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Purpose: X-ray based tomographic blood perfusion imaging requires recovery of contrast time-attenuation-curves from dynamic projection data. When using slowly rotating imaging systems this task is challenging due to non-simultaneous projection acquisition. A dynamic reconstruction method is proposed that aims at compensating the lack of simultaneously acquired information by incorporating prior knowledge about the expected temporal contrast dynamics. Methods: A decomposition model using temporal basis functions to approximate time-attenuation-curves is integrated into an iterative tomographicre construction method. The computationally efficient implementationof the proposed approach makes use of standard forward- and back projections as well as scalar products in image space. The critical issue of projection noise propagation is tackled by application of regularization which is realizedby early stopping of iteration cycles and by proper selection of smooth temporal basis functions. The performance of the proposed dynamic reconstruction approach is evaluated in a simulation study concerning various aspects: noise propagation and regularization, specification of temporal model, and type of acquisition mode. Results: The evaluation based on dynamic phantom data indicates that tomographic recovery of contrast time-attenuation-curves in tissue can be achieved with an average range of accuracy of ca. 2% (with respect todynamic peak attenuation) under ideal noise-free conditions. The relative estimation error for arterial time-attenuation-curves is in the range of 8%, which is due to faster contrast dynamics in the artery. In general, performance depends on the level of acquired information contained in the projection data which is mainly influenced by the type of rotational acquisition mode; restrictions in angular range and speed can lead to limited accuracy. The analysis of propagated projection noise in a statistical Bias-Variance framework reveals relative noise levels in estimated time-attenuation-curves of 3-4% intissue regions and below 1% in vessels when using optimized settingsfor regularization. Here, the effect of noise suppression depends oninterrelation between the model. Conclusions: For usage with slowly rotating imaging systems the presented model-based iterative dynamic reconstruction method is capable of recovering contrast time-attenuation-curves related to tissue perfusion. The proposed regularization framework is an effective means to limit the impact of projection noise which is a factor dominating estimation accuracy in tissue regions.

The lack of understanding of the mechanical behavior of the human skin layers makes the development of drug delivery using microneedles or microjets a challenging task. In particular, the key mechanical properties of the epidermis composed of stratum corneum and viable epidermis, should be better understood. Micro-indentation experiments were applied, using a spherical tip with a large diameter to the sample thickness ratio. The Young's moduli were derived via an analytical and a numerical method. The tests showed that the analytical method was not appropriate to assess the Young's moduli. That is why a numerical model was used to obtain the correct stiffness. When loaded perpendicularly, the stiffness of both the epidermis and stratum corneum vary between 1 and 2 MPa. No significant differences in stiffness between the stratum corneum and viable epidermis were observed.

A systematic investigation into halides and ~oxides showed the high potential of transition metal oxides as visible radiators for highly efficient gas discharge light sources. Zirconium monoxide (ZrO) has been identified as most promising candidate combining highly attractive green and red emission band systems with very high dissociation energy (8.2eV) which assures that the molecule is stable even in the hot plasma centre. Thus far, however, it has been impossible to keep ZrO in the gas phase of a closed discharge vessel, because at wall temperature usually compounds are formed which have negligible vapour pressures. We succeeded in establishing a regenerative chemical cycle by filling ZrX4 (X=Cl, Br, I) together with a stable, but volatile oxygen compound (like MoO2X2) and realized thus highly attractive, novel gas discharge light sources.

Localized surface plasmon polaritons (LSPPs) provide an efficient means of achieving extreme light concentration. In recent years, their active control has become a major aspiration of plasmonic research. Here, we demonstrate direct control of semiconductor bowtie antennas, enabling active excitation of LSPPs, at terahertz (THz) frequencies. We modify the LSPPs by ultrafast optical modulation of the free carrier density in the plasmonic structure itself, allowing for active control of the semiconductor antennas on picosecond timescales. Moreover, this control enables the manipulation of the field intensity enhancements in ranges of four orders of magnitude.

