Motion correction for coronary stent reconstruction from rotational X-ray projection sequences

This paper presents a new method for 3-D tomographic reconstruction of stent in X-ray cardiac rotational angiography. The method relies on 2-D motion correction from two radiopaque markerballs located on each side of the stent. The two markerballs are on a guidewire and linked to the balloon, which is introduced into the artery. Once the balloon has been inflated, deflated, and the stent deployed, a rotational sequence around the patient is acquired. Under the assumption that the guidewire and the stent have the same 3-D motion during rotational acquisition, we developed an algorithm to correct cardiac stent motion on the 2-D X-ray projection images. The 3-D image of the deployed stent is then reconstructed with the Feldkamp algorithm using all the available projections. Although the correction is an approximation, we show that the intrinsic geometrical error of our method has no visual impact on the reconstruction when the 2-D markerball centers are exactly detected and the markerballs have the same 3-D motion as the stent. Qualitative and quantitative results on simulated sequences under different realistic conditions demonstrate the robustness of the method. Finally, results from animal data acquired on a rotational angiography device are presented.     

Left ventricular volume estimation for real-time three-dimensional echocardiography

The application of level set techniques to echocardiographic data is presented. This method allows semiautomatic segmentation of heart chambers, which regularizes the shapes and improves edge fidelity, especially in the presence of gaps, as is common in ultrasound data. The task of the study was to reconstruct left ventricular shape and to evaluate left ventricular volume. Data were acquired with a real-time three-dimensional (3-D) echocardiographic system. The method was applied directly in the three-dimensional domain and was based on a geometric-driven scheme. The numerical scheme for solving the proposed partial differential equation is borrowed from numerical methods for conservation law. Results refer to in vitro and human in vivo acquired 3-D + time echocardiographic data. Quantitative validation was performed on in vitro balloon phantoms. Clinical application of this segmentation technique is reported for 20 patient cases providing measures of left ventricular volumes and ejection fraction.     

4D‐Printed Biodegradable and Remotely Controllable Shape Memory Occlusion Devices

Implantation of occlusion devices is an effective approach for the treatment of congenital heart diseases in the clinic. However, most commercial clinical occlusion devices are currently made of nondegradable metals, which may lead to complications such as perforation, allergies, and erosion. In this work, 4D‐printed novel, biodegradable, remotely controllable, and personalized shape memory occlusion devices are demonstrated and atrial septal defect occluders are exemplified. By incorporating Fe₃O₄ magnetic particles into the shape memory poly(lactic acid) matrix, the deployment of the occluders can be controlled remotely after implantation. The excellent cytocompatibility and histocompatibility are conducive to cell adhesion and ingrowth of granulation tissues into the occluders, thus facilitating rapid endothelialization. In addition, personalized shape memory occluders ensure an ideal fit and provide sufficient support for defects. Therefore, 4D‐printed shape memory occluders can be used as a potential substitute for metal occlusion devices.     

基于LINUX的嵌入式GUI输入接口机制研究

基于操作系统的嵌入式GUI在新型的嵌入式设备上已经开始普及,它作为人机接口必须同时具备功能完整和轻量可靠的特点。我们通过对嵌入式GUI系统的结构和机制进行分析,对轻量级GUI中输入接口的实现进行了完整和详细的研究,并以测试设备终端GUI为例给出了开发自定义输入设备接口的实现方案。     

An agile server for cross-provider service peering and aggregation

Telecommunications and next-generation network IP-based services can be increasingly delivered at network edges and in peered third-party networks. As a result, subscribers bypass operators' services in favor of alternative novel services; accordingly, potential revenue is lost. By bundling existing viable network-based services across providers, however, service providers can create new revenues and avoid further erosion of their market share. Business announcements attest to this growing trend, but thus far cross-provider solutions take the form of point-to-point customized integrations. In the emerging service delivery paradigm, providers must be able to interwork fluidly with partners already operating profitable services, and do so without going through the risky and costly service development cycle, and without the need for extensive customized software development. We outline an intelligent-agent-based service peering and aggregation server whose deployment on service provider networks enables such interworking.     

