Early identification of patients with subclinical cardiovascular or cerebrovascular disease manifestation is highly relevant as organ damage might still be reversible. Imaging can be used for... Show moreEarly identification of patients with subclinical cardiovascular or cerebrovascular disease manifestation is highly relevant as organ damage might still be reversible. Imaging can be used for risk stratification and optimizing individual prevention and treatment strategies in patients with metabolic syndrome. This thesis evaluates MR and CT imaging techniques for identifying risk factors and subclinical disease in metabolic syndrome. Show less
Although mortality in old age has significantly decreased over the last fifty years in the developed world, there still remains a large inter-individual variability in ageing trajectories,... Show more Although mortality in old age has significantly decreased over the last fifty years in the developed world, there still remains a large inter-individual variability in ageing trajectories, morbidity and mortality. In the three parts of this thesis, we examined three interacting systems that have been identified as contributing to a slower pace of ageing, namely glucose/insulin metabolism (part I), the thyroid axis (part II), and the autonomic nervous system (part III). We found that familial longevity is associated with a stronger association of insulin parameters with microstructural brain parameters, and by higher TSH secretion, in the absence of differences in basal energy metabolism or differences in heart rate and its variability. Using specialized MRI techniques, we showed that subtle changes in microstructural brain parenchymal homogeneity in relation to insulin can be detected, even in brain tissue that appears normal on conventional MR imaging sequences. Insulin (rather than glucose), seemed to be a stronger indicator of micro- structural brain integrity in normo-glycemic older adults. Furthermore, intranasal application of insulin improved brain perfusion in parietal and occipital gray matter and in the thalamus of older adults. These results deepen our understanding of the physiological mechanisms and processes that underlie the ageing process. Show less
De belangrijkste resultaten van dit proefschrift: de ASAS classificatie criteria voor axSpA blijken robuust en zijn goed toepasbaar in een setting waarbij de waarschijnlijkheid op axSpA lager is... Show moreDe belangrijkste resultaten van dit proefschrift: de ASAS classificatie criteria voor axSpA blijken robuust en zijn goed toepasbaar in een setting waarbij de waarschijnlijkheid op axSpA lager is dan waarin de criteria ontwikkeld zijn. Daarnaast is er op basis van bevindingen in dit proefschrift een belangrijke aanpassing doorgevoerd in een hulpmiddel dat reumatologen begeleidt in het diagnostische proces van (vroege) axSpA. Tevens is het MRI protocol van het SPACE cohort aangepast nadat de toegevoegde waarde van het toedienen van een contrastvloeistof bij het maken van MRI’s nihil bleek te zijn, met als resultaat dat er sinds april 2012 geen MRI’s meer worden gemaakt met de toediening van gadolinium. Dit proefschrift biedt ook adequate handvatten voor verder onderzoek naar de optimale definitie van een positieve MRI. Bovendien worden discrepanties aangaande de beoordeling door verschillende soorten lezers van afwijkingen in de rug (op röntgenfoto’s en MRI’s) aan het licht gebracht waardoor de vraag naar voren komt of training in het onderscheiden van axSpA afwijkingen en afwijkingen die niet gerelateerd zijn aan axSpA van potentiële belang is op de betrouwbaarheid van het beoordelen van afwijkingen in de rug. De onderzoeken in dit proefschrift leveren een bijdrage aan betere herkenning en behandeling van axSpA. Show less
With increasing age the prevalence of hypertension rises. High blood pressure at midlife is associated with cognitive impairment. Nevertheless, in older persons a lower rather than a higher... Show more With increasing age the prevalence of hypertension rises. High blood pressure at midlife is associated with cognitive impairment. Nevertheless, in older persons a lower rather than a higher blood pressure is associated with incident dementia. The main purpose of the work in this thesis was to explore the role of blood pressure in relation to cerebral structure, neurocognitive functioning and hemodynamics of the brain in old age. Therefore, we sought to determine whether discontinuation of antihypertensive therapy in persons aged 75 years and over with mild cognitive deficits and using antihypertensive medication (the Discontinuation of ANtihypertensive Treatment in Elderly people [DANTE] population) would improve their cognitive and psychological functioning. The assumption was that the increase in blood pressure after the discontinuation of antihypertensives would lead to a direct increase in cerebral blood flow and, as a consequence, to an improvement in cerebral functioning. An additional objective was to investigate possible underlying mechanisms in the relation between blood pressure and neurocognitive functioning. To enable this, brain MRI was used to determine whether (lower) blood pressure was associated with (micro)structural damage, cerebral small vessel disease and blood flow in the brain, and also whether the presence of cerebral (micro)structural damage was related to neurocognitive functioning. Show less
