2,967 research outputs found
Optimization of the management and triage of stroke patients in the acute phase
Acute ischemic stroke (AIS) due to a large vessel occlusion (LVO) is a devastating disease associated with high rates of morbidity and mortality. Currently, the standard of care for patients presenting with a LVO is removal of the clot with specialized catheters (endovascular treatment). Although endovascular treatment has substantially improved the outcomes of AIS patients, still roughly 50% of patients suffer from severe disability or death. Due to the very high time dependency of the treatment effect, strategies to reduce time to treatment to a minimum are highly warranted. As of now no consensus exists on the best possible triage strategy for suspected AIS patients. One possible approach to reduce time delays within the hospital is to transport patients directly from the emergency room to the angiography room for diagnosis of a vessel occlusion and subsequent treatment (One-Stop management) instead of transporting the patient first to the CT room and after diagnosis of a vessel occlusion to the angiography room for treatment (traditional triage pathway). Imaging in the One-Stop management pathway is done with flat detector CT (FDCT) instead of traditional multidetector CT (MDCT). Many clinicians are still hesitant to use this triage pathway due to missing data and lower confidence in the quality of FDCT imaging. Therefore, several research gaps and challenges remain for the optimization of the management and triage of suspected stroke patients in the acute phase, of which we selected three aspects to focus on in the following topics that comprise this PhD thesis.
The first topic focusses on the radiation burden caused by alternative imaging modalities in AIS patients. While flat-detector CT (FDCT) imaging becomes more and more acknowledged as an alternative imaging modality for the diagnosis of an AIS and an LVO, the effective dose to patient of FDCT protocols was not evaluated systematically. For the widespread implementation of FDCT as an imaging modality it must be secured that no excess harm is caused due to a higher burden of radiation. We therefore measured the effective dose to patient and the eye lens dose on two angiography systems and compared it with measurements on the latest generation of commonly used MDCT systems.
The second topic focusses on the presentation of suspected AIS patients. As there is no high-level evidence for the implementation of a One Stop management approach, we are planning to conduct a randomized controlled trial. However, for the conduct of such a trial it is important to have reliable information of the expected patient cohort. We therefore analyzed all patients presenting to a tertiary university hospital in one year to give an estimate on the patient collectives expected for such a trial. The data can further be used to plan resources accordingly in times of expanding indications for endovascular treatment of AIS patients.
The third and final topic summarizes the available evidence regarding One-Stop management and direct to angiography approaches in a systematic review and meta-analysis. It gives an overview over the research conducted so far in this field and is the foundation for the planning of a randomized controlled trial evaluating a One-Stop management approach for suspected AIS patients
3D reconstruction of cerebral blood flow and vessel morphology from x-ray rotational angiography
Three-dimensional (3D) information on blood
flow and vessel morphology is important when
assessing cerebrovascular disease and when monitoring interventions. Rotational angiography
is nowadays routinely used to determine the geometry of the cerebral vasculature. To this end,
contrast agent is injected into one of the supplying arteries and the x-ray system rotates around
the head of the patient while it acquires a sequence of x-ray images. Besides information on the
3D geometry, this sequence also contains information on blood flow, as it is possible to observe
how the contrast agent is transported by the blood. The main goal of this thesis is to exploit
this information for the quantitative analysis of blood flow.
I propose a model-based method, called
flow map fitting, which determines the blood flow
waveform and the mean volumetric flow rate in the large cerebral arteries. The method uses a
model of contrast agent transport to determine the
flow parameters from the spatio-temporal
progression of the contrast agent concentration, represented by a flow map. Furthermore, it
overcomes artefacts due to the rotation (overlapping vessels and foreshortened vessels at some
projection angles) of the c-arm using a reliability map.
For the flow quantification, small changes to the clinical protocol of rotational angiography
are desirable. These, however, hamper the standard 3D reconstruction. Therefore, a new method
for the 3D reconstruction of the vessel morphology which is tailored to this application is also presented.
To the best of my knowledge, I have presented the first quantitative results for blood flow
quantification from rotational angiography. Additionally, the model-based approach overcomes
several problems which are known from flow quantification methods for planar angiography.