A model for optical and thermal analysis of laser balloonangioplasty

Laser balloon angioplasty is modeled using an infinitely long cylinder possessing axisymmetry. The balloon surface is assumed to be uniformly irradiated by diffuse light at 1060 nm delivered from within the inner balloon core. The diffusion approximation to the radiative transport equation is solved for a single layer of homogeneous medium enclosing the transparent fluid-filled balloon. The computed light fluence rate (W.cm-2) just beneath the tissue surface is 4.7 times the primary irradiance, owing to scattering and secondary irradiance from the "integrating cylinder" effect of backscattered light into the inner core. The transient temperature response of the heated tissue is then calculated using an implicit finite difference solution of the heat conduction equation for concentric layers of varying thermal properties. Finally, the extent of damage is analyzed using the Arrhenius rate process model. Changes in optical and thermal properties with temperature and thermal phase transitions have been omitted in all our analyses. Irradiances which decrease with time can produce a "temperature plateau" for a longer time period than a constant irradiance of equal total energy output. This may be clinically important. Flexible boundary conditions at the balloon interface permit simulation of a "hot contact surface," such as a black balloon absorbing all incident laser power. In this situation, the computed surface damage is consistently higher than that obtained by LBA of equivalent energy output.     

Impact of Parylene-A Encapsulation on ZnO Nanobridge Sensors and Sensitivity Enhancement via Continuous Ultraviolet Illumination

The impact of parylene-A encapsulation and the effect of continuous ultraviolet (UV) exposure on ZnO nanobridge sensor response are investigated. ZnO nanowire (NW) devices are fabricated using a novel method that involves selective growth of ZnO nanobridges between lithographically defined pads of carbonized photoresist (C-PR). We find that a thin coating of parylene-A effectively attenuates the response of NW devices to O₂, H₂O vapor, and UV illumination. The accessibility of the amine group on parylene-A for chemical functionalization is verified by transforming the amine groups on the surface of the parylene-A coating into aromatic imine groups, followed by UV–Vis absorption. Our results suggest that, in addition to modulating environmental sensitivity and providing protection of the ZnO NWs for liquid- and vapor-phase sensing, the parylene-A encapsulation may also serve as an activation layer for further specific functionalization targeting selective sensing. We also found that the sensitivity and response time of ZnO nanobridge devices to O₂ are dramatically improved by continuously exposing the nanobridge devices to UV illumination. Finally, we show that the C-PR directed growth method can also be used to isolate free-standing NW carpet.     

Study on Surface States of Zinc Sulfide Electroluminescence Thin Films

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Effects of vessel geometry and catheter position on dose delivery in intracoronary brachytherapy

In-stent restenosis is commonly observed in coronary arteries after intervention. Intravascular brachytherapy has been found effective in reducing the recurrence of restenosis after stent placement. Conventional dosing models for brachytherapy with beta (beta) radiation neglect vessel geometry as well as the position of the delivery catheter. This paper demonstrates in computer simulations on phantoms and on in vivo patient data that the estimated dose distribution varies substantially in curved vessels. In simulated phantoms of 50-mm length with a shape corresponding to a 60 degrees - 180 degrees segment of a respectively sized torus, the average dose in 2-mm depth was decreased by 2.70%-7.48% at the outer curvature and increased by 2.95%-9.70% at the inner curvature as compared with a straight phantom. In vivo data were represented in a geometrically correct three-dimensional model that was derived by fusion of intravascular ultrasound (IVUS) and biplane angiography. These data were compared with a simplified tubular model reflecting common assumptions of conventional dosing schemes. The simplified model yielded significantly lower estimates of the delivered radiation and the dose variability as compared with a geometrically correct model (p < 0.001). The estimated dose in ten vessel segments of eight patients was on average 8.76% lower at the lumen/plaque and 6.52% lower at the media/adventitia interfaces (simplified tubular model relative to geometrically correct model). The differences in dose estimates between the two models were significantly higher in the right coronary artery as compared with the left coronary artery (p < 0.001).     

