1,106 research outputs found
Pulmonary Angiography:Technique, Indications and Complications
No full textPulmonary angiography is still regarded as the reference method for diagnosing pulmonary embolisms (PEs), despite the fact that computed tomography pulmonary angiography is nowadays used as a standard method. It is reserved for patients with non-diagnostic test results and a high probability of PE, and those patients in whom interventions are considered. Nevertheless, it is important that one knows the technique, pitfalls and complications of this imaging technique. In this chapter, these aspects of pulmonary angiography are described.</p
Diagnostic Management Strategies in Patients with Suspected Pulmonary Embolism
No full textAdequate diagnosis is essential to prevent pulmonary embolism (PE)-related mortality and morbidity on the one hand and unnecessary treatment on the other. Preferably, excluding the diagnosis is performed using safe, efficient and non-invasive diagnostic methods. Over the last two decades, many new diagnostic methods and strategies for the diagnostic work-up of patients with suspected PE have been introduced and validated. The first step in the approach to patients with suspected PE is a thorough clinical history and physical examination, in order to determine the clinical probability of the presence of PE. The advantage of using pre-test probability in the exclusion of PE is mainly achieved in combination with a D-dimer test result. In patients with a high or likely pre-test clinical probability or patients with an abnormal D-dimer test, additional imaging is required. If the clinical status of the patient permits, the next recommended step is computed tomography (CT) or ventilation-perfusion scintigraphy, followed by additional testing in case of non-diagnostic test results. Selected patients may require a tailored approach, for instance if there is a contraindication for CT scanning. The implementation of diagnostic strategy in clinical practice will increase diagnostic accuracy and reduce costs.</p
MRI and MRA of the Pulmonary Vasculature
No full textMagnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) of the pulmonary vasculature are still rapidly evolving techniques. However, currently available protocols have already demonstrated high clinical impact. Contrast-enhanced and non-contrast-enhanced angiographic techniques are in widespread use for imaging of the pulmonary vasculature with either high spatial or high temporal resolution. Especially multiphasic protocols, such as MR perfusion, followed by high spatial resolution contrast-enhanced (CE) MRA, seem to be an optimal clinical approach for the assessment of different diseases affecting the pulmonary vasculature. This chapter describes basic knowledge, challenges, considerations and solutions for different MR techniques to be applied to the pulmonary vasculature. Parallel imaging and novel k-space sampling techniques have opened the door for fast volume acquisitions of the pulmonary vasculature. Contrast administration and timing in addition to multiphasic acquisitions are still in the focus to set up an optimal protocol for the pulmonary vasulature. The visualization of the data has to include multiplanar reformats and maximum intensity projections and also volume rendering techniques.</p
Societal need for multifunctional flood defenses: Introduction
No full textProf.dr.ir. Matthijs Kok is Professor of Flood Risk at the Faculty of Civil Engineering and Geosciences at TU Delft; he was Program leader of the ‘Integral and Sustainable Design of Multifunctional Flood Defenses’ research program, funded by the Dutch Science and Technology Foundation STW. Presently, he is Program leader of the STW-Perspectief research program ‘All RISK’, which will study the implementation of new risk standards in the Dutch national flood protection program (2017-2022). Hydraulic Structures and Flood Ris
Quantitative diffusion-weighted imaging in breast and liver tissue
Full text linkDiffusie-gewogen beeldvorming (DWI) is een biomedische toepassing van MRI, gebaseerd op diffusie (de willekeurige verplaatsing) van waterstof protonen in het menselijk lichaam. Met o.a. DWI beelden beoordeelt een radioloog visueel of er afwijkingen aanwezig zijn in het onderzochte orgaan. Visuele beoordeling is echter subjectief. Een alternatief is kwantitatieve analyse, waarbij de diffusie in afwijkingen wordt gemeten, uitgedrukt in een getal en vergeleken met gezond weefsel. Dit heeft als voordeel dat de beoordeling niet of nauwelijks afhangt van diegene die het uitvoert. Er zijn twee modellen onderzocht voor de kwantitatieve analyse van diffusie in de lever en de borst. Het intravoxel incoherent motion (IVIM) model splitst diffusie op in langzame en snelle diffusie. Snelle diffusie komt voor in goed doorbloede weefsels, zoals tumoren. Het tweede model gebruikt een enkele maat, de apparent diffusion coefficient (ADC). De voor- en nadelen van beide modellen zijn onderzocht in DWI studies van de lever. Diffusie is afhankelijk van het vetpercentage en de ADC blijkt bovendien afhankelijk van de meetlocatie in de lever. Er is een nieuwe methode geïntroduceerd waarmee de beoordelaar semiautomatisch een borsttumor kan selecteren en analyseren. IVIM kan hierdoor beter goed- en kwaadaardige borsttumoren van elkaar onderscheiden, vergeleken met de ADC. Ook bleek de methode onafhankelijk van de beoordelaar. In de dagelijkse praktijk ondergaat een groep patiënten met verdenking op borstkanker een invasieve procedure om uitsluitsel te geven. In de toekomst kan mogelijk een aantal van deze invasieve procedures worden voorkomen door het integreren van IVIM in het diagnostische proces
Quantitative STIR MRI as prognostic imaging biomarker for nerve regeneration
