implantation of suitable bone grafts. To overcome the drawbacks of grafts from autologous or allogous sources, modern bone tissue engineering aims to replace lost tissue by cultivating cells in vitro on porous biomaterials. The cell culture on large porous scaffolds has shown to be difficult, requiring bioreactors, which are used for tissue culture and the study of cell behaviour in 3D scaffolds. Of special interest is the mechanical conditioning of the cultured tissue for bioreactor-based bone tissue engineering, which is able to enhance the osteogenic potential of the synthetic grafts.In this work two bioreactor systems were developed to allow insight into bioactive properties of different scaffold materials and the mechanoregulation of cell or tissue behaviour. An in vitro perfusion bioreactor system was developed for the cell seeding and culture on porous biomaterial cylinders. Several studies for the determination of applicable cell seeding parameters were conducted, as well as experiments of cell culture under steady fluid flow with additional mechanical stimulation by alternating fluid flow. A bone chamber system was developed as an in vivo bioreactor. The system produced a large bone defect in dog tibia and allowed the repeated implantation of large porous scaffolds of different material compositions.The ingrowing tissue was observed to allow conclusions about osteoconductive or osteinductive properties of the scaffolds. Additionally a compression device was developed to apply cyclic loading on the scaffolds in vivo to study the effect of mechanical stimulation on tissue development.The studies with the developed in vitro perfusion bioreactor system have shown that it is possible to seed cells throughout large porous scaffolds, which is deemed crucial for the further cell culture. The long time cell culture showed the proliferation of mesenchymal stem cells up to two weeks. The stimulation pattern used in the study enhanced the expression of osteocalcin, indicating an enhanced cell activity, but the absence of RunX2 and collagen I expression rendered the determination of differentiation inconclusive.The developed bone chamber system proved to be functional in the surgical environment during the in vivo experiments. Occurring complications during the experiments did not allow the application of the cyclic loading of implanted scaffolds. Delayed bone formation due to created bone defect and remaining scaffold material did not allow final conclusions about the scaffold material properties. Nevertheless the study provides input for further development of the device and clinical protocol.The conducted studies constitute a novelty regarding the creation of bioreactors for the study of synthetic porous scaffolds of large dimensions in vitro and in vivo. The developed systems form the basis for further studies in mechanobiology of bone cells and tissue.

Under 20 års tid har Perimed AB utvecklat och tillverkat LDPM- och LDPI-instrument som är baserade på en analog filterkonstruktion. De analoga komponenterna i konstruktionen är komplexa och icke-linjära med hänsyn till frekvens och de driver även med temperaturen. Funktionen hos konstruktionen beror också kraftigt av att de analoga komponenterna trimmas in under produktionen. Det här examensarbetet syftar till att ta fram en alternativ design baserad kring en digital signal processor. Den digitala signalbehandlingsmetod som beskrivs baseras på väl förankrade laser-Doppler perfusionsteorier. Den implementerade signalbehandlingsalgoritmen beräknar perfusionen ur en samplad fotodetektorström, som har filtrerats till AC- och DC-komponenter med hjälp av ett analogt detektorkort. Algoritmen producerar en råperfusionssignal genom att beräkna en frekvensviktad summa av fotodetektorströmmens effektspektrum. Kompensation för detektorns brus och normalisering med ljusintensitet har också implementerats. Den presenterade implementationen har verifierats mot ett exemplar av LDPM-enheten PF 5010 som har använts som referensinstrument vid alla mätningar. Mätningar in vitro har påvisat liknande mätresultat som referensinstrumentet för en referensvätska med hög perfusion och även för ett statiskt mätobjekt. Vidare har implementationen verifierats med mätningar in vivo på hud, vilket har påvisat nära nog identiska signalnivåer och gensvar på värmeprovokationer som referensinstrumentet. Den demonstrerade uppfinningen förenklar tillverkningen av instrumenten eftersom antalet komponenter reduceras avsevärt och därmed antalet produktionstester. Användandet av en DSP reducerar dessutom instrumentets temperaturkänslighet eftersom den ersätter flera temperaturkänsliga komponenter. / For 20 years Perimed AB have been developing and manufacturing LDPM and LDPI instruments based on an analog filter construction. The analog components in the construction are complex and suffer from non-linear frequency dependency and temperature drifts. The functionality of the design is also heavily depending on analog components which need to be trimmed in the production. In this thesis, an alternative design employing a digital signal processor is presented. The signal processing method used is based on well established laser Doppler perfusion theories. The implemented signal processing algorithm calculates the perfusion from a sampled photodetector current, pre-filtered into AC and DC components by an analog detector card. The algorithm produces a raw perfusion signal by calculating a frequency weighted sum of the power spectral density, PSD, of the photocurrent. Detector noise compensation and light intensity normalization of the signal has also been implemented. The presented digital implementation has been verified using the PF 5010 LDPM unit as a reference. In vitro measurements have shown similar behaviour as the reference in a highly perfused reference fluid as well as for a static scatterer. Furthermore, the DSP implementation has been verified on in vivo measurements of skin, showing nearly identical signal levels and response to heat provocation as the reference. The demonstrated invention improves the manufacturability of the instruments since it reduces the number of electronic components significantly and thus, the amount of manufacturing tests. The DSP also reduces the temperature sensitivity of the instrument since it replaces several analog components sensitive to temperature changes.