A Dual‐Functional Graphene‐Based Self‐Alarm Health‐Monitoring E‐Skin

Diseases such as cardiovascular problems and sleep apnea cause mass deaths annually due to a lack of timely and portable monitoring and alarm measures. Various wearable devices for health monitoring have been intensely researched to reduce mortality. However, these devices themselves can only detect physiological signals; they cannot sound an alarm. Therefore, they must rely on mobile phones or other peripheral devices such as speakers or vibration motors to sound an alarm, which may result in a patient missing the optimal treatment. It is valuable to develop a self‐alarm health monitoring device with the dual functions of physiological signal detection and sound alarm simultaneously. A one‐step laser‐induced graphene (LIG)‐based electronic skin (E‐skin) is fabricated to perform health monitoring and alarm at the same time, which benefit from its both excellent mechanical and acoustical performance. These customized shutter‐patterned E‐skins have an ultrahigh sensitivity of 316.3 and can detect various biosignals such as wrist pulse, respiratory, etc. They also have a self‐alarm function and can sound an alarm when detecting abnormal situations. This study addresses the multifunctional integration required for multisensors, which will open further applications in wearable sensors and health‐care devices.     

Motion tracking for medical imaging: a nonvisible structured light tracking approach

We present a system for head motion tracking in 3D brain imaging. The system is based on facial surface reconstruction and tracking using a structured light (SL) scanning principle. The system is designed to fit into narrow 3D medical scanner geometries limiting the field of view. It is tested in a clinical setting on the high resolution research tomograph (HRRT), Siemens PET scanner with a head phantom and volunteers. The SL system is compared to a commercial optical tracking system, the Polaris Vicra system, from NDI based on translatory and rotary ground truth motions of the head phantom. The accuracy of the systems was similar, with root mean square (rms) errors of 0.09 degrees for ±20 degrees axial rotations, and rms errors of 0.24 mm for ± 25 mm translations. Tests were made using (1) a light emitting diode (LED) based miniaturized video projector, the Pico projector from Texas Instruments, and (2) a customized version of this projector replacing a visible light LED with a 850 nm near infrared LED. The latter system does not provide additional discomfort by visible light projection into the patient's eyes. The main advantage over existing head motion tracking devices, including the Polaris Vicra system, is that it is not necessary to place markers on the patient. This provides a simpler workflow and eliminates uncertainties related to marker attachment and stability. We show proof of concept of a marker less tracking system especially designed for clinical use with promising results.     

High‐Performance Ultraviolet Photodetector Based on a Few‐Layered 2D NiPS3 Nanosheet

2D materials, represented by transition metal dichalcogenides (TMDs), have attracted tremendous research interests in photoelectronic and electronic devices. However, for their relatively small bandgap (<2 eV), the application of traditional TMDs into solar‐blind ultraviolet (UV) photodetection is restricted. Here, for the first time, NiPS₃ nanosheets are grown via chemical vapor deposition method. The nanosheets thinning to 3.2 nm with the lateral size of dozens of micrometers are acquired. Based on the various nanosheets, a linearity is found between the Raman intensity of specific A_g modes and the thickness, providing a convenient method to determine their layer numbers. Furthermore, a UV photodetector is fabricated using few‐layered 2D NiPS₃ nanosheets. It shows an ultrafast rise time shorter than 5 ms with an ultralow dark current less than 10 fA. Notably, this UV photodetector demonstrates a high detectivity of 1.22 × 10¹² Jones, outperforming some traditional wide‐bandgap UV detectors. The wavelength‐dependent photoresponsivity measurement allows the direct observation of an admirable cut‐off wavelength at 360 nm, which indicates a superior spectral selectivity. The promising photodetector performance, accompanied with the controllable fabrication and transfer process of nanosheet, lays the foundation of applying 2D semiconductors for ultrafast UV light detection.     