Full text linkA transection of a forearm nerve e.g., because of an accident, has tremendous impact on a patient's daily life, as a number of hand muscles is paralyzed and part of the hand will suffer from sensory loss. Despite advances in surgery many patients will have remaining loss of function. If nerve regeneration fails, a re-operation may be attempted, preferably within 6 months after initial trauma. Therefore, it is of utmost importance to monitor whether nerve fibers grow towards the target muscles, to be able to intervene if necessary. The current method used for monitoring is electromyography (EMG), which has several disadvantages. The aim of the research described in this thesis was to investigate whether magnetic resonance imaging (MRI) scans of the hand muscles can be used for monitoring of nerve regeneration. In patients with a complete transection of one of the forearm nerves, changes in signal intensity were examined over time. This can be seen/measured in the MRI scans. In patients with poor function recovery, signal intensities of muscle remained elevated for at least one year, while in patients with good function recovery the measured signal intensities returned to normal. In conclusion, MRI-scans can be used as a new, objective method for monitoring nerve regeneration and show differences between denervated and re-innervated muscles for at least one year
Quantitative CT myocardial perfusion: Development of a new imaging biomarker
Full text linkRecente ontwikkelingen in CT technieken hebben er voor gezorgd dat de evaluatie van ziekte in de kransslagaderen (coronaire hartziekte) is verschoven van het visueel opsporen van gebieden met verminderde doorbloeding, naar het kwantitatief beoordelen van de doorbloeding van het hart (perfusie). In dit proefschrift zijn CT metingen van de doorbloeding van het hart onderzocht door gebruik te maken van een varkenshart model, dat geoptimaliseerd is voor gebruik in een CT omgeving. Daarnaast geeft het model directe controle over fysiologische eigenschappen zoals bloeddruk en bloedflow en er kan een controleerbare vernauwing in één van de kransslagaderen aangelegd worden. Kwantitatieve metingen van bloedflow met CT identificeerden verminderde doorbloeding als gevolg van de aangelegde vernauwing. Echter, er is ook aangetoond dat de bloedflowwaarden behoorlijk worden onderschat. In dit proefschrift laten we zien dat dit mogelijk komt doordat er te weinig beelden gemaakt zijn om de bloedflow nauwkeurig te kunnen schatten. We kunnen dus wel aantonen dat er verschillen tussen normale en verminderde bloedflow zijn, maar de flow wordt in beide gevallen wel onderschat. Dual-energy CT is een andere techniek die kan worden gebruikt voor het verkrijgen van een semi-kwantitatieve marker voor CT perfusie. Het vermogen van dual-energy CT voor het bepalen van jodium concentraties leverde goede resultaten op bij fantoom metingen in twee high-end CT scanners. Deze scans moeten echter wel gemaakt worden binnen het optimale scanwindow van 8 seconden. De uitgevoerde experimenten tonen aan dat kwantificatie van hartperfusie met CT een meerwaarde heeft boven visuele analyse bij het detecteren van coronaire hartziekte
Flexible needle steering for computed tomography-guided interventions
Full text linkIn the last few decades, the surgical tools and procedures have developed significantly. Invasive surgeries are avoided as much as possible and minimally-invasive or non-invasive procedures are preferred. Needles are among the common tools which are used in clinical procedures, such as brachytherapy, microwave and radio frequency ablations and biopsies. Needle insertions usually require alignment of the needle with a lesion or a tumor, which is a challenging task even for experienced clinicians. Furthermore, the needles tend to deflect while being inserted into the tissue, since the clinical needles usually have an asymmetric tip, and the cutting force deflects the needle in a certain direction. In this thesis, a robotic system is developed which is used to steer a flexible needle within the tissue. The robot is designed for the procedure on the lung and liver, which are commonly performed under CT guidance. A review of the available solutions in the market and in the literature is discussed and the design and evaluation of the proposed CT-compatible needle steering robot is presented. Functional tests prove the design concept, and experiments in biological tissue and human cadaver validate the steering concept. A data fusion scheme based on unscented Kalman filter is developed in order to combine the tracking information from multiple devices. Finally, a motion compensation algorithm is presented which can be used to compensate patients voluntary or non-voluntary motions (such as breathing) while the needle is being inserted into the body
Feasibility of cardiovascular population-based CT screening
Full text linkThe prevalence of cardiovascular disease (CVD) is high in The Netherlands, with annual incidence of 123,200 (only coronary heart disease). There is an urgent need for large-scale population-based randomized-controlled trials showing the impact of CVD screening followed by treatment in high risk individuals according to their CVD risk based on classical factors and/or based on coronary calcium quantified with CT. The goal of CVD CT screening is to determine the amount of coronary calcium of an individual and to stratify individuals with high levels of coronary calcium and to reduce the morbidity and mortality by offering these individuals treatment at an early stage to stop or delay progression of subclinical CVD. One of the challenges in CVD CT screening is to secure the validity of coronary calcium quantification to perform proper risk stratification on one hand, while screening large populations at a radiation dose as-low-as-possible on the other hand.The results described in this thesis show that cardiovascular population-based CT screening is feasible with a standardized and validated imaging biomarker (in this case coronary calcium) protocol. This protocol was applied in the ROBINSCA trial in which 13,000 participants were screened. Combining screening protocols, optimizing scan parameters and using latest generation of dual-source CT can significantly reduce the radiation dose. An imaging biomarker profile including quality control guidelines for coronary calcium is needed to ensure proper use of dose-reduced protocols in population-based screening in the future
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