The stability of an electrowetting system is dependent upon the choice of liquids, the dielectric material and the operating voltage.Substantial progress is reported herein on use of 300 nm thick poly-tetrafluoro-para-xylylene) (Parylene HT) films for almost 100° of reliable electrowetting modulation at only 15 V. Not only does Parylene HT exhibit improved resistance to dielectric failure as compared to poly(2-chloro-para-xylylene) (Parylene C), but Parylene HT is shown to sustain continuous DC electrowetting to <70° for > 6 hours. Furthermore, Parylene HT has a surface energy such that when electrowetting in an alkane oil ambient, a Young’s angle of about 170° can beachieved without the traditional fluoropolymer top-coat. Also presented is a new and simple model for calculating electric field enhancement when electrowetting in an oil bath. It is shown that Parylene HT is a promising candidate for low-voltage and large-area electrowetting devices such as displays and lab-on-chip.

Using the inverse-electron-demand Diels Alder reaction we demonstrated non-invasive pretargeted tumor imaging in mice bearing LS174T colorectal xenografts. Anti-TAG72 mAb CC49 functionalized with trans-cyclooctene moieties was administered, followed 24 h later by 111In-labeled tetrazine. Pronounced tumor uptake of the 111In-tetrazine was demonstrated by SPECT/CT imaging of live mice up to 3 h post injection (tumor-to-muscle ratio: 13.1), while no tumor binding occurred in mice treated with unmodified CC49. The components exhibited a remarkable 52-57 % chemical reaction yield in mice. We are currently optimizing this system for cancer therapy.

Multi-access networks may exhibit severe unfairness in throughput,in the sense that some nodes receive structurally higher throughputthan others. Recent studies show that this unfairness is due tolocal differences in the neighborhood structure: Nodes with fewerneighbors receive better access. We study the unfairness in satura-ted linear networks,and adapt the multi-access CSMA protocol toremove the unfairness completely,by choosing the activation ratesof nodes as a specific function of the number of neighbors. We theninvestigate the consequences of this choice of activation rates onthe network-average saturated throughput, and we show that theserates perform well in non-saturated settings.

Background: Percutaneous cardiac interventions are currently performed under X-ray guidance. Magnetic resonance imaging has been employed to guide intravascular interventions in the past, but mainly in animals. Translation of MR-guided interventions into humans has been limited by the lack of fully MR-compatible and safe devices, such as MR guidewires with mechanical characteristics similar to standard guidewires. The aim of the present study was to evaluate the safety and efficacy of a newly developed MR-safe and compatible passive guidewire in aiding MR-guided cardiac interventions in a swine model and describe the two first-in-man solely MR-guided interventions. Methods and Results: In the preclinical trial, the new MR compatible wire aided the performance of 20 interventions in 5 swine. These consisted of balloon dilation of nondiseased pulmonary and aortic valves, aortic arch and branch pulmonary arteries. Catheter manipulations were monitored with real time MRI sequence with interactive modification of imaging plane and slice position. Following ethics and regulatory authority approval the two first-in-man MR-guided interventions were performed in a child and an adult, both with elements of valvar pulmonary stenosis. Both patients had successful relief of the valvar stenosis and were discharged home a few hours later with no complications. Conclusions: The described pre-clinical study and case reports are encouraging that with the availability of the new MR compatible and safe guidewire, certain percutaneous cardiac interventions will become feasible to perform solely under MR-guidance. The benefits are clear with elimination of the use of ionising radiation and improvement of visualisation of the target lesions.

Many approaches to facial expression recognition focus on assessing the six basic emotions (anger, disgust, happiness, fear, sadness, and surprise). Real-life situations proved to produce many more subtle facial expressions. A reliable way of analyzing the facial behavior is the Facial Action Coding System (FACS) developed by Ekman and Friesen, which decomposes the face into 46 action units (AU) and is usually performed by a human observer. Each AU is related to the contraction of one or more specific facial muscles. In this study we present an approach towards automatic AU recognition enabling recognition of an extensive palette of facial expressions. As distinctive features we used motion flow estimators between every two consecutive frames, calculated in special regions of interest (ROI). Even though a lot has been published on the facial expression recognition theme, it is still difficult to draw a conclusion regarding the best methodology as there is no common basis for comparison. Therefore our main contributions reside in the comparison of different ROI selections proposed by us, different optical flow estimation methods, and also in the comparison of two spatial-temporal classification methods: Hidden Markov Models (HMM) and Dynamic Bayesian Networks (DBN). The classifiers have been trained and tested on the Cohn-Kanade database. The experiments showed that under the same conditions regarding initialization, labeling and sampling, both methods produced similar results, achieving the same recognition rate of 89% for the classification of facial AUs. Still, by enabling non-fixed sampling and using HTK, HMMs rendered a better performance of 93% suggesting that are better suited for the special task of AUs recognition.

