Intravascular ultrasound: validation and clinical application

Atherogenesis is a process with an insidious onset and course. Once clinical signs and symptoms have become manifest, the obstructive lesion is usually at an advanced stage. Arteriography is the standard method for evaluation of atherosclerotic disease and has been useful in identifying the location and approximate severity of the stenotic lesion. Although arteriography provides a silhouette of the vessel lumen, it does not provide accurate knowledge on cross-sectional lumen area, vessel area, shape and morphology of the stenotic lesion. Intravascular ultrasound (lVUS) may overcome these limitations by providing a tomographic image of the vessel. The aim of this work is to validate IVUS and to evaluate subsequent clinical application of this imaging technique. The subjects dealt with in this dissertation are categorised into 5 main topics. I) displacement sensing device; 2) validation of IVUS-derived parameters; 3) the spectrum of vascular morphology before and after intervention determined by IVUS; 4) IVUS as a research tool; 5) IVUS as a clinical too

Glastuinbouw: stikstofverbruik in kaart gebracht

Dit artikel beschrijft het jaarlijkse stikstofverbruik uit kunstmest in de glastuinbouw op gewasniveau. Het gebruik van dierlijke mest bedraagt in de glastuinbouw minder dan 1% van het totale meststofgebruik en wordt daarom buiten beschouwing gelaten. De analyse is gebaseerd op gegevens uit het Informatienet van het LEI. De resultaten zijn vervolgens vergeleken met de gebruiksnormen per gewas voor stikstof in het Besluit Glastuinbouw dat in 2002 in werking trad. De gebruiksnormen voor stikstof (N) en fosfaat voor substraatteelten (teelten die los van de grond/ondergrond) plaatsvinden zullen waarschijnlijk binnen enkele jaren vervangen worden door emissienormen. Aangezien bij substraatteelt in beginsel geen onderlinge uitwisseling van meststoffen plaats vindt tussen het productiesysteem en de bodem of het grondwater, zijn emissienormen een goede indicator voor de milieubelastin

What have we learned from in vitro intravascular ultrasound?

In vitro studies have established that intravascular ultrasound is a reliable technique for accurate assessment of vascular anatomic structure and disease conditions before and after intervention. In addition, quantitative data from intravascular ultrasound studies correspond well with histologic findings, which serve as the gold standard. These in vitro studies permit the understanding and interpretation of ultrasound images obtained in vivo, although differences between the two settings should be taken into account. New ultrasound modalities currently being developed may enhance the diagnostic differentiation of plaque morphologic characteristics and facilitate on-line quantitative assessment of vessel structure

Strategic Cooperation in Peripheral Ports: The Case of Atlantic Canada’s Ports

This paper examines ports on the geographical periphery of the port business: they are off the main shipping routes or not located proximal to large domestic markets. These ports have development potential, but reaching it requires specific strategies. The paper first discusses the nature of peripheral ports followed by a conceptualization of two development strategies: cooperation among seaports and coordination of supply chain operators with the emphasis on cooperation. The paper considers Atlantic Canada’s ports and their current cooperation initiatives concluding with recommendations on how these ports may better serve their interests through applying cooperation strategies found elsewhere

Kleine bedrijven hebben weinig vertrouwen in de toekomst van het bedrijf

Het vertrouwen van boeren en tuinders in de toekomst van hun bedrijf is een graadmeter voor de economische gesteldheid van de agrarische sector. Een groot deel van de agrariërs ziet de toekomst op korte termijn optimistisch tegemoet. Op lange termijn hebben ondernemers op grotere bedrijven meer vertrouwen in de toekomst dan die op kleinere bedrijve

Low-Dose Computed Tomography With Two- and Three-Dimensional Postprocessing as an Alternative to Plain Radiography for Intrathecal Catheter Visualization: A Phantom Pilot Study

Objectives: In intrathecal drug delivery, visualization of the device has been performed with plain radiography. However, the visibility of the related structures can be problematic. In troubleshooting, after the contrast material injection via the cathe

Reduced cortical complexity in children with prader-willi syndrome and its association with cognitive impairment and developmental delay

Background: Prader-Willi Syndrome (PWS) is a complex neurogenetic disorder with symptoms involving not only hypothalamic, but also a global, central nervous system dysfunction. Previously, qualitative studies reported polymicrogyria in adults with PWS. However, there have been no quantitative neuroimaging studies of cortical morphology in PWS and no studies to date in children with PWS. Thus, our aim was to investigate and quantify cortical complexity in children with PWS compared to healthy controls. In addition, we investigated differences between genetic subtypes of PWS and the relationship between cortical complexity and intelligence within the PWS group.Methods: High-resolution structural magnetic resonance images were acquired in 24 children with genetically confirmed PWS (12 carrying a deletion (DEL), 12 with maternal uniparental disomy (mUPD)) and 11 age- and sex-matched typically developing siblings as healthy controls. Local gyrification index (lGI) was obtained using the FreeSurfer software suite.Results: Four large clusters, two in each hemisphere, comprising frontal, parietal and temporal lobes, had lower lGI in children with PWS, compared to healthy controls. Clusters with lower lGI also had significantly lower cortical surface area in children with PWS. No differences in cortical thickness of the clusters were found between the PWS and healthy controls. lGI correlated significantly with cortical surface area, but not with cortical thickness. Within the PWS group, lGI in both hemispheres correlated with Total IQ and Verbal IQ, but not with Performance IQ. Children with mUPD, compared to children with DEL, had two small clusters with lower lGI in the right hemisphere. lGI of these clusters correlated with cortical surface area, but not with cortical thickness or IQ.Conclusions: These results suggest that lower cortical complexity in children with PWS partially underlies cognitive impairment and developmental delay, probably due to alterations in gene networks that play a prominent role in early brain development