The method was mainly validated on images from different phantom experiments. In most
cases, the relative error was between 5% and 10% for the volumetric mean flow rate and between
10% and 15% for the blood flow waveform. Additionally, the applicability of the flow model was shown on clinical images from planar angiographic acquisitions. From this, I conclude that the method has the potential to give quantitative estimates of blood flow parameters during
cerebrovascular interventions
Angioplasty, Various Techniques and Challenges in Treatment of Congenital and Acquired Vascular Stenoses
The field of performing transcatheter interventions to treat vascular lesions has exploded over the past 20 years. Not only has the technology changed, especially in the arena of balloon/stent devices, but the techniques of approaching complex lesions has evolved over the past decade. Lesions that no one would have imagined treating back in the 1990's are now being done routinely in the catheterization suite. This book provides an update on the current techniques and devices used to treat a wide variety of lesions. Though, at first, the outward appearance of the topics appears to be varied, they are all related by the common thread of treating vascular lesions. We hope, by publishing this book, to accomplish two things: First, to offer insight from experts in their field to treat, both medically and procedurally, complex vascular lesions that we frequently encounter. Secondly, we hope to promote increased communication between areas of medicine that frequently don't communicate, between adult interventional cardiologists, pediatric interventional cardiologists, interventional radiologists, and neurosurgeons. Much can be learned from our respective colleagues in these areas which can further our own world of interventions
Automatic Spatiotemporal Analysis of Cardiac Image Series
RĂSUMĂ
Ă ce jour, les maladies cardiovasculaires demeurent au premier rang des principales causes de
dĂ©cĂšs en AmĂ©rique du Nord. Chez lâadulte et au sein de populations de plus en plus jeunes,
la soi-disant Ă©pidĂ©mie dâobĂ©sitĂ© entraĂźnĂ©e par certaines habitudes de vie tels que la mauvaise
alimentation, le manque dâexercice et le tabagisme est lourde de consĂ©quences pour les personnes
affectées, mais aussi sur le systÚme de santé. La principale cause de morbidité et de
mortalitĂ© chez ces patients est lâathĂ©rosclĂ©rose, une accumulation de plaque Ă lâintĂ©rieur des
vaisseaux sanguins à hautes pressions telles que les artÚres coronaires. Les lésions athérosclérotiques
peuvent entraĂźner lâischĂ©mie en bloquant la circulation sanguine et/ou en provoquant
une thrombose. Cela mĂšne souvent Ă de graves consĂ©quences telles quâun infarctus. Outre les
problÚmes liés à la sténose, les parois artérielles des régions criblées de plaque augmentent la
rigidité des parois vasculaires, ce qui peut aggraver la condition du patient. Dans la population
pédiatrique, la pathologie cardiovasculaire acquise la plus fréquente est la maladie de
Kawasaki. Il sâagit dâune vasculite aigĂŒe pouvant affecter lâintĂ©gritĂ© structurale des parois des
artĂšres coronaires et mener Ă la formation dâanĂ©vrismes. Dans certains cas, ceux-ci entravent
lâhĂ©modynamie artĂ©rielle en engendrant une perfusion myocardique insuffisante et en activant
la formation de thromboses.
Le diagnostic de ces deux maladies coronariennes sont traditionnellement effectuĂ©s Ă lâaide
dâangiographies par fluoroscopie. Pendant ces examens paracliniques, plusieurs centaines de
projections radiographiques sont acquises en sĂ©ries suite Ă lâinfusion artĂ©rielle dâun agent de
contraste. Ces images révÚlent la lumiÚre des vaisseaux sanguins et la présence de lésions
potentiellement pathologiques, sâil y a lieu. Parce que les sĂ©ries acquises contiennent de lâinformation
trĂšs dynamique en termes de mouvement du patient volontaire et involontaire (ex.
