Pulse Oxigraphy: And other new in-depth perspectives through the near infrared window

The aim of this thesis was to investigate the feasability of contactless imaging pulse oximetry (proposed term: pulse oxigraphy). The patent disclosed in chapter 2 claims that such pulse oxigraphy can be achieved with camera-derived photoplethysmographic pulse waves at three wavelengths, preferably being 660, 810 and 940nm. From the absorption curves of hemoglobin and oxyhemoglobin it can be easily derived that two of these wavelengths (660 and 940nm) contain oxygenation-related information, and they have proven to be useful for conventional pulse oximetry (in transmission- mode as well as in reflectance-mode). The additional third wavelength (810nm) lies at a so-called isobestic point where the absorption curves of hemoglobin and oxyhemoglobin intersect. Thus, images and/or plethysmographic pulse waves recorded at 810nm do not contain oxygenation-related information, which is useful for reference purposes when dealing with shadows, reflections, movement artifacts and variations in geometry. With regard to pulse oxigraphy the following results were obtained: In chapter 3 we proved that it is possible to derive photoplethysmographic pulse waves containing the heart rythm of a living person at all three required wavelengths from camera recordings collected at a distance of 72 cm. To investigate and validate the capabilities for pulse oxigraphy with this set up, direct measurements on volunteers were sub optimal, because of: Signal-to-noise issues, sequentially recorded heartbeats for oxygen saturation calculations, and lack of a method to induce prolonged stable and adjustable oxygen saturation levels

Magnetic Resonance Imaging of Susceptibility Effects in Carotid Atherosclerosis

This thesis explores the use of susceptibility-weighted imaging (SWI) and quantitative susceptibility mapping (QSM), to characterize carotid artery plaques with and without the use of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle contrast agents. The overall hypothesis is that QSM can serve to differentiate carotid artery plaque features of different susceptibility and provide a positive contrast mechanism for imaging the uptake of USPIOs. Chapter 1 describes the pathophysiology of carotid atherosclerosis. Vulnerable plaques, i.e. those at risk of rupture, can be characterized by the presence of a lipid rich necrotic core (LRNC), intraplaque haemorrhage (IPH), and inflammation. In addition, plaques may develop calcifications that may be protective of rupture. The chapter describes the established multi-contrast imaging protocols used for characterizing plaques. Furthermore, the use of USPIO-contrast agents to image inflammation is described. Chapter 2 describes the physical principles of MR image generation including the sensitivity to magnetic susceptibility. The principles of T2*w imaging, and susceptibility weighted imaging (SWI) are explained. Chapter 3 reviews the principles and post-processing steps involved in commonly used algorithms for QSM in terms of the underlying physical and mathematical principles which are then demonstrated in the form of numerical simulations. Chapter 4 presents the application of SWI to a group of patients who underwent USPIO enhanced MRI on a 1.5T MRI system. Images were acquired prior to infusion and 48 hours post infusion. SWI and gradient echo phase images were used to depict the field inhomogeneities generated by diamagnetic and paramagnetic materials within the plaques, calcification and USPIO-uptake. These results were then compared to a conventional carotid multi-contrast protocol, which includes R2*-mapping and T2*w imaging, and, where available, CT and histology. In chapter 5 QSM is performed in the carotid artery wall of a cohort of normal volunteers on a 1.5T MRI system. Unlike the brain, the neck contains fat which can cause severe errors in the field estimate, which propagate into the susceptibility map. Therefore, QSM was combined with water-fat separation for application in the neck to correct for these artifacts. This correctly estimated a high fat-fraction in fatty tissue in the neck and allowed for a detailed depiction of the anatomy of healthy volunteers. The susceptibility value measured in fatty tissue agreed with literature values. Chapter 6 applies QSM with water-fat separation to a subset of the patient group on a 1.5T MRI system. On pre-contrast scans QSM successfully identified calcification as diamagnetic tissue and the water-fat separation identified a lipid core. On the post-contrast susceptibility maps, USPIO-uptake was identified as hyperintense signal. This allows QSM to provide quantitative contrast in carotid imaging that can identify multiple features simultaneously and to simplify the imaging of USPIO-contrast. The results were confirmed using the multi-contrast carotid MRI protocol and, where available, histology and CT. Chapter 7 discusses the limitations of the current studies and the potential future improvements of the current methodology in terms of MR acquisition, post-processing algorithms and MR protocols. Future studies could serve to further evaluate the potential of QSM in carotid imaging and use it as a novel tool to quantify USPIO uptake in atherosclerotic carotid arteries