Clinical competence in performing and recognising a mediolateral episiotomy of protective angle and length: a systematic review

Objective: It is assumed that all doctors and midwives understand and apply evidence‐based principles in performing episiotomies in their everyday practice. However, remarkable discrepancies between even the most reputable literature sources in defining and describing the technique of performing mediolateral episiotomy (MLE) suggest that there is much ambiguity and confusion for both researchers and clinicians alike. Design: The systematic review protocol was written prior to starting the review and registered in the international prospective register of systematic reviews (PROSPERO/ID CRD42017070523) last updated on December 15, 2017. The review is reported using the Preferred Reporting Items for Systematic Reviews and Meta‐Analysis (PRISMA) guidelines. Methods: A database search was performed using: Medline, CINAHL, Scopus, Informit, the Cochrane Library and PubMed from database inception to 17 September 2017, with a final search on 10 February 2017. Studies were included if they examined clinicians' competency in performing an 'ideal' or 'correct' mediolateral episiotomy, as well as those studies that compared the performance of different professional roles. Studies usually defined an 'ideal' incision as one that met the criteria of an acceptable angle of incision from the midline, starting incision point distance from the midline and in terms of the length of the incision created. Results: While many of the studies included in this review were not of high quality (author self‐assessment) and had their own study criteria for a MLE, the literature suggests clinicians are generally unable to perform or simulate episiotomies within such standards. Overall, most of the literature reported doctors were performing more 'ideal', lateral and longer incisions compared to midwives; however, there were studies that found the opposite, showing statistically significant results in favour of midwives performing more protective episiotomies. There was no association between clinicians' participation in formal training courses and their ability to perform the 'ideal' incision, though one study did find an increased number of episiotomies performed under supervision improved clinicians competency. Conclusion: The obvious lack of understanding around defining and performing MLE for clinicians of various professional roles suggests the need to produce a uniform set of guidelines, and to develop a universal, low‐cost approach for teaching and performing the MLE technique in any clinical environment around the world

Model-based cap thickness and peak cap stress prediction for carotid MRI

A rupture-prone carotid plaque can potentially be identified by calculating the peak cap stress (PCS). For these calculations, plaque geometry from MRI is often used. Unfortunately, MRI is hampered by a low resolution, leading to an overestimation of cap thickness and an underestimation of PCS. We developed a model to reconstruct the cap based on plaque geometry to better predict cap thickness and PCS. We used histological stained plaques from 34 patients. These plaques were segmented and served as the ground truth. Sections of these plaques contained 93 necrotic cores with a cap thickness <0.62 mm which were used to generate a geometry-based model. The histological data was used to simulate in vivo MRI images, which were manually delineated by three experienced MRI readers. Caps below the MRI resolution (n = 31) were (digitally removed and) reconstructed according to the geometry-based model. Cap thickness and PCS were determined for the ground truth, readers, and reconstructed geometries. Cap thickness was 0.07 mm for the ground truth, 0.23 mm for the readers, and 0.12 mm for the reconstructed geometries. The model predicts cap thickness significantly better than the readers. PCS was 464 kPa for the ground truth, 262 kPa for the readers and 384 kPa for the reconstructed geometries. The model did not predict the PCS significantly better than the readers. The geometry-based model provided a significant improvement for cap thickness estimation and can potentially help in rupture-risk prediction, solely based on cap thickness. Estimation of PCS estimation did not improve, probably due to the complex shape of the plaques

Maximization of Regional probabilities using Optimal Surface Graphs: Application to Carotid Artery Segmentation in MRI

__Purpose__ We present a segmentation method that maximizes regional probabilities enclosed by coupled surfaces using an Optimal Surface Graph (OSG) cut approach. This OSG cut determines the globally optimal solution given a graph constructed around an initial surface. While most methods for vessel wall segmentation only use edge information, we show that maximizing regional probabilities using an OSG improves the segmentation results. We applied this to automatically segment the vessel wall of the carotid artery in magnetic resonance images. __Methods__ First, voxel-wise regional probability maps were obtained using a Support Vector Machine classifier trained on local image features. Then the OSG segments the regions which maximizes the regional probabilities considering smoothness and topological constraints. __Results__ The method was evaluated on 49 carotid arteries from 30 subjects. The proposed method shows good accuracy with a Dice wall overlap of 74:1%+-4:3%, and significantly outperforms a published method based on an OSG using only surface information, the obtained segmentations using voxel-wise classification alone, and another published artery wall segmentation method based on a deformable surface model. Intra-class correlations (ICC) with manually measured lumen and wall volumes were similar to those obtained between observers. Finally, we show a good reproducibility of the method with ICC = 0:86 between the volumes measured in scans repeated within a short time interval. __Conclusions__ In this work a new segmentation method that uses both an OSG and regional probabilities is presented. The method shows good segmentations of the carotid artery in MRI and outperformed another segmentation method that uses OSG and edge information and the voxel-wise segmentation using the probability maps