The main aim of this thesis is to determine the role of magnetic resonance imaging (MRI) in early rheumatoid arthritis (RA). We set out to improve the MRI protocol and sequences used in arthritis... Show moreThe main aim of this thesis is to determine the role of magnetic resonance imaging (MRI) in early rheumatoid arthritis (RA). We set out to improve the MRI protocol and sequences used in arthritis patients, to detect subclinical inflammation in various patient groups and to describe the clinical implications of MRI. Chapter 1 provides a general introduction to this thesis, in chapter 2 the earliest disease stages of rheumatoid arthritis and the concept of pre-rheumatoid arthritis are further explored. In chapters 3-5 various ways are described to optimize the scanning protocol for arthritis patients. In chapters 6-8 we looked at the presence of inflammation on MRI when no inflammation can be detected at physical examination, i.e. subclinical inflammation. In chapters 9 and 10 we explore some of the clinical implications of the MRI findings. Chapter 11 provides a summary of the thesis and a discussion of the main findings. Show less
This thesis describes neuroimaging techniques to investigate brain networks in healthy aging and dementia. Functional and structural brain networks change with healthy and pathological... Show more This thesis describes neuroimaging techniques to investigate brain networks in healthy aging and dementia. Functional and structural brain networks change with healthy and pathological aging, with differences in network degeneration between different types of dementia. These disease-specific network differences suggest the potential of brain networks to improve diagnostic accuracy. However, at this moment, our findings are only applicable for groups of patients and not yet suitable as a diagnostic tool on an individual basis. Show less
Patients with structural heart disease - e.g. after myocardial infarction or due to a cardiomyopathy - are at increased risk for sudden cardiac death because of arrhythmia. The department of... Show morePatients with structural heart disease - e.g. after myocardial infarction or due to a cardiomyopathy - are at increased risk for sudden cardiac death because of arrhythmia. The department of Cardiology at the Leiden University Medical Center has a strong interest for the underlying substrate and mechanisms of ventricular arrhythmias. Since 2011, research fellow Sebastiaan Piers and his supervisor prof. dr. Katja Zeppenfeld have performed innovative studies, combining advanced electrophysiological data with detailed imaging data derived from CT and MRI. These studies have led to important insights into the substrate and mechanisms of ventricular arrhythmia in patients after myocardial infarction or with a cardiomyopathy. An improved understanding may be the most important prerequisite for the development of effective, individualized and substrate-based therapies for ventricular arrhythmias in the future. Sebastiaan Piers will defend his thesis "Understanding Ventricular Tachycardia: Towards Individualized Substrate-based Therapy" on Thursday January 28th 2016. Show less
This thesis reports on the utility of high permittivity dielectric materials for adjusting the radiofrequency (RF) field in high field MR. The performance-driven trend towards higher static... Show moreThis thesis reports on the utility of high permittivity dielectric materials for adjusting the radiofrequency (RF) field in high field MR. The performance-driven trend towards higher static magnetic field strengths drives MR operation into the regime where the dimensions of the body section being imaged are comparable to the RF wavelength. This results in areas of RF interference within the body, and associated variations in signal intensity and tissue contrast, which can severely reduce the diagnostic image quality. However, the underlying electromagnetic interactions raise the question of whether these mechanisms may also be exploited to establish a remediation. This approach is termed "dielectric shimming," and is the subject of this thesis. The main conclusions from this thesis are that dielectric shimming presents a very simple and effective method for improving MR operation at high field strength. The high permittivity materials allow for tailoring the B1 field without increasing SAR. The technique improves body applications at 3T as well as neuro applications at 7T, and theoretical foundations are presented to harness and exploit this approach. The obtained solutions are low-cost, vendor-independent, do not require any major hardware or software modifications and can therefore be very easily implemented in clinical protocols. Show less