battements cardiaques, respiration et dĂ©placement dâorganes), le clinicien base gĂ©nĂ©ralement
son interprĂ©tation sur une seule image angiographique oĂč des mesures gĂ©omĂ©triques sont effectuĂ©es
manuellement ou semi-automatiquement par un technicien en radiologie. Bien que
lâangiographie par fluoroscopie soit frĂ©quemment utilisĂ© partout dans le monde et souvent
considĂ©rĂ© comme lâoutil de diagnostic âgold-standardâ pour de nombreuses maladies vasculaires,
la nature bidimensionnelle de cette modalitĂ© dâimagerie est malheureusement trĂšs
limitante en termes de spécification géométrique des différentes régions pathologiques. En effet,
la structure tridimensionnelle des stĂ©noses et des anĂ©vrismes ne peut pas ĂȘtre pleinement
appréciée en 2D car les caractéristiques observées varient selon la configuration angulaire de
lâimageur. De plus, la prĂ©sence de lĂ©sions affectant les artĂšres coronaires peut ne pas reflĂ©ter
la véritable santé du myocarde, car des mécanismes compensatoires naturels (ex. vaisseaux----------ABSTRACT
Cardiovascular disease continues to be the leading cause of death in North America. In adult
and, alarmingly, ever younger populations, the so-called obesity epidemic largely driven by
lifestyle factors that include poor diet, lack of exercise and smoking, incurs enormous stresses
on the healthcare system. The primary cause of serious morbidity and mortality for these
patients is atherosclerosis, the build up of plaque inside high pressure vessels like the coronary
arteries. These lesions can lead to ischemic disease and may progress to precarious blood
flow blockage or thrombosis, often with infarction or other severe consequences. Besides
the stenosis-related outcomes, the arterial walls of plaque-ridden regions manifest increased
stiffness, which may exacerbate negative patient prognosis. In pediatric populations, the
most prevalent acquired cardiovascular pathology is Kawasaki disease. This acute vasculitis
may affect the structural integrity of coronary artery walls and progress to aneurysmal lesions.
These can hinder the blood flowâs hemodynamics, leading to inadequate downstream
perfusion, and may activate thrombus formation which may lead to precarious prognosis.
Diagnosing these two prominent coronary artery diseases is traditionally performed using
fluoroscopic angiography. Several hundred serial x-ray projections are acquired during selective
arterial infusion of a radiodense contrast agent, which reveals the vesselsâ luminal
area and possible pathological lesions. The acquired series contain highly dynamic information
on voluntary and involuntary patient movement: respiration, organ displacement and
heartbeat, for example. Current clinical analysis is largely limited to a single angiographic
image where geometrical measures will be performed manually or semi-automatically by a
radiological technician. Although widely used around the world and generally considered
the gold-standard diagnosis tool for many vascular diseases, the two-dimensional nature of
this imaging modality is limiting in terms of specifying the geometry of various pathological
regions. Indeed, the 3D structures of stenotic or aneurysmal lesions may not be fully appreciated
in 2D because their observable features are dependent on the angular configuration of
the imaging gantry. Furthermore, the presence of lesions in the coronary arteries may not
reflect the true health of the myocardium, as natural compensatory mechanisms may obviate
the need for further intervention. In light of this, cardiac magnetic resonance perfusion
imaging is increasingly gaining attention and clinical implementation, as it offers a direct
assessment of myocardial tissue viability following infarction or suspected coronary artery
disease. This type of modality is plagued, however, by motion similar to that present in fluoroscopic
imaging. This issue predisposes clinicians to laborious manual intervention in order
to align anatomical structures in sequential perfusion frames, thus hindering automation o
Clinical advances in cardiovascular magnetic resonace imaging and angiography