Facial image analysis, including face detection, face recognition,facial expression analysis, facial demographic classification, and so on, is an important and interesting research topic in the computervision and image processing area, which has many important applications such as human-computer interaction and visual surveillance. Acritical step for successful facial image analysis is to derive an effective facial representation from the original face images. In recent years, Local Binary Patterns (LBP) has received increasing attention for facial description. This paper presents a comprehensive survey of LBP methodology in the context of facial image analysis. Different aspects are addressed, including recent development of LBP, LBP feature selection, its applications in different facial image analysis tasks and existing systems, and so on. With more than 100 papers reviewed, this is the first extensive review on LBP-based facial image analysis.

X-ray attenuation properties of matter (i.e. human body in medicalComputed Tomography) are energy and material dependent. This dependency is largely neglected in conventional CT techniques, which require the introduction of correction algorithms in order to prevent image artefacts. The exploitation of the inherent energy information contained in the x-ray spectrum allows distinguishing the two main physical causes of energy-dependent attenuation (photo-electric effect and Compton effect). Currently a number of methods exist that allow assessing the energy-dependent attenuation in conventional systems. These methods consist of using two distinct spectra (kVp switching ordual source) or by discriminating low and high energy photons by means of stacking two detectors. Further improvements can be achievedby transitioning to direct-conversion technologies and counting-modedetection, which inherently exhibits a better signal-to-noise ratio.Further including energy discrimination, enables new applications,which are not feasible with dual-energy techniques, e.g. the possibility to discriminate K-edge features (contrast agents, e.g. Gadolinium) from the other contributions to the x-ray attenuation of a human body. The capability of providing energy-resolved information withtwo or more independent measurements is referred as Spectral CT.A new proprietary photon counting ASIC (ChromAIX) has been developedto provide high count-rate capabilities while offering energy discrimination. The ChromAIX consists of a pixel array with an isotropicpitch of 300 µm. Each pixel contains independent discriminators which enable the possibility to discretize incoming photons into a number of energy levels. Extensive electrical characterization has been carried out to assess the performance in terms of count-rate performance and noise. Observed rates exceeding 10 Mcps/pixel (Poissonian, mean incoming rates > 27 Mcps). The energy resolution is better than4.1 keV FWHM and has been shown to be consistent with simulations. Pile-up behaviour and count-rate dependency have also been evaluated. Electrical crosstalk among pixels in terms of count-rate activity and threshold position has been assessed and show no measureable influences across the array. X-ray tests have also been performed onsamples directly flip-chip bonded to CdTe and CZT crystals. The pulse shape and spectrum obtained from a 241Am source is consistent with simulations.

During the last decade, a number of research activities have been performed to enable user interfaces and the underlying user activities to be migrated from one device to another. We call this “Nomadic User Interfaces”. The primary goal of these research activities has been to develop the technologies to enable this. However, not much is known about the usability aspects of Nomadic User Interfaces. In this paper we present the results of three different user tests that we conducted to investigate the usefulness and the usability issues of several prototype Nomadic User Interface systems that we developed.

Temporal subtraction techniques using 2D image registration improve the detectability of interval changes from chest radiographs. Although such methods are well known for some time they are not widely used in radiologic practice. The reason are strong pose differences between these follow-up acquisitions with a time interval of months to years in between. Such strong perspective differences occur in a reasonable number of cases. They cannot be compensated by available image registration methods and thus mask interval changes to be undetectable. A method is proposed to estimate a 3D pose difference by the adaptation of a 3D rib cage model to both projections. The difference between both is then compensated for, thus producing a subtraction image with virtually no change in pose. No 3D image data is used. The accuracy of pose estimation is validated with chest phantom images under controlled geometric conditions.

Lasers will bring a further step in terms of compactness and efficiency for projection systems. However, the availability of suitable green laser sources limits the advent of laser projection. Blue diode pumped solid-state lasers are presented here as one promising way to realize green, red and orange lasers that are specifically suitedfor projection applications.