Universal Electron Injection Dynamics at Nanointerfaces in Dye‐Sensitized Solar Cells

Initial nanointerfacial electron transfer dynamics are studied in dye‐sensitized solar cells (DSSCs) in which the free energy and kinetics vary over a broad range. Surprisingly, it is found that the decay profiles, reflecting the electron transfer behavior, show a universal shape despite the different kinds of dye and semiconductor nanocrystalline films, even across different device types. This renews intuitive knowledge about the electron injection process in DSSCs. In order to quantitatively comprehend the universal behavior, a static inhomogeneous electronic coupling model with a Gaussian distribution of local injection energetics is proposed in which only the electron injection rate is a variant. It is confirmed that this model can be extended to CdSe quantum dot‐sensitized films. These unambiguous results indicate exactly the same physical distribution in electron injection process of different sensitization films, providing limited simple and important parameters describing the electron injection process including electronic coupling constant and reorganization energy. The results provide insight into photoconversion physics and the design of optimal metal‐free organic dye‐sensitized photovoltaic devices by molecular engineering.     

Real-time control of angioplasty balloon inflation based on feedback from intravascular optical coherence tomography: experimental validation on an excised heart and a beating heart model

We report on real-time control of balloon inflation inside porcine arteries. In the first step, experiments were done in a coronary artery of an excised heart. In the second step, experiments were done in a beating heart setup providing conditions very close to in vivo conditions without the complications. A programmable syringe pump was used to inflate a compliant balloon in arteries, while intravascular optical coherence tomography (IVOCT) monitoring was performed. In a feedback loop, IVOCT images were processed to provide the balloon diameter values in real time to control the pump action in order to achieve a target diameter. In different experiments, various flow rates and target diameters were used. In the excised heart experiment, there was good convergence to target diameters resulting in a satisfactory balloon inflation control. In the beating heart experiment, there were oscillations in the diameter values due to cyclic arterial contractions. In these experiments, the control system maintained diameter averages satisfactorily close to predetermined target values. Real-time control of balloon inflation could not only provide a safer outcome for angioplasty procedures, but could also provide additional information for diagnostics since it implicitly provides information about the artery response to the inflation process.     

Enhancing QoS of Mobile Devices by a New Handover Process in PMIPv6 Networks

The handover processes in present IP mobility management protocols incur significant latency, thus aggravating QoS of consumer devices. In this paper, we introduce an enhanced handover process for the Proxy Mobile IPv6 (PMIPv6) protocol, which is a recently developed IP mobility management protocol aiming at providing network-based mobility support. The proposed handover process further improves handover performance of PMIPv6 by allowing a new access network obtains handover context before a consumer??s mobile node (MN) moves to the new access network. Data packets destined for the MN are buffered to prevent packet loss and immediately delivered to the MN as the MN moves to the new access network. We evaluate the handover latency and data packet loss of the proposed handover process compared to the basic one of PMIPv6. The conducted analysis results confirm that the proposed handover process yields the reduced handover latency compared to that of the basic PMIPv6 and also prevents data packet loss. We moreover evaluate the buffering cost of the proposed handover process.     

From synchronous to GALS: A new architecture for FPGAs

The conflictual demand of faster and larger designs is increasingly difficult to answer by the advances of solid state technology alone. At some point, it is expected that designers and manufacturers will have to give up the traditional synchronous design methodology for a Globally Asynchronous Locally Synchronous (GALS) one. Such changes imply more synchronization constraints, but also more flexibility. Consequently, this paper proposes a novel Field-Programmable Gate Arrays (FPGA) architecture that is compatible with existing devices and that can also support GALS designs. The main objective is simple: the proposed architecture must appear unchanged for synchronous design, but it must also include a minimal amount of basic components to prevent metastability for efficient asynchronous communications. Thus, the paper presents the constraint equations required to implement such a circuit. It also presents a pausible clock generator application and simulation results for the proposed architecture. All results demonstrate that with a few additional customized circuits, a standard FPGA cell can become appropriate for GALS methodologies.     