As a non-invasive method, functional MRI (fMRI) has been widely used for human brain mapping. Although many applications have been done, there are still some critical issues associated with fMRI. Perfusion-weighted fMRI (PWI) with exogenous contrast agent suffered from the problems of recirculation, which could contaminate the cerebral blood flow (CBF) estimation and make its ability of prediction "tissue-at-risk" in debate. We propose a rapid and effective method that combines matched-filter-fitting (MFF) and ICA where ICA was used for regions with a prolonged TTP and MFF was utilized for the remaining areas. The calculation of cerebral hemodynamics afterwards demonstrates that the proposed method may lead to a more accurate estimation of CBF. The extent to which CBF is reduced in relationship to normal values has been utilized as an indicator to discern ischemic injury. However, despite the well known difference in CBF between gray and white matter, relatively little attention has been given as to how CBF may be differently altered in gray and white matter during ischemia due to the inability to accurately separate gray and white matter. To this end, we propose a robust clustering method for automatic classification of perfusion compartments. The method is first to apply a robust principal component analysis to reduce dimension and then to use a mixture model of multivariate T distribution for clustering. Our results in ischemic stroke patients at the hyperacute phase show the clear advantage over the conventional technique. BOLD fMRI, as a feasible and preferred method for developmental neuroimaging, is seldom conducted in pediatric subjects and therefore the information about brain functional development in the early age is somewhat lacking. To this end, this dissertation also focuses on how functional brain connectivity may be present in pediatric subjects in a sleeping condition. We propose a statistical method to delineate frequency-dependent brain connectivity among brain activation regions, and an automatic procedure combined with spatial ICA approach to determine the brain functional connectivity. Our results suggest that functional connectivity exists as young as two weeks old for both sensorimotor and visual cortices and that functional connectivity is highly age-dependent. / Dissertation