Advanced Sensing and Image Processing Techniques for Healthcare Applications

This Special Issue aims to attract the latest research and findings in the design, development and experimentation of healthcare-related technologies. This includes, but is not limited to, using novel sensing, imaging, data processing, machine learning, and artificially intelligent devices and algorithms to assist/monitor the elderly, patients, and the disabled population

Development of Novel Collagen-targeted Protein-based MRI Contrast Agent for Imaging of Chronic Liver and Heart Diseases

Chronic diseases and conditions such as liver and heart diseases are among the most common, costly, and preventable of all health problems. As of 2012 in the U.S., about half of all adults—117 million people—had one or more chronic health conditions. Aortic aneurysm and liver fibrosis are among the most common chronic diseases which are generated by the formation and deposition of excess extracellular matrix proteins (largely type I collagen) as a result of a reparative process, represents one of the most major global health problems. Collagen type I is one of the major diagnostic biomarkers and therapeutic targets for many chronic diseases including heart and liver diseases. Early diagnosis, noninvasive detection and staging of these diseases, remain as one of the major clinical barriers which can lead to effective treatment and stop further progression toward major clinical consequences. MRI as one the popular imaging modalities has several unique advantages for monitoring slow progression and detection of disease with high resolution without using radiation, however, there is an unmet medical need to develop MRI contrast agents with desired sensitivity and collagen specificity. In this dissertation, the successful design of a protein-based contrast agent with collagen type I targeting capability (ProCA32.collagen1) is reported to diagnose and stage liver and heart diseases in many mouse models of caner, fibrosis and aortic aneurysm. ProCA32.collagen1 exhibits the highest relaxivity values for r1 (34 ± 0.12 mM-1.s-1) and r2 (50 ± 0.16 mM-1.s-1) per Gd3+ at 1.4 T and r1 (21.3 ± 0.5 mM-1.s-1) and r2 (108.5 ± 1.2 mM-1.s-1) at 7.0 T. ProCA32.collagen1 can detect both early (Ishak 3 of 6) and late stage mouse liver fibrosis as well as early stage nonalcoholic steatohepatitis (Ishak 1 of 6) in different models with strong metal binding affinity and selectivity. The targeted contrast agent is also capable of detecting disease heterogeneity with high collagen type I binding affinity with dissociation constant of Kd=1.42 ± 0.2 mM. ProCA32.collagen1 has largely reduced dose and strong resistance against transmetallation (104-1012-fold higher metal selectivity for Gd3+ over Ca2+ and Zn2+) compared to existing contrast agents. ProCA32.collagen1 is expected to have strong translational potential to improve detection of different diseases at early stages with high confidence, and subsequently monitor disease progression and patient response to treatment

Molecular Imaging

The present book gives an exceptional overview of molecular imaging. Practical approach represents the red thread through the whole book, covering at the same time detailed background information that goes very deep into molecular as well as cellular level. Ideas how molecular imaging will develop in the near future present a special delicacy. This should be of special interest as the contributors are members of leading research groups from all over the world

Preclinical MRI of the Kidney

This Open Access volume provides readers with an open access protocol collection and wide-ranging recommendations for preclinical renal MRI used in translational research. The chapters in this book are interdisciplinary in nature and bridge the gaps between physics, physiology, and medicine. They are designed to enhance training in renal MRI sciences and improve the reproducibility of renal imaging research. Chapters provide guidance for exploring, using and developing small animal renal MRI in your laboratory as a unique tool for advanced in vivo phenotyping, diagnostic imaging, and research into potential new therapies. Written in the highly successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls. Cutting-edge and thorough, Preclinical MRI of the Kidney: Methods and Protocols is a valuable resource and will be of importance to anyone interested in the preclinical aspect of renal and cardiorenal diseases in the fields of physiology, nephrology, radiology, and cardiology. This publication is based upon work from COST Action PARENCHIMA, supported by European Cooperation in Science and Technology (COST). COST (www.cost.eu) is a funding agency for research and innovation networks. COST Actions help connect research initiatives across Europe and enable scientists to grow their ideas by sharing them with their peers. This boosts their research, career and innovation. PARENCHIMA (renalmri.org) is a community-driven Action in the COST program of the European Union, which unites more than 200 experts in renal MRI from 30 countries with the aim to improve the reproducibility and standardization of renal MRI biomarkers