We study the effects of digital photo sharing on social connectedness of people with special needs. We target people dealing with a transition in life that forced them to live away from their family and friends. Our study included four people with spinal-cord injury staying in a rehabilitation centre and eight elderly people staying in a nursing home. Each participant was provided with a web-enabled digital photo frame and their family members were provided with a camera phone. The results of our study show positive effects. For rehabilitants photo sharing simplified the way they could reconnect to their family. For the elderly people, photo sharing served as 'food for talk'.

In this paper we present the “Breathe with the Ocean” system concept, which is a breathing guidance system that aims to help a user relax. It provides an immersive experience where the user is virtually present at an ocean shore. We describe the design and implementation of three embodiments of this concept and preliminary evaluations based on trial sessions. The feedback provided by the three systems to the user is in the form of audio, haptic (tactile) and visual (light) stimuli. Haptic stimuli are provided through a novel actuation device that we developed, the Touch Blanket. The three systems introduced are respectively a fixed-rate breathing guidance system, an adaptive breathing following system and an adaptive-rate breathing guidance system that maximizes heart-rate variability amplitude. We discuss the advantages and disadvantages of using open-loop versus closed-loop implementations of these types of systems, as well as our experiences so far in using multimodal stimuli for breathing guidance.

Breathing motion complicates many image-guided interventions working on the thorax or upper abdomen. However, prior knowledge provided by a statistical breathing model, can reduce the uncertainties of organ location. In this paper, a prediction framework for statistical motion modeling is presented and different representations of the dynamic data for motion model building of the lungs are investigated. Evaluation carried out on 4D-CT data sets of 10 patients showed that a displacement vector-based representation can reduce most of the respiratory motion with a prediction error of about 2 mm, when assuming the diaphragm motion to be known.

As a complement to maximum intensity projection (MIP) and direct volume rendering of the Hounsfield densities, a Hesse rendering can show the local curvature of structures rather than the densities. Color coding of the local curvatures, or simply of the eigenvalues of the local second derivatives, can provide an intuitive navigation device to blob-like anomalies in the lung such as pulmonary nodules and lymph nodes. Evaluation results based on the LIDC-IDRI lung image database indicate that the more radiologists agree on a certain anomaly to be a lung nodule, the brighter it appears in the Hesse rendering. The Hesse-rendering might thus be a complementary approach to classical computer aided detection approaches with explicit markers.

Basic electrowetting theory predicts that a continued increase in applied voltage will allow contact angle modulation to zero degrees. In practice, the effect of contact angle saturation has always been observed to limit the contact angle modulation, often only down to a contact angle of 60 to 70°. The physical origins of contact angle saturation have not yet been explained successfully and unequivocally. At best, scientists have produced multiple disconnected hypotheses (droplet ejection, charge injection, a thermodynamic limit, etc.) that do not satisfactorily hold for the large body of electrowetting experimental results. Herein we experimentally demonstrate that when using DC voltage, electrowetting contact angle saturation is invariant with electric field, contact line profile, interfacial tension, choice of non-polar insulating fluid, and type of polar conductive fluid or ionic content. The selected experiments were performed and designed using conventional electrowetting materials, without bias toward supporting a particular theory. Because the experimental results show such a strong invariance of saturation to multiple parameters, a new theory for electrowetting saturation is suggested: micro-droplet ejection through “Taylor saturation”. Although this work does not unequivocally prove what does cause contact angle saturation, it reveals what factors play a very limited or no role, and how dominant factors causing saturation may change with time of voltage application. This study thereby provides additional direction to the continued pursuit of a universal theory for electrowetting saturation.

The design, manufacturing and application of electrowetting-based liquid lenses in optical devices are discussed. Results are presentedof applying this lens in miniature autofocus and zoom cameras, optical recording and illumination systems. Conclusions: We presented the working principle and a concept for mass manufacturing of liquid lenses and we demonstrated that they can be used for focusing and zooming in miniature cameras, for dual-layer readout inBlu-ray Disc optical recording systems and for dynamic effects in illumination systems. This shows that liquid lenses can have a significant impact on future miniature optical devices.