Individuals with spinal cord injury (SCI) demonstrate reduced limb blood flow and muscle spasticity. It is plausible that the accumulation of metabolites, resulting from reduced perfusion, could exacerbate spasticity via activation of fusimotor neurons by Group III and IV afferents. PURPOSE: To determine the association between peripheral blood flow and muscle spasticity in persons with SCI. METHODS: A total of 16 individuals with SCI were classified into high (N=6), low (N=5), and no (N=5) spasticity groups according to their spasticity levels indicated by the modified Ashworth scale scores. Blood flow was measured in femoral and brachial arteries using duplex Doppler ultrasound and was normalized to limb lean mass obtained with dual energy X-ray absorptiometry. RESULTS: There were no significant group differences in age (30.5±4.15, 38.48±4.61, 32.6±4.89 years), time post SCI (8.5±4.2, 12.6±4.74, 6.8±1.66 years), American SCI Association motor scores (39.2±7.78, 59±12.34, 53.4±1.08), or sensory scores (96±22.1, 144.4±13.97, 130±13.8). Femoral artery blood flow, adjusted for limb lean mass, was significantly different (p=0.002) across the three leg spasticity groups (high 76.03±6.44, low 95.12±15.49, no 142.53±10.86 ml/min/kg).Total leg muscle spasticity scores were significantly and negatively correlated with femoral artery blood flow (r=-0.60, p=0.014). There was no significant difference in brachial artery blood flow between the three groups, indicating that the reduction in blood flow was confined to injured limbs and not due to systemic cardiovascular disorder. CONCLUSION: Among SCI patients, whole-leg blood flow is progressively lower in individuals with greater spasticity scores. These results suggest that a reduction in lower limb perfusion, among other factors, plays a significant role in the pathogenesis leading to muscle spasticity after SCI. / text

My PhD research involves multi-disciplinary areas of study such as measuring perfusion of blood vessels in hamster dorsal skin using laser speckle imaging technique. In this study the changes were measured in blood flow velocity and diameters of micro vasculatures after the influence of glycerol application. The second study identifies the changes in morphology and optical properties of eye tissue after applying hyper-osmotic agent such as 100% anhydrous glycerol. Further investigation on the reversal process was performed without any application of 0.9% saline. The third study identified the variation in fluorescence in hamster dorsal skin tissue and enucleated porcine eyes with temperature. This study investigated the variation in fluorescence intensity with temperatures starting at 14°C and compared in vivo and in vitro results for consistency. The fourth study investigated an implantable drug delivery package that was fabricated using PMMA and implanted between the sub-conjunctival and super-scleral space and release the content of the device by either mechanical pressure or light-activated ophthalmic Nd:YAG laser after optically clearing the eye tissue by topical application of a hyper-osmotic agent, 100% anhydrous glycerol. A hyper-osmotic agent creates a transport region in the conjunctiva and sclera to get visual access of the compartments in the drug delivery package. This new technology would provide the option to the patient of one time implantation of the carrier system containing the drug. Each time the patient requires medication a ND-YAG or other laser beam will propagate through the cleared eye tissue to release the drug in measurable doses at the discretion of the doctor from the package directly in to the vitreous humor. In this study we have measured half-life of the dye in the vitreous humor or posterior chamber and biocompatibility. The last study had drawn distinction between the fluorescence signals based on the location (anterior or posterior chamber) of the 10% Na fluorescence dye in the in vivo rabbit and ex vivo pig eyes. / text

In the early 1920s, Otto Warburg demonstrated that tumor cells have a capacity to convert glucose and other substrates into lactic acid instead of CO2 and water, even under aerobic conditions. Consequently, Warburg assumed that the intracellular pH (pHi) of tumor was acidic. However, later studies have shown that maintenance of pHi within a pH range of 7.0-7.2 is necessary for normal cellular proliferation and that the extracellular pH (pHe) is partially acidic in solid tumors. A low pHe may be an important factor inducing invasive behavior in tumor cells. Research into causes and consequences of this acid pH of tumors are highly dependent on accurate, precise and reproducible measurements. Techniques for measuring tissue pHi and pHe have undergone great changes since 1950s. From microelectrode and dye distribution studies, measurement of pH underwent a revolution with the advent of pH-sensitive dyes that could be loaded into the cytosol. Further significant advances have come from the measurement of cell and tissue pH in whole organisms by magnetic resonance spectroscopy (MRS), magnetic resonance imaging (MRI) and pH-sensitive Positron Emission Tomography (PET) radiotracers.