Deformable,Programmable, and Shape‐Memorizing Micro‐Optics

The use of shape memory polymers is demonstrated for deformable, programmable, and shape‐memorizing micro‐optical devices. A semi‐crystalline shape memory elastomer, crosslinked poly(ethylene‐co‐vinyl acetate), is used to prepare various micro‐optic components, ranging from microlens and microprism arrays to diffraction gratings and holograms. The precise replication of surface features at the micro‐ and nanoscale and the formation of crosslinked shape memory polymer networks can be achieved in a single step via compression molding. Further deformation via hot pressing or stretching of micro‐optics formed in this manner allows manipulation of the microscopic surface features, and thus the corresponding optical properties. Due to the shape memory effect, the original surface structures and the optical properties can be recovered and the devices be reprogrammed, with excellent reversibility in the optical properties. Furthermore, arrays of transparent resistive microheaters can be integrated with deformed micro‐optical devices to selectively trigger the recovery of surface features in a spatially programmable manner, thereby providing additional capabilities in user‐definable optics.     

A Personalized Multifunctional 3D Printed Shape Memory-Displaying,Drug Releasing Tracheal Stent

The ability to engineer custom-made medical devices and to implant them minimally invasively are two important trends in modern surgery. The personalization of the device is achieved by 3D printing it, while the capacity to deploy it minimally invasively harnesses the shape memory behavior displayed by the inks used. This study introduces a 3D printed, shape memory-displaying tracheal stent based on novel, flexible photo-polymerizable inks comprising polypropylene glycol/polycaprolactone triblocks. This research introduces the in situ welding strategy, whereby thin and flexible layers of the stent are separately printed, sequentially deployed, and then welded together at the tracheal site. By doing so, the insertion profile of the device is dramatically reduced and its flexibility largely increased. Porous stents are 3D printed seeking to prevent mucus plugging. By combining more than one ink, their properties are further fine-tuned. Polyethylene glycol chains are covalently bonded to the stent surface to minimize biofilm formation, an important drawback of current tracheal stents. The in vitro cell viability and cell adhesion behavior of the treated surfaces reveal their compatibility and anti-adhesive behavior. In order to prevent implant-related infections, ciprofloxacin is added to the ink, and released in vitro over time, rendering the stent with antibacterial activity.     

LV volume quantification via spatiotemporal analysis of real-time3-D echocardiography

This paper presents a method of four-dimensional (4-D) (3-D + Time) space-frequency analysis for directional denoising and enhancement of real-time three-dimensional (RT3D) ultrasound and quantitative measures in diagnostic cardiac ultrasound. Expansion of echocardiographic volumes is performed with complex exponential wavelet-like basis functions called brushlets. These functions offer good localization in time and frequency and decompose a signal into distinct patterns of oriented harmonics, which are invariant to intensity and contrast range. Deformable-model segmentation is carried out on denoised data after thresholding of transform coefficients. This process attenuates speckle noise while preserving cardiac structure location. The superiority of 4-D over 3-D analysis for decorrelating additive white noise and multiplicative speckle noise on a 4-D phantom volume expanding in time is demonstrated. Quantitative validation, computed for contours and volumes, is performed on in vitro balloon phantoms. Clinical applications of this spaciotemporal analysis tool are reported for six patient cases providing measures of left ventricular volumes and ejection fraction.     

Resource discovery and management in computational GRID environments

Corporations are currently using computational GRIDs to improve their operations. Future GRIDs will allow an organization to take advantage of computational GRIDs without having to develop a custom in‐house solution. GRID resource providers (GRPs) make resources available on the GRID so that others may subscribe and use these resources. GRPs will allow companies to make use of a range of resources such as processing power or mass storage. However, simply providing resources is not enough to ensure the success of a computational GRID: Access to these resources must be controlled otherwise computational GRIDs will simply evolve to become a victim of their own success, unable to offer a suitable quality of service (QoS) to any user. The task of providing a standard querying mechanism for computational GRID environments (CGE) has already witnessed considerable work from groups such as the Globus project who have delivered the Metacomputing Directory Service (MDS), which provides a means to query devices attached to the GRID. This paper presents a review of existing resource discovery mechanisms within CGE. Copyright © 2005 John Wiley & Sons, Ltd.