Cardiovascular magnetic resonance imaging is an important noninvasive imaging modality for the diagnosis, clinical workâup and treatment planning in patients suspected for a wide range of cardiovascular pathology. CMR imaging is accurate and reliable, and provides invaluable information to evaluate the cardiovascular system without the need of ionizing radiation. The studies described in this thesis evaluate new CMR imaging techniques in clinical practice and explore the prognostic value of new CMR imaging biomarkers in patients with symptomatic peripheral arterial occlusive disease. New advances and innovations in MR imaging technology improve and further expand the clinical applications of cardiovascular imaging in daily clinical practice. In this thesis, a new, fast freeâbreathing 2D delayedâenhancement MRI sequence is validated and demonstrated to be a reliable tool for detecting myocardial infarction. Furthermore, new technical developments allow singleâinjection, threeâstation, movingâtable MRA protocol at 3Tesla with similar diagnostic performance when compared to 1.5Tesla. Additionally, submillimeter isotropic voxel acquisition in the lower legs at 1.5Tesla improves the diagnostic accuracy and depicts more open infragenual arterial segments.Additionally, it is demonstrated that new MRI biomarkers as distal aortic pulse wave velocity statistically significantly correlate with stenosis severity in symptomatic patients with peripheral arterial occlusive disease. Finally, we showed that CMR derived biomarkers relating to stenosis severity, aortic stiffness and left ventricular function play a role in prognosis of outcome in patients with symptomatic PAOD. In the future, incorporation of the described new MRI biomarkers in the clinical workup of peripheral arterial occlusive disease may play an important role for full vascular risk assessment and ultimately, patients may benefit in clinical practice.LUMC / Geneeskunde Repositoriu
The computation of blood flow waveforms from digital X-ray angiographic data
This thesis investigates a novel technique for the quantitative measurement of pulsatile blood flow waveforms and mean blood flow rates using digital X-ray angiographic data. Blood flow waveforms were determined following an intra-arterial injection of contrast material. Instantaneous blood velocities were estimated by generating a 'parametric image' from dynamic X-ray angiographic images in which the image grey-level represented contrast material concentration as a function of time and true distance in three dimensions along a vessel segment. Adjacent concentration-distance profiles in the parametric image of iodine concentration versus distance and time were shifted along the vessel axis until a match occurred. A match was defined as the point where the mean sum of the squares of the differences between the two profiles was a minimum. The distance translated per frame interval gave the instantaneous contrast material bolus velocity. The technique initially was validated using synthetic data from a computer simulation of angiographic data which included the effect of pulsatile blood flow and X-ray quantum noise. The data were generated for a range of vessels from 2 mm to 6 mm in diameter. Different injection techniques and their effects on the accuracy of blood flow measurements were studied. Validation of the technique was performed using an experimental phantom of blood circulation, consisting of a pump, flexible plastic tubing, the tubular probe of an electromagnetic flowmeter and a solenoid to simulate a pulsatile flow waveform which included reverse flow. The technique was validated for both two- and three-dimensional representations of the blood vessel, for various flow rates and calibre sizes. The effects of various physical factors were studied, including the distance between injection and imaging sites and the length of artery analysed. Finally, this method was applied to clinical data from femoral arteries and arteries in the head and neck
2019 Guidelines for the Management of Hypertension â Part 8â9
RECOMMENDATIONS OF THE POLISH SOCIETY OF HYPERTENSIONÂ
GUIDELINEÂ EDITORS: Andrzej Tykarski, Krzysztof J. Filipiak, Andrzej Januszewicz, MieczysĆaw Litwin, Krzysztof Narkiewicz, Aleksander Prejbisz, Danuta Ostalska-Nowicka, Krystyna Widecka, Katarzyna Kostka-Jeziorny
EXPERTS: Marcin Adamczak, Marta Buraczewska, Ludwina Szczepaniak-ChicheĆ, Marzena Chrostowska, Danuta Czarnecka, Piotr Dobrowolski, Grzegorz Dzida, Zbigniew Gaciong, Jerzy GÄ
sowski, Tomasz Grodzicki, Dagmara Hering, Beata WoĆŒakowska-KapĆon, PrzemysĆaw KosiĆski, Beata Begier-KrasiĆska, Jan Krekora, Jacek Manitius, MaĆgorzata MyĆliwiec, Anna Niemirska, Arkadiusz Niklas, Ćukasz Obrycki, Agnieszka Olszanecka, Sylwester Prokurat, GraĆŒyna BrzeziĆska-Rajszys, Marek Rajzer, Katarzyna Stolarz-Skrzypek, Agnieszka Szadkowska, Filip M. SzymaĆski, Anna Szyndler, Andrzej WiÄcek, Barbara Wizner, Jacek Wolf, Tomasz Zdrojewsk
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