Correction of spatial distortion in magnetic resonance imaging

Dissertation to Obtain the Degree of Master in Biomedical EngineeringMagnetic Resonance Imaging (MRI) has been a major investigation and research focus among scientific and medical communities. So, new hardware with superior magnetic fields and faster sequences has been developed. However, these improvements result in intensity and spatial distortions, particularly in fast sequences, as Echo Plana Imaging (EPI), used in functional and diffusion-weighed MRI (fMRI and DW-MRI). Therefore, correction of spatial distortion is useful to obtain a higher quality in this kind of images. This project contains two major parts. The first part consists in simulating MRI data required for assessing the performance of Registration methods and optimizing parameters. To assess the methods five evaluation metrics were calculated between the corrected data and an undistorted EPI, namely: Root Mean Square (RMS); Normalized Mutual Information (NMI), Squared Correlation Coefficient(SCC); Euclidean Distance of Centres of Mass (CM) and Dice Coefficient of segmented images. In brief, this part validates the applied Registration correction method. The project’s second part includes correction of real images, obtained at a Clinical Partner. Real images are diffusion weighted MRI data with different b-values (gradient strength coefficient), allowing performance assessment of different methods on images with increasing b-values and decreasing SNR. The methods tested on real data were Registration, Field Map correction and a new proposed pipeline, which consists in performing a Field Map correction after a registration process. To assess the accuracy of these methods on real data, we used the same evaluation metrics, as for simulated data, except RMS and Dice Coefficient. At the end, it was concluded that Registration-based methods are better than Field Map, and that the new proposed pipeline produces some improvements in the registration. Regarding the influence of b-value on the correction, it is important to say that the methods performed using images with higher b’s showed more improvements in regarding metric values, but the behaviour is similar for all b-values

Ultrasound Imaging

This book provides an overview of ultrafast ultrasound imaging, 3D high-quality ultrasonic imaging, correction of phase aberrations in medical ultrasound images, etc. Several interesting medical and clinical applications areas are also discussed in the book, like the use of three dimensional ultrasound imaging in evaluation of Asherman's syndrome, the role of 3D ultrasound in assessment of endometrial receptivity and follicular vascularity to predict the quality oocyte, ultrasound imaging in vascular diseases and the fetal palate, clinical application of ultrasound molecular imaging, Doppler abdominal ultrasound in small animals and so on

Evaluation of Traumatic Brain Injury Using Magnetic Resonance Spectroscopy

Traumatic brain injury (TBI) is responsible for a third of all injury-related deaths in the United States. With the lack of structural imaging biomarkers available for the detection and evaluation of TBI sequelae, unambiguous diagnosis and prognosis in TBI still remain a huge challenge. Furthermore, complications arising from TBI can lead to cognitive, social, emotional and behavioral defects later in life. Even in confirmed cases of head injury, computed tomography (CT) and conventional MR techniques are limited in their ability to predict the neuropsychological outcome of patients. While the initial trauma can induce structural impairment of brain tissue, the bulk of the cerebral dysfunction ensuing from TBI is due to alterations in cellular biochemical processes that occur in the days and weeks following the traumatic incident. There is therefore a need for advanced imaging modalities that are able to probe the more underlying cellular changes that are induced by TBI. Understanding such cellular changes will be useful in predicting patient outcome and designing interventions to alleviate the injury sequelae. Magnetic Resonance Spectroscopy (MRS) is a non-invasive imaging modality that is capable of detecting cellular metabolic changes in in vivo tissue. In this study we will assess the use of MRS as a clinically relevant tool in the diagnostic and prognostic evaluation of TBI. To this end, we have laid out the following specific aims: (i) To understand the nature and implications of neurometabolic sequelae in mild traumatic brain injury (mTBI) by carrying out cross-sectional comparisons of mTBI patients to neurologically healthy subjects at different stages of injury and to determine associations between early neurometabolic patterns and chronic neuropsychological performance in mTBI patients (ii) To develop novel MRS pulse sequence acquisition and data processing techniques that will enable a more thorough neurometabolic evaluation of TBI and enhance quantification of MRS data (iii) To develop automated classification systems in mTBI using early neurometabolic information that will aid discrimination between subjects with and without injury related sequelae and allow the prediction of symptomatic outcome at the later stages of injury. The research presented herein will help to enhance the utility of MRS in the evaluation of TBI